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A + P II > SKELETAL PT 2 > Flashcards

SKELETAL PT 2 Flashcards

1
Q

describe how muscle fiber type shifts

A

with loading (exercise training), IIX goes down and with unloading (like a space flight or spinal cord injury), IIX amount goes up

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2
Q

why do IIX fibers increase with inactivity

A

because I and IIA use a lot of oxygen, so it’s a lot of work to keep them up

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3
Q

describe aerobic training and muscle fiber type

A

less IIA, more I

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4
Q

describe motor units

A

vary in size; consists of a motor neuron and all muscle fibers they supply

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5
Q

how are muscle fibers dispersed through a muscle

A

muscle fibers from a motor unit spread throughout the whole muscle, so stimulation of a single motor unit causes only weak contraction of muscle

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6
Q

what principle so motor units follow

A

all or none principle

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7
Q

what are the three types of muscle fibers

A

type I (slow), type IIA (fast fatigue-resistant), type IIX (fast fatiguable)

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8
Q

describe type IIX motor fibers

A

fast fatiguable, large motor units with high innervation ratio, fast twitch

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9
Q

describe IIA motor fibers

A

large motor units, more sustained but less dramatic twitch; more fatigue resistant but still fatiguable

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10
Q

describe type I fibers

A

small motor neurons, low innervation ratio, slow twitch and fatigue resistant

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11
Q

what is excitation-contraction coupling

A

process of pairing electrical events (motor neuron AP) to mechanical events (muscle contraction); aka events that occur between excitation and coupling

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12
Q

where does EC coupling occur

A

synapse of junction of motor neuron axon terminal with muscle fiber motor end plate (very excitable region of muscle fiber plasma membrane)

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13
Q

what neurotransmitter is released at neuromuscular junction

A

acetylcholine

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14
Q

describe the first step of EC coupling process

A

have signal that sent do somatic motor neuron,
which is a depolaorizing event

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15
Q

describe the second step in EC process

A

at neuromuscular junction, we release Ach, which binds
to receptors on skeletal muscle membrane, which allows for depolairzation
of skeletal muscle membrane

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16
Q

describe the third step in EC process

A

opening of Na channels, which causes influx of Na which causes depolirzation

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17
Q

describe the fourth step in the EC process

A

depolariization goes down t-tubules; along t-tubules on either side is a bunched up
part of the sarcoplasmic reticulum

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18
Q

describe the 5th step in the EC coupling process

A

ca binds to tropnin, which tells tropomyosin to move from actin

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19
Q

describe the sixth step of EC process

A

myosin can bind to actin and allow for contraction

20
Q

whats the cross bridge

A

binding site of ATP on each molecule

21
Q

what is cross bridge formation triggered by

A

Ca2+ cycle

22
Q

whats the first step in cross bridge formation

A

active site on actin is exposed as Ca binds to troponin

23
Q

whats the second step in cross bridge formation

A

myosin head forms a cross-bridge with actin

24
Q

whats the third step of cross bridge formation

A

during power stroke, myosin head bends and ADP and phosphate are released

25
Q

whats the fourth step in cross bridge formation

A

a new molecule of ATP attaches to the myosin head, causing the cross-bridge to detach

26
Q

whats the fifth step in crossbirdge formation

A

ATP hydrolyzes to ADP and phosphate, which returns myosin to cocked position

27
Q

describe the skeletal muscle length-tension relationship

A

describes the amount of tension that is produced by a muscle as a feature of it’s length

28
Q

what are skeletal muscle satellite cells

A

skeletal muscle stem cells, that are multipotent and give rise to more satellite cells, differtnited skeletal muscle cells, myonuclei

29
Q

how much nuclear material belongs to true myonuclei

A

85 - 95% (i.e. located inside plasma membrane)

30
Q

how much of nuclear material are satellite cells

A

5 - 15%; located between basement membrane and plasma membrane

31
Q

how many nuclei per fiber length do satellite cells have

A

approx. 200 - 300 nuclei per mm of fiber length (contrast to many other cells in our body which are usually single nucleus)

32
Q

why are satellite cells/myonuclei important

A

growth + development of muscle
adaptive capacity of skeletal muscle
recovery from injury or neuromuscular disease

33
Q

where is nuclear material located

A

between myofiber basement and plasma membrane

34
Q

describe satellite cell role in myofiber hypertrophy

A

not completely known; but as fiber grows, there is need for new myonuclei to maintain myonuclear domains

35
Q

whats the myonuclear domain theory

A

every nuclei within the muscle fiber
is responsible for a specific amount
of volume within the cell, so we can only
make muscle grow if we get more nuceli
involved

so satellite cells donate

36
Q

describe the first step in myonuclear donoation

A

untrained muscle fiber

37
Q

describe the second step in myofiber donation

A

training muscle fiber increases in size; each myonuclei is near its domain ceiling

38
Q

describe the third step in myonuclei donation

A

satellite cells fuse to the muscle fiber, donating nuclei

39
Q

describe the fourth step of myofiber / myonuclear donation

A

muscle fiber now has more nuclei; therefore, it’s growth capacity has increased

40
Q

different between the two possible response to fiber stress

A

hypertrophy (fibers grow in size - humans); hyperplasia (fibers grow in number)

41
Q

describe regenerating normall musclle fiber

A

myonuclei + satellite cell

42
Q

describe regenerating damaged muscle fiber

A

activated + proliferating satellite cells

43
Q

describe regenerating repairing muscle fibers

A

muscle precursors cells derive from satellite cells have fused

44
Q

describe generating regenerated muscle fibers

A

with new satellite cell and centrally-placed, newly-generated myonuclei

45
Q

describe the calcium/tropnonin/tropomyosin relationship

A

Ca connects to troponon,
which tells tropomyosin to get off binding sites so myosin can attach

46
Q

where is calcium stored and what happens when that thing is depolarized

A

Ca stores in sarcoplasmic reticulum;
when depolaorized, Ca ion channels open up and let Ca into sarcoplasm which lets
everything happen

47
Q

what are the three parts of the power stroke

A
  • adp and P on myosin = myosin can grab actin
  • adp and P leave myosin, nothing on myosin and can pull in
  • atp on myosin, myosin releases actin

A + P II (31 decks)

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