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282 Cards in this Set

  • Front
  • Back
Which muscle have the largest mitochondria
Cardiac muscles have the largest
Exposure to clostridium tetani causes continuous release of ACh, what is the effect on smooth muscle
The continuous release of ACh has no effect of this muscle after the introduction of Clostridium Tetani
Competitive weight lifters work to increase the
average number of myofibrils/muscle fibers
In treppe, twitches become progressively ________ because
Twitches become progressively stronger calcium accumulates in the sarcoplasm faster than the sarcoplasmic reticulum can reabsorb it
Sarcolemma of a resting muscle fiber is most permeable to
potassium
Why does cardiac muscle have very little capacity for regenerating
Because it lacks satellite discs
When does skeletal muscle generate the greatest tension?
Skeletal muscle generates the greatest tension when it is partially stretched before being stimulated
What is the function of creatine kinase?
It catalyzes transfer from phosphate from CP to ADP
Deficiency in ACh receptors leads to
muscle paralysis in myasthenia gravis
What is incomplete tetanus?
Incomplete tetanus is if one nerve stimulus arrives at a muscle fiber so soon that the fiber has only partially relaxed from the previous twitch
What is an isotonic contraction?
Shortening of a muscle while maintaining constant tension
In a relaxed muscle fiber, the active sites of the actin are blocked by _______
Tropomyosin
What is the purpose of a triad?
A triad allows for calcium release when the muscle is excited
One somatic neuron is stimulated by ____ muscle fibers?
One somatic neuron is stimulated by zero muscle fibers
A myofilament that connects a thick filament and anchors it into a z disc called an ______ _______
elastic filament
Skeletal muscles depend solely on
the sarcoplasmic reticulum and its calcium source
Smooth muscle contracts and relaxes _____ ______ than skeletal muscle
more slowly
Varicosities release
norepinephrine
What would happen if ACh was inhibited at the synapse?
Tetanus
Collagen is
elastic
What is the smooth ER of a muscle fiber?
Sarcoplasmic reticulum
What are intercalated discs of cardiac muscle?
Numerous gap junctions in muscular tissue
What makes a triad?
two terminal cisternau and one t-tubule make a
The deltoid muscle is
extrinsic
Calcium channel blockers
prevent calcium from entering the smooth muscle, allowing smooth muscle to relax

as a result, blood pressure decreases because the arteries vasodilate
During an isometric contraction, what happens to muscle length?
The muscle length does not change.
The minimum stimulus needed to cause muscle contraction is called
the threshold
The contraction strength of smooth muscle is relatively independent of its resting length partly because
it does not have Z discs.
Muscle fibers are arranged in bundles called
fascicles
Loss of muscle mass from lack of activity is termed
atrophy
Release of ACh
increases permeability of the sarcolemma.
Which muscle(s) can contract without the need for nervous stimulation?
cardiac and smooth muscles can contract without the need for nervous stimulation
Which of the following would be caused by contraction of smooth muscle?
goose bumps
The protein that acts as a calcium receptor in skeletal muscle is
troponin
Where are single-unit smooth muscles found?
most blood vessels and viscera as circular and longitudinal muscles
Periosteum is
NOT a muscle tissue
The ability of the muscle cell to stretch under tension is known as
extensibility
T-tubules are extensions of the _____ in skeletal muscle.
sarcolemma (plasma membrane)
One motor neuron can stimulate up to _____ muscle fiber(s).
1000
Fatigue can be caused by all of the following except

Low acetylcholine supplies
pH imbalance
Excess of myoglobin
Excess of lactic acid
Reduced ATP concentration
excess myoglobin

Myoglobin supplies oxygen for a limited amount of aerobic respiration at onset; it is rapidly depleted
What are the contractile proteins?
Actin
Myosin
Muscle fibers are grouped in bundles called fascicles by which layer of connective tissue?
perimysium
A brief activity using maximum muscular effort (weight-lifting) is fueled best by the
glycogen-lactic acid system (anaerobic)
Smooth muscles lack..
T-tubules
What is the major purpose of the muscular system?
Converting the chemical energy in ATP into the mechanical energy of motion
This connective tissue of the muscle separates neighboring muscles or muscle groups from each other and the subcutaneous tissue

This tissue is made of dense regular connective tissue
Fascia
This layer of connective tissue of muscle forms a fibrous sheath around the entire muscle, is made of denser regular connective tissue
Epimysium; its outer surface grades into the fascia
This layer of connective tissue surround fascicles (bundles of muscle fibers), and carry larger nerves and blood vessels and stretch receptors
Perimysium
This layer of connective tissue of muscle is a thin sleeve of loose connective tissue that surrounds each muscle fiber (cell)
it allows room for capillaries and nerve fibers to reach each muscle fiber
Endomysium
List the layers of connective tissue of muscle from superficial to deep
Fascia
Epimysium
Perimysium
Endomysium
Deep Fascia are found between
adjacent muscles
Superficial fascia, AKA _________ are found between ________________________ and contain _________________
between skin and muscles and contain adipose tissue
Characteristics of tendons
Attachments between muscle and bone
Dense-regular connective tissue composed of collagen fibers
The epimysium surrounding the entire muscle is continuous with collagen fibers of tendons
Which in turn, are continuous with connective tissue (periosteum) of bone
Collagen is somewhat
extensible and elastic
Characteristics of collagen
Collagen stretches slightly under tension and recoils when released
-resists excessive stretching and protects muscle from injury
-returns muscle to its resting length
-contribute to power output and muscle efficiency
What determines the strength of a muscle and the direction of its pull?
Shape and orientation of its fascicles
Fusiform muscles are
thick in the middle and tapered at the ends
Triangular (convergent) muscles are
broad at origin and tapering to a narrower insertion
Parallel muscles have ______ fascicles and ______________________________
parallel fascicles; can span longer distances than other shapes
Circular muscles
are skeletal muscles that act as sphincters, and ring around the body opening
Pennate muscles
fascicles insert obliquely on a tendon (feather shaped)
Tendons attach _____ to ______
muscle to bone
Aponeurosis
tendon is a broad, flat sheet
Which skeletal muscles do not insert on bone, but in dermis of the skin
muscles of facial expression
This type of muscle modifies the direction of movement, stabilizes the nearby joints and aids the prime mover
synergist
This type of muscle prevents excessive movement and injury, relaxes to give the prime mover control over an action
antagonist- also opposes the prime mover
This type of muscle prevents movement of bone
fixator
Intrinsic muscles
contained within a region, both of its origin and insertion are in the same region (phalanges)
Extrinsic muscles
act on a designated region but have orgins elsewhere
Responsiveness (exciteability)
to chemical signals, stretch and electrical changes across the plasma membrane
Conductivity
local electrical change triggers a wave of excitation that travels along the muscle fiber
Contractility
shortens when stimulated
Extensibility
capable of being stretched between contractions
Elasticity
returns to its original resting length after being stretched
This muscles is

voluntary
striated
and attached to one or more bones
Skeletal muscle
What are striations a result of?
Overlapping of internal contractile proteins
What is a skeletal muscle made of
muscle cells, called muscle fibers or myofibers
How long are muscle fibers or myofibers of a skeletal muscle?
30 cm long
Myofibers are muscle cells composed of _________ which are composed of _________
myofibrils; myofilaments
Myofibrils are
long protein bundles that occupies the main portion of the interior of a muscle fiber.

They make up myofibers

Myofibrils are composed of myofilaments
Myofilaments make up ______ which make up __________; they are
myofibrils which make up myofibers; they are a protein microfilament responsible for muscle cell contraction
Myofilaments are composed of ______ or ______ proteins
myosin or actin proteins
Sarcolemma
plasma membrane of a muscle fiber
Sarcoplasma
cytoplasm of a muscle fiber
Mitochondria
packed in spaces between myofibrils
Terminal Cisternae
dilated end-sacs of SR which cross muscle fiber from one side to the other- store calcium
T tubule
tubular infoldings of the sarcolemma which penetrate through the cell and emerge on the other side
What are the two internal proteins of myofibers?
Glycogen and Myoglobin
Glycogen, an internal protein of myofibers, are
stored in abundance to provide energy with heightened exercise
Myoglobin, an internal protein of myofibers, are
red pigment that stores oxygen needed for muscle activity
Glycogen and myoglobin are long protein bundles that occupy the main portion of the sarcoplasm, AKA ______ that make up ______
internal proteins that make up myofibers
How do myofibers repair?
by fibrosis rather than regeneration of functional muscle
Myofibers are made up of multiple nuclei that are pressed against the inside of the sarcolemma, as well as stem cells that fuse to form each muscle fiber called ______ and unspecializd myoblasts remaining between the muscle fiber and endomysium called _________ ________
myoblasts are stem cells that fuse to form each muscle fiber

satellite cells are unspecialized myoblasts remaining between the muscle fiber and endomysium
The three kinds of myofilaments found in a myofibril are called
Thin, thick and elastic filaments
These are stem cells that fuse to form each muscle fiber
Myoblasts
These are unspecialized myoblasts remaining between the muscle fiber and endomysium
Satellite cells
Thin filaments are found in myofibrils that are made of
myosin protein
Thick filaments are found in myofibrils that are made of
primarily actin proteins
Elastic filaments are found in myofibrils that are made of
titin (connectin) proteins
Thick myofilaments are made of several hundred _________ molecules. Their heads are directed ______ in a helical array around the bundle.
myosin; outward
Thin myofilaments are made of three things:
Fibrous (F) actin
Tropomyosin
and
Troponin complex
Fibrous (F) actin, found in ______ ______, are
found in thin myofilaments, are two intertwined strands, a string of globular (G) actin subunits each with an active site that can bind to head of myosin molecule
Tropomyosin, found in ____ _____________,
thin myofilaments, each block 6 or 7 active sites on G actin subunits
The troponin complex of ______ ________ are
thin myofilaments, are small, calcium-binding proteins on each tropomyosin molecule
Elastic Myofilaments are made of _______ (______)
titin (connectin)
titin (connectin) make up _____ ________ and are characterized as
elastic myofilaments and are characterized by huge springy protein, they flank each thick filament and anchor it to the Z disc, help the cell recoil to its resting length (elastiity), keep thick and thin filaments aligned (help stabilize the thick filament and center it between the thin filaments), and prevent overstretching
The regulatory proteins, _____ and ______, act
tropomyosin and troponin, act like a switch that states and stops contraction
How i contraction activated?
By the release of calcium into sarcoplasm and its binding to troponin
What happens after calcium enters the sarcoplasm and binds to troponin?
Troponin changes shape and moves tropomyosin off the active sites on actin
What are the function of accessory proteins
Accessory proteins of thick and thin filaments act to anchor the myofilaments, regulate length of myofilaments, and align myofilaments for optimal effectiveness
What is the most clinically important accessory protein? What is its function?
Dystrophin – most clinically important
links actin in outermost myofilaments to transmembrane proteins and eventually to fibrous endomysium surrounding the entire muscle cell
transfers forces of muscle contraction to connective tissue around myofiber
genetic defects in dystrophin produce disabling disease muscular dystrophy
Group of hereditary diseases in which skeletal muscles degenerate & are replaced with scar tissue and adipose tissue
Muscular Dystrophy
Fascioscapulohumeral MD is
facial & shoulder muscle only
affects both sexes equally
Myostatin is a protein that limits muscle growth. Some mutations in the gene coding for myostatin can lead to the production of non-functional protein. What would be the phenotypic result of this mutation in a baby?
Baby is abnormally muscular
What is the function of myosin and actin
function in cellular motility, mitosis, transport of intracellular material
A band
– dark – A stands for anisotropic
part of A band where thick and thin filaments overlap is especially dark
H band in the middle of A band – just thick filaments
M is in the middle of the H band
H band
middle of A band- just thick filaments
I band
alternating lighter band-
I= isotropic
Z disc
– provides anchorage for thin filaments and elastic filaments
bisects I band
M is the middle of the
H band
A sarcomere is a
segment of the myofibril from one z disc to the next
functional contractile unit of the muscle fiber
Sarcomere
Muscles shorten when
individual sarcomeres shorten and pull z discs closer to eachother as thick and thin filaments slide past eachother
Segment from Z disc to Z disc
Sarcomere
During muscle contraction, what happens the the thick and thin filaments?
Neither change length during shortening, only the amount of overlap changes
Skeletal muscle must be stimulated by a ______ or it will not contract
nerve
What happens if nerve connections are severed or poisoned, a muscle is _________
paralyzed
Denervation atrophy is
shrinkage of paralyzed muscle when connection not restored
Somatic motor neurons
stimulate skeletal muscle
cell bodies are located in the brainstem and spinal cord
Somatic motor fibers
– axons of somatic motor neurons
lead to the skeletal muscle
each nerve fiber branches out to a number of muscle fibers
200 myofibers on average are controlled by a single somatic motor neuron
each myofiber is supplied by only one motor neuron
one nerve fiber and all the muscle fibers innervated by it is a motor unit
Motor unit=
one nerve fiber and all the muscle fibers innervated by it
Myofibers of one motor unit
dispersed throughout the muscle
contract in unison
produce weak contraction over wide area
provides ability to sustain long-term contraction as motor units take turns contracting
postural control
effective contraction usually requires the contraction of several motor units at once
Average motor unit
200 muscle fibers/neuron
Small motor units
fine degree of control
3-6 muscle fibers per neuron
eye and hand muscles
Where are small motor units found?
Eye and hand muscles
Large motor units have more _______ then _______
strength than control
Large motor units
powerful contractions supplied by large motor units
many muscle fibers per motor unit
gastrocnemius – 1000 myofibers per neuron
Synapse
point where a nerve fiber meets its target cell
Neuromuscular junction (NMJ)
- when target cell is a muscle fiber
each terminal branch of the nerve fiber within the NMJ forms separate synapse with the muscle fiber
one nerve fiber stimulates the muscle fiber at several points within the NMJ
Synaptic knob
swollen end of a nerve fiber
The synaptic knob contains ______ _______ filled with _________
synaptic vesicles filled with acetylcholine (ACh)
Synaptic vesicles undergo _______ releasing ACh into synaptic cleft
exocytosis
Synaptic cleft
- tiny gap between synaptic knob and muscle sarcolemma
Schwann cell
envelops & isolates all of the NMJ from surrounding tissue fluid
How many Ach receptors– proteins are incorporated into muscle cell plasma membrane
50 million
ACh receptors are
junctional folds of sarcolemma
increases surface area holding ACh receptors
The lack of ACh receptors can lead to
paralysis
Basal lamina
thin layer of collagen and glycoprotein separates Schwann cell and entire muscle cell from surrounding tissues

contains acetylcholinesterase (AChE)
What is acetylcholinesterase (AChE)? Where is it found?
breaks down ACh after contraction causing relaxation, found in the basal lamina
cholinesterase inhibitors
bind to acetylcholinesterase and prevent it from degrading ACh
which leads to spastic paralysis - - a state of continual contraction of the muscles
possible suffocation
Tetanus
(lockjaw) is a form of spastic paralysis caused by toxin of Clostridium tetani
glycine (inhibitory neurotransmitter) in the spinal cord normally stops motor neurons from producing unwanted muscle contractions
tetanus toxin blocks glycine release in the spinal cord and causes overstimulation and spastic paralysis of the muscles
tetanus toxin blocks ____________ release in the spinal cord and causes overstimulation and spastic paralysis of the muscles
glycine
Flaccid paralysis
a state in which the muscles are limp and cannot contract
Curare is an example of
flaccid paralysis; curare – plant poison used by South American natives to poison blowgun darts
In __________ _________, compete with ACh for receptor sites, but do not stimulate the muscles
flaccid paralysis
Botulism occurs wen a bacterium releases a neurotoxin that prevent motor neurons from releaseing Ach. Now which of te following is not an effect of botulism flaccid paralysis
Tetany- muscle gets contracted and cant relax
______ ______ and _______ are electrically excitable cells
muscle fibers and neurons
Electrophysiology
- the study of the electrical activity of cells
In an unstimulated (resting) cell
there are more anions (negative ions) on the inside of the plasma membrane than on the outside
the plasma membrane is electrically polarized(charged)
there are excess sodium ions (Na+) in the extracellular fluid (ECF)
there are excess potassium ions (K+) in the intracellular fluid (ICF)
also in the ICF, there are anions such as proteins, nucleic acids, and phosphates that cannot penetrate the plasma membrane
The inside of the plasma membrane is negatively charged by comparison to its outer surface
Voltage (electrical potential)
a difference in electrical charge from one point to another
Resting membrane potential (RMP) of a myofiber is about _____ ____ and is maintained by
90 mV

maintained by sodium-potassium pump
Slide 10
Muscles part 2
4 major phases of contraction and relaxation
Excitation
Excitation- contraction coupling
Contraction
Relaxation
Excitation
the process in which nerve action potentials lead to muscle action potentials
Excitation-contraction coupling
events that link the action potentials on the sarcolemma to activation of the myofilaments, thereby preparing them to contract
Contraction
step in which the muscle fiber develops tension and may shorten
Relaxation
when its work is done, a muscle fiber relaxes and returns to its resting length
Excitation (steps 1 and 2)
Nerve signal opens voltage-gated calcium channels in synaptic knob
Calcium stimulates exocytosis of ACh from synaptic vesicles
ACh released into synaptic cleft
Excitation (steps 3 and 4)
2 ACh molecules bind to each receptor protein, opening Na+ and K+ channels.
Na+ enters shifting RMP goes from -90mV to +75mV, then K+ exits and RMP returns to -90mV
quick voltage shift is called an end-plate potential (EPP)
Excitation (step 5)
Voltage change (EPP) in end-plate region opens nearby voltage-gated channels producing an action potential that spreads over muscle surface
Excitation-Contraction Coupling (steps 6 and 7)
Action potential spreads down into T tubules
Opens voltage-gated ion channels in T tubules and Ca+2 channels in SR
Ca+2 enters the cytosol
Excitation-Contraction Coupling (steps 8 and 9)
Calcium binds to troponin in thin filaments
Troponin-tropomyosin complex changes shape and exposes active sites on actin
Contraction (steps 10 and 11)
Myosin ATPase enzyme in myosin head hydrolyzes an ATP molecule

Activates the head “cocking” it in an extended position
ADP + Pi remain attached

Head binds to actin active site forming a myosin - actin cross-bridge
Contraction (steps 12 and 13)
Myosin head releases ADP and Pi, flexes pulling thin filament past thick - power stroke

Upon binding more ATP, myosin releases actin and process is repeated
each head performs 5 power strokes per second
each stroke utilizes one molecule of ATP
Relaxation (steps 14 and 15)
Nerve stimulation & ACh release stop
AChE breaks down ACh & fragments reabsorbed into synaptic knob
Stimulation by ACh stops
Relaxation (step 16)
Ca+2 pumped back into SR by active transport. Ca+2 binds to calsequestrin while in storage in SR
ATP is needed for muscle relaxation as well as muscle contraction
Relaxation (steps 17 and 18)
Ca+2 removed from troponin is pumped back into SR

Tropomyosin reblocks the active sites

Muscle fiber ceases to produce or maintain tension

Muscle fiber returns to its resting length
due to recoil of elastic components & contraction of antagonistic muscles
Rigor Mortis
hardening of muscles and stiffening of body beginning 3 to 4 hours after death
deteriorating sarcoplasmic reticulum releases Ca+2
deteriorating sarcolemma allows Ca+2 to enter cytosol
Ca+2 activates myosin-actin cross-bridging
muscle contracts, but can not relax
Rigor mortis peaks about ____ hours after death, then diminishes over the next ____ to ____ hours
12; 48-60 hours
What causes no contraction
If signal doesn’t go down neuron
If Ach not present or not released
If Ach cant bind to receptors
If SR doesn’t release Calcium
Length-Tension Relationship
the amount of tension generated by a muscle and the force of contraction depends on how stretched or contracted it was before it was stimulated
Overly contracted
contracted at rest, a weak contraction results
thick filaments too close to Z discs and can’t slide
Too stretched
before stimulated, a weak contraction results
little overlap of thin and thick does not allow for many cross bridges to form
Optimum resting length
produces greatest force when muscle contracts



CNS continually monitors & adjusts length of the resting muscle
maintains a state of partial contraction – muscle tone (tonus)
maintains optimum length and makes the muscles ideally ready for action
Myogram
chart of timing & strength of a muscle contraction
A weak, subthreshold, electrical stimulus causes
no contraction
Threshold
the minimum voltage necessary to generate an action potential in the muscle fiber and produce a contraction
Twitch
a quick cycle of contraction when stimulus is at threshold or higher
Phases of a twitch contraction
latent period
contraction phase
relaxation phase
Latent period
2 msec delay between the onset of stimulus and onset of twitch response
time required for excitation, excitation-contraction coupling and tensing of elastic components of the muscle
internal tension
– force generated during latent period and no shortening of the muscle occurs
Contraction phase
phase in which filaments slide and the muscle shortens


once elastic components are taut, muscle begins to produce external tension – in muscle that moves a load
short-lived phase
Relaxation
last phase of twitch contraction


SR quickly reabsorbs Ca+2, myosin releases the thin filaments and tension declines
muscle returns to resting length
entire twitch lasts from 7 to 100 msec
Subthreshold stimulus
– no contraction at all
Threshold intensity and above
a twitch is produced
twitches caused by increased voltage are no stronger than those at threshold
Muscle Tissue Part 2
Slides 30-36
Myoglobin
supplies oxygen for a limited amount of aerobic respiration at onset
rapidly depleted
Muscles meet most of ATP demand by borrowing ______________ from other molecules and transferring them to ___
phosphate groups; ADP
2 enzyme systems control these phosphate transfers
myokinase
creatinekinase
myokinase
transfers Pi from one ADP to another converting the latter to ATP
creatinekinase
obtains Pi from a phosphate-storage molecule creatine phosphate (CP)
fast-acting system that helps maintain the ATP level while other ATP-generating mechanisms are being activated
Posphagen system
ATP and CP collectively
provides nearly all energy used for short bursts of intense activity
one minute of brisk walking
6 seconds of sprinting or fast swimming
important in activities requiring brief but maximum effort
football, baseball, and weight lifting
As the posphagen system is exhausted..

Muscles shift to ___________ ________________
anaerobic fermentation
During anaerobic fermentation
muscles obtain glucose from blood and their own stored glycogen
in the absence of oxygen, glycolysis can generate a net gain of 2 ATP for every glucose molecule consumed
converts glucose to lactic acid
Glycogen-lactic acid system
the pathway from glycogen to lactic acid
produces enough ATP for 30 – 40 seconds of maximum activity
After ~40 sec
the respiratory and cardiovascular systems “catch up” and deliver oxygen to the muscles fast enough for aerobic respiration to meet most of the ATP demands
During aerobic respiration
___ to ______ ATP/glucose are produce
36 to 38
During aerobic respiration
efficient means of meeting the ATP demands of prolonged exercise
one’s rate of oxygen consumption rises for 3 to 4 minutes and levels off to a steady state in which aerobic ATP production keeps pace with demand
little lactic acid accumulates under steady state conditions
depletion of glycogen and blood glucose, together with the loss of fluid and electrolytes through sweating, set limits on endurance and performance
Muscle fatigue
progressive weakness and loss of contractility from prolonged use of the muscles
Causes of muscle fatigue
ATP synthesis declines as glycogen is consumed
ATP shortage slows down the Na+ - K + pumps
compromises their ability to maintain the resting membrane potential and excitability of the muscle fibers
Lactic acid lowers pH of sarcoplasm
inhibits enzymes involved in contraction, ATP synthesis, and other aspects of muscle function
Release of K+ with each action potential causes the accumulation of extracellular K+
hyperpolarizes the cell and makes the muscle fiber less excitable
Motor nerve fibers use up their ACh
less capable of stimulating muscle fibers – junctional fatigue
Central nervous system fatigues by unknown processes
less signal output to the skeletal muscles
Endurance
the ability to maintain high-intensity exercise for more than 4 to 5 minutes
What determines endurance
determined in large part by one’s maximum O2 uptake(VO2max)
maximum oxygen uptake
the point at which the rate of oxygen consumption reaches a plateau and does not increase further with an added workload
Maximum oxygen uptake characteristics
proportional to body size
peaks at around age 20
usually greater in males than females
can be twice as great in trained endurance athletes as in untrained person
results in twice the ATP production
Oxygen Debt
Heavy breathing continues after strenuous exercise
excess post-exercise oxygen consumption (EPOC)
the difference between the resting rate of oxygen consumption and the elevated rate following exercise
Oxygen Debt is needed
replace oxygen reserves that were depleted in the first minute of exercise

replenishing the phosphagen system


oxidizing lactic acid


serving the elevated metabolic rate
Oral creatine supplement
increases level of creatine phosphate in muscle tissue and increases speed of ATP regeneration


useful in burst type exercises – weight-lifting
Carbohydrate loading
dietary regimen
packs extra glycogen into muscle cells
extra glycogen is hydrophilic and adds 2.7 g water/ g glycogen
some athletes feel sense of heaviness outweighs benefits of extra available glycogen
Fatigue can be caused by all of the following except

Low acetylcholine supplies
pH imbalance
Excess of myoglobin
Excess of lactic acid
Reduced ATP concentration
excess myoglobin
Slow oxidative (SO), slow-twitch, red, or type I fibers
“dark meat”
abundant mitochondria, myoglobin and capillaries - deep red color
adapted for aerobic respiration and fatigue resistance
relative long twitch lasting about 100 msec
soleus of calf and postural muscles of the back
Fast glycolytic (FG), fast-twitch, white, or type II fibers
“white meat”
fibers are well adapted for quick responses, but not for fatigue resistance
rich in enzymes of phosphagen and glycogen-lactic acid systems
generate lactic acid causing fatigue
less mitochondria, myoglobin, and blood capillaries which gives paler appearance
SR releases & reabsorbs Ca+2 quickly so contractions are quicker
(7.5 msec/twitch)
extrinsic eye muscles, gastrocnemius and biceps brachii
You would expect a body-builder to have more _______ muscle fibers than a marathon runner. Slow oxidative fibers Fast glycolytic fibers
Fast- glycolytic fibers
A single muscle has both
FG and SO muscle fibers but differ in ratio
Ratio of different fiber types have
genetic predisposition
gastrocnemius is predominantly
___ for quick movements
FG
soleus is predominantly _____ used for endurance (jogging)
SO
Muscular strength depends primarily on
muscle size
fascicle arrangement
vs
strength
pennate are stronger than parallel, and parallel stronger than circular
Size of motor units

vs strength
larger the motor unit the stronger the contraction
multiple motor unit summation – recruitment

vs strength
when stronger contraction is required, the nervous system activates more motor units
temporal summation
nerve impulses usually arrive at a muscle in a series of closely spaced action potentials
the greater the stimulation frequency, the more strongly a muscle contracts
length – tension relationship
a muscle resting at optimal length is prepared to contract more forcefully than a muscle that is excessively contracted or stretched
Resistance training (weight lifting)
contraction of a muscles against a load that resist movement
a few minutes of resistance exercise a few times a week is enough to stimulate muscle growth
growth is from cellular enlargement
muscle fibers synthesize more myofilaments and myofibrils and grow thicker
Endurance training (aerobic exercise)
improves fatigue resistant muscles
slow twitch fibers produce more mitochondria, glycogen, and acquire a greater density of blood capillaries
improves skeletal strength
increases the red blood cell count and oxygen transport capacity of the blood
enhances the function of the cardiovascular, respiratory, and nervous systems
Required properties of cardiac muscle
contraction with regular rhythm

muscle cells of each chamber must contract in unison

contractions must last long enough to expel blood

must work in sleep or wakefulness, with out fail, and without conscious attention

must be highly resistant to fatigue
Characteristics of cardiac muscle cells
Striated (like skeletal muscle)
Myocytes (cardiocytes or cardiomyocytes) are shorter and thicker

Each myocyte is joined to several others at the uneven, notched linkages – intercalated discs
appear as thick dark lines in stained tissue sections
electrical gap junctions allow each myocyte to directly stimulate its neighbors
mechanical junctions that keep the myocytes from pulling apart

Sarcoplasmic reticulum less developed, but T tubules are larger and admit supplemental Ca2+ from the extracellular fluid

Damaged cardiac muscle cells repair by fibrosis
a little mitosis observed following heart attacks
not in significant amounts to regenerate functional muscle
_________ stimulation
contains a built-in __________ that rhythmically sets off a wave of electrical excitation
wave travels through the muscle and triggers ___________ of heart chambers
___________ – because of its ability to contract rhythmically and independently
Can contract without need for nervous stimulation
contains a built-in pacemaker that rhythmically sets off a wave of electrical excitation
wave travels through the muscle and triggers contraction of heart chambers
autorhythmic – because of its ability to contract rhythmically and independently
Autonomic nervous system (ANS) does send ______fibers to the heart
can increase or decrease heart rate and contraction strength
nerve
Smooth muscle twitches are
Very slow twitches - does not exhibit quick twitches like skeletal muscle
maintains tension for about 200 to 250 msec
gives the heart time to expel blood
Cardiac muscle uses __________ respiration
aerobic respiration almost exclusively


rich in myoglobin and glycogen
has especially large mitochondria
25% of volume of cardiac muscle cell
2% of skeletal muscle cell with smaller mitochondria
Cardiac muscle

Very adaptable with respect to fuel used

Very vulnerable to interruptions of __________ ____________

Highly ________ resistant
Very adaptable with respect to fuel used

Very vulnerable to interruptions of oxygen supply

Highly fatigue resistant
Smooth muscle


Composed of ________ that have a ________ shape
myocytes, fusiform
if injured smooth muscle
Smooth muscle


Capable of mitosis and hyperplasia

regenerates well
Some smooth muscles lack ______ ________, while others receive ________ fibers, not ________ motor fibers as in skeletal muscle
Some smooth muscles lack nerve supply, while others receive autonomic fibers, not somatic motor fibers as in skeletal muscle
________ needed for muscle contraction comes from the _______ by way of ____________ channels in the sarcolemma
calcium; ECF; calcium
Sarcoplasmic reticulum of smooth muscle have no
T tubules
Intermediate filaments in the cytoplasm of smooth muscle provide
mechanical linkages between the thin myofilaments and the plasma membrane
In smooth muscle, Z discs
are absent and replaced by protein plaques well ordered array of protein masses in cytoplasm
dense bodies on the inner face of the plasma membrane
Smooth muscle,
are named smooth muscle because
reason for the name ‘smooth muscle’
thick and thin filaments are present, but not aligned with each other
Multiunit smooth muscle

occurs in
some of the largest arteries and pulmonary air passages, in piloerector muscles of hair follicle, and in the iris of the eye
Multiunit smooth muscle have a autonomic innervation
similar to skeletal muscle
terminal branches of a nerve fiber synapse with individual myocytes and form a motor unit
each motor unit contracts independently of the others
Single-unit smooth muscle
are more widespread, and occur in
most blood vessels, in the digestive, respiratory, urinary, and reproductive tracts – also called visceral muscle
often in two layers
inner circular
outer longitudinal
Single-unit smooth muscle

myocytes of this cell type are electrically coupled to each other by
gap junctions
Single-unit smooth muscle

directly stimulate each other
and a large number of cells contract as a single unit
Smooth muscle is involuntary and can contract without __________ ____________
nervous stimulation
Most smooth muscle is innervated by
autonomic nerve fibers
stimulate smooth muscle with either _______ or _________
stimulate smooth muscle with either acetylcholine or norepinephrine
In single unit smooth, each autonomic nerve fibers has up to 20,000 beadlike swelling called ________________
In single unit smooth, each autonomic nerve fibers has up to 20,000 beadlike swelling called varicosities
Each varicosity of smooth muscle contains
each contains synaptic vesicles and a few mitochondria
nerve fiber passes amid several myocytes and stimulates all of them at once when it releases its neurotransmitter
diffuse junctions – no motor end plates; receptors scattered throughout surface
no one-to-one relationship between nerve fiber and myocyte
Contraction is triggered by
Contraction is triggered by Ca+2, energized by ATP, and achieved by sliding thin past thick filaments
During contraction and relaxation Calcium binds to __________ on thick filaments
Calcium binds to calmodulin on thick filaments
Calcium binds to calmodulin on thick filaments, myosin light-chain kinase is activated
adds phosphate to regulatory protein on myosin head
activates myosin ________ - hydrolyzes ATP
enables myosin similar power and recovery strokes like skeletal muscle
Calcium binds to calmodulin on thick filaments, myosin light-chain kinase is activated
adds phosphate to regulatory protein on myosin head
activates myosin ATPase - hydrolyzes ATP
enables myosin similar power and recovery strokes like skeletal muscle
thick filaments pull on thin ones, thin ones pull on dense bodies and membrane plaques
force is transferred to plasma membrane and entire cell shortens
puckers and twists like someone wringing out a wet towel
Contraction and relaxation of smooth muscle are very different in comparison to skeletal muscle

latent period in skeletal 2 msec, smooth muscle __ - ___ msec
tension peaks at about ___ msec (0.5 sec)
declines over a period of _____-_____seconds
slows myosin ATPase enzyme and slow pumps that remove Ca+2
Ca+2 binds to calmodulin instead of __________
activates kinases and ATPases that hydrolyze ATP
latent period in skeletal 2 msec, smooth muscle 50 - 100 msec
tension peaks at about 500 msec (0.5 sec)
declines over a period of 1 – 2 seconds
slows myosin ATPase enzyme and slow pumps that remove Ca+2
Ca+2 binds to calmodulin instead of troponin
activates kinases and ATPases that hydrolyze ATP
latch-bridge mechanism
latch-bridge mechanism is resistant to fatigue
heads of myosin molecules do not detach from actin immediately
do not consume any more ATP
maintains tetanus tonic contraction (smooth muscle tone)
arteries – vasomotor tone; intestinal tone; bladder tone
makes most of its ATP aerobically
Stretching smooth muscle
can open mechanically-gated calcium channels in the sarcolemma causing contraction
peristalsis
waves of contraction brought about by food distending the esophagus or feces distending the colon
propels contents along the organ
Stress-relaxation response
(receptive relaxation) -helps hollow organs gradually fill (urinary bladder)
when stretched, tissue briefly contracts then relaxes – helps prevent emptying while filling
Skeletal muscle cannot contract forcefully if ________________
Skeletal muscle cannot contract forcefully if overstretched
Smooth muscle contracts forcefully ____________________________ this
allows hollow organs such as the stomach and bladder to fill and then expel their contents efficiently
Smooth muscle contracts forcefully even when greatly stretched
allows hollow organs such as the stomach and bladder to fill and then expel their contents efficiently
Smooth muscle can be anywhere from _________ to __________ its resting length and still contract powerfully
Smooth muscle can be anywhere from half to twice its resting length and still contract powerfully
Smooth muscle can be anywhere from half to twice its resting length and still contract powerfully

3 reasons:
there are no _____ _______, so thick filaments cannot butt against them and stop contraction
since the thick and thin filaments are not arranged in orderly sarcomeres, stretching does not cause a situation where there is too little overlap for cross-bridges to form
the thick filaments of smooth muscle have myosin heads along their entire length, so cross-bridges can form anywhere
Smooth muscle contracts forcefully even when greatly stretched
allows hollow organs such as the stomach and bladder to fill and then expel their contents efficiently

Smooth muscle can be anywhere from half to twice its resting length and still contract powerfully

3 reasons:
there are no z discs, so thick filaments cannot butt against them and stop contraction
since the thick and thin filaments are not arranged in orderly sarcomeres, stretching does not cause a situation where there is too little overlap for cross-bridges to form
the thick filaments of smooth muscle have myosin heads along their entire length, so cross-bridges can form anywhere
plasticity
the ability to adjust its tension to the degree of stretch
a hollow organ such as the bladder can be greatly stretched yet not become flabby when it is empty
Myasthenia GravisAutoimmune disease in which antibodies attack neuromuscular junctions and bind ACh receptors together in clusters
disease mainly of women between 20 and 40
muscle fibers then remove the clusters of receptors from the sarcolemma by endocytosis
fiber becomes less and less sensitive to ACh
effects usually first appear in facial muscles
drooping eyelids and double vision, difficulty swallowing, and weakness of the limbs
Myasthenia Gravis
Strabismus
inability to fixate on the same point with both eyes
Which of the following would NOT occur as a result of living in near zer-gravty conditions?
Bone loss
Cardiac muscle atrophy
Joint luxation
Skeletal muscle atrophy
Joint luxation (dislocation)

- zero gravity does not take much effort for your muscles to do work, they don’t have stress on them, they instead are not being stressed and bone loss results from inactivity, the heart does not work as hard either and the heart muscle weakens
Treatments for myasthenia gravis
cholinesterase inhibitors retard breakdown of ACh allowing it to stimulate the muscle longer
Immunosuppressive agents suppress the production of antibodies that destroy ACh receptors
thymus removal (tymectomy) – helps to dampen the overactive immune response that causes myasthenia gravis
plasmapheresis –technique to remove harmful antibodies from blood plasma
cholinesterase inhibitors
retard breakdown of ACh allowing it to stimulate the muscle longer
Immunosuppressive agents
suppress the production of antibodies that destroy ACh receptors
thymus removal (tymectomy)
helps to dampen the overactive immune response that causes myasthenia gravis
plasmapheresis
technique to remove harmful antibodies from blood plasma
You would expect a body-builder to have more _______ muscle fibers than a marathon runner. Slow oxidative fibers Fast glycolytic fibers
Fast- glycolytic fibers