Anatomy & Physiology 34A Lecture
Muscular Tissue & Physiology
I.
Overview
A. Types of Muscle Tissue
B. Skeletal Muscle
C. Microscopic Anatomy of Skeletal Muscle
D. Nerve-Muscle Relationship
E. Behavior of Skeletal Muscle Fibers
F. Behavior of Whole Muscles
G. Muscle Metabolism
H. Cardiac Muscle
I. Smooth Muscle
J. Disorders of Muscle Tissue
II. Characteristics & Types of Muscle Tissue
A. Characteristics of all muscle tissues:
1.
_________________ – neurotransmitters from nerves stimulate electrical changes in
muscle cells’ plasma membranes
2.
_________________ – electrical impulses initiate cellular processes leading to
muscle contraction
3.
4.
_____________ - muscle cells shorten & generate pulling force
_______________ - after contraction, muscles can be stretched by contraction of an
opposing muscle
5. _______________ - after stretching, muscles can recoil to their resting length
B. Types of Muscle ____________
1.
___________ muscle – straited, multinucleate cells. Functions:
a. _________ Movement via skeletal muscles attached to bones
b. Maintenance of _______ via contractions of skeletal muscles
c. Joint stabilization via muscle _______ - a constant, low level of force generated keeps tension on tendons that cross joints
d. _______ generation - helps to maintain a constant body temp.
2.
_________ muscle – involuntary, straited, uninucleate cells separated by intercalated
discs. Functions:
a. _______________, composes heart myocardium
b. Cells contract ______________ in synchronized rhythm
c. Regulated by the ________________ nervous system
3.
__________ muscle - involuntary nonstraited, uninucleate cells. Functions:
a. Found in the walls of body ________ (e.g.: GI, respiratory, urogenital tracts, blood
vessels)
b. Promotes wavelike peristaltic contractions in the GI tract
2
c. Responsible for vasodilation and vasoconstriction of blood vessels and bronchioles
III. Skeletal Muscle
A. Blood & Nerve Supply to Skeletal Muscle
1.
Each skeletal muscle is supplied by at least one ________, one artery, and one or
more veins
2.
The nerves and vessels branch off in the muscle CT, so each muscle _________ has
its own neuron axon & capillaries
3.
A _________________ junction is the point at which a neuron signals a muscle fiber
to contract
IV. Microscopic Anatomy of Skeletal Muscle Tissue
A. Skeletal Muscles are composed of muscle fibers (cells). Muscle structures from large to
small include: whole muscle → fascicle groups → muscle fibers → myofibrils →
myofilaments
B. Skeletal muscle cells are
1.
Long cells consisting of many ____________ composed of
a.
b.
_____________ of actin (thin) and myosin (thick) protein fibers
____________ - contractile units in myofibrils, between Z lines.
1) ___ bands - are light bands of __________ only
2) ___ bands - are dark bands of __________ and ________
3) ___ zone - central part of A band with ________, no actin
4) ___ line - center of H zone with rods that hold _________ together
5) ___ discs - protein discs where ________ filaments attach; distance between Z
lines shortens during contraction.
2.
3.
4.
5.
6.
Each cell is ________nucleate, with peripheral nuclei.
7.
Sarcoplasmic reticulum (____) - smooth E. R. that surrounds each ____________
within the sarcolemma; contains ____ ions necessary for muscle contraction.
8.
9.
Terminal ___________ - sac-like portions of the S. R. on both sides of the T-tubules.
Cells have many ______________
Sarco_________ – muscle cell cytoplasm
Sarco_______ (plasma membrane) surrounds each muscle cell.
______________ (T) tubules - infoldings of the sarco_____ through the muscle cell;
carries electrical impulse into the cell
_______ - complex of a T tubule between two terminal cisternae
B. Three types of ______________ (protein microfilaments) compose a myofibril
1. _____ filaments - “golf club”-like myosin proteins composed of
a. 2 intertwined polypeptides forming the shaftlike ______ and
b. A double ____________ protein head projecting from the tail at an angle.
3
c. A thick filament is a bundle of 200-500 _______ “golf clubs” with their heads
spiraling outward from the bundle
2. _______ filaments – contain actin, tropomyosin, and troponin proteins.
a. __________ proteins are composed of
1) ___________ (F) actin – 2 intertwined strands of protein “beads” called
2) _____________ (G) actin, each of which has an active (myosin-binding) site
that can bind a myosin head
b. __________________ is a fibrous protein that blocks actin’s myosin binding sites
when the muscle cell is relaxed
c. ______________ is a small calcium-binding protein attached to the tropomyosin
molecule at regular intervals
3. __________ filaments – springy titin proteins that connect the thick filament to the
___ disc and keep the thick and thin filaments aligned, to resist muscle overstretching
V. Nerve – Muscle Relationship
A. ________ neurons – somatic motor neuron axons extend from cell bodies in brain stem
and spinal cord to innervate _____________ muscle cells
B. Motor ________ - a neuron and all the muscle cells it stimulates
1. Muscles that require ______ motor control, such as eye muscles, finger muscles, etc.,
have ___ muscle fibers per neuron (e.g., 25/1)
2. Muscles involved in __________, such as in the back, legs, etc., have ______ muscle
fibers per neuron (e.g., 1,000/1)
C. Neuromuscular Junction (____________) - area where a neuron axon meets a muscle
cell
1.
The axon end (synaptic bulb) fits into a depression in the muscle sarcolemma called
the _____________________, with a minute gap between the bulb and end plate
2.
Synaptic _______ – microscopic fluid-filled gap between axon synaptic bulb and
muscle cell motor end plate
3.
Synaptic ___________ filled with a neuro_____________ (acetylcholine = ____)
are found within the axon synaptic bulbs
4.
ACh _____________ found in the muscle motor end plate bind ACh when it is
released by the axon synaptic bulb, which stimulates the muscle cell
5.
Acetylcholinesterase (______) is released from the sarcolemma to degrade ____ in
the cleft and end muscle stimulation
VI. Behavior of Skeletal Muscle Fibers
A. Muscle contraction and relaxation occurs in 4 major __________: excitation, excitationcontraction coupling, contraction, and relaxation
1. _______________ – the process by which the electrical nerve impulse is transmitted to
the muscle cell
a. A nerve impulse stimulates the uptake of _____ ions into the axon synaptic bulb
b. Ca2+ ions stimulate the exocytosis of _____ from synaptic vesicles into the synaptic
cleft
4
c. ACh diffuses across the cleft and binds to ACh ___________ (sodium ion channels)
in the sarcolemma motor end plate
d. An ____________ impulse is initiated in the motor end plate as sodium enters the
muscle cell through the ion channels
2. Excitation-contraction ______________ – events that link the electrical impulse on
the sarcolemma to the activation of the myofilaments, preparing them to contract
a. The electrical impulse ripples across the ________ end plate, then down into the
sarcoplasm via the ___-tubules
b. The impulse causes the sarcoplasmic reticulum ___________ to release _____ ions
into the cytosol
c. Ca2+ ions bind to the _________ of the thin filaments, causing a shape change that
removes ______________ from the myosin- binding sites of __________
3. ____________ – the ________ ______ theory of muscle contraction describes how
thin filaments slide over thick filaments to cause muscle contration
a. ATP bound to myosin heads is hydrolyzed to _____ + ____, “cocking” the heads
into an extended, high energy position
b. Energized myosin heads bind to exposed myosin-binding sites on ________,
forming _______-__________
c. ________ stroke - myosin heads release the ADP + Pi and ______ into a bent, low
energy position, pulling the _______ filaments toward the center of the sarcomere
d. _____________ stroke – _____binds to myosin heads, which causes the myosin to
_____________ from the actin
4. ______________ – muscle fiber relaxes and returns to its resting length
a. Nerve impulses cease, and ____ is no longer released by the synaptic bulb
b. ACh separates from motor end plate _____________, and is broken down by
_______, which ends muscle stimulation
c. ____ ions separate from troponin and are actively transported from the cytosol back
into the SR terminal _____________
d. _________________ returns to its position blocking myosin-binding sites on actin
B. ___________ (muscle tone) - the normal state of skeletal muscle, in which a muscle rests
in a state of ____________ contraction.
1. Keeps the muscle ready to _________ to a stimulus
2. Helps to maintain ___________
3. Aids the return of _________ to the heart
VII. Behavior of Whole Muscles
A. Threshold, Latent Period, & Twitch
1. _________ is the minimum voltage required to produce a muscle contraction; lower
voltages do not cause muscle contraction
2. A ________ is one cycle of muscle contraction and relaxation
3. The minute time between the stimulus and the twitch is the _________ period (about 2
millisec)
4. For a few millisec after contraction, the muscle cannot contract again, no matter how
much stimulus is received, this is the ____________ period
5
B. Contraction _________ of Twitches is achieved by three methods: optimal sarcomere
length, recruitment of motor units, and high frequency stimulation
1. The tension of a muscle twitch is determined by the length of individual sarcomeres
a. Each sarcomere will contract with optimum force if the __________ and ________
are at optimum length before contraction
b. ____________ exercises before strenuous activity help sarcomeres to be at optimal
length, and prevent muscle tears
2. __________ (multiple motor unit summation)– as more strength is needed, more
neurons “fire,” activating more motor _______
3. High _______________ stimulation
a. Less than 10 stimuli/sec allows muscle to fully recover between stimuli, generates
________ muscle tension
b. 10-20 stimuli/sec causes each twitch to develop more tension than the twitch before it
(the staircase phenomenon = _______)
c. 20-40 stimuli/sec allows twitchs to “piggyback” on each other, generating higher
tension (________ ____________), produces sustained partial contraction called
incomplete __________
d. At 40-50 stimuli/sec, the muscle does not relax between stimuli, so twitches blend
into a smooth, prolonged contraction called __________ _____________ (not the
same as lockjaw tetanus)
C. Isometric & Isotonic Contraction
1. _____________ contraction involves an increase muscle _________ without a change
in muscle length; no external muscle movement occurs
2. ____________ contraction is a decrease in muscle ___________ without a change in
muscle tension; muscle tension overcomes external resistance and moves
3. Isometric and isotonic are ______ involved in normal muscle contraction
VIII. Muscle Metabolism
A. ATP Sources – two main pathways of ____ synthesis are anaerobic fermentation and
aerobic respiration
1. _____________ fermentation occurs when a cell metabolizes glucose the absence of
______________; __________ acid and ____ ATP are generated
a. Advantage – allows the cell to produce ATP without ________
b. Disadvantage – produces _______ acid, a toxic product that contributes to muscle
fatigue, and depletes glycogen in the liver
2. __________ respiration occurs mostly in the mitochondria in the presence of ______;
glucose is broken down and its energy is used to regenerate about ____ ATP
molecules. Waste products are CO2 and H2O.
a. Advantage – produces more _____ and less toxic by-products
b. Disadvantage – requires continuous _________ supply
3. Immediate Energy for short (15 sec), intense exercise is provided by two enzyme
systems
a. ______________ - transfers Pi groups from one ADP to another, forming ATP
6
b. __________ kinase obtains Pi from creatine phosphate and donates it to ADP,
forming ATP (and creatine)
4. Short-term Energy – after the immediate energy is exhausted, for the next minute or
so, _________ from the blood and __________ stored in muscles is used to produce
ATP (_____________)
5. Long-term Energy – in the next minute, the respiratory and cardiovascular systems
“catch up” and deliver oxygen to the muscles for ______________ respiration
B. Oxygen _______ is the difference between the resting rate of oxygen consumption and the
elevated rate following strenuous exercise
1. At rest or ___________ activity, the respiratory and circulatory systems can supply the
muscles with enough _______________ for aerobic respiration
2. With ___________ exercise, there is not enough oxygen for aerobic respiration, so the
muscle uses ______________ respiration for energy
3. Extra _____________ consumed after strenous exercise is used to
a. Replenish the body’s oxygen reserves in ______globin and ________globin
b. Oxidize _______ acid to pyruvic acid, then to ___________ in the liver, where it is
stored as ______________
C. Muscle ____________ – progressive weakness and loss of muscle contractility with use.
Causes include:
1. ______________ in muscles and liver declines
2. _____ synthesis declines
3. Accumulating ________ acid lowers the sarcoplasm ___, inhibiting ___________
involved in contraction, ATP synthesis, etc.
4. Motor nerves deplete their _____
D. Muscle _______ – muscle contraction without relaxation, due to lack of _____, which is
needed to:
1. Actively transport _____ back into the SR after contraction
2. Detach _________ heads from actin after contraction
E. Types of Skeletal Muscle Fibers
1.
Red _______-twitch (slow ______________) fibers (dark meat)
a.
b.
c.
d.
2.
Look red due to abundant ___________, the oxygen storing protein in muscle
Have many capillaries and a large number of mitochondria for ______ respiration
Fibers contract ________ and are resistant to fatigue as long as oxygen is present
Abundant in lower ______ muscles that contract continuously to maintain posture
White _______-twitch (fast _______________) fibers (white meat)
a.
b.
c.
d.
Look pale due to less ______________
Are about twice the ___________ of red fibers
Contain more _________________ and generate more power, but fatigue quickly
Have fewer __________ & capillaries but many glycogen containing glycosomes
7
e.
f.
3.
_______________ respiration is their main energy source
Common in upper _________ muscles that lift heavy objects briefly
___________________ fast-twitch (fast oxidative) fibers
a.
b.
c.
Have diameters, power, and fatigue resistance ___________ red & white fibers
d.
Abundant in lower ________ muscles for walking
Contract ____________ like white fibers
Like red fibers, are oxygen dependent, have much ________________ and many
capillaries
4.
Muscles contain a mixture of the ___ muscle types, so they can do different things at
different times
5.
The proportion of red to white to intermediate fibers one has is believed to be
______________ determined
V. Cardiac Muscle
A. Cardiac muscle tissue is found in the heart wall (______________)
B. The cells are involuntary, ____________, single uninucleate cells, not voluntary fused
multinucleate cells like skeletal muscle cells
C. A cardiac muscle _________ is a long row of joined cardiac muscle cells
D. Cardiac muscle contracts via the sliding _______ mechanism, similar to skeletal muscle
E. Cardiac cells branch and join together at complex junctions, called _______________
discs, which are composed of
1.
2.
______________ and fascia adherans that hold the cells together
______ junctions that allow ions to pass from cell to cell to synchronize muscle
contractions
F. Not all cardiac muscle cells are innervated; they can contract rhythmically without
innervation (_________________)
VI. Smooth Muscle
A. Smooth muscle cells are small, single, ___________ shaped, and unstriated, with a single
centrally located nucleus
1. Thick and thin filaments form spiral bundles (___________) within the cell, but no
visible striations and no sarcomeres
2. ________________ is present, but not troponin, instead another Ca2+ binding protein
called ______________ is present
3. No Z-disks are present, thin filaments are attached to the cytoskeleton via protein
___________ ____________ on the inner sarcolemma
4. Noncontractile _____________ filaments form a cytoskeletal matrix that supports the
contractile filaments
5. Sarcoplasmic ________________ is sparse and there are no T-tubules
8
6. Ca2+ to activate muscle contraction comes from ______________ fluid through Ca2+
channels in the sarcolemma
7. Not all smooth muscle is innervated, when nerves are present, they are ____________,
not somatic motor fibers
B. Two types of smooth muscle are multiunit and single-unit smooth muscle
1. ____________ SM is found in large arteries, bronchi, arrector pili muscles, and the iris
a. Though ________________, innervation is similar to skeletal muscle
b. Terminal branches of a nerve fiber synapse with individual myocytes to form a
_________ unit
c. Each motor unit contracts ______________
2. ___________-unit (_________) SM is found in most blood vessels, and the digestive,
respiratory, urinary, and reproductive tracts
a. Usually forms an inner __________ and outer ______________ layer in walls of
hollow viscera
b. Myocytes are joined by _____ junctions that allow ions to flow freely from cell to
cell, thus many cells contract as a unit
C. Stimulation of Smooth Muscle (SM)
1. SM can contract without ________ stimuli
2. Some SM contracts in response to _________, CO2, low pH, O2 deficiency, and stretch
3. Single-unit SM in the GI tract has ___________ cells that set off wavelike contractions
through the muscle layer (______________)
4. SM is innervated by _________ nerve fibers that can trigger or modify its contractions
5. SM cells don’t have motor end plates, they have ____________ junctions
a. Their _____________ sites are scattered across their surface
b. One nerve fiber with beadlike ______________ passes along many muscle cells
and stimulates all of them at once
D. Contraction & Relaxation of Smooth Muscle
1. SM contraction is similar to _____________ muscle in that:
a. Actin and myosin interact by a sliding _______________ mechanism
b. Rise in ______ level triggers contraction
c. ______ energizes the sliding process
2. SM contraction ____________ in that:
a. Ca2+ can diffuse through the cell _____________ to initiate contraction
b. Ca2+ interacts with components of the __________ filament, namely ___________
and a ___________ enzyme to activate myosin
3. Sequence of SM Contraction Events
a. _____ binds calmodulin
b. ________________ is activated
c. Calmodulin activates the ___________ enzyme
d. The kinase transfers a phosphate from ______ to myosin
e. Myosin interacts with __________ (power & recovery strokes)
f. Relaxation occurs when
1) Intracellular ____ is ‘pumped” out of the myocyte by active transport
2) Myosin is de________________ by myosin phosphatase
9
4. SM contraction is _________ than skeletal muscle, but more sustained and resistant
to fatigue
a. Small blood vessels and visceral organs maintain a degree of sustained contraction
(_________) without fatiguing due to:
1) ____ efficient contraction
2) Lower _________ requirement than skeletal muscle
3) _______ contraction time (30x longer than skeletal mus.)
b. Because SM has low ___________ requirements, it has
1) Few ______________
2) Mostly _______________ ATP pathways
5. Regulation of SM Contraction is ____________ to skeletal mus. in that:
a. Neuro_____________ are released in response to a nerve impulse
b. Neurotransmitters bind to _______________ in the SM sarcolemma
c. _____ is released into the sarcoplasm and triggers contraction
6. SM regulation is ______________ to skeletal mus. in that:
a. Not all neural signals to SM result in _____________
b. Not all activation is due to ________ signals, some SM can contract in response to
___________ & mechanical stimuli
c. SM ____________ motor neurons release two types of neurotransmitters:
1) Acetylcholine (____)
2) _____________________
d. Both neurotransmitters may be either _____________ or _____________, because
there are excitatory and inhibitory ____________ in SM membranes. Examples:
1) ACh __________ smooth muscles in bronchioles
2) Norepinephrine ____________ smooth muscle in bronchioles
3) Norepinephrine ____________ smooth muscle in blood vessels
7. Some ___________ stimuli affect SM Ca2+ levels, causing the myocytes to contract or
relax
a. ______________, such as gastrin from stomach and small intestine, cause SM
contraction
b. Lack of __________ or excess _____ relaxes SM (e.g., in lung bronchioles)
c. Low blood _____ relaxes SM
E. SM Response to ___________
1. Skeletal and cardiac muscle contract _____________ when stretched
2. The SM “_________-relaxation response” is much __________, which allows
a. SM fibers can remain ___________ to accomodate an enlarged lumen (e.g., in the
stomach and urinary bladder)
b. Digestive materials can pass slowly through the intestines via _____________
contractions, allowing time for maximum absorption of nutrients
F. Muscle length and tension changes
1. Organization of _________________ limits the stretch of skeletal muscle
2. Overlapping, __________ arrangement of SM filaments allow them to generate force,
even when stretched
G. Hyperplasia & Hypertrophy in muscle tissue
10
1. All muscle cells experience ______________ (increase in size) in response to stress
2. Most skeletal and cardiac muscle cells do not undergo ____________ (increase in cell
number), but some smooth muscle cells do. Examples:
a. At puberty, ____________ binds to uterine smooth muscle receptors and stimulates
synthesis of more smooth muscle fibers
b. During pregnancy, ________ stimulates uterine hyperplasia to accomodate the fetus
VII. Disorders of Muscle Tissue
A. Muscular ______________
1. A group of _________ muscle destroying diseases that usually appear in childhood
2. Skeletal muscle degenerates and is gradually replaced by _________ and fibrous tissue
3. ___________ muscular dystrophy is the most serious and is inherited as a sex-linked
recessive disease, thus affects more ______ than females. Patients rarely live beyond
age 20
4. ______________ dystrophy is also inherited and can appear at any age; symptoms
include skeletal muscle spasms, muscle weakness, and abnormal __________ rhythm
B. ________________ Pain Syndrome
1. Affects up to ____% of all people 30 - 60 yr. old
2. Pain is caused by tightened bands of muscle fibers that _________ when the skin over
them is touched
3.
4.
Often associated with strained ______________ muscles
Treated with _______________ anti-inflammatory drugs, stretching, and massage
C. Fibro___________
1. Chronic pain syndrome of ______________ cause
2. Symptoms include severe __________skeletal pain, fatigue, sleep abnormalities, and
headache
3.
To be _____________ as fibromyalgia, pain must be present in at least 11 of 18
standardized points on the body
4.
Treatments include anti_______________, exercise, and pain relievers