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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?

A

troponin

23
Q

what contractile protein are troponin and tropomyosin located on

A

actin

24
Q

what happens to troponin and tropomyosin when Ca2+ is release from SR

A

Ca2+ binds to troponin that causes a position change in tropomyosin to allow active sites on actin to be uncovered.

25
Q

what breaks the connection between myosin and actin after a power stroke

A

new ATP attached to myosin to energize it for another power stroke

26
Q

what signals to stop muscular contraction

A

absence of nerve impulse at neuromuscular junction

27
Q

define muscle fatigue

A

reduction in muscle power output
- decrease in muscle force generation
- decrease in shortening velocity

28
Q

what are the metabolites that contribute to muscle fatigue

A
  1. increased phosphate ions
  2. lactate ions
  3. hydrogen ions
  4. free radicals
29
Q

how do metabolites influence calcium release

A

decrease Ca2+ sensitivity in myofilaments and reduced muscle force production

30
Q

how does phosphate ion and free radical accumulation inhibits muscular contraction

A

modify myosin to reduce cross-bridging

31
Q

how does H+ ions inhibit contraction

A

binds to Ca2+ sites on troponin to block it

32
Q

what is the reason for muscular fatigue in moderate or continuous exercise

A

-free radicals inhibiting myosin cross-bridge
- depletion of muscle glycogen

33
Q

what type of exercise are exercise-induced cramps usually associated with?

A

pronlonged high-intensity

34
Q

what are exercise-induced cramps caused by

A

spasmodic (irregular) involuntary muscle contraction (nervous system origin)

35
Q

what is the dehydration & electrolyte imbalance theory

A

electrolyte imbalance in the interstitial space causes an uncontrolled release of acetylcholine causes spasmodic muscle contractions

36
Q

what are three reasons to disprove dehydration & electrolyte imbalance theory

A
  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
Q

what is the altered neuromuscular control theory for muscle cramping

A

motor neurons excitability is increased from increased excitatory input from muscle spindles and decreased inhibitory input from golgi tendon organ

38
Q

what is the function of the golgi tendon organ

A

provides information about muscle force generation to CNS

39
Q

what are the muscle fiber types

A
  1. slow twitch (type 1)
  2. fast twich (type 2 - with subcategories 2a and 2x)
40
Q

what influences the amount and type of muscle fibers someone has

A
  1. genetics
  2. hormone levels
  3. exercise habits
41
Q

what are the three biochemical characteristics of muscle

A
  1. oxidative capacity
    2, type of myosin isoform
  2. abundance of contractile protein
42
Q

what determines the oxidative capacity of a muscle fiber

A
  1. number of mitochondria
  2. number of capillaries
  3. amount of myoglobin (shuttle for O2 from capillary to mitochondria)
43
Q

what are the four contractile properties of skeletal muscle

A
  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
Q

characteristics of slow twitch muscle fibers (type 1)

A
  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
Q

fast-twitch (type 2x) characteristics

A
  1. rich in glycolytic enzymes (large anaerobic capacity)
  2. specific force similar to 2a both higher than type 1
  3. highest ATPase activity = HIGHEST Vmax
  4. least efficient
46
Q

characteristics of type 2a muscle fiber type (“intermediate fiber”)

A

thought to be an in-between of type 1 and 2

47
Q

what are three facts relating to fiber types and performance

A
  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
Q

what are the factors in force regulation in a muscle

A
  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
Q

number and type of motor units recruited explained

A
  1. motor units recruited based on size
  2. fast fibers have greater specific force than slow fibers
50
Q

describe the nature of neural stimulation

A

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
Q

what type of muscle contraction occur during normal body movements

A

tetanic - some motor units are contracting while others are relaxing resulting in smooth contraction that aides in sustaining coordinated muscle

52
Q

prior contractile activity of muscle

A
  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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