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Cronk Muscular Tissue
Chapter 10
98
Biology
Undergraduate 1
05/06/2012

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Term
Skeletal Muscle Tissue
Definition
attached to & moves bones, occasionally skin or other muscles, striated, voluntary as a rule, , body position and stabilization
Term
Cardiac Muscle Tissue
Definition
forms most of heart wall and pumps blood, striated, involuntary
Term
autorhythmicity
Definition
built in rhythm, a pacemaker initiates contraction
Term
Smooth Muscle
Definition
located in the walls of hollow organs, nonstriated, usually involuntary
Term
Functions of Muscular Tissue: 1. Electrical excitability
Definition
The ability to respond to certain stimuli by producing electrical signals known as action potentials.
Term
Properties of Muscular Tissue: 2. Contractility
Definition
ability of muscular tissue to contract forcibly when stimulated by an action potential.
Term
Properties of Muscular Tissue: 3. Extensibility
Definition
The ability of muscular tissue to stretch without being damaged.
Term
Elasticity
Definition
the ability of muscular tissue to return to its original length and shape after contraction or extension.
Term
Muscle fibers, myofibrils
Definition
skeletal muscle cells
Term
Connective Tissue Components
Definition
surrounds and protects muscular tissue.
Term
Subcutaneous layer/hypodermis
Definition
composed of areolar and adipose connective
tissue.
Term
Deep fascia
Definition
dense irregular connective tissue that lines the body wall, limbs
and muscles with similar functions as well as fills spaces between muscles
Term
Epimysium
Definition
C.T. that surrounds the entire muscle.
Term
Perimysium
Definition
C.T that surrounds a group of muscle fibers.
Term
Endomysium
Definition
C.T that surrounds and separates individual muscle fibers
Term
Fascicle
Definition
bundle of 10-100 muscle fibers
Term
Tendon
Definition
cord-like C.T. of dense regular C.T. that attaches the muscle to the
periosteum of bone.
Term
Aponeurosis
Definition
broad, flat C.T that connects the muscle to muscle or muscle to
bone.
Term
Tendon sheaths
Definition
C.T. that encloses tendons to reduce friction as they slide
back and forth. Similar to bursae. Cavity between the layers is filled with synovial fluid.
Term
Nerve and Blood Supply
Definition
generally one artery and one or two veins accompany each nerve that penetrates a skeletal muscle.
Term
Myoblasts
Definition
fusion of 100 or more mesodermal cells in each muscle fiber during embryonic development.
Term
hypertrophy
Definition
muscle growth after birth, an enlargement of existing muscle fibers
Term
Satellite cells
Definition
myoblasts which persist in mature skeletal muscle fibers may fuse with one and regenerate muscle fibers to a small extent
Term
Fibrosis
Definition
replacement of muscle fibers by fibrous scar tissue due to damage or degeneration
Term
Sarcolemma
Definition
plasma membrane of a muscle cell.
Term
Transverse (T) Tubules
Definition
tiny invaginations of the sarcolemma tunnel into the
center of the muscle fiber.
Term
Sarcoplasm
Definition
The cytoplasm of a muscle fiber.
Term
Myofibrils
Definition
Thread-like organelles of contraction
Term
Sarcoplasmic reticulum
Definition
sleave-like membranous sac that encircle each
myofibril
Term
Terminal Cisterns
Definition
dialated end sacs of the sarcoplasmic reticulum.
Term
Triad
Definition
a transverse tubule and two terminal cisterns
Term
Filaments and the Sarcomere
Definition
filaments are arranged in sarcomeres. The thin and thick filaments overlap one another creating striations.
Term
Thin filaments
Definition
8 nm in diameter and 1-2 um long
Term
Thick filaments
Definition
16 nm in diameter and 1-2 um long
Term
Sarcomeres
Definition
the basic functional units of the myofibril that extend from one Z
disc to the next
Term
Z discs
Definition
structural proteins that separate one sarcomere from the next.
Term
A band
Definition
the dark middle part of the sarcomere that extends the entire length of
the thick filament
Term
Zone of overlap
Definition
thick and thin filaments lie side by side
Term
I band
Definition
lighter, less dense area that contains only thin filament
Term
H zone
Definition
a narrow region in the center of each A band that contains thick
filaments but no thin filaments.
Term
M line
Definition
structural proteins in the middle of the H zone that hold the thick
filaments together
Term
Muscle Proteins
Definition
Myofibrils are built from three kinds of proteins: see chart 10.2
Term
Contractile proteins
Definition
myosin and actin, are the main components of thick and thin
filaments
Term
Myosin
Definition
functions as a motor protein. They bind to myosin sites on actin
molecules during muscle contraction
Term
Actin
Definition
Actin molecules join together to form an actin filament, twisted into a
helix. On each actin molecule is a myosin binding site for the myosin head.
Term
Regulatory Proteins
Definition
Two regulatory proteins are also part of the thin filament.
Term
Tropomyosin
Definition
covers the myosin binding sites on actin when the muscle is
relaxed.
Term
Troponin
Definition
Troponin holds tropomyosin in place.
Term
Structural Proteins
Definition
Muscle contains a dozen structural proteins which contribute to the alignment, stability, extensibility and elasticity of myofibrils.
Term
Tintin
Definition
(gigantic) Each Tintin molecule connects a Z disc to the M line of the sarcomere and helps to stabilize the position of the thick filament.
Term
Dystrophin
Definition
a cytoskeletal protein that links thin filaments of the sarcomere to integral membrane proteins of the sarcolemma, which are attached in turn to proteins in the connective tissue extracellular matrix
Term
The Sliding Filament Mechanism
Definition
muscle contraction occurs because myosin heads attach to and “walk along” the thin filaments at both ends of the sarcomere, pulling the thin filaments toward the M line and may even overlap. As a result the Z discs move closer together.
Term
The Contraction Cycle
Definition
the Sarcoplasmic reticulum releases calcium ions. Once the myoin binding sites are free the contraction cycle begins. It has four steps: See pages: 312-313
Term
Contraction cycle
Definition
the repeating sequence of events that causes the filaments to slide 1. ATP hydrolysis 2. Attachment of myosin to actin to form crossbridges 3. Power Stroke 4. Detachment of myosin from actin
Term
Excitation-Contraction Coupling
Definition
The events that connect excitation (action potential) to contraction (sliding filaments).
Term
Length-Tension Relationship
Definition
• When the sarcomere length is close to resting length the zone of overlap is
maximal for the muscle fiber to develop maximal tension • When there is no overlap of the thick and thin filaments, muscle cannot contract
and the tension is zero • When sarcomere length shortens, the tension decreases with few myosin heads
making contact with thin filament.
Term
The Neuromuscular junction
Definition
NMJ, A synapse between the axon terminals of a somatic motor neuron and the sarcolemma of a muscle fiber.
Term
Synapse
Definition
a region where communication occurs between two neurons or between a neuron and a target cell.
Term
Synaptic cleft
Definition
a small gap at a synapse.
Term
Neurotransmitter
Definition
the chemical communication between the first cell and the
second
Term
Synaptic vesicles
Definition
membrane-enclosed sacs located in synaptic end bulbs
containing neurotransmitters
Term
Motor End Plate
Definition
the region of the sarcolemma opposite the synaptic end bulb.
Term
Junctional folds
Definition
Deep grooves in the motor end plate that increase the surface
area for neurotransmitters
Term
Muscle Metabolism
Definition
Muscle fibers have three ways to produce ATP
Term
Muscle Metabolism 1. Creatine Phosphate
Definition
produced when muscle fibers are relaxed and more ATP is
available than needed for resting muscle metabolism.
Term
Muscle Metabolism 2. Anerobic Cellular Respiration
Definition
ATP producing reactions that do not require
oxygen.
Term
Muscle Metabolism3. Aerobic Cellular Respiration
Definition
Muscular activity that lasts longer than a half a
minute depends increasingly on ACR, oxygen-requiring reactions
Term
Oxygen debt
Definition
refers to the added oxygen, over and above the resting oxygen
consumption, that is taken into the body after exercise.
Term
Frequency of Stimulation
Definition
# of impulses per second.
Term
Motor unit
Definition
a somatic motor neuron and all the skeletal muscle fibers it
stimulates
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 unit.
Term
Myogram
Definition
record of a muscle contraction.
Term
Latent period
Definition
the delay (2 milliseconds) between the application of the
stimulus and the beginning of contraction.
Term
Contraction Period
Definition
Ca++ binds to troponin, myosin-binding sites are revealed, crossbridges formed and peak tension develops in the muscle fiber. 10-100msec
Term
Relaxation Period
Definition
Ca++ is actively transported back into the SR, myosin
binding sites are covered and tension in the muscle fiber decreases, 10-100msec
Term
Refractory period
Definition
The period of lost excitability where the muscle fiber cannot
respond.
Term
Wave Summation
Definition
phenomenon in which stimuli arriving at different times cause larger contractions.
Term
Unfused (incomplete) tetanus
Definition
When a skeletal muscle fiber is stimulated at a rate of 20 to 30 times per second, it can only partially relax between stimuli.
Term
Fused (complete) tetanus
Definition
When a skeletal muscle fibers is stimulated at a higher rate of 80 to 100 times per second, it does not relax at all.
Term
Motor Unit Recruitment
Definition
the process in which the number of active motor units increases.
Term
Muscle Tone
Definition
a small amount of tautness or tension in the muscle due to weak involuntary contractions of its motor units.
Term
Flaccid
Definition
a state of limpness in which muscle tone is lost.
Term
Isotonic contraction
Definition
the tension (force of contraction) developed by the muscle
remains almost constant while the muscle changes its length.
Term
Concentric isotonic contraction
Definition
if the tension generated is great enough to
overcome the resistance of the object to be moved
Term
Eccentric Isotonic Contraction
Definition
when the length of a muscle increases
during a contraction.
Term
Isometric contraction
Definition
the tension generated is not enough to exceed the
resistance of the object to be moved and the muscle does not change its length.
Term
Types of Skeletal Muscle Fibers
Definition
classification of skeletal muscle fibers into 3 types: Slow Oxidative (SO) fibers, Fast Oxidative-Glycolytic Fibers (FOG), Fast Glycolytic Fibers (FG). See pages 324-5 and table 10.3
Term
Myoglobin
Definition
the red-colored protein that binds oxygen in muscle fibers
Term
Red muscle fibers
Definition
skeletal muscle fibers that have a high myoglobin content,
more mitochrondia and more capillaries
Term
White muscle fibers
Definition
skeletal muscle fibers that have a low myoglobin content
Term
Fast/slow fiber
Definition
speed at which the ATPase in the myosin heads hydrolyzes
ATP
Term
Visceral (single-unit) smooth muscle tissue
Definition
most common type. Fibers
connect to one another via gap junctions. It is autorhythmic.
Term
Multiunit smooth muscle tissue
Definition
consists of individual fibers, few gap junctions. Stimulation of one multiunit fiber causes contraction of only that fiber
Term
Regeneration of Muscular Tissue
Definition
Satellite cells divide slowly and fuse with existing fibers to assist both in muscle growth and in repair of damage fibers.
Term
Development of muscle
Definition
All the muscles of the body are derived from mesoderm. They develop on either side of the developing nervous system and undergo segmentation into a series of cube-shaped structures called somites. The somites differentiate into three regions:
Term
A myotome
Definition
forms the skeletal muscles of the head, neck, and limbs
Term
A dermatome
Definition
which forms the connective tissues, including the dermis of the skin
Term
A sclerotome
Definition
which gives rise to vertebrae.
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