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CSUS Bio 25 Chapter 10
Christina Strandgaard study guide chapter 10 (Muscle Tissue and Muscles)
105
Anatomy
Undergraduate 2
11/16/2008

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Term
What features distinguish the three types of muscle tissue?1
Definition
Skeletal: Function of most skeletal muscles is to move bones of the skeleton. *striated *voluntary Cardiac: Only present in the heart *striated *involuntary *autorythmicity Smooth: located in the walls of hollow internal structures. (i.e. blood vessels, airways, most organs of the abdominopelvic cavity), also found in skin attached hair follicles. *nonstriated *involuntary
Term
Summarize the functions of muscle tissue.
Definition
1) producing body movement
-integrated functioning of bones, joints, and skeletal muscle.
2) Stabilizing body positions (maintaining posture, stabilizing joints)
-contractions stabilize joints and help maintain body positions, such as standing or sitting
3) Regulating organ volume
-sphincters (valves) prevent the outflow of the contents of hollow organs.
4)moving substances within the body
-cardiac muscle contractions: movement of blood
-contraction and relaxation of smooth muscle in the wall of blood vessels:helps adjust their diameter and therefore, rate of blood flow.
5)producing heat
Term
What are the four functional characteristics of muscle tissue?
Definition
1)electrical excitability(irritability): the ability to respond to certain stimuli by producing electrical signals. (action potentials)
2)contractiblity: the ability to contract (shorten) forcefully when stimulated by an action potential
3)extensibility: the ability to stretch without being damaged
4)elasticity: the ability of muscle tissue to return to its original length and shape after contraction or extension.
Term
Why are skeletal muscle fibers multinucleated?
Definition
They are myonucleated because during embryonic development, each skeletal muscle fiber arises from the fusion of myoblasts, which is how they form multinucleated muscle cells.
Term
Describe the three types of fascia that cover skeletal muscles.
Definition
1)epimysium: outer most layer; encircles the whole muscle
-it is connected to the deep fascia
2)perimysium: surrounds groups of 10-100 individual muscle fibers; separates them into bundles called fasicles
-it contains blood vessels and nerves for the muscle fibers from one another
3)endomysium: separates individual muscle fibers from one another
-it contains a capillary network, satellite cells and nerve fibers controlling the muscle.
Term
Why is a rich blood supply important to muscle contraction?
Definition
In general, each muscle is served by one nerve, one artery and one or several veins.
-Skeletal muscle is well supplied by capillaries so you have oxygen and energy.
Term
Somatic motor neuron
Definition
Neurons that stimulate skeletal muscle to contract.
-each somatic motor neuron has an axon that extends from the brain or spinal cord to a group of skeletal muscle fibers.
Term
Sarcolemma
Definition
the plasma membrane of the skeletal muscle fiber. It has a characteristic transmembrane potential due to the unequal distribution of postive and negative charges across the membrane.
Term
T tubules
Definition
tiny invaginations of the sarcolemma tunnel from the surface toward the center of each muscle fiber. They are open to the outside.They are filled with extracellular fluid and therefore have the same general properties of sacolemma. THE ACTION POTENTIALS ARE THE TIGGERS FOR MUSCLE FIBER CONTRACTIONS
Term
Sarcoplasm
Definition
the cytoplasm of a muscle fiber
-contains glycogen and myoglobin(a red pigment that stores oxygen within the muscle cell)
Term
Myofibrils
Definition
contactile elements of skeletal muscle.
-consist of bundles of myofilaments (protein filaments)
-within myofibrils are two types of filaments; thin filaments(primarily actin) and thick filaments(primarily myosin)
Term
Sarcoplasmic reticulum
Definition
fluid filled system of membranous sacs that encircles each myofibril
Term
Terminal cisterns
Definition
dilated end sacs of the sarcoplasmic reticulum; they butt against the T tubule from both sides
-located at the zones of overlap
Term
Triad
Definition
formed by one transverse tubule and the 2 terminal cisterns on either side of it
*it stores ca++ and releases it on demand when the muscle fiber is stimulated to contract
*the release of calcium ions from the terminal cisterns of the SR triggers muscle contraction.
Term
Sarcomere
Definition
A sarcomere contains thick filaments, thin filaments, stabilizing proteins for positions of thick and thin filaments and regulatory proteins.
Term
Z lines
Definition
separate one sarcomere from the next
*the Z lines consists of proteins (actinins) that interconnect thin filaments of adjacent sarcomeres
*each Z line is surrounded by a mesh of intermediate filaments that interconnect adjacent myofibrils
Term
A band
Definition
extends the entire length of the thick filament
Term
H zone
Definition
(in the center of each A band) contains thick but no thin filamnets
Term
M line
Definition
supporting proteins that hold the thick filaments together at the center of the H zone
Term
zone of overlap
Definition
toward each end of the A band
Term
I band
Definition
contains the rest of the thin filaments, but no thick filaments
-a Z disc passes throough the center of each I band
Term
Contractile proteins
Definition
generate force during contraction
Term
myosin
Definition
this contractile protein functions as a motor protein in all three types of muscle tissue
*forms the thick filaments
Term
myosin tails
Definition
points toward the M line in the center of the sarcomere
Term
myosin heads(cross bridges)
Definition
each head extends toward one of the 6 thin filaments that surrounds the thick filaments. It includes ATP binding sites and ATPase
Term
Actin
Definition
main component of thin filaments
*individual actin molecules join to form an actin filament that is twisted into a helix: Active site (myosin binding site) site of myosin head attachment
Term
regulatory proteins
Definition
help switch the contraction process on and off
-they regulate the interactions between the thick and thin filaments
-troponin and tropomyosin: part of thin filaments
Term
Troponin
Definition
1. Ca++ binding site
2. binding site for tropomyosin
3. binding site for actin
Term
Structural (stabilizing) proteins
Definition
-keep the thick and thin filaments in proper alignment
-give the myofibril elasticity and extensibility
-link the myofibrils to the sarcolemma and extracellular matrix
Term
Titin
Definition
each thick filament has a core of titin
*the portion of the titin strand exposed within the I band is elastic and will recoil after stretching
*in a resting muscle the titin strands are completely relaxed
Term
Nebulin
Definition
extend along the actin strand and hold them together.
Term
Sliding Filament mechanism
Definition
Skeletal muscles shortens during contraction because the thick and thin filaments slide past one another.
-the length of the individual thick and thin filament do not change.
-shortening of the sarcomere causes shortening of the whole muscle fibers, and ultimately shortening of the entire muscle.
Since myofibrils are attached to the sarcolemma at each Z line, and at either end of the muscle fiber, the muscle fiber shortens too.
Term
Excitation-contraction Coupling
Definition
The series of events linking the electrical signals to contraction is known as excitation-contraction coupling: Excitation-contraction coupling is the sequence of events by which transmission of an action potential along the sarcolemma leads to the sliding of myofilaments. THE FIRST STEP IN EXCITATION-CONTRACTION COUPLING IS THE RELEASE OF CALCIUM IONS FROM THE CISTERNEA OF THE SARCOPLASMIC RETICULUM FROM VOLTAGE GATED CALCIUM CHANNELS.
Term
Neuromuscular Junction
Definition
the point of contact (synapse) between the motor neuron and the muscle fiber
Term
Synapse
Definition
a region where communication occurs between 1)two neurons and 2)a neuron and a target cell
Term
synaptic cleft
Definition
a small gap at synapses; it separates two cells.
*since the cells do not phyically touch, an action potential cannot jump from one cell to the other; instead the first cell communicates with the second cell indirectly by releasing a chemical called a neurotransmitter.
Term
synaptic bulb
Definition
at the neuromuscular junction the motor neuron axon terminal divides into a cluster of synaptic end bulbs.
Term
synaptic vesicles
Definition
are suspended in the cytosol of synaptic bulbs. The neurotransmitter molecule acetycholine is present in the synaptic vesicles.
Term
Motor end plate
Definition
the region of the sarcolemma that is adjacent to the synaptic end bulb.
*the motor end plate contains receptors for acetylcholine (gated ion channels)
*the motor end plate is highly folded(junctional folds)
Term
Leakage channels(passive)
Definition
*always open
-plasma membranes have many more K+ leakage channels than Na+ leakage channels
Term
Gated channels(active)
Definition
*open and close in response to a stimulus
-the presence of gated ion channels in the plasma membranes of neurons and muscle fibers gives these cells their property of electrical excitability
Term
What are the three types of gated ion channels present in excitable cells?
Definition
1)voltage-gated
2)ligand-gated(chemically gated)
3)mechanically gated
Term
Voltage-gated ion channel
Definition
-opens in response to a change in membrane potential
-used in the generation and conduction of action potentials
-found on the membranes of excitable cells:
*axons of unipolar and multipolar neurons
*sarcolemma and T tubules of skeletal muscle fibers
*cardiac cells
Term
Chemically gated
Definition
-opens and closes in response to a specific chemical stimulus(i.e neurotransmitters, hormones, ions)
-found greatly on dendrites and cell body of neurons
Term
Mechanically gated
Definition
-opens and closes in response to mechanical stimulation (i.e vibration, pressure, tissue stretching)
Term
5 steps of a nerve impulse
Definition
1)an action potential arrives at the synaptic end bulbs of a somatic motor neuron.
2)ACh is released from synaptic vesicles
3)Ach binds to it receptors
4)muscle action potential is produced
5)Ach is broken down by acetylcholinesterase.
Term
Contraction cycle:
Active site exposure
Definition
At the onset of contraction:
-the sarcoplasmic reticulum releases calcium ions
-the Ca++ binds to troponin and cause troponin-tropomyosin complexes to move away from the myosin-binding sites on actin.
Term
Contraction Cycle:
Cross bridge attachment
Definition
attachment of myosin to actin to form cross bridges:
-the activated myosin heads(high energy configuration) are strongly attracted to the exposed binding sites on actin
-ADP and inorganic phosphate are attached to the myosin head
-in resting sarcomere, each myosin head is already energized.
Term
Contraction Cycle:
Pivoting (swiveling) of myosin head
Definition
(The working power stroke) the releases of the phosphate group triggers the power stroke of contraction
*the myosin head generates force as it rotates toward the center of the sarcomere, sliding the thin filamnt past the thick filament toward the M line.
Term
Contraction Cycle:
Cross bridge detachment
Definition
Detachment of myosin from actin
-at the end of the power stroke, the myosin head remains firmly attached to actin until it binds another molecule of ATP.
-As a new ATP molecule binds to the ATP binding pocket on the myosin head, the myosin head detaches from actin.
-the active site on actin is once again exposed, and it can form another cross bridge.
Term
Contraction Cycle:
ATP Hydrolysis/Myosin reactivation
Definition
-the hydrolysis of ATP (to ADP and Pi) by the myosin head energizes the myosin head
-the products of hydrolysis remain attached to myosin head
Term
Muscle Relaxation
Definition
The duration of skeletal muscle contraction depends on:
1. duration of stimulation at the neuromuscular junction.
2. presence of free calcium ions in the sarcoplasm
3. ATP availability
- the return to resting length after a contraction can involve elastic forces, the contractions of opposing muscle groups and gravity.
Term
Force of Contraction
Definition
The force of muscle contraction is affected by:
1. the number of muscle fibers contracting
*the more motor units that are recruited, the greater the muscle force
2. the relative size of the muscle
*the bulkier the muscle, the more tension it can develop and therefore, the greater its strength
3. the degree of muscle stretch
*the optimal resting length for muscle fibers is the length at which they can generate maximum force.
Term
Tension produced by muscle fibers
Definition
The total tension that a single fiber can produce depends:
1. mainly on the rate at which nerve impulses arrive at the neuromuscular junction
*FREQUENCY OF STIMULATION
2)nutrient and oxygen availability
3)the amount of stretch prior to contraction (LENGTH-TENSION RELATIONSHIP)
Term
Length-tension relationship
Definition
The forcefulness of muscle contraction depends on the length of the sarcomere within a muscle before contraction begins.
-The amount of tension generated during a contraction depends on the number of pivoting cross bridges in all the sarcomere along all the myofibrils.
*the number of cross bridges that can be formed in turn depends on the degree of overlap between the thick filaments and thin filaments present in the sarcomere.
Term
Twitch contraction
Definition
A brief contraction of all the muscle fibers in a motor unit in response to a single action potential in its motor neuron
Term
Latent period
Definition
a brief delay between application of the stimulus and the beginning of the contraction.
Term
During the Latent period
Definition
1. the action potential propagates along the sarcolemma.
2. Ca++ are being released from the SR
*since the contraction cycle has not yet begun, no tension is produced
Term
Contraction period
Definition
1. The filaments start to exert tension
2. shortening begins
Term
Relaxation period
Definition
tension begins to fall due to the active transport of calcium ions back into the SR.
-the actual duration of the periods depends on the type of muscle (fast-twitch vs. slow-twitch muscles)
Term
Refractory Period
Definition
If two stimuli are applied (one immediately after the other), the muscle will respond to only the first stimulus.
-When a muscle fiber receives enough stimulation to contract, it temporarily loses its excitability and cannot respond for a time.
Term
Graded muscle responses
Definition
- Our muscle contractions are relatively smooth and vary in strength based on the demands placed on them
*variations in the degree of muscle contraction are called graded responses:
-muscle contraction can be graded in two ways:
1. By changing the frequency (speed) of stimulation -ATP-
2. By changing the strength of the stimulus -higher voltage-
Term
Treppe
Definition
-the increase in peak tension will continue over the first 30-50 simulations
*after that, the amount of tension produced will remain constant
-treppe (the rise) may be due to a gradual increase in the concentration of calcium ions in the sarcoplasm.
*this is the basic for warming up
Term
Wave summation
Definition
The phenomenon in which stimuli arriving at different times cause larger contractions:
-due to additional Ca++ released from the SR
-also due to the stretch of the elastic elements
Term
Unfused tetany
Definition
When skeletal muscle is stimulated at a rate 20-30 times per second, it can only partially relax between stimuli:
-the result is a sustained but wavering contraction known as unfused (incomplete) tetany
Term
Fused (complete) tetany
Definition
When skeletal muscle is stimulated at a rate of 80-100 stimuli per second, the result is fused (complete) tetany (a sustained contraction in which individual twitches cannot be discerned)
-almost all normal muscular contractions involve complete tetanus of the participating muscle.
Term
Muscle tension
Definition
The force exerted on an object by a contracting muscle
Term
Muscle tension depends on..
Definition
-The tension produced by the stimulated muscle fibers
-the total number of muscle fibers stimulated
Term
isometric contraction
Definition
if tension develops but the load is not moved. (same length)
Term
isotonic contraction
Definition
if the tension developed overcomes the load and muscle shortening occurs. (same tension)Used for body movements and for moving external objects.
Term
Motor unit
Definition
a somatic motor neuron plus all the skeletal muscle fibers it stimulates
*all the muscle fibers in one motor unit contract in unison.
It depends on:
-how large the motor units are and
-how many motor units are activated at the same time.
*Muscle that control precise movements consist of many small motor units.
*Muscle that control large-scale and powerful movements have larger motor units.
Term
Motor Unit response
Definition
The process in which the number of active units is increased.
Term
Asynchronous motor unit summation
Definition
The various motor neurons to a whole muscle fibers asynchronously.
* this pattern of motor unit activity delays muscle fatigue
*the weakest motor units are recruited first, with progressively stronger motor units being added if the task requires more force.
Term
Muscle tone
Definition
-to sustain muscle tone, small groups of motor units are alternately active and inactive in a constantly shifting pattern.
*muscle tone is due to spinal reflexes that activate first one group of motor units and then another in response to activation of stretch receptors in muscles and tendons.
*a muscle with little or no muscle tone appears limp and flacid, while one with moderate tone is firm and solid.
Term
Muscle tone is important...
Definition
-stabilizing the position of bones and joints (muscles of balance and posture)
-preventing sudden uncontrolled changes in positions of bones and joints.
Term
Concentric isotonic contraction
Definition
a muscle shortens and pulls on another structure to produce movement and to reduce the angle at a joint. (i.e tendon)
Term
Eccentric isotonic contraction
Definition
When the overall length of a muscle increases during a contraction. (Move arm down)
Term
Isometric contraction
Definition
important for maintaining posture and for supporting objects in a fixed position, important in stabilizing some joints as others are moved.
-in isometric contractions tension is generated without shortening of the muscle.
Term
Contraction of muscle requires a great amount of ATP for:
Definition
1)powering the contraction cycle
2)pumping CA++ back into the SR to achieve muscle relaxation
3)other metabolic reactions
Term
Creatine phosphate
Definition
Unique to muscle fibers
-the enzyme creatine kinase catalyzes the transfer of one high energy phosphate group of ATP to creatine forming creatine phosphate and ADP.
-when the muscle needs energy, the reverse reaction takes place.
*this allow rapid formation of ATP
Term
Anaerobic Cellular Respiration
Definition
Series of ATP producing reactions that do not require oxygen.
* A series of reactions known as glycolysis, quickly break down each glucose molecule into two molecules of pyruvic acid.
Term
Aerobic Cellular respiration
Definition
Takes place in the mitochondria, and requires the presence of oxygen.
-36 molecules of ATP are produced from each molecule of glucose
*this is sufficient for prolonged activities.
Term
Sources of muscle tissue oxygen
Definition
1)oxygen that diffuses into muscle fibers from the blood.
2)oxygen released by myoglobin within muscle fibers.
Term
Muscle Fatigue
Definition
The inability of a muscle to contract forcefully after prolonged activity
Term
Oxygen Debt
Definition
added oxygen needed over and above the resting oxygen consumption, that is taken into the body after exercise.
Term
Muscle performance load
Definition
the greater the load, the longer the latent period, the slower the contraction, and the shorter the duration of contraction
Term
Muscle performance recruitment
Definition
the more motor units contracting, the faster and more prolonged the contraction
Term
Fast Fibers
Definition
They produce rapid and powerful contractions of relatively brief duration.
*large in diameter
*contain densely packed myofibrils
*large glycogen stores
*few mitochondria
*anaerobic
*they fatigue easily
Term
Slow Fibers
Definition
Designed to continue contracting for extended periods.
*they take 3 times as long to contract after stimulation
*abundant mitochondria
*extensive capillary supply
*high concentrations of myoglobin
Term
White muscles
Definition
Muscles dominated by fast fibers appears pale
Term
Red muscle
Definition
Muscle dominated by slow fibers are rich in myoglobin
Term
Muscle Hypertrophy
Definition
enlargement of a stimulated muscle
-this occurs in muscles that have been repeatedly stimulated to produce near maximal tension.
-the number of muscle fibers does not change
Term
Cardiac Muscle
Definition
principle tissue in the heart wall.
-have same arrangement of actin and myosin and same bands, zones and Z discs as skeletal muscle fibers.
-ends of cardiac muscle fibers connect to adjacent fibers by intercalated discs
*the intercalated discs contains desmosomes (help stabilize the adjacent cells) and gap junctions (allow small molecules to move from one cell to another)
-longer contraction period than skeletal muscle
-involuntary
-almost completely dependent on aerobic metabolism
Term
Smooth Muscle
Definition
-spindle shaped
-lack transverse tubules, myofibrils and sarcomeres.
-the thin filaments are attached to dense bodies
*dense bodies attach adjacent smooth muscle cells to each other.
Term
Visceral smooth muscle tissue
Definition
-single unit smooth muscle has electrically coupled fibers that contract synchronously an often spontaneously
Term
Visceral smooth muscle tissue locations
Definition
Found in:
-walls of small arteries and veins
-walls of hollow viscera:stomach, intestines, uterus, urinary bladder
*autorythmic
-they lack a direct contact with any motor neuron
Term
Multiunit smooth muscle tissue
Definition
Consists of individual fibers, each with their own motor neuron connected to more than a single motor neuron.
-stimulation of one motor unit fiber causes contraction of that fiber only.
-stimulation is via autonomic nerves or hormones.
Term
Multiunit smooth muscle tissue location
Definition
Found in the walls of large arteries, airways, and in arrector pilli.
*not usually found in the digestive tract.
Term
Contraction of Smooth Muscle
Definition
1. excitation contraction coupling
2.length-tension relationship
3. control of contraction
Term
calmodulin
Definition
a cytoplasmic calcium binding protein
Term
myosin light chain kinase
Definition
a kinase enzyme
-the thin filaments lack troponin and son are always ready for contraction
Term
Plasticity
Definition
Smooth muscle can both shorten and stretch to a greater degree than other muscle types
Term
Smooth muscle tone
Definition
Both multiunit and visceral smooth muscle tissues have tone
Term
Regeneration of muscle tissue
Definition
-Skeletal muscle fibers cannot divide and have limited powers of regeneration.
-Cardiac muscle fibers cannot divide or regenerate.
-Smooth muscle fibers have limited capacity for division and regeneration.
Term
Fibrosis
Definition
the replacement of muscle fibers by fibrous scar tissue.
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