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PHSL101 > Skeletal Muscle > Flashcards

Skeletal Muscle Flashcards

1
Q

what is the electricity from neurotransmitters (action potentials) called

A

bioelectricity

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2
Q

order of muscle fibres largest to smallest

A

muscle, fascicle, cells (myofibres), myofibrils, myofilaments (actin and myosin)

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3
Q

sarcolemma

A

surrounds each myofibre acting as a barrier and keeping it all together (cell membrane)

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4
Q

sarcomere

A

comprised of filaments, contractile unit

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5
Q

t-tubules

A

extensions of the sarcolemma that dive deep into the muscle

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6
Q

sarcomeres are _____ muscle (not meaning skeletal)

A

striated

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7
Q

is actin thin or thick filament

A

thin

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8
Q

is myosin thin or thick filament

A

thick

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9
Q

when you work at the gym what are you doing to myofibres

A

increasing the size of them (building more sarcomeres inside them) and building more myofibres

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10
Q

a motor unit is comprised of

A

a motor neuron and all the muscle fibres it innervates

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11
Q

where are the somas of the motor neurons

A

in the anterior part of the spinal cord

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12
Q

each axon innervates one or multiple

A

myofibres

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13
Q

ions require ___ and a __ to diffuse across the cell membrane

A

channels, gradient

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14
Q

RMP

A

-70mV, established by the Na+/K+ ATPase pump

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15
Q

cells establish an electrochemical gradient using

A

Na+/K+ ATPase pump which pumps ions against their electrochemical gradient

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16
Q

high Na+ concentration ___ the cell

A

outside

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17
Q

high K+ concentration ___ the cell

A

inside

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18
Q

voltage gated ion channels are ___ when the RMP is -70mV

A

closed

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19
Q

voltage gated Na+ channels open when the voltage is

A

-60mV

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20
Q

voltage gated K+ channels open when the voltage in

A

+30mV

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21
Q

early depolarisation

A

input into the cell causes the threshold to reach -60mV and Na+ enters the cell down its electrochemical gradient

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22
Q

depolarisation

A

Na+ enters the cell until the membrane potential reaches +30mV

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23
Q

repolarisation

A

at +30mV the voltage gated Na+ channels close and the voltage gated K+ channels open. this allows K+ to leave the cell down its electrochemical gradient

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24
Q

hyperpolarisation

A

as K+ leaves the cell, the inside of the cell becomes more negative and when the voltage reaches -40mV the voltage gated K+ channels begin to slowly close. when -80mV is reached the voltage gated K+ channels close

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25
Q

resting membrane potential (after hyperpolarisation)

A

both voltage gated Na+ and K+ channels are closed, the Na+/K+ ATPase pump re-establishes the -70mV RMP

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26
Q

refractory period

A

not able to generate another action potential during this period. the voltage gated Na+ channels are either already open (causing depolarisation) or inactive (during hyperpolarisation)

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27
Q

chemically gated ion channels

A

require neurotransmitter to bind to the receptor for it to be opened

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28
Q

excitatory nuerotransmitter

A

Na+ enters the neuron and brings the membrane potential close to threshold (depolarising)

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29
Q

inhibitory neurotransmitter

A

Na+ leaves neuron, moves the membrane potential further away form threshold (hyper polarising)

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30
Q

cells usually have a combination of ___ and ___ nuerotransmitters

A

excitatory and inhibitory

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31
Q

integration at the axon hillock

A

if the combination of excitatory and inhibitory local potentials reach the threshold an action potential will fire

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32
Q

local potentials use __ gated ion channels

A

chemically

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33
Q

action potentials use __ gated ion channels

A

voltage

34
Q

myelin in the PNS is made by

A

Schwann cells

35
Q

at the synapse, the control goes from __ at the action potential, __ at the neurotransmitter and __ at the next action potential

A

electrical, chemical, electrical

36
Q

depolarisation of axon terminal in synaptic junction causes

A

voltage gated Ca2+ channels to open and Ca2+ enters axon terminal

37
Q

fourth step of output of the synaptic junction, after neurotransmitter diffuses across synaptic cleft

A

neurotransmitter binds to its receptor (chemically gated ion channel) on the post-synaptic membrane

38
Q

fifth step of output in the synaptic junction, after neurotransmitter binds to receptor (chemically gated ion channel)

A

Na+ enters the post-synaptic cell and depolarises it

39
Q

chemically gated ion channels exist in the ___ and cause __

A

dendrites and soma, local potentials

40
Q

voltage gated ion channels exist in the __ and cause ___

A

axon hillock, axon and axon terminals, action potentials

41
Q

what is excitation-contraction coupling

A

excitation, contraction and relaxation of the muscle

42
Q

first step of excitation (NMJ)

A

depolarisation of axon terminal causing voltage gated Ca2+ channels to open and Ca2+ enters axon terminal

43
Q

second step of excitation (NMJ), after Ca2+ enters axon terminal

A

Ca2+ triggers neurotransmitter (ACh) release from vesicles into the synaptic cleft

44
Q

third step of excitation (NMJ), after neurotransmitter release into synaptic cleft

A

ACh diffuses across synaptic cleft

45
Q

fourth step of excitation (NMJ), after ACh diffusion across synaptic cleft

A

ACh binds to ACh-receptor (chemically gated Na+ channel) on the motor end plate of the myofiber

46
Q

fifth step of excitation (NMJ), after ACh binding

A

Na+ enters the myofiber, increasing the membrane potential from -70 to -60 (depolarisation)

47
Q

sixth step of excitation (NMJ), after depolarisation

A

action potential propagates along the sarcolemma of the myofiber

48
Q

what happens after an action potential propagates along the sarcolemma

A

the sarcolemma dives into the t-tubule, action potential is sent here, initiating Ca2+ release from the SR

49
Q

what happens after Ca2+ is released from the SR

A

Ca2+ from the sarcoplasm diffuses to the myofilaments initiating cross bridge cycling, sarcomere shortens and muscle contracts

50
Q

what processes are involved in the relaxation of muscles

A

Ca2+ in the sarcoplasm diffuses away from the myofilaments and the Ca2+ is re-uptaken into the SR, this consumes ATP and stops cross bridge cycling

51
Q

what occurs in the cross bridge formation of the cross bridge cycling process

A

Ca2+ binds to troponin, moving tropomyosin of myosin binding sites (on actin) and myosin binds to actin

52
Q

what happens in the power stroke of cross bridge cycling

A

ADP + Pi dissociates (separates) from myosin and the myosin head flexes (power stroke) sarcomere shortens and tension is developed

53
Q

what processes occur when the cross bridge detaches

A

ATP binds to myosin head causing it to detach from actin

54
Q

what happens for the myosin head to reactivate

A

ATP is hydrolysed into ADP + Pi and the myosin head is ‘recocked’ into an active state

55
Q

length-tension relationship, short

A

overlap between actin and myosin is too much and the myosin cannot effectively move the Z-lines closer together, can’t get any closer, no shortening possible

56
Q

length-tension relationship, wide

A

myosin cannot effectively bind to actin to create cross bridges as they are too far apart

57
Q

length-tension relationship, medium

A

all myosin heads can attach to the actin and can get maximum contraction

58
Q

the amount of tension a muscle can produce is proportional to the

A

frequency of its stimulation

59
Q

a single action potential produces a short duration of contraction

A

twitch

60
Q

as the frequency of action potentials increases the amount of tension produced also increases, this is called

A

summation

61
Q

force produced by a fibre at its maximum, this is called

A

tetanic contraction (tetanus)

62
Q

when is summation created

A

when a fibre is stimulated causing Ca2+ to be released before the remaining Ca2+ is re-uptaken and the fibre can relax, the subsequent contraction develops a higher tension due to the extra Ca2+ present, if this keeps happening the tension will increase consecutively

63
Q

what is incomplete tetanus

A

a muscle fibre producing maximum tension during rapid cycles of contraction and relaxation, still some Ca2+ being removed from sarcoplasm between stimuli

64
Q

what is complete tetanus

A

when relaxation phase is eliminated by higher frequency stimuli, no time for Ca2+ to be removed from sarcoplasm between stimuli

65
Q

what does activation of different motor units in turn (rotating basis) allow

A

recovery of some motor units, maintaining whole muscle tension and preventing muscle fatigue

66
Q

a single twitch will only occur in

A

ocular muscles

67
Q

what is an isometric contraction

A

muscle remains the same length while developing tension

68
Q

what is an isotonic contraction

A

muscle length shortens or lengthens while developing tension

69
Q

what is a concentric contraction

A

muscle length shortens while contracting

70
Q

what is an eccentric contraction

A

muscle length lengthens while contracting

71
Q

what energy source is used in the first 6 seconds of exercise

A

ATP storage

72
Q

what energy source is used between 6-10 seconds of exercise

A

Creatine posphate

73
Q

what energy source is used from 30-40 seconds of exercise

A

Anaerobic

74
Q

what energy source is used for prolonged exercise

A

Aerobic

75
Q

what are the three fibre types

A

fast, intermediate, slow

76
Q

what is the main energy source of fast twitch fibres

A

anaerobic glycolysis

77
Q

what is the energy source of intermediate fibres

A

mixture of aerobic and anaerobic energy sources

78
Q

what is the protein that carries oxygen in muscle cells

A

myoglobin

79
Q

what muscle fibre type has the most myoglobin

A

slow twitch

80
Q

what is the main energy source of slow twitch fibres

A

oxidative phosphorylation

PHSL101 (10 decks)

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