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FC2O Lecture MCQ2 > L23 Muscle Physiology > Flashcards

L23 Muscle Physiology Flashcards

1
Q

How do muscles contract?

A

interactions between actin and myosin filaments

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2
Q

what 2 tissues can generate action potentials? (muscle, nerve, connective and epithelial)

A

nerve and muscle

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3
Q

what system controls/ regulates skeletal muscles?

A

efferent neurons ->motor system

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4
Q

what system controls/ regulates smooth muscle like lungs and cardiac muscle like heart?

A

efferent neurons-> autonomic nervous system

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5
Q

how are skeletal muscles paired?

A

antagonistically - they work opposingly to eachother

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6
Q

what occurs in the skeletal muscle when moving lower forearm upwards?

A

bicep contracts, tricep relaxes (flexion)

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7
Q

what occurs in skeletal muscle when lowering forearm?

A

biceps relax and triceps contract (extension)

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8
Q

skeletal muscle are made of bundles of long fibres, what are they made of?

A

smaller myofibrils ‘striped’

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9
Q

what is the functional unit of a muscle cell?

A

sacromere which is bordered by z lines

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10
Q

what is m-line?

A

the middle of myosin and actin filaments stacked within sacromere unit

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11
Q

what happens during muscle contraction?

A

sacromere contracts and shortens, z lines come closer together, this happens along whole myofibril - all myofibrils in skeletal muscle contract together

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12
Q

how does muscle contraction occur at molecular level?

A

1) globular head of myosin combines with actin forming a crossbridge
2) power stroke - crossbridge allows myosin to pull actin towards centre/ m-line of sacromere (shortening)
3) cross-bridge cycling - repeated cycles of binding and release (causes muscle contraction)

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13
Q

what is the energy source for cross-bridge cycling?

A

ATP

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14
Q

What type of reaction is muscle contraction/ cross-bridge cycling?

A

thermogenic = heat generating

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15
Q

what are shivers?

A

involuntary contraction of muscles to generate heat

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16
Q

why does muscle fatigue?

A

lack of ATP

17
Q

what happens during exercise/ oxygen depletion?

A

we use lactic acid fermentation to produce ATP

18
Q

What neurotransmitter is muscle contraction dependent on?

A

calcium

19
Q

how does calcium control muscle contraction?

A

free calcium binds to tropomyosin and troponin proteins allowing myosin and actin to bind - crossbridge occuring

20
Q

what happens when Ca2+ concentrations are low?

A

muscle contraction cannot occur

21
Q

what initiates the repsonse of muscle contraction?

A

acetylcholine neurotransmitters from motor neurons

22
Q

how does muscle contraction initiation occur at action potential level?

A

1) pre-synaptic terminal releases ACh
2) ACh neurotransmitter binds to nicotinic receptor on muscle
3) depolarisation of muscle
4) action potential in muscle
5) electroexcitation of muscle causes sarcoplasmic reticulum to release calcium
5) calcium binds to troponin - freeing myosin binding sites to bind with actin
6) sarcomere shortens continuously - muscle contraction

23
Q

what is required for muscle contraction?

A

motor nerve, ATP, calcium, Ach at neuro-muscular junction

24
Q

how does the nervous system grade the response of muscle contraction (strong/weak)

A

1) varying number of fibres that contract

2) vary rate at which fibres are stimulated

25
Q

what is tetanus?

A

series of action potentials at high freqency - no repolarisation or relaxation

26
Q

what happens in motor-neuron disease?

A

lack of input from motor nerves

27
Q

what happens in myasthenia gravis?

A

autoimmune disease attacks acetylcholine receptors - muscle weakness

28
Q

what happens in multiple sclerosis?

A

motor nerves are demyelinated

29
Q

what happens in duchenne muscular dystrophy?

A

no dystrophin protein - muscle is fatigued and degenerates over time

30
Q

where is cardiac muscle found?

A

only in the heart

31
Q

what does cardiac muscle consist of?

A

straited cells in intercalated disks containing gap junctions that act as electrical synpases

32
Q

what is responsible for cardiac muscle generating its own action potential? no neurons

A

pace maker

33
Q

why does cardiac muscle never fatigue?

A

excessive mitochondria

34
Q

what is hypertrophy?

A

muscle growth

35
Q

what is muscle atrophy?

A

muscle shrinkage

36
Q

how do we gain muscle?

A

lifting weights causes more protein synthesis - increased muscle cells under influence of testosterone

37
Q

what affect does significant cardio training have on heart?

A

increase heart chamber volume - pump even more blood, resting rate drops

38
Q

what effect does weight training have on heart?

A

heart chambers increase in MASS, more force generated for pumping blood around body

39
Q

why does hart conformation change in absence of gravity?

A

anti-gravity muscles aren’t used

overcome by exercise

FC2O Lecture MCQ2 (14 decks)

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