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A&P I Lecture Exam III
Chapter 9
565
Anatomy
03/25/2012

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Term
skeletal
cardiac
smooth
Definition
what are the three types of muscle tissue?
Term
muscle fibers
Definition
skeletal and smooth muscle cells are elongated and for this reason are called __
Term
myo
mys
sarco
Definition
what prefixes are in reference to muscle?
Term
skeletal muscle tissue
Definition
__ is packaged into the skeletal muscles
Term
skeletal muscles
Definition
organs that attach to and cover the bony skeleton
Term
bones
skin
Definition
skeletal muscle tissue is attached to __ and __
Term
longest
Definition
skeletal muscle fibers are the __ muscle cells
Term
striations
Definition
skeletal muscle have obvious stripes called __
Term
voluntary muscle
Definition
although it is often activated by reflexes, skeletal muscle is called _ because it is the only type subject to conscious control
Term
mobility
Definition
skeletal muscle is responsible for overall body __
Term
easily
Definition
skeletal muscle can contract rapidly, but it tires __ and must rest after short periods of activity
Term
power
Definition
skeletal muscle can exert tremendous __
Term
cardiac muscle tissue
Definition
occurs only in the heart, where it constitutes the bulk of the heart walls
Term
striated
Definition
like skeletal muscle cells, cardiac muscle cells are __
Term
not voluntary (involuntary)
Definition
unlike skeletal muscle cells, cardiac muscle is __
Term
rate
Definition
cardiac muscle usually contracts at a fairly steady __ set by the heart's pacemaker, but neural controls allow the heart to speed up for brief periods
Term
smooth muscle tissue
Definition
found in the walls of hollow visceral organs, such as the stomach, urinary bladder, and respiratory passages
Term
to force fluids and other substances through internal body channels
Definition
what is the role of smooth muscle tissue?
Term
no striations (not striated)
Definition
smooth muscle cells like skeletal muscle cells are elongated "fibers," but smooth muscle has __
Term
voluntary control
involuntary
Definition
like cardiac muscle, smooth muscle is not subject to __, so it is __
Term
slow
sustained
Definition
contractions of smooth muscle fibers are __ and __
Term
excitability
(responsiveness)
(irritability)
Definition
__ is the ability to receive and respond to a stimulus, that is, any change in the environment either inside or outside the body
Term
chemical
Definition
in the case of muscle, the stimulus is usually a __
Term
skeletal muscle
Definition
__ body location: attached to bones or (some facial muscles) to skin
Term
cardiac muscle
Definition
__ body location: walls of the heart
Term
smooth muscle
Definition
__ body location: single-unit muscle in walls of hollow visceral organs (other than the heart); multiunit muscle in intrinsic eye muscles, airways, large arteries
Term
smooth muscle
Definition
__ cell shape and appearance: single, fusiform, uninucleate; no strations
Term
skeletal muscle
Definition
__ cell shape and appearance: single, very long, cylindrical, multinucleate cells with obvious striations
Term
cardiac muscle
Definition
__ cell shape and appearance: branching chains of cells; uni- or binucleate; striations
Term
the response (conductivity)
Definition
__ is generation of an electrical impulse that passes along the plasma membrane of the muscle cell and causes the cell to contract
Term
contractility
Definition
__ is the ability to shorten forcibly when adequately stimulated
Term
contractility
Definition
this ability sets muscle apart from all other tissue types
Term
extensibility
Definition
__ is the ability to be stretched or extended
Term
shorten
Definition
muscle cells __ when contracting, but they can be stretched, even beyond their resting length, when relaxed
Term
elasticity
Definition
__ is the ability of a muscle cell to recoil and resume its resting length after being stretched
Term
1. excitability (responsiveness or irritability)
2. contractility
3. extensibility
4. elasticity
Definition
what are the special characteristics of muscle tissue?
Term
1. produces movement (bones or fluid movement --> ex: blood)
2. maintains posture and body position
3. stabilizes joints
4. generates heat (especially skeletal muscle)
Definition
what are the important functions that muscle preforms for the body?
Term
muscle contraction
Definition
just about all movements of the human body and its parts result from __
Term
skeletal
Definition
__ muscles are responsible for all locomotion and manipulation
Term
stabilize
strengthen
Definition
even as muscles pull on bones to cause movements, they __ and __ the joints of the skeleton
Term
heat
Definition
muscles generate __ as they contract
Term
body temperature
Definition
the heat that muscles generate is important in maintaining normal __
Term
40%
Definition
skeletal muscle accounts for at least __ of body mass
Term
skeletal
Definition
__ muscle is the muscle type most responsible for generating heat
Term
enclosing
Definition
skeletal muscles protect the more fragile internal organs (the viscera) by __ them
Term
valves
dilates
constricts
arrector pili
Definition
smooth muscle also forms __ to regulate the passage of substances through internal body openings, __ and __ the pupils of your eyes, and forms the __ muscles attached to hair follicles
Term
skeletal muscle
Definition
each __ is a discrete organ, made up of several kinds of tissues. skeletal muscle fibers predominate, but blood vessels, nerve fibers, and substantial amounts of connective tissue are also present
Term
one artery, one nerve, and one or more veins
Definition
Each muscle is served by __
Term
nerve stimulation
Definition
cardiac and smooth muscle tissues can contract in the absence of __
Term
nerve ending
Definition
each skeletal muscle fiber is supplied with a __ that controls its activity
Term
blood
Definition
skeletal muscle has a rich __ supply
Term
oxygen
nutrients
Definition
contracting muscle fibers use huge amounts of energy and require more or less continuous delivery of __ and __ via the arteries
Term
veins
Definition
muscle cells also give off large amounts of metabolic wastes that must be removed through __ if contraction is to remain efficient
Term
muscle capillaries
Definition
__, the smallest of the body's blood vessels, are long and winding and have numerous cross-links, features that accommodate changes in muscle length
Term
straighten
contort
Definition
muscle capillaries __ when the muscle is stretched and __ when the muscle contracts
Term
connective tissue sheaths
Definition
in an intact muscle, the individual muscle fibers are wrapped and held together by several different __
Term
bursting
Definition
together these connective tissue sheaths support each cell and reinforce the muscle as a whole, preventing the bulging muscles from __ during exceptionally strong contractions
Term
1. epimysium
2. perimysium and fascicles
3. endomysium
Definition
what are the three types of connective tissue sheaths of skeletal muscle?
Term
epimysium
Definition
an "overcoat" of dense irregular connective tissue that surrounds the whole muscle
Term
epimysium
Definition
sometimes the __ blends with the deep fascia that lies between neighboring muscles or the superficial fascia deep to the skin
Term
fascicles
Definition
within each skeletal muscle, the muscle fibers are grouped into __ that resemble bundles of sticks
Term
perimysium
Definition
surrounding each fascicle is a layer of fibrous connective tissue called __
Term
endomysium
Definition
the __ is a whispy sheath of connective tissue that surrounds each individual muscle fiber. it consists of fine areolar connective tissue
Term
epimysium
Definition
connective tissue sheath of skeletal muscle that is dense regular connective tissue, surrounding the entire muscle
Term
perimysium
Definition
connective tissue sheath of skeletal muscle that is fibrous connective tissue, surrounding the fascicles (groups of muscle fibers)
Term
endomysium
Definition
connective tissue sheath of skeletal muscle that is fine areolar connective tissue, surrounding each muscle fiber
Term
continuous
Definition
the epimysium, perimysium and fascicles, and endomysium connective tissue sheaths are __ with one another as well as with the tendons that join muscles to bones
Term
bone
Definition
when muscle fibers contract, they pull on the connective tissue sheaths, which in turn transmit the pulling force to the __ to be moved
Term
muscle tissue
blood vessels
nerve fibers
Definition
the connective tissue sheaths contribute somewhat to the natural elasticity of __, and also provide entry and exit routes for the __ and __ that serve the muscle
Term
insertion
origin
Definition
most skeletal muscles span joints and are attached to bones (or other structures) in at least two places, and that when a muscle contracts, the movable bone, the muscle's __, moves toward the immovable or less movable bone, the muscle's __
Term
proximal
Definition
in the muscles of the limbs, the origin typically lies __ to the insertion
Term
direct
indirect
Definition
muscle attachments, whether origin or insertion, may be __ or __
Term
direct (or fleshy)
Definition
in __ muscle attachments, the epimysium of the muscle is fused to the periosteum of a bone or perichondrium of a cartilage
Term
indirect
Definition
in __ muscle attachments, the muscle's connective tissue wrappings extend beyond the muscle either as a ropelike tendon or as a sheetlike aponeurosis
Term
connective tissue
fascia
Definition
in indirect muscle attachments, the tendon or aponeurosis anchors the muscle to the __ covering of a skeletal element (bone or cartilage) or to the __ of other muscles
Term
indirect
Definition
__ attachments are much more common because of their durability and small size
Term
tendons
Definition
__ are mostly tough collagen fibers which can withstand the abrasion of rough bony projections that would tear apart the more delicate muscle tissues
Term
muscle
Definition
a __ consists of hundreds to thousands of muscle cells, plus connective tissue wrappings, blood vessels, and nerve fibers. it is covered externally by the epimysium
Term
fascicle
Definition
a __ is a discrete bundle of muscle cells, segregated from the rest of the muscle by a connective tissue sheath. is is surrounded by a perimysium
Term
muscle fiber
Definition
a __ is an elongated multinucleate cell; it has a banded (striated) appearance. it is surrounded by endomysium
Term
sacrolemma
Definition
each skeletal muscle fiber is a long cylindrical cell with multiple oval nuclei just beneath its __ or plasma membrane. skeletal muscle fibers are huge cells.
Term
10-100 um
30cm
Definition
the skeletal muscle fiber's diameter typically ranges from __ to __ and their length is up to __ long
Term
sarcoplasm
Definition
__ is the cytoplasm of a muscle cell
Term
glycosomes
myoglobin
Definition
sarcoplasm, the cytoplasm of a muscle cell contains unusually large amounts of __ and __
Term
glycosomes
Definition
granules of stored glycogen that provide glucose during periods of muscle cell activity
Term
myoglobin
Definition
a red pigment that stores oxygen
Term
myofibrils, the sarcoplasmic reticulum, and T tubules
Definition
what organelles are highly modified in muscle fibers?
Term
nuclei
mitochondria
Definition
skeletal muscle fibers have multiple peripheral __ and many __
Term
parallel
Definition
each muscle fiber contains many rodlike myofibrils that run __ to its length
Term
1-2 um
Definition
the myofibrils, each __ in diameter, are so densely packed in the fiber that mitochondria and other organelles appear to be squeezed between them
Term
80%
Definition
hundreds to thousands of myofibrils are in a single muscle fiber, depending on its size, and they account for about __ of cellular volume
Term
myofibril or fibril
Definition
__ is a complex organelle composed of bundles of myofilaments
Term
myofibrils
Definition
__ are rodlike contractile elements that occupy most of the muscle cell volume. composed of sarcomeres arranged end to end, they appear banded
Term
aligned
Definition
bands of adjacent myofibrils are __
Term
sacromeres
Definition
myofibrils contain the contractile elements of skeletal muscle cells, the __
Term
myofilaments
Definition
the sacromeres contain even smaller rodlike structures called __
Term
sarcomere
Definition
a __ is a segment of a myofibril
Term
sarcomere
Definition
a __ is the contractile unit, composed of myofilaments made up of contractile proteins
Term
dark A bands
light I bands
Definition
myofibrils exhibit striations ; perfectly aligned repeating series of __ and __
Term
thick and thin
Definition
what are the two types of contractile myofilaments?
Term
thick myofilaments
thin myofilaments
Definition
the __ contain bundled myosin molecules; the __ contain actin molecules (plus other proteins)
Term
muscle shortening
Definition
the sliding of the thin myofilaments past the thick myofilaments produces __
Term
elastic
Definition
__ filaments maintain the organization of the A band and provide for elastic recoil when muscle contraction ends
Term
striations
Definition
__, a repeating series of dark and light bands, are evident along the length of each myofibril
Term
A bands
I bands
Definition
in an intact muscle fiber, the dark __ and light __ are nearly perfectly aligned with one another, giving the cell as a whole its striated appearance
Term
H zone
Definition
a dark A band has a lighter region in its midsection called the __, where filaments do not overlap
Term
M line
Definition
each H zone is bisected vertically by a dark line called the __ formed by molecules of the protein myomesin
Term
Z disc (or Z line)
Definition
the light I bands also have a midline interruption, a darker area called the __
Term
sarcomere
Definition
a __ is the smallest contractile unit of a muscle fiber - the functional unit of skeletal muscle
Term
2um
Definition
the sarcomere averages __ long
Term
sarcomere
Definition
a __ is the region of a myofibril between two successive Z discs
Term
A band
I band
Definition
a sarcomere contains an __ flanked by half an __ at each end
Term
end-to-end (like boxcars in a train)
Definition
within each myofibril, the sarcomeres are aligned __
Term
sarcomere's
Definition
__ are composed of thick and thin myofilaments made of contractile proteins
Term
myofilaments
filaments
Definition
if we examine the banding pattern of a myofibril at the molecular level, we see that it arises from an orderly arrangement of two types of even smaller structures, the __ or __, within the sarcomeres
Term
actin
myosin
Definition
proteins __ and __ play a role in motility and shape changes in virtually every cell in the body
Term
thick filaments
Definition
the central __ containing myosin extend the entire length of the A band
Term
thin filaments
Definition
the more lateral __ containing actin extend across the I band and partway into the A band
Term
Z disc
Definition
the __, a coin-shaped sheet composed largely of the protein alpha-actinin, anchors the thin filaments and connects myofibrils to one another
Term
intermediate filaments
Definition
__ extending from the Z disc connect each myofibril to the next throughout the width of the muscle cell
Term
thin filaments
Definition
the H zone of the A band appears less dense because the __ do not extend into this region
Term
thick filaments
Definition
the M line in the center of the H zone is slightly darker because of the presence there of fine protein strands that hold adjacent __ together
Term
Z discs
M lines
Definition
the myofilaments are connected to the sarcolemma and held in register at the __ and the __
Term
thin filaments
thick filaments
Definition
in the outer edge of the A band, each thick filament is actually surrounded by a hexagonal arrangement of six __, and each thin filament is enclosed by three __
Term
muscle contraction
Definition
__ depends on the myosin- and actin-containing myofilaments
Term
M line
Definition
__ = line of protein myomesin that holds adjacent thick filaments together
Term
myosin
Definition
thick filaments are composed primarily of the protein __
Term
myosin
Definition
each __ molecule consists of two heavy and four light polypeptide chains, and has a rodlike tail attached by a flexible hinge to two globular heads
Term
polypeptide heavy chains
Definition
the myosin molecules tail consists of two intertwined helical __
Term
light polypeptide chains
Definition
the globular heads of a myosin molecule are each associated with two __ and are the 'business end' of myosin
Term
cross bridges
Definition
the 2 light polypeptide chains in a myosin molecules head link the thick and thin filaments together, forming __, and swivel around their point of attachment during contraction
Term
tension
Definition
the cross bridges formed during contraction in a myosin molecules head act as motors to generate the __ developed by a contracting muscle cell
Term
300
tails
heads
Definition
each thick filament contains about __ myosin molecules bundled together with their __ forming the central part of the thick filament and their __ facing outward and at each end
Term
actin
ATP
Definition
a myosin molecules head contains binding sites for __ of thin filaments and binding sites for __
Term
ATPase
Definition
a myosin molecules head contains __ enzymes that split ATP to generate energy for muscle contraction
Term
smooth
studded
Definition
because of the structure of how myosin molecules make thick filaments, the central portion of a thick filament (in the H zone) is __, but its ends are __ with a staggered array of myosin heads
Term
actin
Definition
the thin filaments are composed chiefly of the protein __
Term
globular actin
G actin
Definition
actin has kidney-shaped polypeptide subunits called __ or __, which bear the active sites to which the myosin heads attach during contraction
Term
fibrous
F actin
Definition
in the thin filaments, G actin subunits are polymerized into long actin filaments called __ or __
Term
actin filaments
Definition
the backbone of each thin filament appears to be formed by two intertwined __
Term
F actin
Definition
the ultrastructure of thin filament is a twisted double strand of fibrous protein __
Term
tropomyosin
troponin
Definition
several regulatory proteins are also present in thin filaments, like __ and __
Term
tropomyosin
Definition
polypeptide strands of __, a rodshaped protein, spiral about the actin core and help stiffen and stabilize it.
Term
relaxed
Definition
successive tropomyosin molecules are arranged end-to-end along the actin filaments, and in a __ muscle fiber, tropomyosin molecules block myosin-binding sites on actin so that they myosin heads on the thick filaments cannot bind to the thin filaments
Term
troponin
Definition
the other major protein in thin filaments is __, a globular three-polypeptide complex.
Term
TnI
Definition
one of troponin's polypeptides __ is an inhibitory subunit that binds to actin
Term
TnT
Definition
one of troponin's polypeptides __ binds to tropomyosin and helps position it on actin
Term
TnC
Definition
one of troponin's polypeptides __ binds calcium ions
Term
tropomyosin
troponin
Definition
both __ and __ help control the myosin-actin interactions involved in contraction
Term
heads
Definition
in the center of the sarcomere, the thick filaments lack myosin __.
Term
myosin-actin
Definition
myosin heads are present only in areas of __ overlap
Term
thick filament
Definition
each __ consists of many myosin molecules whose heads protrude at opposite ends of the filament
Term
thin filament
Definition
a __ consists of two strands of actin subunits twisted into a helix plus two types of regulatory proteins (troponin and tropomyosin)
Term
titin
Definition
the elastic filament is composed of the giant protein __, which extends from the Z disc to the thick filament, and then runs within the thick filament (forming its core) to attach to the M line
Term
elastic filament (made of protien titin)
Definition
the __ holds the thick filaments in place, thus maintaining the organization of the A band, and helps the muscle cell to spring back into shape after being stretched
Term
titin
Definition
__ does not resist stretching in the ordinary range of extension, but it stiffens as it uncoils, helping the muscle to resist excessive stretching, which might pull the sarcomeres apart
Term
dystrophin
Definition
another important structural protein is __, which links the thin filaments to the integral proteins of the sarcolemma
Term
nebulin
myomesin
C proteins
Definition
other proteins that act to bind filaments or sarcomeres together and maintain their alignment include __, __, and __
Term
the sarcoplasmic reticulum
T tubules
Definition
skeletal muscle fibers contain two sets of intracellular tubules that participate in regulation of muscle contration: 1. __ and 2.__
Term
sarcoplasmic reticulum (SR)
Definition
an elaborate smooth endoplasmic reticulum. its interconnecting tubules surround each myofibril
Term
H zone
Definition
most of the tubules of the sarcoplasmic reticulum (SR) run longitudinally along the myofibril communicating at the __
Term
terminal cisternae
Definition
other tubules of the sarcoplasmic reticulum (SR) called __ form larger, perpendicular cross channels at the A band - I band junctions and they always occur in pairs
Term
mitochondria
glycogen granules
Definition
closely associated with the sarcoplasmic reticulum (SR) are large numbers of __ and __, both involved in producing the energy used during contraction
Term
ionic calcium (Ca^2+)
Definition
the major role of the sarcoplasmic reticulum (SR) is to regulate intracellular levels of __
Term
contract
Definition
the sarcoplasmic reticulum (SR) stores calcium and releases it on demand when the muscle fiber is stimulated to __
Term
calcium
Definition
__ provide the final "go" signal for contraction
Term
T tubule
Definition
at each A band - I band junction, the sarcolemma of the muscle cell protrudes deep into the cell interior, forming an elongated tube called the __
Term
T tubules
Definition
the __ tremendously increase the muscle fiber's surface area
Term
sarcolemma
Definition
T tubules are continuous with the __
Term
triads
Definition
along its length, each T tubule runs between the paired terminal cisternae of the sarcoplasmic reticulum (SR), forming __, successive groupings of the three membranous structures (terminal cisterna, T tubule, and terminal cisterna).
Term
sarcomere
Definition
as they pass from one myofibril to the next, the T tubules also encircle each __
Term
sarcomere
Definition
T tubules associate with the paired terminal cisternae to form triads that encircle each __
Term
T tubules
Definition
muscle contraction is ultimately controlled by nerve-initiated electrical impulses that travel along the sarcolemma. because the __ are continuous of the sarcolemma, they conduct impulses to the deepest regions of the muscle cell and to every sarcomere. these impulses signal for the release of calcium from the adjacent terminal cisternae
Term
T tubules
Definition
__ ensure that every myofibril in the muscle fiber contracts at virtually the same time
Term
T tubules
Definition
__ conduct impulses deep into muscle fiber
Term
voltage sensors
foot proteins
Definition
Integral proteins protrude into the intermembrane space from T tubule and SR cisternae membranes. the protruding integral proteins of the T tubule act as __. Those of the SR, called __, form gated channels through which Ca^2+ can be released from the SR cisternae
Term
contraction
Definition
the activation of myosin's cross bridges, which are the force-generating sites (generation of force)
Term
contraction
Definition
__ does not necessarily cause shortening of the fiber
Term
shortening
Definition
__ occurs if and when the tension generated by the cross bridges on the thin filaments exceeds the forces opposing shortening and pulls the thin filaments toward the M line
Term
contraction
Definition
__ ends when the cross bridges become inactive and the tension declines, inducing relaxation of the muscle fiber
Term
sliding filament model of contraction
Definition
the __ states that during contraction the thin filaments slide past the thick filaments so that the actin and myosin filaments overlap to a greater degree
Term
relaxed
Definition
in a __ muscle fiber, the thick and thin filaments overlap only slightly at the ends of the A band
Term
thin filaments
Definition
when muscle fibers are stimulated by the nervous system, the myosin heads on the thick filaments latch onto myosin-binding sites on actin in the __, and the sliding begins
Term
M line
Definition
During contraction, myosin heads bind to actin, detach, and bind again, to propel the thin filaments toward the __
Term
length
Definition
as a muscle cell shortens, the I bands shorten, the distance between successive Z discs is reduced, the H zones disappear, and the contiguous A bands move closer together but do not change in __
Term
shortens
Definition
As H zones shorten and disappear, sarcomeres shorten, muscle cells shorten, and the whole muscle __
Term
1. it must be activated
2. it must have an action potential
3. it must have a rise in intracellular calcium ion levels
Definition
what are the requirements for a skeletal muscle fiber to contract?
Term
activated
Definition
the first thing for a skeletal muscle fiber to contract is that it must be __, that is, stimulated by a nerve ending so that a change in membrane potential occurs
Term
ation potential
Definition
the second thing for a skeletal muscle fiber to contract is that it must generate and propagate an electrical current, called an __, along its sarcolemma
Term
calcium ion
Definition
the third thing for a skeletal muscle fiber to contract is that there must be a short-lived rise in intracellular __ levels, which is the final trigger for contraction to occur
Term
neuromuscular junction
Definition
step 1 for a skeletal muscle fiber to contract, the activation step, occurs at the __ and sets the stage for the events that follow
Term
excitation-contraction coupling
Definition
steps two and three for a skeletal muscle fiber to contract, which link the electrical signal to contraction are called __
Term
somatic motor neurons or motor neurons OR the somatic (voluntary) nervous system
Definition
the nerve cells that activate skeletal muscle fibers are called __
Term
brain or spinal cord
Definition
somatic motor neurons "reside" in the __
Term
axons
Definition
the somatic motor neurons have long threadlike extensions called __ that travel from the central nervous system via nerves to skeletal muscles
Term
muscle
Definition
each axons forms several branches as it enters a __
Term
neuromuscular junction
Definition
each axons ending gives off several short, curling branches that collectively form an elliptical __ with a single muscle fiber
Term
midway
Definition
as a rule, each muscle fiber has only one neuromuscular junction, located approximately __ along its length
Term
synaptic cleft
Definition
the axon terminal and the muscle fiber are exceedingly close, but they remain separated by a space, the __, which is filled with a gel-like extracellular substance rich in glycoproteins and collagen fibers
Term
synaptic vesicles
Definition
within the moundlike axon terminal are __, small membranous sacs containing the neurotransmitter acetylcholine or ACh
Term
ACh receptors
Definition
the trough-like part of the muscle fiber's sarcolemma that helps form the neuromuscular junction is highly folded. these junctional folds provide a large surface area for the millions of __ located there
Term
axonal endings
synaptic cleft
junctional folds of the sarcolemma
Definition
what all does the neuromuscular junction include?
Term
when a nerve impulse reaches the end of an axon, the axon terminal releases ACh into the synaptic cleft. ACh diffuses across the cleft and attaches the ACh receptors on the sarcolemma of the muscle fiber, which triggers electrical events that ultimately cause action potential generation
Definition
how does a motor neuron stimulate a skeletal muscle fiber?
Term
acetic acid
choline
Definition
after ACh binds to the ACh receptors, its effects are quickly terminated by its enzymatic breakdown to its building blocks, __ and __
Term
acetylcholinesterase
Definition
what enzyme breaks down ACh into acetic acid and choline after it binds to the ACh receptors?
Term
acetylcholinesterase
Definition
an enzyme located in the synaptic cleft
Term
muscle fiber contraction
Definition
when the enzyme acetylcholinesterase breaks down ACh, the removal of ACh prevents continued (and most likely undesirable) __ in the absence of additional nervous system stimulation
Term
action potential
Definition
Electrical events lead to the generation of an __
Term
myasthenia gravis
Definition
a disease characterized by drooping upper eyelids, difficulty swallowing and talking, and generalized muscle weakness, involves a shortage of ACh receptors
Term
polarized
Definition
like the plasma membranes of all cells, a resting sacrolemma is __. that is, a voltmeter would show there is a potential difference (voltage) across the membrane and the inside is negative relative to the outer membrane face
Term
action potential (AP)
Definition
the __ is the result of a predictable sequence of electrical charges that once initiated occurs along the entire surface of the sarcolemma
Term
1. local depolarization and generation of an end plate potential
2. generation and propagation of the action potential
3. repolarization
Definition
what are the three steps in generation of an action potential?
Term
Na+ and K+
(step 1 of generation of an action potential - local depolarization and generation of an end plate potential)
Definition
in step 1 in generation of an action potential, binding of ACh molecules to ACh receptors at the neuromuscular junction opens chemically (ligand) gated ion channels that allow __ and __ to pass
Term
depolarization
(step 1 of generation of an action potential - local depolarization and generation of an end plate potential)
Definition
because more Na+ diffuses in that K+ diffuses out, a transient charge in membrane potential occurs as the interior of the sarcolemma become slightly less negative, an event called __
Term
end plate potential
(step 2 in generation of an action potential - generation and propagation of the action potential)
Definition
in step 2 of generation of an actoin potential, inital depolarization is a local electrical event called an __, but it ignites the action potential that spreads in all directions from the neuromuscular junction across the sarcolemma
Term
sodium channels
(step 2 in generation of an action potential - generation and propagation of the action potential)
Definition
after the action potential spreads in all directions, local depolarization (end plate potential) then spreads to adjacent membrane areas and opens voltage-gated __ there
Term
threshold
(step 2 in generation of an action potential - generation and propagation of the action potential)
Definition
after local depolarization spreads to adjacent membrane areas and opens voltage-gated sodium channels, Na+ enters, following its electrochemical gradient, and once a certain membrane voltage, referred to as __, is reached, action potential is generated (initiated).
Term
propagated
(step 2 in generation of an action potential - generation and propagation of the action potential)
Definition
after an action potential is initiated, the action potential is __ (moved along the length of the sarcolemma) as the local depolarization wave spreads to adjacent areas of the sarcolemma and opens voltage-gated sodium channels there. Again, Na+ diffuses into the cell following its electrochemical gradient.
Term
repolarization
(step 3 in generation of an action potential - repolarization)
Definition
in step three of generation of an action potential the sarcolemma is restored to its inital polarized state during __
Term
permeability
(step 3 in generation of an action potential - repolarization)
Definition
the repolarization wave, like the depolarization wave, is a consequence of changes in membrane __
Term
close
open
(step 3 in generation of an action potential - repolarization)
Definition
in repolarization of the sarcolemma in step 3 of generation of an action potential, Na+ channels __ and voltage-gated K+ channels __
Term
negatively
(step 3 in generation of an action potential - repolarization)
Definition
since the potassium ion concentration is substantially higher inside the cell than in the extracellular fluid in repolarization of the sarcolemma in step 3 of generation of an action potential, K+ diffuses rapidly out of the muscle fiber, restoring __ charge conditions inside
Term
Step 1 - Local depolarization and generation of an end plate potential
Definition
-ACh binding opens chemically (ligand) gated ion channels
-Simultaneous diffusion of Na+ (inward) and K+ (outward)
-More Na+ diffuses, so the interior of the sarcolemma becomes less negative
-Local depolarization – end plate potential

at what step in generation of an action potential does this occur?
Term
step 2 - generation and propagation of the action potential
Definition
-End plate potential spreads to adjacent membrane areas
-Voltage-gated Na+ channels open
-Na+ influx decreases the membrane voltage toward a critical threshold
-If threshold is reached, an action potential is generated
-Local depolarization wave continues to spread, changing the permeability of the sarcolemma
-Voltage-regulated Na+ channels open in the adjacent patch, causing it to depolarize to threshold

at what step in generation of an action potential does this occur?
Term
step 3 - repolarization
Definition
-Na+ channels close and voltage-gated K+ channels open
-K+ efflux rapidly restores the resting polarity
-Fiber cannot be stimulated and is in a refractory period until repolarization is complete
-Ionic conditions of the resting state are restored by the Na+-K+ pump

at what step in generation of an action potential does this occur?
Term
refractory period
Definition
during repolarization, a muscle fiber is said to be in a __ because the cell cannot be stimulated again until repolarization is complete
Term
electrical conditions
Definition
repolarization restores only the __ of the resting (polarized) state.
Term
ionic conditions
Definition
the ATP-dependent Na+ - K+ pump restores the __ of the resting state, but hundreds of action potentials can occur before ionic imbalances interfere with contractile activity
Term
unstoppable
Definition
once initiated, the action potential is __, and it ultimately results in contraction of the muscle fiber
Term
electrical
Definition
although the action potential itself is very brief, only 1-2 milliseconds (ms), the contraction phase of a muscle fiber may persist for 100 ms or more and far outlasts the __ event that triggers it
Term
excitation-contraction (E-C) coupling
Definition
__ is the sequencing of events by which transmission of an action potential along the sarcolemma leads to the sliding of myofilaments
Term
latent period
Definition
the events of excitation-contraction coupling occur during the __, between action potential initiation and the beginning of mechanical activity (contraction).
Term
calcium
Definition
the electrical signal does not act directly on the myofilaments, but instead causes the rise in intracellular __ ion concentration that allows the filaments to slide
Term
T tubules
Definition
action potential is propagated along sarcomere to __
Term
Ca^2+
Definition
voltage-sensitive proteins stimulate __ release from sarcoplasmic reticulum which is necessary for contraction
Term
1. process initiated when the nerve impulse reaches the neuron terminal and open voltage-gated calcium channels in the axonal membrane. calcium entry triggers release of ACh into the synaptic cleft.
2. release ACh binds to ACh receptors in the sarcolemma, opening chemically gated Na+ - K+ channels. greater influx of Na+ causes a local voltage change (the end plate potential)
3. local depolarization opens voltage-gated sodium channels in the neighboring region of the sarcolemma. this allows more sodium to enter, which further depolarizes the sarcolemma, resulting in action potential generation and propagation.
4. transmission of an action potential along the T tubules changes the shape of voltage-sensative proteins in the T tubules, which in turn stimulate sarcoplasmic reticulum calcium release channels to release Ca^2+ into the cytosol
Definition
in summary, the process in initiating muscle contraction involves activation of what four sets of ion channels?
Term
1. action potential is propagated along the sarcolemma and down the T tubules
2. calcium ions are released
3. calcium binds to troponin and removes the blocking action of tropomyosin
4. contraction begins
Definition
what are the steps in excitation-contraction coupling?
Term
Ca2+
Definition
cross bridge formation, (attachment of myosin heads to actin) requires __
Term
low
Definition
when intracellular calcium levels are __, the muscle cell is relaxed, and the active (myosin-blocking) sites on actin are physically blocked by tropomyosin molecules so myosin heads cannot attach to actin
Term
troponin
Definition
as intracellular levels of Ca2+ rise, the ions bind to regulatory sites on __
Term
calcium ions
shape
tropomyosin
Definition
to activate its group of seven actins, a troponin must bind two __, change __, and then roll __ into the groove of the actin helix, away from the myosin-binding sites
Term
calcium
Definition
the tropomyosin "blockade" is removed when sufficient __ is present
Term
actin
Definition
once binding sites on __ are exposed, the events of the cross bridge cycle occur in rapid succession
Term
calcium signal
adequate ATP
Definition
sliding of thin filaments continues as long as the __ and __ are present
Term
high
Definition
at __ intracellular Ca2+ concentrations, Ca2+ binds to troponin, troponin changes shape and moves tropomyosin away from active sites, and events of the cross bridge cycle occur
Term
sarcoplasmic reticulum
shape
contraction
Definition
when nervous stimulation ceases, Ca2+ is pumped back into the __, troponin again changes __, actin's myosin-binding sites are again covered by tropomyosin, and the __ ends and the muscle fibers relax
Term
thin filament
Definition
when the cross bridge cycle is back where it started, the myosin head is in its upright high-energy configuration, ready to take another "step" and attach to an actin site farther along the __
Term
myosin heads
Definition
thin filaments cannot slide backward as the cross bridge cycle repeats again and again because some __ are always in contact with actin
Term
many times
Definition
contracting muscles shorten by 30-35% of their total resting length, so each myosin cross bridge attaches and detaches __ during a single contraction
Term
undetectably low
Definition
except for the brief period following muscle cell excitation, calcium ion concentrations in the cytosol are kept almost __
Term
because ATP is the cell's energy souce, and its hydrolysis yields inorganic phosphate. this inorganic phosphate would combine with calcium ions to form hydroxyapatite crystals, the stony-hard salts found in bone matrix, is calcium ion concentrations were always high. such calcified muscle cells would die
Definition
why are calcium ion concentration kep low except for the brief period following muscle cell excitation?
Term
cross bridge formation
Definition
__ - high-energy myosin head attaches to thin filament
Term
working (power) stroke
Definition
__ - myosin head pivots and pulls thin filament toward M line
Term
cross bridge detachment
Definition
__ - ATP attaches to myosin head and the cross bridge detaches
Term
“Cocking” of the myosin head
Definition
__ - energy from hydrolysis of ATP cocks the myosin head into the high-energy state
Term
the same
Definition
the principles governing contraction of a single muscle fiber and of a skeletal muscle consisting of a large number of fibers are __
Term
Same principles apply to contraction of a single fiber and a whole muscle
Definition
__ principles apply to contraction of a single fiber and a whole muscle
Term
muscle tension
Definition
the force exerted by a contracting muscle on an object is called __
Term
load
Definition
the opposing force exerted on the muscle by the weight of the object to be moved is called the __
Term
tension
Definition
Contraction produces __, the force exerted on the load or object to be moved
Term
shorten
move
Definition
a contracting muscle does not always __ and __ the load
Term
isometric
Definition
if muscle tension develops but the load is not moved, the contraction is called __
Term
isotonic
Definition
if the muscle tension developed overcomes the load and muscle shortening occurs, the contraction is __
Term
increasing muscle tension
Definition
__ is measured for isometric contractions
Term
amount of muscle shortening (distance in millimeters)
Definition
__ is measured for isotonic contractions
Term
Isometric contraction
Definition
__: no shortening; muscle tension increases but does not exceed the load
Term
Isotonic contraction
Definition
__: muscle shortens because muscle tension exceeds the load
Term
force
time
Definition
a skeletal muscle contracts with varying __ and for different periods of __ in response to stimuli of varying frequencies and intensities.
Term
frequencies
intensities
Definition
Force and duration of contraction vary in response to stimuli of different __ and __
Term
motor nerve
Definition
each muscle is served by at least one __ and each of these contains axons (fibrous extensions) of up to hundreds of motor neurons
Term
motor unit
Definition
a __ consists of a motor neuron and all (four to several hundred) the muscle fibers it supplies
Term
contract
Definition
when a motor neuron fires (transmits an action potential), all the muscle fibers it innervates __
Term
small
Definition
muscles that exert fine control (such as those controlling the fingers and eyes) have __ motor units
Term
large
Definition
large, weight-bearing muscles, whose movements are less precise (such as hip muscles), have __ motor units
Term
clustered together
spread
Definition
the muscle fibers in a single motor unit are not __ but are __ throughout the muscle
Term
entire
Definition
stimulation of a single motor unit causes a weak contraction of the __ muscle
Term
asynchronously
Definition
motor units in a muscle usually contract __ which helps to prevent fatigue
Term
myogram
tracing
Definition
in investigating muscle contraction in the lab the muscle is attached to an apparatus that produces a __, a graphic recording of contractile activity. the line recording the activity is called a __
Term
muscle twitch
Definition
the response of a motor unit to a single action potential of its motor neuron is called a __. the muscle fibers contract quickly and then relax
Term
1. latent period
2. period of contraction
3. period of relaxation
Definition
every twitch myogram has three distinct phases, what are they?
Term
latent period
(first phase in twitch myogram)
Definition
the __ is the first few milliseconds following stimulation when excitation-contraction coupling is ocurring. during this period, muscle tension is beginning to increase but no response is seen on the myogram
Term
period of contraction
(2nd phase of twitch myogram)
Definition
the __ is when cross bridges are active, from the onset to the peak of tension development, and the myogram tracing rises to a peak. this period lasts 10-100ms. if the tension (pull) become great enough to overcome the resistance of a load, the muscle shortens.
Term
period of relaxation
(3rd phase of twitch myogram)
Definition
the period of contraction is followed by the __. this final phase, lasting 10-100ms, is initiated by reentry of Ca2+ into the sarcoplasmic reticulum. because contractile force is declining, muscle tension decreases to zero and the tracing returns to the baseline. if the muscle shortened during contraction, it now returns to its initial length.
Term
faster
Definition
a muscle contracts __ than it relaxes
Term
metabolic properties
enzymes
Definition
Different strength and duration of twitches are due to variations in __ and __ between muscles
Term
smooth
Definition
healthy muscle contractions are relatively __ and vary in strength as different demands are placed on them
Term
skeletal movement
graded muscle responses
Definition
the strength variations of muscle contractions are needed for proper control of __ and are referred to as __
Term
1. by changing the frequency of stimulation
2. by changing the strength of stimulation
Definition
in general, muscle contraction can be graded in what two ways?
Term
increasing
Definition
the nervous system achieves greater muscular force by __ the firing rate of motor neurons
Term
muscle twitch
Definition
a single stimulus results in a single contractile response - a __
Term
temporal
wave stimulation
Definition
if two identical stimuli (electrical shocks or nerve impulses) are delivered to a muscle in rapid succession, the second twitch will be stronger than the first. on a myogram the second twitch will appear to ride on the shoulders of the first. this phenomenon, called __ or __, occurs because the second contraction occurs before the muscle has completely relaxed
Term
unfused
incomplete tetanus
Definition
if the stimulus strength is held constant and the muscle is stimulated at an increasingly faster rate, the relaxation time between the twitches becomes shorter and shorter, the concentration of Ca2+ in the cytosol higher and higher, and the degree of wave summation greater and greater, progressing to a sustained but quivering contraction reffered to as __ or __
Term
fused
complete tetanus
Definition
if stimulation continually increases, muscle tension increases until a maximal tension is reached. at this point all evidence of muscle relaxation disappears and the contractions fuse into a smooth, sustained contraction plateau called __ or __
Term
fused
Definition
in the real world, __ tetanus happens infrequently
Term
muscle fatigue
Definition
prolonged tetanus inevitably leads to __, a situation in which the muscle is unable to contract and its tension drops to zero
Term
recruitment
multiple motor unit summation
Definition
the force of contraction is controlled more precisely by __, also called __, which brings more and more muscle fibers into action
Term
subthreshold stimuli
Definition
stimuli that produce no observable contractions are called __
Term
threshold stimulus
Definition
the stimulus at which the first observable contraction occurs is called the __
Term
maximal stimulus
Definition
the __ is the strongest stimulus that produces increased contractile force. it represents the point at which all the muscle's motor units are recruited
Term
size principle
Definition
the recruitment process is not random. instead it is dictated by the __. in any muscle, motor units with the smallest muscle fibers are controlled by small, highly excitable motor neurons, and these motor units tend to be activated first. as motor units with larger and larger muscle fibers begin to be excited, contractile strength increases
Term
asynchronously
Definition
although all the motor units of a muscle may be recruited simultaneously to produce an exceptionally strong contraction, motor units are more commonly activated __ in the body
Term
muscle tone
Definition
skeletal muscles are described as voluntary, but even relaxed muscles are almost always slightly contracted, a phenomenon called __
Term
muscle tone
Definition
__ is due to spinal reflexes that activate first one group of motor units and then another in response to activation of stretch receptors in the muscles
Term
active
Definition
muscle tone does not produce __ movements
Term
firm
healthy
ready to respond
Definition
muscle tone keeps the muscles __, __, and __ to stimulation
Term
joints
posture
Definition
skeletal muscle tone also helps stabilize __ and maintain __
Term
isotonic contractions
Definition
In __, muscle length changes and moves the load
Term
concentric and eccentric
Definition
what are the two types of isotonic contractions?
Term
concentric contractions
Definition
__ are an isotonic contractions in which the muscle shortens and does work
Term
eccentric contractions
Definition
__ are isotonic contractions in which the muscle generates force as it lengthens
Term
50%
Definition
eccentric contractions are about __ more forceful than concentric ones at the same load and more often cause delayed-onset muscle soreness
Term
concentrically
Definition
eccentric contractions put the body in position to contract __
Term
jumping
throwing
Definition
all __ and __ activities involve both concentric contractions and eccentric contractions
Term
isometric
Definition
in __ contractions, tension may build to the muscle's peak tension-producing capacity, but the muscle neither shortens nor lengthens
Term
isometric
Definition
__ contractions occur when a muscle attempts to move a load that is greater than the force (tension) the muscle is able to develop
Term
posture
joints
Definition
muscles contract isometrically when they act primarily to maintain upright __ or to hold __ in stationary positions while movements occur at other joints
Term
identical
Definition
electrochemical and mechanical events occurring within a muscle are __ in both isotonic and isometric contractions
Term
isotonic
Definition
in __ contractions, the thin filaments are sliding
Term
isometric
Definition
in __ contractions, the cross bridges are generating force but are not moving the thin filaments, so there is no change in the banding pattern from that of the resting state
Term
concentric isotonic
Definition
__ contraction = on stimulation, muscle develops enough tension (force) to lift the load (weight). once the resistance is overcome, the muscle shortens, and the tension remains constant for the rest of the contraction
Term
isometric
Definition
__ contraction = muscle is attached to a weight that exceeds the muscle's peak tension-developing capabilities. when stimulated, the tension increases to the muscle's peak tension-developing capability, but the muscle does not shorten
Term
ATP
Definition
__ is the only source used directly for contractile activities
Term
as a muscle contracts, ATP supplies the energy for cross bridge movement and detachment and for operation of the calcium pump in the sarcoplasmic reticulum
Definition
how does the body provide the energy needed for contraction?
Term
4-6 seconds
Definition
muscles store very limited reserves of ATP. they store __ worth at most, just enough to get you going
Term
regenerated
Definition
because ATP is the only energy source used directly for contractile activities, it must be __ as fast as it is broken down is contraction is to continue
Term
1. direct phosphorylation of ADP by creatine phosphate (CP)
2. the anaerobic pathway called glycolysis, which converts glucose to lactic acid
3. aerobic respiration
Definition
after ATP is hydrolyzed to ADP and inorganic phosphate in muscle fibers, it is regenerated within a fraction of a second by one or more of the three pathways for regenerating ATP during muscle activity. what are the three pathways?
Term
glycolysis
aerobic respiration
Definition
all body cells use __ and __ to produce ATP
Term
creatine phosphate (CP)
Definition
__ - a unique high-energy molecule stored in muscles that is used to regenerate ATP while the metabolic pathways are adjusting to a sudden higher demand for ATP
Term
ATP
Definition
the result of coupling creatine phosphate (CP) with ADP is almost instant transfer of energy and a phosphate group from CP to ADP to form __
Term
creatine + ATP
Definition
creatine phosphate (CP) + ADP yields __ with the help of the enzyme creatine kinase
Term
two
three
Definition
muscle cells store __ to __ times as much CP as ATP
Term
creatine kinase
Definition
the CP-ADP reaction, catalyzed by the enzyme __, is so efficient that the amount of ATP in muscle cells changes very little during the initial period of contraction
Term
14-16
Definition
together, stored ATP and CP provide maximum muscle power for __ seconds - long enough to energize a 100-meter dash (slightly longer is the activity is less vigorous)
Term
reversible
Definition
the reaction of CP + ADP --> creatine + ATP is __
Term
rest
inactivity
Definition
to keep CP readily available, CP reserves are replenished during periods of __ or __
Term
direct phosphorylation
aerobic respiration
Definition
the fastest pathway for regenerating ATP during muscle activity is __ and the slowest pathway is __
Term
direct phosphorylation for regenerating ATP during muscle activity
Definition
__ = coupled reaction of creatine phosphate (CP) and ADP
Term
creatine phosphate (CP)
Definition
what is the energy source in direct phosphorylation for regenerating ATP during muscle activity?
Term
none
Definition
how much oxygen is used in direct phosphorylation for regenerating ATP during muscle activity?
Term
1 ATP per creatine phosphate (CP), and creatine
Definition
what is the product of direct phosphorylation for regenerating ATP during muscle activity?
Term
15 seconds
Definition
what is the duration of energy provision for direct phosphorylation for regenerating ATP during muscle activity?
Term
glucose
Definition
as stored ATP and CP are exhausted, more ATP is generated by breakdown (catabolism) of __ obtained from the blood or of glycogen stored in the muscle
Term
glycolysis
Definition
the initial phase of glucose breakdown is __ ("sugar splitting")
Term
oxygen
Definition
the anaerobic pathway: glycolysis and lactic acid formation, occurs in both the presence and the absence of __
Term
anaerobic
Definition
the glycolysis and lactic acid pathway for regenerating ATP during muscle activity is an __ pathway
Term
pyruvic acid
Definition
during glycolysis, glucose is broken down to two __ molecules, releasing enough energy to form small amounts of ATP
Term
lactic acid
Definition
in anaerobic conditions, most of the pyruvic acid produced during glycolysis is converted into __
Term
anaerobic glycolysis
Definition
__ = energy-yielding conversion of glucose to lactic acid in various tissues, notably muscle, when sufficient oxygen is not available
Term
bloodstream
Definition
most of the lactic acid formed during anaerobic glycolysis diffuses out of the muscles into the __ and is gone from the muscle tissue within 30 minutes after exercise stops
Term
liver
heart
kidney
Definition
when lactic acid is in the bloodstream, the lactic acid is picked up by the __, __, or __ cells which can use it as an energy source
Term
pyruvic acid
glucose
glycogen
Definition
liver cells can reconvert lactic acid to __ or __ and release it back into the bloodstream for muscle use, or convert it to __ for storage
Term
5%
2&1/2
Definition
the anaerobic pathway harvests only about __ as much ATP from each glucose molecule as the aerobic pathway, but it produces ATP about __ times faster
Term
glycolysis
Definition
when large amounts of ATP are needed for moderate periods (30-40 seconds) of strenuous muscle activity, __ can provide most of the ATP needed as long as the required fuels and enzymes are available
Term
minute
Definition
together, stored ATP and CP and the glycolysis-lactic acid pathway can support strenuous muscle activity for nearly a __
Term
70%
Definition
when muscles contract vigorously and contractile activity reaches about __ of the maximum possible, the bulging muscles compress the blood vessels within them, impairing blood flow and oxygen delivery
Term
anaerobic pathway for regenerating ATP during muscle activity
Definition
__ = glycolysis and lactic acid formation
Term
glucose
Definition
what is the energy source for the anaerobic pathway for regenerating ATP during muscle activity?
Term
none
Definition
how much oxygen is used in the anaerobic pathway for regenerating ATP during muscle activity?
Term
2 ATP per glucose ; lactic acid
Definition
what are the products of the anaerobic pathway for regenerating ATP during muscle activity?
Term
60 seconds, or slightly more
Definition
what is the duration of energy provision for the anaerobic pathway for regenerating ATP during muscle activity?
Term
95%
Definition
during rest and light to moderate exercise, even if prolonged, __ of the ATP used for muscle activity comes from aerobic respiration
Term
aerobic respiration
Definition
__ occurs in the mitochondria, requires oxygen, and involves a sequence of chemical reactions in which the bonds of fuel molecules are broken and the energy released is used to make ATP
Term
ATP
Definition
during aerobic respiration, the pyruvic acid produced during glycolysis enters the mitochondria and reacts with oxygen to produce more __
Term
water
carbon dioxide
ATP
Definition
during aerobic respiration, which includes glycolysis and the reactions that take place in the mitochondria, glucose is broken down entirely, yielding __, __, and large amounts of __ as the final products
Term
direct phosphorylation of ADP by Creatine Phosphate
Definition
creatine phosphate + ADP --> creatine + ATP
Term
aerobic respiration
Definition
Glucose + oxygen --> carbon dioxide + water + ATP
Term
lungs
Definition
the carbon dioxide released during aerobic respiration diffuses out of the muscle tissue into the blood and is removed from the body by the __
Term
glycogen
(aerobic respiration)
Definition
as exercise begins, muscle __ provides most of the fuel
Term
glucose
pyruvic acid
free fatty acids
Definition
shortly after exercise begins, bloodborne __, __ from glycolysis, and __ are the major sources of fuels
Term
32
slow
Definition
aerobic respiration provides a high yield of ATP about __ ATP per glucose, but it is __ because of its many steps and it requires continuous delivery of oxygen and nutrient fuels to keep it going
Term
aerobic pathway for regenerating ATP during muscle activity
Definition
__ = aerobic cellular respiration
Term
glucose; pyruvic acid; free fatty acids from adipose tissue; amino acids from protein catabolism
Definition
what is the energy source for the aerobic pathway for regenerating ATP during muscle activity?
Term
required
Definition
what is the oxygen use in the aerobic pathway for regenerating ATP during muscle activity?
Term
32 ATP per glucose; CO2; H2O
Definition
what are the products of the aerobic pathway for regenerating ATP during muscle activity?
Term
hours
Definition
what is the duration of energy provision for the aerobic pathway for regenerating ATP during muscle activity?
Term
-ATP stored in muscles is used first
-ATP is formed from creatine phosphate and ADP
-Glycogen stored in muscles is broken down to glucose, which is oxidized to generate ATP
Definition
short duration exercise: 6 seconds = __; 10 seconds = __; 30-40 seconds & end of exercise = __
Term
ATP is generated by breakdown of several nutrient energy fuels by aerobic pathway. this pathway uses oxygen released from myoglobin or delivered in the blood by hemoglobin. when it ends, the oxygen deficit is paid back
Definition
prolonged-duration exercise: hours = __
Term
as long as it has enough oxygen, a muscle cell will form ATP by the aerobic pathway
Definition
which pathways predominate during exercise?
Term
hours
Definition
when ATP demands are within the capacity of the aerobic pathway, light to moderate muscular activity can continue for several __ in well-conditioned individuals
Term
glycolysis
Definition
when exercise demands begin to exceed the ability of the muscle cells to carry out the necessary reactions quickly enough, __ begins to contribute more and more of the total ATP generated
Term
aerobic endurance
Definition
the length of time a muscle can continue to contract using aerobic pathways is called __
Term
anaerobic threshold
Definition
the point at which muscle metabolism converts to anaerobic glycolysis is called __
Term
ATP and CP stores
Definition
activities that require a surge of power but last only a few seconds, such as weight lifting, diving, and sprinting, rely entirely on __
Term
anaerobic glycolysis
Definition
the more on-and-off or burst-like activities of tennis, soccer, and a 100-meter swim appear to be fueled almost entirely by __
Term
aerobic respiration
Definition
prolonged activities such as marathon runs and jogging, where endurance rather than power is the goal, depend mainly on __
Term
CP
ATP
Definition
levels of __ and __ don't change much during prolonged exercise because ATP is generated at the same rate as it is used
Term
muscle fatigue
Definition
__ is a state of physiological inability to contract even though the muscle still may be receiving stimuli
Term
excitation-contraction coupling
neuromuscular junction
Definition
most experimental evidence indicates that fatigue is due to a problem in __ or, in rare cases, problems at the __
Term
fatigue-producing
Definition
availability of ATP declines during contraction, but normally it is unusual for a muscle to totally run out of ATP. so ATP, is not a __ factor in moderate exercise
Term
contractures
Definition
a total lack of ATP results in __, states of continuous contraction because the cross bridges are unable to detach (not unlike what happens in rigor mortis)
Term
muscle fatigue
Definition
as action potentials are transmitted, potassium is lost from the muscle cells, and the Na+-K+ pumps are inadequate to reverse the ionic imbalances quickly, so K+ accumulates in the fluids of the T tubules. this ionic change disturbs the membrane potential of the muscle cells and halts Ca2+ release from the sarcoplasmic reticulum. this in means that the muscles cannot contract, so it causes __
Term
muscle fatigue
Definition
in short duration exercise, an accumulation of inorganic phosphate from CP and ATP breakdown may interfere with calcium release from the sarcoplasmic reticulum or alternatively with the release of inorganic phosphate from myosin and thus hamper myosin's power strokes. both cause __, the physiological inability to contract
Term
lactic acid
Definition
__ seems to be more important in provoking psychological fatigue rather than physiological fatigue. it has also recently been shown to counteract high K+ levels, which do lead to muscle fatigue.
Term
excitation-contraction (E-C) coupling
Definition
intense exercise of short duration produces muscle fatigue rapidly via ionic imbalances (K+, Ca2+, inorganic phosphate) that interfere with __, but recovery is also rapid
Term
hours
Definition
the slow developing fatigue of prolonged low intensity exercise may require several __ for complete recovery
Term
prolonged low intensity
Definition
__ exercise damages the sarcoplasmic reticulum, interfering with Ca2+ regulation and release, and therefore with muscle activation. which causes muscle fatigue
Term
-oxygen reserves must be replenished
-the accumulated lactic acid must be reconverted to pyruvic acid
-glycogen stores must be replaced
-ATP and creatine phosphate reserves must be resynthesized
-the liver must convert any lactic acid persisting in blood to glucose of glycogen
Definition
what has to happen for a muscle to return to its resting state?
Term
oxygen deficit
Definition
__ = the extra amount of oxygen that the body must take in for the replenishment of oxygen reserves, glycogen stores, ATP and CP reserves, and conversion of lactic acid to pyruvic acid in the muscle
Term
actually used
Definition
the oxygen deficit represents the difference between the amount of oxygen needed for totally aerobic muscle activity and the amount __. all anaerobic sources of ATP used during muscle activity contribute to this deficit as well.
Term
40%
Definition
only about __ of the energy released during muscle contraction is converted to useful work.
Term
heat (60%)
Definition
the energy released during muscle contraction that isn't converted to useful work is given off as __, which has to be dealt with if body homeostasis is to be maintained
Term
sweating
radiation of heat from the skin surface
Definition
heat buildup in the body is prevented from reaching dangerous levels by several homeostatic processes, including __ and __
Term
shivering
Definition
__ represents the opposite side of homeostatic balance, in which muscle contractions are used to produce more heat
Term
1. the number of muscle fibers stimulated (recruitment)
2. the relative size of the fibers
3. the frequency of stimulation
4. the degree of muscle stretch
Definition
the force of muscle contraction is affected by what?
Term
muscle force
(number of muscle fibers stimulated affects the force of muscle contraction)
Definition
the more motor units that are recruited, the greater the __
Term
strength
(size of muscle fibers affects the force of muscle contraction)
Definition
the bulkier the muscle (the greater its cross-sectional area), the more tension it can develop and the greater its __
Term
hypertrophy
(size of muscle fibers affects the force of muscle contraction)
Definition
regular resistance exercise increases muscle force by causing muscle cells to __, or increase in size
Term
internal tension
Definition
as a muscle begins to contract, the force generated by the cross bridges - the __ - stretches the connective tissue sheaths (noncontractile components)
Term
external tension
Definition
as a muscle contracts the connective tissue sheaths (noncontractile components) become taut and transfer their tension, called the __, to the load (muscle insertion)
Term
noncontractile components
Definition
when the contraction ends, the recoiling of the __ helps to return the muscle to its resting length
Term
declining
Definition
time is required to take up slack and stretch the noncontractile components, and while this is happening, the internal tension is already __
Term
less
Definition
in brief twitch contractions, the external tension is always __ than the internal tension
Term
tetanus
Definition
when a muscle is stimulated rapidly, contractions are summed, becoming stronger and more vigorous and ultimately producing __
Term
force
Definition
during tetanic contractions more time is available to stretch the noncontractile components, and external tension approaches the internal tension. so the more rapidly a muscle is stimulated, the greater the __ it exerts
Term
noncontractile components
Definition
higher frequency of stimulation allows time for more effective transfer of tension to __
Term
force
Definition
the optimal operating length for muscle fibers is the length at which they can generate maximum __
Term
length-tension relationship
Definition
within a sarcomere, the ideal __ occurs when a muscle is slightly stretched and the thin and thick filaments overlap optimally, because this relationship permits sliding along nearly the entire length of the thin filaments
Term
tension
Definition
if a muscle fiber is stretched so much that the thin and thick filaments do not overlap, the myosin heads have nothing to attach to and cannot generate __
Term
shortening
Definition
if the sarcomeres are so compressed and cramped that the Z discs abut the thick myofilaments, and the thin filaments touch and interfere with one another, little or no further __ can occur
Term
length
Definition
if you stretch a muscle to various extents and then stimulate it tetanically, the active tension the muscle can generate varies with __
Term
tension
Definition
a severely stretch muscle (say one over 180% of its optimal length) cannot develop __
Term
force generation (or shortening)
Definition
at 75% of a muscle's resting length, __ is limited because the actin myofilaments in its sarcomeres overlap and the thick filaments run into the Z discs, restricting further shortening
Term
80-120%
Definition
length-tension relationships of sarcomeres in skeletal muscles: maximum force is generated when the muscle is between __ of its optimal resting length. increases and decreases beyond this optimal range result in decreased force and inability to generate tension
Term
bones
joints
Definition
in the body, skeletal muscles are maintained near their optimal operating length by the way they are attached to __. the __ normally prevent the bone movements that would stretch attached muscles beyond their optimal range
Term
fast
long
Definition
muscles vary in how __ they can contract and in how __ they can continue to contract before they fatigue
Term
muscle fiber type
load
recruitment
Definition
how fast a muscle can contract and how long a muscle can continue to contract is influenced by __, __, and __
Term
slow fibers
fast fibers
Definition
on the basis of speed of shortening, or contraction, there are __ and __
Term
myosin ATPases split ATP
electrical
Definition
the difference in the speed of shortening, or contraction, which determines if it is slow fiber or fast fiber, reflects how fast their __, and on the pattern of __ activity of their motor neurons
Term
cytosol
sarcoplasmic reticulum (SR)
Definition
duration of contraction also varies with fiber type and depends on how quickly Ca2+ is moved from the __ into the __
Term
oxidative fibers
glycolytic fibers
Definition
the cells that rely mostly on they oxygen-using areobic pathways for ATP generation are __, and those that rely more on anaerobic glycolysis are __
Term
slow oxidative (SO) fibers
fast oxidative (FO) fibers
fast glycolytic (FG) fibers
Definition
what are the three types of skeletal muscle cells/fibers?
Term
1. speed of contraction
2. metabolic pathways for ATP synthesis (the major pathways for forming ATP)
Definition
muscle fiber type is classified according to what two characteristics?
Term
slow
(because its myosin ATPases are slow)
Definition
slow oxidative fibers have a __ speed of contraction
Term
slow
Definition
slow oxidative fibers have __ myosin ATPase activity
Term
aerobic
(because it depends on oxygen delivery)
Definition
slow oxidative fibers primary pathway for ATP synthesis is __
Term
high
(because it uses an aerobic pathway and needs a lot of oxygen and myoglobin stores O2 and aids diffusion of O2 through the cell)
Definition
slow oxidative fibers myoglobin content is __
Term
low
(because it doesn't use glycolysis for its ATP pathway)
Definition
slow oxidative fibers glycogen stores is __
Term
slow (fatigue-resistant)
(because fatigue resistance is typical of fibers that depend on aerobic metabolism)
Definition
slow oxidative fibers rate of fatigue is __
Term
endurance-type activites (ex: running a marathon)
(because a thin cell can contain only a limited number of myofibrils, it has little power and so it is best suited for low power activities(one that don't use a lot of force))
Definition
activites best suited for slow oxidative fibers is __
Term
red
(because of the abundance of myoglobin, muscle's oxygen-binding pigment that stores O2 reserves in the cell and aids diffusion of O2 through the cell)
Definition
a slow oxidative fibers color is __
Term
small
(this makes it thin, which makes sense because a large amount of cytoplasm impedes diffusion of O2 and nutrients from the blood and since this fiber is uses an aerobic pathway is needs to be thin for a high diffusion of O2)
Definition
a slow oxidative fibers diameter is __
Term
many
(because mitochondria are the actual sites of oxygen use and because it uses an aerobic pathway)
Definition
a slow oxidative fiber has __ mitochondria
Term
many
(because it uses an aerobic pathway, it needs a high oxygen supply and a high capillary supply is higher to deliver bloodborne O2)
Definition
a slow oxidative fiber has __ capillaries
Term
fast
(because of fast myosin ATPases)
Definition
fast glycolytic fibers have a __ speed of contraction
Term
fast
Definition
fast glycolytic fibers have a __ myosin ATPase activity
Term
anaerobic glycolysis
(because it does not use oxygen)
Definition
fast glycolytic fibers primary pathway for ATP synthesis is __
Term
low
(because it does not depend on oxygen for ATP so it doesn't need as much myoglobin)
Definition
fast glycolytic fibers myoglobin content is __
Term
high
(because it uses glycogen for fuel rather than on blood-delivered nutrients)
Definition
fast glycolytic fibers glycogen stores is __
Term
fast (fatigable)
(because glycogen reserves are short-lived and lactic acid accumulates quickly, making it a fatigable fiber)
Definition
fast glycolytic fibers rate of fatigue is __
Term
short-term intense or powerful movements (ex: hitting a baseball)
(because it uses an anaerobic pathway is energy doesn't last for a very long time)
Definition
activities best suited for fast glycolytic fibers is __
Term
white (pale)
(because it has few mitochondria, little myoglobin, and low capillary density)
Definition
a fast glycolytic fibers color is __
Term
large
(because it has a large diameter, it has plentiful contractile myofilaments that allow it to contract powerfully before it "poops out"
Definition
a fast glycolytic fibers diameter is __
Term
few
(because it doesn't need oxygen)
Definition
a fast glycolytic fiber has __ mitochondria
Term
few
(because it doesn't need oxygen)
Definition
a fast glycolytic fiber has __ capillaries
Term
fast
(because its myosin ATPases are fast)
Definition
fast oxidative fibers have a __ speed of contraction
Term
fast
Definition
fast oxidative fibers have __ myosin ATPase activity
Term
aerobic (some anaerobic glycolysis)
Definition
fast oxidative fibers primary pathway for ATP synthesis is __
Term
high
Definition
fast oxidative fibers myoglobin content is __
Term
intermediate
Definition
fast oxidative fibers glycogen stores is __
Term
intermediate (moderately fatigue-resistant)
Definition
fast oxidative fibers rate of fatigue is __
Term
red to pink
Definition
a fast oxidative fibers color is __
Term
intermediate
Definition
a fast oxidative fibers diameter is __
Term
many
Definition
a fast oxidative fiber has __ mitochondria
Term
many
Definition
a fast oxidative fiber has __ capillaries
Term
contractile speeds
fatigue resistance
Definition
some muscles have a predominance of one fiber type, but most contain a mixture of fiber types, which gives them a range of __ and __
Term
the same type
Definition
all muscle fibers in a particular motor unit are of __
Term
resistance or load
Definition
because muscles are attached to bones, they are always pitted against some __ when they contract
Term
longer
slower
shorter
Definition
a greater load results in a __ latent period, a __ contraction, and a __ duration of contraction
Term
zero
isometric
Definition
if the load exceeds the muscle's maximum tension, the speed of shortening is __ and the concentration is __
Term
faster
prolonged
Definition
the more motor units that are contracting, the __ and more __ the contraction
Term
size
strength
Definition
when used actively or strenuously, muscles may increase in __ or __ or become more efficient and fatigue resistant
Term
weakness
wasting
Definition
muscle inactivity always leads to muscle __ and __
Term
aerobic or endurance exercise
Definition
__ results in several recognizable changes in skeletal muscles. there is an increase in the number of capillaries surrounding the muscle fibers, and in the number of mitochondria within them, and the fibers synthesize more myoglobin
Term
slow oxidative fibers
Definition
aerobic (endurance) exercise leading to increased muscle cappilaries, number of mitochondria, and myoglobin synthesis occurs in all fiber types, but are most dramatic in __, which depend primarily on aerobic pathways
Term
endurance
strength
fatigue resistance
Definition
aerobic (endurance) exercise leading to increased muscle cappilaries, number of mitochondria, and myoglobin synthesis also results in more efficient muscle metabolism and in greater __, __, and __
Term
fast oxidative fibers
Definition
regular endurance exercise may convert fast glycolytic fibers into __
Term
hypertrophy
Definition
the moderately weak but sustained muscle activity require for endurance exercise does not promote significant skeletal muscle __, even though the exercise may go on for hours
Term
resistance exercise (typically under anaerobic conditions)
Definition
muscle hypertrophy results mainly from high-intensity __ such as weight lifting or isometric exercise, in which the muscles are pitted against high-resistance or immovable forces
Term
individual
Definition
the increased muscle bulk largely reflects increases in the size of __ muscle fibers (particularly the fast glycolytic variety) rather than an increased number of muscle fibers
Term
mitochondria
myofilaments
glycogen stores
connective tissue
Definition
resistance exercise (typically anaerobic) results in increased __, __, __, and __ in the muscle fiber
Term
fast glycolytic
Definition
fast oxidative fibers can be shifted to __ fibers in response to resistance exercise
Term
muscle-bound
Definition
when muscle training is not balanced, individuals can become __, which means they lack flexibility, have a generally awkward stance, and are unable to make full use of their muscles
Term
overload principle
Definition
__ - forcing a muscle to work hard promotes increased muscle strength and endurance, and as muscles adapt to the increased demands, they must be overloaded even more to produce further gains
Term
overuse injuries
Definition
doing too much too soon, or ignoring the warning signs of muscle or joint pain, increases the risk of __ that may prevent future sports activity, or even lead to lifetime disability
Term
disuse atrophy (degeneration and loss of mass)
Definition
complete immobilization due to enforced bed rest or loss of neural stimulation results in __, which begins almost as soon as the muscles are immobilized
Term
smooth
Definition
except for the heart, the muscle in the walls of all the body's hollow organs is almost entirely __ muscle
Term
spindle
one
Definition
smooth muscle fibers are __ shaped cells of variable size, with __ centrally located nucleus
Term
connective tissue sheaths
Definition
smooth muscle lacks the coarse __ seen in skeletal muscle
Term
between
Definition
a small amount of fine connective tissue (endomysium), secreted by the smooth muscles themselves and containing blood vessels and nerves is found __ smooth muscle fibers
Term
longitudinal layer
circular layer
Definition
two sheets of smooth muscle are present, what are they?
Term
longitudinal
Definition
in the __ layer of smooth muscle, the muscle fibers run parallel to the long axis of the organ. when the muscle contracts, the organ dilates and shortens
Term
circular
Definition
in the __ layer of smooth muscle, the fibers run around the circumference of the organ. contraction of this layer constricts the lumen (cavity) of the organ and causes the organ to elongate
Term
peristalsis
Definition
alternating contraction and relaxation of the longitudinal layer and circular layer of smooth muscle mixes substances in the lumen and squeezes them through the organ's internal pathway. this propulsive action is called __
Term
varicosities
Definition
in smooth muscle, the innervating nerve fibers, which are part of the autonomic (involuntary) nervous system, have numerous bulbous swellings called __.
Term
diffuse junctions
Definition
the varicosities release neurotransmitter into a wide synaptic cleft in the general area of the smooth muscle cells. such junctions are called __
Term
sarcoplasmic reticulum
Definition
the __ of smooth muscle fibers is much less developed than that of skeletal muscle and lacks a specific pattern relative to the myofilaments
Term
caveolae
Definition
the sarcolemma of the smooth muscle fiber has multiple __, pouchlike infoldings that squester bits of extracellular fluid containing a high concentration of Ca2+ close to the membrane
Term
sarcomeres
myofibrils
T tubules
Definition
a smooth muscle fiber has no __, __, or __
Term
extracellular space
Definition
in contrast to the skeletal muscle fiber which does not depend on extracellular Ca2+ for excitation-contraction coupling, a smooth muscle fiber gets its calcium that triggers contraction through calcium channels directly from the __
Term
fewer
Definition
in smooth muscle fibers, thick filaments are __ but have myosin heads along their entire length
Term
lower
Definition
the ratio of thick to thin filaments in smooth muscle (1:13) is much __ than in skeletal muscle (1:2)
Term
troponin
Definition
in smooth muscle fibers there is no _ complex in thin filaments. instead a protein called calmodulin acts as the calcium-binding site
Term
diagonally
Definition
in smooth muscle fibers thick and thin filaments are arranged __
Term
spirally
Definition
myofilaments in smooth muscle are __ arranged, causing smooth muscle to contract in a corkscrew manner
Term
intermediate filaments
Definition
smooth muscle fibers contain a lattice-like arrangement of noncontractile __ that resist tension
Term
dense bodies
Definition
smooth muscle fibers intermediate filaments attach at regular intervals to cytoplasmic structures called __, which are also tethered to the sarcolemma and act as anchoring points for thin filaments and therefore correspond to Z discs of skeletal muscle
Term
slow
synchronized
Definition
in most cases, adjacent smooth muscle fibers exhibit __, __ contrations, the whole sheet responding to stimulus in unison
Term
gap junctions
Definition
smooth muscle cells are electrically coupled by __, which allow smooth muscles to transmit action potentials from fiber to fiber
Term
pacemaker
Definition
some smooth muscle fibers in the stomach and small intestine are __ cells and, once excited, they act as "drummers" to set the contractile pace for the entire muscle sheet
Term
depolarize
Definition
pacemaker cells have fluctuating membrane potentials and are self-excitatory, that is, they _ spontaneously in the absence of external stimuli
Term
1. actin and myosin interact by the sliding filament mechanism
2. the final trigger for contraction is a rise in the intracellular calcium ion level
3. the sliding process is energized by ATP
Definition
contraction in smooth muscle is like that in skeletal muscle in what ways?
Term
neural
chemical
Definition
rate and intensity of contraction of smooth muscle may be modified by __ and __ stimuli
Term
sarcoplasmic reticulum
extracellular space
Definition
the final trigger for contraction of smooth muscle is a rise in intracellular Ca2+, the Ca2+ is obtained from the __ and __
Term
myosin kinase
myosin light chain kinase
Definition
by binding Ca2+ to calmodulin, the calmodulin in turn interacts with a kinase enzyme called __ or __ which phosphorylates the myosin, activating it and cross bridges interact with actin
Term
Ca2+
Definition
smooth muscle relaxes when intracellular __ levels drop
Term
slow
Definition
the contraction of smooth muscle is very energy efficient which means __ ATPases
Term
prolonged
Definition
in contraction of smooth muscle, myofilaments may maintain a latch state for __ contractions
Term
Ca2+
sarcoplasmic reticulum
extracellular fluid
dephosphorylation
Definition
relaxation of smooth muscle requires __ detachments from calmodulin, active transport of Ca2+ into __ and __, and __ of myosin to reduce myosin ATPase activity
Term
nerves
hormones
local chemical changes
Definition
the contraction of smooth muscle can be regulated by __, __, or __
Term
graded (local electrical signals)
Definition
in some cases the activation of smooth muscle by a neural stimulus is identical to that in skeletal muscle: an action potential is generated by neurotransmitter binding, and is coupled to a rise in calcium ions in the cytosol. however, some types of smooth muscle respond to neural stimulation with __ potentials only
Term
neurostransmitter
receptor
Definition
in neural regulation of smooth muscle contraction, response depends on the __ released and the type of __ molecules
Term
neural
chemical
Definition
not all smooth muscle activation results from neural signals. some smooth muscle layers have no nerve supply at all. instead, they depolarize spontaneously or in response to chemical stimuli that bind to G protein-linked receptors. others respond to both __ and __ stimuli
Term
enhancing
inhibiting
Definition
chemical factors that cause smooth muscle contraction or relaxation without an action potential are done by __ or __ Ca2+ entry into the sarcoplasm
Term
stress-relaxation response
Definition
stretching of smooth muscle also provokes contraction, which automatically moves substances along an internal tract. however, the increased tension persists only briefly, and soon the muscle adapts to its new length and relaxes, while still retaining the ability to contract on demand. this __ allows a hollow organ to fill or expand slowly to accommodate a greater volume without promoting strong contractions that would expel its contents
Term
stretches
tension
Definition
smooth muscle __ much more than skeletal muscle and generates more __ than skeletal muscles to a comparable extent.
Term
force
Definition
in smooth muscle, the lack of sarcomeres and the irregular, overlapping arrangement of smooth muscle filaments allow them to generate considerable __, even when they are substantially stretched
Term
twice
half
Definition
smooth muscle can contract when it is anywhere from __ to __ its resting length, which allows hollow organs to tolerate tremendous changes in volume without becoming flabby when they empty
Term
divide
increase
Definition
besides being able to hypertrophy (increase in cell size), which is common to all muscle cells, certain smooth muscle fibers can __ and __ their numbers
Term
1. fiber arrangement and organization
2. innervation
3. responsiveness to various stimuli
Definition
the smooth muscle in different body organs varies substantially how?
Term
single-unit
multiunit
Definition
smooth muscle is usually categorized into what two major types?
Term
single-unit smooth muscle
visceral muscle
Definition
__ commonly called __ because it is in the walls of all hollow organs except the heart, is far more common
Term
opposing (longitudinal and circular)
Definition
the cells of a single-unit smooth muscle are arranged in __ sheets
Term
ANS varicosities
Definition
the cells of a single-unit smooth muscle are innervated by __ and often exhibit rhythmic spontaneous action potentials
Term
gap junctions
Definition
the cells of a single-unit smooth muscle are electrically coupled by __ and so contract as a unit (for this reason recruitment is not an option in smooth muscle)
Term
chemical
Definition
the cells of a single-unit smooth muscle respond to various __ stimuli
Term
multiunit smooth muscle
Definition
the smooth muscles in large airways to the lungs and in large arteries, the arrector pilli muscles attached to hair follicles, and the internal eye muscles that adjust pupil size and allow the eye to focus are all examples of __
Term
gap junctions
Definition
in multiunit smooth muscle __ are rare, and spontaneous synchronous depolarizations are infrequent
Term
independent
Definition
multiunit smooth muscle consists of muscle fibers that are structurally __ of one another
Term
nerve endings
Definition
multiunit smooth muscle is richly supplied with __, each of which forms a motor unit with a number of muscle fibers
Term
neural
Definition
multiunit smooth muscle responds to __ stimulation with graded contractions that involve recruitment
Term
autonomic (involuntary)
Definition
multinit smooth muscle is innervated by the __ division of the nervous system and is also responsive to hormonal controls
Term
myoblasts
Definition
all three types of muscle tissue develop from embryonic mesoderm cells called __
Term
fusion
Definition
Multinucleated skeletal muscle cells form by __
Term
agrin
Definition
Growth factor __ stimulates clustering of ACh receptors at neuromuscular junctions
Term
gap junctions
Definition
Cardiac and smooth muscle myoblasts develop __
Term
lengthen and thicken
Definition
Cardiac and skeletal muscle become amitotic, but can __
Term
regenerative
Definition
Myoblast-like skeletal muscle satellite cells have limited __ ability
Term
connective tissue
Definition
Injured heart muscle is mostly replaced by __
Term
life
Definition
Smooth muscle regenerates throughout __
Term
neuromuscular
Definition
Muscular development reflects __ coordination
Term
head
toe
proximal
distal
Definition
Development occurs __ to __, and __ to __
Term
midadolescence
Definition
Peak natural neural control occurs by __
Term
Athletics
training
Definition
__ and __ can improve neuromuscular control
Term
36%
Definition
Female skeletal muscle makes up __ of body mass
Term
42%
Definition
Male skeletal muscle makes up __ of body mass, primarily due to testosterone
Term
same
Definition
Body strength per unit muscle mass is the __ in both sexes
Term
increases
decrease
Definition
With age, connective tissue __ and muscle fibers __
Term
30
Definition
By age __, loss of muscle mass (sarcopenia) begins
Term
sarcopenia
Definition
Regular exercise reverses __
Term
Atherosclerosis
Definition
__ may block distal arteries, leading to intermittent claudication and severe pain in leg muscles
Term
muscular dystrophy
Definition
__ refers to a group of inherited muscle-destroying diseases that generally appear during childhood. the muscles enlarge due to fat and connective tissue deposits. the muscle fibers atrophy and degenerate
Term
duchenne muscular dystrophy (DMD)
Definition
the most common and severe type of muscular dystrophy is __
Term
duchenne muscular dystrophy (DMD)
Definition
Inherited, sex-linked, carried by females and expressed in males (1/3500) as lack of dystrophin
Term
duchenne muscular dystrophy (DMD)
Definition
Victims become clumsy and fall frequently; usually die of respiratory failure in their 20s
Term
duchenne muscular dystrophy (DMD)
Definition
No cure, but viral gene therapy or infusion of stem cells with correct dystrophin genes show promise