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MBChB YR2 MSK > Physiology: Skeletal Muscle Physiology > Flashcards

Physiology: Skeletal Muscle Physiology Flashcards

1
Q

What is tetanus?

A

Maximal sustained contraction of a muscle fibre that results from repeated stimulations so close together than the fibre does not have time to relax between stimuli

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2
Q

What are 𝛾-motor neurons?

A

Efferent (motor) supply of muscle spindles

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3
Q

Describe the structure of skeletal muscle

A

Parallel muscle fibres (skeletal muscle cells) bundled by connective tissue

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4
Q

What causes the striation of skeletal muscle?

A

Alternating dark bands (myocin) and light bands (actin)

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5
Q

Define isometric contraction

A

Muscle tension develops at constant muscle length

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6
Q

Define isotonic contraction

A

Muscle tension remains constant as the muscle length changes

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7
Q

What is excitation-contraction coupling?

A

The process whereby surface action potential results in activation of the contractile structures of the muscle fibre via Ca2+

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8
Q

What are slow oxidative (type I) muscle fibres?

A

Aerobic fibres used mainly for prolonged relatively low work aerobic activities e.g. maintenance of posture, walking

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9
Q

What is electromyography?

A

Electrodes detect frequency and amplitude of muscle fibre action potentials

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10
Q

What is the Z-line of a sarcomere?

A

The sarcomere is found between two Z lines - connect the thin filaments of 2 adjoining sarcomeres

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11
Q

What is isometric contraction used for?

A

Supporting objects in fixed positions and maintaining body posture

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12
Q

What is the A-band of a sarcomere?

A

Made up of thick filaments along with portions of thin filaments that overlap in both ends of thick filaments

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13
Q

Where do Ca2+ ions bind to in the sliding filament theory of muscle contraction?

A

Troponin (on actin filaments)

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14
Q

What is a muscle spindle (intrafusal fibres)?

A

Collection of specialised muscle fibres which act as sensory receptors for the stretch reflex

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15
Q

What is the sliding filament theory?

A

Muscle tension is produced by sliding of actin filaments on myocin filaments

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16
Q

Which muscle type is non-striated and involuntary?

A

Smooth muscle

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17
Q

How is muscle tension from contraction transmitted to bone?

A

Via the elastic components of muscle

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18
Q

What are fast glycolytic (type IIx) muscle fibres?

A

Anaerobic fibres used mainly used for short-term high intensity activities e.g. jumping

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19
Q

What is the optimal length of skeletal muscle?

A

The resting length of a skeletal muscle is approximately its optimum length

20
Q

What is ATP required for in the generation of muscle tension?

A

Contraction (powers cross bridges) and relaxation (release of cross bridges and to pump Ca2+ back into SR)

21
Q

Define a sarcomere

A

The functional unit of muscle

22
Q

What is the function of 𝛾-motor neurons?

A

Adjust tension in muscle spindles to maintain sensitivity during contraction, when the muscle shortens

23
Q

Which muscle type is striated and voluntary?

A

Skeletal muscle

24
Q

What are fast oxidative (type IIa) muscle fibres?

A

Use both aerobic and anaerobic metabolism and are useful in prolonged relatively moderate work activities e.g. jogging

25
Q

What are nerve conduction studies?

A

Determine the functional integrity of peripheral nerves

26
Q

What is a reflex action?

A

Stereotyped response to a specific stimulus - simplest form of coordinated movement

27
Q

How does a skeletal muscle’s function affect the number of muscle fibres per motor unit?

A

If a muscle serves fine movements, it will have fewer fibres per motor unit, and vice versa

28
Q

What triggers the release of Ca2+ in skeletal muscle?

A

Action potential reaches T-tubules

29
Q

What are annulospiral fibres?

A

Sensory nerve endings of muscle spindles

30
Q

What is Ca2+ required for in the generation of muscle tension?

A

Cross bridge formation

31
Q

Define myotonia

A

Delayed reaction after voluntary contraction

32
Q

How do Ca2+ ions allow the formation of cross-bridges in the sliding filament theory of muscle contraction?

A

Bind to troponin which moves tropomyosin aside to uncover the cross-bridge binding sites on the actin, allowing myosin to bind

33
Q

Which muscle type is striated and involuntary?

A

Cardiac muscle

34
Q

What is the H-zone of a sarcomere?

A

Lighter area within middle of A-band where thin filaments don’t reach

35
Q

When a skeletal muscle fibre receives an action potential, where will Ca2+ be released from?

A

The lateral sacs of the sarcoplasmic reticulum

36
Q

What are reflex pathways used for in a clinical context?

A

To identify lesions in the motor system e.g. knee jerk (stretch reflex)

37
Q

What is the I-band of a sarcomere?

A

Consists of remaining potion of thin filaments that do not project in the A-band

38
Q

What is the M-line of a sarcomere?

A

Extends vertically down the middle of A-band within the centre of H-zone

39
Q

What is a twitch?

A

A single contraction of a muscle fibre following a single stimulation

40
Q

What are T-tubules in skeletal muscle?

A

Extensions of the surface membrane that dip into the muscle fibre

41
Q

What is isotonic contraction used for?

A

Body movements and moving objects

42
Q

Define a motor unit

A

A single alpha motor neuron and all the skeletal muscle fibres it innervates

43
Q

Describe the structure of a myofibril

A

Actin and myocin arranged into sarcomeres

44
Q

Where are muscle spindles found?

A

In the belly of muscles, run parallel to ordinary muscle fibres

45
Q

What usually attaches skeletal muscles to the skeleton?

A

Tendons

46
Q

Define myalgia

A

Muscle pain

MBChB YR2 MSK (36 decks)

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