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HES 403 > Chapter 8: skeletal muscle > Flashcards

Chapter 8: skeletal muscle Flashcards

1
Q

what is a tendon?

A

connective tissue that attaches muscle to bone

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2
Q

what are the three functions of skeletal muscle

A
  1. force generation for locomotion and breathing
  2. force generation for postural support
  3. heat production during clod stress
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3
Q

what is the connective tissue that separates muscles

A

fascia

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4
Q

what are the three layers of fascia in muscles

A
  1. epimysium
  2. perimysium
  3. endomysium
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5
Q

what fascia surrounds the entire muscle

A

epimysium

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6
Q

what fascia surrounds individual bundles of muscle fiber (also called fascicle)

A

perimysium

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7
Q

what fascia surrounds each muscle fiber (cell) within the fascicle?

A

endomysium

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8
Q

what are satellite cells?

A

undifferentiated cells that if stimulated can divide and increase myonuclei amount - helps with muscle growth

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9
Q

what is myonuclear domain

A

ratio of cell volume to nucleus ( want to maintain)

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10
Q

sarcolemma

A

cell membrane surrounding muscle fiber cell

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10
Q

myofibrils

A

contain the contractile proteins (myosin and actin)

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11
Q

what myofibril protein is found in the dark portion (A band)

A

myosin

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12
Q

what myofibril protein in found in the light portion (I band)

A

actin

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13
Q

what is the process to release Ca2+ from sarcoplasmic reticulum

A

alpha motor neuron depolarizies -> causes depolarization of transverse tubules & dihydropyridine -> open Ca2+ channels on terminal cisternae -> release Ca2+ from SR

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14
Q

where motor neuron and muscle cell meet

A

neuromuscular junction

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15
Q

what forms the synpatic cleft

A

sarcolemma

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16
Q

what happens with a nerve impulse reaches the end of the motor nerve?

A

causes release of acetylcholine from synaptic vesicles and travels through synaptic cleft to bind with receptor on motor end plate

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17
Q

what happens after acetylcholine binds to receptor on motor end-plate (muscle side of neuromuscular junction)

A

sodium channels on sarcolemma open which depolarizes the muscle cells and signals it is ready to contract

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18
Q

what is the effect of exercise on the neuromuscular junction

A
  1. increase size of NMJ
  2. increased amount of synaptic vesicles (acetylcholine)
  3. more receptors on postsynaptic membrane
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19
Q

explain cross-bridging

A

myosin (golf club) pulls actin in shortening the z-z distance to generate force

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20
Q

how much can the muscle shorten during a single power stroke

A

1%

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21
Q

what is the purpose of the dihydropyridine receptor?

A

voltage sensor to signal to ryanadine receptor to open Ca2+ channels and release large amount in to cytosol to trigger muscle contraction

22
Q

what does Ca2+ bind to?

23
Q

what contractile protein are troponin and tropomyosin located on

24
what happens to troponin and tropomyosin when Ca2+ is release from SR
Ca2+ binds to troponin that causes a position change in tropomyosin to allow active sites on actin to be uncovered.
25
what breaks the connection between myosin and actin after a power stroke
new ATP attached to myosin to energize it for another power stroke
26
what signals to stop muscular contraction
absence of nerve impulse at neuromuscular junction
27
define muscle fatigue
reduction in muscle power output - decrease in muscle force generation - decrease in shortening velocity
28
what are the metabolites that contribute to muscle fatigue
1. increased phosphate ions 2. lactate ions 3. hydrogen ions 4. free radicals
29
how do metabolites influence calcium release
decrease Ca2+ sensitivity in myofilaments and reduced muscle force production
30
how does phosphate ion and free radical accumulation inhibits muscular contraction
modify myosin to reduce cross-bridging
31
how does H+ ions inhibit contraction
binds to Ca2+ sites on troponin to block it
32
what is the reason for muscular fatigue in moderate or continuous exercise
-free radicals inhibiting myosin cross-bridge - depletion of muscle glycogen
33
what type of exercise are exercise-induced cramps usually associated with?
pronlonged high-intensity
34
what are exercise-induced cramps caused by
spasmodic (irregular) involuntary muscle contraction (nervous system origin)
35
what is the dehydration & electrolyte imbalance theory
electrolyte imbalance in the interstitial space causes an uncontrolled release of acetylcholine causes spasmodic muscle contractions
36
what are three reasons to disprove dehydration & electrolyte imbalance theory
1. dehydration & electrolyte imbalance impacts the whole body yet only exercising muscle is impacted 2. repeated ele. stim of muscle induces cramping 3. static stretching helps cramp
37
what is the altered neuromuscular control theory for muscle cramping
motor neurons excitability is increased from increased excitatory input from muscle spindles and decreased inhibitory input from golgi tendon organ
38
what is the function of the golgi tendon organ
provides information about muscle force generation to CNS
39
what are the muscle fiber types
1. slow twitch (type 1) 2. fast twich (type 2 - with subcategories 2a and 2x)
40
what influences the amount and type of muscle fibers someone has
1. genetics 2. hormone levels 3. exercise habits
41
what are the three biochemical characteristics of muscle
1. oxidative capacity 2, type of myosin isoform 3. abundance of contractile protein
42
what determines the oxidative capacity of a muscle fiber
1. number of mitochondria 2. number of capillaries 3. amount of myoglobin (shuttle for O2 from capillary to mitochondria)
43
what are the four contractile properties of skeletal muscle
1. max force production 2. speed of contraction (Vmax relates to more ATPase activity) 3. max power output (force x shortening velocity) 4. efficiency of contraction (ATP used / force produced)
44
characteristics of slow twitch muscle fibers (type 1)
1. higher oxidative capacity (more mitochondria, capillaries, myoglobin) 2. lower specific force (less actin and myosin present) 3, more efficient ( lower rate of ATP turnovers)
45
fast-twitch (type 2x) characteristics
1. rich in glycolytic enzymes (large anaerobic capacity) 2. specific force similar to 2a both higher than type 1 2. highest ATPase activity = HIGHEST Vmax 3. least efficient
46
characteristics of type 2a muscle fiber type ("intermediate fiber")
thought to be an in-between of type 1 and 2
47
what are three facts relating to fiber types and performance
1. no sex difference in fiber distribution 2. average sedentary individual have 50% slow fibers 3. power athletes have more fast fibers and endurance have slow fibers
48
what are the factors in force regulation in a muscle
1. number and type of motor units 2. initial length of muscle 3. nature of neural stimulation of motor units 4. contractile history of muscle
49
number and type of motor units recruited explained
1. motor units recruited based on size 2. fast fibers have greater specific force than slow fibers
50
describe the nature of neural stimulation
frequency of neural stimulation chances the force produced - no time to relax = summation - if taken further the contractions will blend together and make tetanus (which will continue till stimulus stops or muscle fatigues)
51
what type of muscle contraction occur during normal body movements
tetanic - some motor units are contracting while others are relaxing resulting in smooth contraction that aides in sustaining coordinated muscle
52
prior contractile activity of muscle
1. if already performed fatiguing exercise the force production will be decreased 2. can increase force through PAP (postactivation potentiation) causes phosphorylation and increases muscle sensitivity to Ca2+

HES 403 (5 decks)

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