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2 MSK > Skeletal Muscle Physiology 2 > Flashcards

Skeletal Muscle Physiology 2 Flashcards

1
Q

what two factors does the gradation of skeletal muscle tension depend on

A

Number of muscle fibres contracting

Tension developed by each contracting muscle fibre

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2
Q

how can you achieve a stronger muscle contraction

A

by stimulating more motor units: motor unit recruitment

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3
Q

how is muscle fatigue prevented in sub maximal contractions

A

by asynchronous motor unit recruitment

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4
Q

what factors make up the tension developed by each contracting muscle fibre

A

frequency of stimulation
summation of contractions
length of muscle fibre
thickness of muscle fibre

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5
Q

why does a skeletal muscle twitch

A

the action potential is much shorter than the duration

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6
Q

how can twitches be used to give a stronger contraction

A

summate twitches give repetitive fast stimulation

twitch after twitch after twitch not allowing a break

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7
Q

what is tetanus

A

when the muscle fibre is stimulated so rapidly it is not allowed to rest it leads to a maximal sustained contraction

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8
Q

Cardiac and skeletal muscle can be tetanised true/false

A

false

cardiac muscle has long refractory periods to prevent tetanic contraction

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9
Q

what is it called when the skeletal muscle is stimulated once

A

twitch

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10
Q

how can you increase muscle tension without increasing frequency of stimulation

A

twitches overlap as there is not time for the muscle to rest, the second twitch adds to the first creating greater muscle tension

eventually produces a much stronger sustained contraction

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11
Q

what is an important mechanism for modulating the force of contraction in skeletal muscle

A

the frequency of stimulation

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12
Q

when is the muscle capable of achieving maximum contraction

A

when it is at its optimum length before the onset of contraction

RESTING LENGTH

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13
Q

how is muscle tension transmitted to bone

A

via the stretching and tightening of muscle connective tissue and tendon

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14
Q

what are the two types of skeletal muscle contraction

A

isotonic

isometric

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15
Q

what is isotonic contraction

A

used for body movements and moving objects

muscle tension remains constant ad the muscle length changes

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16
Q

what is isometric contraction

A

used for supporting objects and maintaining body posture

muscle tension develops at constant muscle length

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17
Q

what decreased the velocity of muscle shortening

A

the load eg. how heavy the object you’re picking up is

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18
Q

what are the main differences between skeletal muscle fibres

A

enzyme pathways
resistance to fatigue
activity of myosin ATPase

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19
Q

how many types of muscle fibre are in one muscle unit

A

two

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20
Q

muscle fibres with greater capacity to synthesise ATP are more resistant to fatigue true/fasle

A

true

21
Q

what does the activity of myosin ATPase determine

A

the speed at which anergy is made available for cross bridge cycling
eg. speed of contraction

22
Q

what does ATPase in muscle do

A

splits ATP to power power cross-bridge stroking

23
Q

what is ATP needed in muscle relaxation

A

to pump calcium back into the lateral sacs of the sarcoplasmic reticulum

24
Q

what are the metabolic pathways that produce ATP for skeletal muscle

A

Creatine phosphate
oxidative phosphorylation
Glycolysis

25
Q

what does creatine phosphate do

A

transfers high energy phosphate from creatine phosphate to ADP to create an immediate source of ATP

26
Q

what is the main source of ATP to muscles when O2 is present

A

oxidative phosphorylation

27
Q

what is the main source of ATP to muscles when O2 isn’t present

A

Glycolysis

28
Q

what are the three types of skeletal muscle fibre

A

slow-oxidative
fast-oxidative
fast- glyhcotic

29
Q

what are type 1 muscle fibres

A

slow (slow twitch)
resistant to fatigue
used for prolonged relatively low work aerobic activities eg. posture maintenance

30
Q

type 2 muscle fibres

A

(intermediate twitch)
fast oxidative
use aerobic and anaerobic
useful in prolonged moderate activities eg. jogging

31
Q

type 2x muscle fibres

A

fast glycotic
(fast twitch fibres)
anaerobic metabolism
short term, high intensity activities eg. jumping

32
Q

what inputs influence the motor units

A

brain inputs

inputs from a variety of receptors

33
Q

what is a reflex

A

a stereotyped response to a specific stimulus

34
Q

what makes reflexes important

A

they’re important for localising lesions in the motor system

35
Q

what is the simplest monosynaptic spinal reflex

A

stretch reflex

36
Q

what is the sense receptor in the stretch reflex

A

the muscle spindle

37
Q

what does stretching of the muscle spindle cause

A

firing of afferent neurons

38
Q

where do the afferent neurons fired in the stretch reflex go and what do they synapse with

A

synapse in spinal cord with the alpha motor neurons which innervate the stretched muscles

39
Q

how do you elicit a stretch reflex

A

tapping a muscle tendon with a rubber hammer

40
Q

what are muscle spindles

A

a collection of specialised muscle fibres

Intrafusal fibres

41
Q

what are extrafusal fibres

A

normal muscle fibres

42
Q

what are the sensory nerve endings of muscle spindles called

A

annulospiral

43
Q

the discharge from muscle spindle sensory nerve endings decrease as the muscle is stretch true/false

A

false

increase

44
Q

what are the efferent neurons that supply muscle spindles called

A

gamma motor neurons

45
Q

what do gamma motor neurons do

A

adjust the level of tension in the muscle spindles to maintain their sensitivity when the muscles shorten during contraction

46
Q

the contraction of intramural fibres doesn’t contribute to overall strength of muscle true/false

A

true

47
Q

causes of intrinsic muscle disease

A

genetically determines myopathies
acquired myopathies eg.

inflammatory, non-inflammaroy, endocrine, toxic

48
Q

symptoms of muscle disease

A

muscle weakness/tiredness
delayed relaxation after voluntary contraction (myotonia)
muscle pain (myalgia)
muscle stiffness

49
Q

investigations in neuromuscular disease

A 
EMG (electromyography) -electrodes detect the presence of muscular activity 
nerve conduction studies 
muscle enzymes (eg. creatine kinase) 
inflammatory markers (CRP) 
muscle biopsy

2 MSK (35 decks)

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