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Exercise Physiology Chapter 8
Huang-Skeletal Muscle
190
Physiology
Undergraduate 3
03/10/2014

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Term
What are the three types of muscle?
Definition
smooth
cardiac
skeletal
Term
T/F All three types of muscle are striated.
Definition
False
smooth muscle is non-striated
Term
T/F Cardiac and smooth muscle both deal with involuntary movements.
Definition
true
Term
T/F Skeletal muscle is the only muscle that deals with involuntary movements.
Definition
false
deals with voluntary movements
Term
What is the difference between skeletal and cardiac muscle?
Definition
cardiac is striated and involuntary movements
skeletal is striated and voluntary movements
Term
how many skeletal muscle is there?
Definition
over 650
Term
What is the percent of body weight that skeletal muscle accounts for?
Definition
40-50%
Term
what are the three functions of skeletal muscle?
Definition
force production for locomotion and breathing
force production for postural support
heat production during cold stress
Term
what are the two types of muscles that create the muscle actions?
Definition
flexors
extensors
Term
what do flexors do?
Definition
decrease muscle angle
Term
what is the function of extensors?
Definition
increase joint angles
Term
what is the epimysium?
Definition
surrounds the entire muscle
Term
what surrounds the bundles of fibers?
Definition
perimysium
Term
what is the name for the bundles of muscle fibers?
Definition
fascicles
Term
what is the endomysium?
Definition
surrounds individual muscle fibers
Term
what is the sarcolemma?
Definition
muscle cell membrane
Term
T/F the sarcolemma is just on top of the endomysium.
Definition
false
the sarcolemma is just BENEATH the endomysium
Term
what is the sarcoplasm?
Definition
cytoplasm of the muscle cell
fluid matrix of the cell
Term
T/F one muscle has many fascicles->one fascicles has many fibers->i fiber has many myofibrils
Definition
true
Term
Why do you stretch?
Definition
to increase blood flow to speed recovery
Term
what activates satellite cells?
Definition
macrophages
Term
What happens when you break muscle?
Definition
muscle damage
muscle pain
Term
T/F no matter the intensity muscle will suffer damage
Definition
true
Term
T/F when muscle fibers are destroyed they can divide to replace to damaged ones
Definition
false
muscle fibers CANNOT divide to replace damaged ones
Term
What is the marker in muscle that indicates muscle damage?
Definition
creatine kinase
myoglobin
tripoin 1
Term
What is the best marker of muscle damage?
Definition
tripoin 1
Term
How are damaged muscles fixed?
Definition
satellite cells
Term
How do satellite cells work?
Definition
proliferate after injury and form myotubes which fuse to form muscle fibers
Term
Does muscle hypertrophy associate with satellite cells?
Definition
yes
Term
Does muscle atrophy associate with satellite cells?
Definition
yes
Term
What are the immune cells in muscle tissue?
Definition
macrophages
Term
What increases with hypertrophy?
Definition
nuclei
Term
What decreases with age in muscle?
Definition
satellite cells
Term
What is the function of myostatin?
Definition
inhibit functions of satellite cells
Term
by blocking myostatin, can we delay muscle mass loss with age?
Definition
yes
Term
What is the distance between the Z line called?
Definition
sarcomere
Term
what is a sarcomere?
Definition
the distance between the z lines
Term
T/F
muscles->
fasicles->
fibers->
myofibril->
filaments->
Definition
true
Term
What is eccentric exercise?
Definition
lengthening of the muscle
Term
T/F eccentric exercise causes more damage.
Definition
true
Term
During muscle contraction which myofilament moves?
Definition
actin
Term
T/F during muscle contraction actin doesn't move.
Definition
false
myosin doesn't move
Term
In relation to the cross bridges, what happens during muscle contraction?
Definition
increases the number of cross bridges
Term
What is a cross bridge?
Definition
myosin head binding to actin
Term
What myofilament is the A band associated with?
Does it change size during muscle contraction?
Definition
myosin
no
Term
what is the Z line?
Definition
space separating two sarcomeres
Term
what is the M line?
Definition
Term
what is the H zone?
Definition
portion of myosin filament, no overlap with actin
Term
what is the A band?
Definition
the dark region
myosin
Term
what is the I band?
Definition
light region
actin
Term
Which band will change?
Definition
actin
I band
Term
Which band won't change?
Definition
myosin
A band
Term
What is the ratio of myosin to actin in one myofibril?
Definition
1500:3000
Term
describe myosin.
Definition
thick filament
comprises about 60% of muscle protein
1500 myosin filaments in each myofibril
Term
describe actin.
Definition
thin filament
contains troponin and tripomyosin
3000 actin filaments in each myofibril
Term
T/F muscle contraction needs ATP.
Definition
true
Term
what are the contractile proteins?
Definition
actin
myosin
Term
what are the regulatory proteins?
Definition
troponin
tripomyosin
Term
Where do we use ATP?
Definition
myosin head
Term
in relation to muscle damage markers, how long does it take for troponin I to reach peak in blood after exercise?
Definition
6 hours
Term
in relation to muscle damage markers, how long does it take for myoglobin to reach peak in blood after exercise?
Definition
6-8 hours
Term
in relation to muscle damage markers, how long does it take for creatine kinase to reach peak in blood after exercise?
Definition
24 hours
Term
Why is troponin I the most important direct marker of muscle damage?
Definition
comes directly from the muscle
only takes 6 hours after exercise to be detected
Term
What does the SR store?
Definition
calcium
Term
What is the function of the t tubule?
Definition
transmit nerve impulse to induce release of Ca from the SR
Term
what must happen for the muscle to contract?
Definition
depolarization
Term
which of the following can store Ca?
terminal cisternae
SR
t tubule
Definition
terminal cisternae
SR
Term
What is the major site of Ca storage?
Definition
SR
Term
what is the sarcoplasmic reticulum (SR)?
Definition
longitudinal network of channels surrounding myofibril storage sites for Ca
Term
what are the transverse tubules?
Definition
t tubules
extensions of the sarcolemma and run perpendicular through the muscle fiber
PERMIT NERVOUS IMPULSES TO PENETRATE TO MYOFIBRILS
Term
what is another name for the terminal cisternae?
Definition
lateral sac
Term
what is the terminal cisternae?
Definition
enlarged portions of the SR
pass between two terminal cisternae
Term
What does the neuromuscular junction consist of?
Definition
motor unit
neuromuscular joint
motor end plate
neuromuscular cleft
Term
what is the motor unit?
Definition
motor neuron and all the muscle fibers it innervates
Term
what is the neuromuscular joint?
Definition
site where motor neuron meets the muscle fiber
Term
what is the motor end plate?
Definition
pocket formed around motor neuron by sarcolemma
Term
what is the neuromuscular cleft?
Definition
short gap between motor neuron and sarcolemma
Term
What happens in the neuromuscular junction?
Definition
ACh is released from the motor unit and diffuses across the neuromuscular cleft
Term
What happens to the end plate when ACh diffuses across the neuromuscular cleft?
Definition
causes an end-plate potential
Term
what is end-plate potential (EPP)?
Definition
depolarization of muscle fiber
Term
T/F EPPs never exceed threshold.
Definition
false
always exceed threshold
Term
T/F EPSPs are sometimes referred to as mini-EPPs.
Definition
true
Term
What happens if you increase the number of cross bridges?
Definition
increase muscle contraction
Term
What is the sliding filament model mean?
Definition
muscle shortens due to the movement of the actin filament over the myosin filament

formation of cross-bridges between actin and myosin filaments

reduction in the distance between Z lines of the sarcomere
Term
what happens to the H zone during muscle contraction?
Definition
becomes narrow
Term
What happens to the A band during muscle contraction?
Definition
remains unchanges
Term
What happens to the I band during muscle contraction?
Definition
becomes narrow
Term
What happens to the actin filaments when the muscle is fully contracted?
Definition
actin filaments overlap
Term
what happens to the H zone when the muscle is fully contracted?
Definition
disappears
Term
What are the two binding sites on the myosin head?
Definition
ATP
actin
Term
T/F the myosin head is called a cross bridge when is it bound to actin.
Definition
true
Term
What covers the myosin binding site on actin during rest?
Definition
tropomyosin
Term
What are the two heads of myosin for?
Definition
ATP binding site
actin-binding
Term
T/F actin does not have myosin binding site.
Definition
false
actin has a myosin binding site
Term
What is the action of tropomyosin for muscle contraction to occur?
Definition
tropomyosin must be moved away from the myosin-binding site so actin and myosin can interact
Term
How is tropomyosin moved away from the myosin-binding site?
Definition
troponin is activated by the release of Ca
Term
What are the three proteins troponin consists of?
Definition
troponin T
troponin I
troponin C
Term
what is the function of troponin T?
Definition
t for tropomyosin
at the troponin T loosely binds to tropomyosin to prevent it from moving off from actin
Term
what is the function of troponin I?
Definition
i for inhibition
covers the myosin-binding site on actin to inhibit the interaction of actin and myosin at rest
Term
what is the function of troponin C?
Definition
c for calcium
Ca-binding protein
when there is an increase in intracellular Ca, Ca binds to troponin C and causes a change in the troponin complex to allow tropomyosin off the myosin-binding site
Term
what are the sources for ATP for muscle contraction?
Definition
fat, carb, and protein metabolism
Term
how do we use ATP for muscle contraction?
Definition
power stroke produced by P to slide actin over myosin
Term
does relaxation require energy?
where?
Definition
yes, on the myosin head ATP binding site
Term
where does the P come from for the power stroke?
Definition
when the cross bridge is formed P is released from ATP
Term
What is the role of P in muscle contraction?
Definition
causes a conformational change in the myosin head
results in a power stroke
produce the sliding of the thin filament over the thick filament
causing muscle contraction
Term
What happens at rest to keep intracellular Ca low?
Definition
Ca ATPase helps to pump Ca into the SR to keep intracellular Ca low
Term
What are the steps of excitation-contraction coupling?
Definition
1-electrical impuse
2-Ca release
3-bind to troponin C, move tropomyosin
4-ATP binds to myosin ATP binding site
5-ATP needed to pump Ca into SR
6-Ca detaches from troponin C, tropomyosin covers myosin-binding site
Term
What happens in step one of excitation-contraction coupling?
Definition
action potentials in the muscle cell membrane transmitted to t tubule by the spread of local currents
Term
what happens in step two of excitation-contraction coupling?
Definition
depolarization of the t tubules causes Ca channels to open-> Ca is released from the SR into the intracellular fluid of the muscle fiber
Term
what happens in step three of excitation-contraction coupling?
Definition
Ca binds to troponin C-> producing a conformational change in the troponin complex to allow tropomyosin off the myosin-binding site
Term
what happens in step four of excitation-contraction coupling?
Definition
after the myosin head binds to actin to form a cross bridge, P is released from ATP.
P causes a conformational change to the myosin head, which results in the power stroke and sliding the thin over thick filament causing muscle contraction
Term
what happens in step five of excitation-contraction coupling?
Definition
Ca ATPase helps to pump Ca from intracellular fluid into SR to keep the intracellular Ca low
Term
what happens in step six of excitation-contraction coupling?
Definition
after Ca is removed from troponin C, tropomyosin is back to cover myosin-binding sites so that actin and myosin cannot interact
Term
What do we need to pump Ca into the SR?
Definition
otherwise the muscle would be contracted all the time
waste of energy
Term
what is muscle fatigue?
Definition
reduced ability to do work
accumulation of ADP and P because ATP cannot be made
Term
what does it mean when there is a decrease in muscle force production?
Definition
reduced ability to perform work
Term
what are the contributing factors to muscle fatigue during high intensity exercise?
Definition
accumulation of lactate, H, ADP, P, and free radicals
Term
what are the contributing factors to muscle fatigue during long duration exercise?
Definition
accumulation of free radicals
electrolyte imbalance
glycogen depletion
reduced motor drive to muscle from CNS
Term
If you have central fatigue do you have muscle fatigue?
Definition
not always, reduced ACh reduces the muscle contraction because the muscle cannot transmit and impulse
Term
What the the three muscle fiber types?
Definition
type 1
type 2a
type 2x
Term
what is the role of ATPase?
Definition
breakdown ATP
Term
What are the two classifications of muscle fiber types?
Definition
biochemical properties
contractile properties
Term
what are the biochemical properties?
Definition
oxidative capacity=# of capillaries, mitochondria, & myoglobin
type of myosin ATPase=speed of ATP degregation
Term
what are the biochemical properties of type I muscle fibers?
Definition
slow
more mitochondria
more capillaries for increased gas exchange
more myoglobin to carry oxygen to the skeletal muscles
slower speed of ATP degradation
Term
what is another name for type 1 fibers?
Definition
slow-twitch muscle fibers
Term
what is another name for type 2 fibers?
Definition
fast-twitch muscle fibers
Term
how can we measure the number of mitochondria?
Definition
muscle biopsy
Term
what are the contractile properties?
Definition
maximal force production=force per unit of cross sectional area
speed of contraction=myosin ATPase activity
muscle fiber efficiency
Term
what are the biochemical properties of type 2 fibers?
Definition
less mitochondria
less capillaries
less myoglobin
fast speed of ATP degradation
Term
what are the characteristics of type 2x fibers?
Definition
fast-twitch fibers
fast-glycolytic fibers
high myosin ATPase activity
Term
what are the characteristics of type 2a fibers?
Definition
intermediate fibers
fast-oxidative glycolytic fibers
medium-high myosin ATPase activity
Term
what are the characteristics of type 1 fibers?
Definition
slow-twitch fibers
slow-oxidative fibers
low myosin ATPase activity
Term
what fibers are used during intense exercise?
Definition
use more fast glycolysis, more type 2x and type 2a
Term
how are muscle fibers typed?
Definition
muscle biopsy
Term
what is a muscle biopsy?
Definition
small piece of muscle is removed
slides stained to show different fibers
Term
what does the staining mean in a muscle biopsy?
Definition
darkest=type 1
lightest= type 2a
in between= type 2x
Term
what are the factors that effect exercise performance in relation to fast twitch muscle fibers?
Definition
genetics
Term
do fast twitch fibers exert more force than slow twitch?
Definition
yes
Term
T/F maximal force per cross sectional area is 10-20% higher in slow twitch fibers compared to fast fibers.
Definition
false
10-20% higher force in fast fibers (type 2a and 2x) compared to slow fibers
Term
T/F force production is related to the number of myosin cross-bridges in strong binding sites.
Definition
true
Term
why is there a high maximal velocity in type 2x fibers compared to type 1 fibers?
Definition
the myosin ATPase activity
Term
T/F high force means high fatigue.
Definition
true
Term
what does it mean in relation of VO2 when someone has more slow twitch fibers? more fast twitch fibers?
Definition
more slow twitch means greater VO2 max
more fast twitch means lower VO2 max
Term
what are the percentages of fiber types in non athletes?
Definition
~50% slow and 50% fast
Term
Power athletes, sprinters, have more of which fiber?
Definition
more fast fibers
Term
describe type 1 fibers.
# of mitochondria?
resistance to fatigue?
predominant energy system?
ATPase activity?
speed of shortening?
efficiency?
specific tension?
Definition
high
high
aerobic
low
low
high
moderate
Term
describe type 2a fibers.
# of mitochondria?
resistance to fatigue?
predominant energy system?
ATPase activity?
speed of shortening?
efficiency?
specific tension?
Definition
high/moderate
high/moderate
combination
high
high
moderate
high
Term
describe type 2x fibers.
# of mitochondria?
resistance to fatigue?
predominant energy system?
ATPase activity?
speed of shortening?
efficiency?
specific tension?
Definition
low
low
anaerobic
highest
highest
low
high
Term
How can you use a VO2 max test to estimate the fiber types?
Definition
a higher VO2 max most likely indicates more type 1 fibers
a lower VO2 max lost likely indicates more type 2a and 2x fibers
Term
endurance athletes, distance runners, how more of which fibers?
Definition
higher percentage of slow fibers
Term
T/F fiber type is the only variable that determines success in an athletic event.
Definition
false
Term
what is the distribution of fiber types in distance runners?
Definition
70-80:30-20
slow:fast
Term
what is the distribution of fiber types in track sprinters?
Definition
25-30:70-75
slow:fast
Term
what is the distribution of fiber types in non athletes?
Definition
47-53:47-53
Term
can muscle fiber types be altered with training?
Definition
yes, a small percentage
determined by genetics
Term
T/F you can change fiber types from slow to fast.
Definition
false
cannot change fiber types but can make them more oxidative, shifting type 2x to 2a
Term
what exercise can shift fiber types?
Definition
long-endurance exercise training
Term
what are the effects long-endurance exercise training on fiber types?
Definition
shift from type 2x to type 2a
type 2a can be converted to type 1, if training persists
Term
how long do you have to train to change type 2a fibers to type 1 fibers?
Definition
about 4 months
3-4 days a week
Term
how does strength training change skeletal muscles?
Definition
hypertrophy
hyperplasia
Term
what is hypertrophy?
Definition
increase in muscle fiber size
Term
what is hyperplasia?
Definition
increase in muscle fiber number
Term
how dos endurance training change skeletal muscle?
Definition
increase oxidative capacity
Term
T/F age is associated with a loss of muscle mass.
Definition
true
Term
how much muscle mass is lost between ages 25-50?
Definition
10%
Term
how much muscle mass is lost between ages 50-80?
Definition
40%
Term
T/F as age increases fast fiber numbers increase.
Definition
fasle
as age increases fast fibers decrease
Term
T/F even with increase in age, increase in regular exercise training can improve strength and endurance, but cannot completely eliminate muscle mass loss with age.
Definition
true
Term
T/F muscle mass loss with age is linked to lower GH concentration.
Definition
true
Term
What are the two types of muscle action?
Definition
isometric
isotonic
Term
what is isometric muscle action?
Definition
muscle exerts force without changing length
pulling against immoveable object
postural muscles
Term
what is isotonic (dynamic) muscle action?
Definition
concentric=muscle shortens during force production
eccentric=muscle produces more force but length increases
Term
which isotonic muscle action produces more muscle damage?
Definition
eccentric
Term
match muscle action and muscle length:
concentric
eccentric
isometric
with
no change
decreases
increases
Definition
concentric-decreases
eccentric-increases
isometric-no change
Term
explain a muscle twitch.
Definition
contraction as a result of a single stimulus
latent period-5ms
contraction-tension developed-40ms
relaxation-50ms
Term
what are the three parts of a muscle twitch?
Definition
latent period
contraction
relaxation
Term
why is the speed of shortening greater in fast fibers?
Definition
SR releases Ca at a faster rate
higher myosin ATPase activity
Term
what are the three factors that regulate force generation?
Definition
1)types and number of motor units recruited
2)initial muscle length (at time of contraction)
3)nature of the neural stimulation of motor units
Term
what types and number of motor units produce the most force?
Definition
more motor units
fast motor units
Term
what is the ideal length for a skeletal muscle to produce the most force?
Definition
2.0-2.2 nanometers
Term
T/F at the time of contraction,the muscle must be at the ideal length to produce the most force.
Definition
true
Term
T/F an increase in cross bridge formation will increase force.
Definition
true
Term
explain the frequency of stimulation.
Definition
simple twitch: low frequency low force
summation: increasing frequency, increasing force
tetanus: highest frequency, highest force, steady state
Term
T/F at any absolute force, the speed of movement is greater in muscle with higher percent of fast fibers
Definition
true
Term
T/F the maximal velocity of shortening is greatest at greatest force.
Definition
false
the maximal velocity of shortening is greatest at lowest force.
Term
T/F an increase in velocity = increase in force
Definition
false
increase in velocity, does not mean an increase in force
Term
T/F increase in velocity = decrease in force production
Definition
true
Term
what happens after training in relation to force production?
Definition
same work load will generate more velocity
Term
What are the two reasons fast twitch shorten faster?
Definition
Ca release
myosin ATPase activity
Term
T/F fast twitch fibers always produce less force.
Definition
false
more force
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