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MSK > Physiology > Flashcards

Physiology Flashcards

1
Q

Functions of Skeletal muscle

A

Maintainposture, purposeful movement, resp movements, heat production, contributes to metabolism

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2
Q

Skeletal muscle features

A

Striated and voluntary (innervated by somatic nervous system), no gap junctions, neurogenic initiation (acteylcholine neurotransmitter @ neuromuscular junction), calcium entirely from SR

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3
Q

Cardiac muscle features

A

striated and involuntary (autonomic)

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4
Q

Smooth muscle

A

unstriated and involuntary (autonomic)

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5
Q

Motor unit

A

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

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6
Q

Precision > ….

A

Power

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7
Q

Fine movements have …

A

fewer fibres per motor unit (10 or so)

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8
Q

Powefful movements have …

A

more fibres per motor unit (100s -1000s)

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9
Q

Breakdown of muscle

A

Muscle > Muscle fibre > Myofibril > Sarcomere

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10
Q

Sarcomere contains …

A

Myocin and actin (actin slides over myocin)

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11
Q

Actin is …

A

thin and light

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12
Q

Myocin is …

A

thick and dark

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13
Q

skeletal muscle consists of …

A

parallel muscle bundled by connective tissue (fibres suually exteend entire length of muscle)

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14
Q

Sarcomeres are found….

A

between two Z lines (

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15
Q

Sarcomeres contain four zones

A

A band, H zone, M line and I band

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16
Q

How calcium is released in skeletal muscles…

A

In fibres Ca2+ is released from the lateral sacs of the SR when the surface action potential spreads down the transverse tubules (T-tubules)

17
Q

ATP is needed:

A
  • during muscle contraction (to power cross bridges)

- During relaxation to release cross bridges and to pump Ca2+ back into SR

18
Q

Skeletal muscle tension is dpendent on

A

number of muscle fibres contracting and the tension developed by each contracting muscle fibre (depends on frequency of stimulation and summation of contractions)

19
Q

In skeletal muscle the duration of action potential is …

A

much shorter than the resulting twitch

20
Q

Stronger contractions can be achieved by …

A

summating twitches through repetitive fast stimulation of skeletal muscle

21
Q

Tetanus

A

muscle fibre stimulated so rapidly that it has no oppurutnity to relax (e.g. lock jaw)

22
Q

Why can’t cardiac muscle tetanus

A

it has too long a refractory period

23
Q

Increasing frequency of stimulation of skeletal muscle causes

A

stonger contraction

24
Q

Maximal contraction can be achieved when

A

the muscle is at its optimal length before the onset of contraction

25
Q

Isotonic contraction

A

used for body movements and moving objects. Tension remains constant as the muscle changes

26
Q

Isometric contraction

A

used for supporting objects in fixed positions and maintain body posture. Muscle tension develops at constant muscle length.

27
Q

Slow oxidative

A

type 1 = slow contraction, high reisstance to fatigue, low work aerobic e.g. walking

28
Q

Fast oxidative

A

type IIa = fast contraction, average resistance to fatigue, aerobic and anaerobic e.g. jogging

29
Q

Fast-glycolytic

A

type IIx = fast contraction, low resistance, to fatigue, anaerobic, short term high intensity e.g. jumping

30
Q

reflex action

A

stereotyped response to a specific stimulus

31
Q

stretch reflex

A

a negative feedback that resists passive change in muscle length to maintain optimal resting length of muscle.

32
Q

Muscle spindle

A

sensory receptor in muscle stretch (afferent neurons increase firing to motor units)

33
Q

example of stretch reflex

A

tendon hammer on patellar tendon (checks femoral nerve L3, L4)

34
Q

causes of imapired skeletal muscle function

A

intrinsic disease of muscle
diseae of NMJ
disease of lower motor neurons which supply muscle
disruption of input to motor nerves (e.g. MND)

35
Q

Genetic causes of intrinsic muscle disease

A 
Congenital myopathies (reduced contractility of musles)
Chronic degeneration (e.g. muscular dystrophy)
Abnormalities in membrane ion channels (e.g. myotonia)
36
Q

Acquired causes of intrinsic muscle disease

A

inflammatory myopathies (polymositis)
Non-inflammatory (fibromyalgia)
Endocrine (cushing syndrome, thyroid disease)
Toxic (alcohol, statins)

37
Q

Symptoms of muscle disease

A

muscle weakness, delayed relaxation post voluntary contraction (myotonia), muscle pain (myalgia), msucle stiffness

38
Q

Invx in neuromsucular disease

A

Electromyography (EMG) [electrodes detect muscular activity] > Nerve conduction studies (done with EMG, checks function of peripheral nerves) > Muscle enzymes (CK) > Inflammatory markers (CRP, Plasma Viscocity) > Muscle Biopsy

MSK (9 decks)

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