Lecture #25 - Skeletal muscle: structure & function

Question 1

Why do we need muscle?
Cardiac (1)
Smooth (1)
Skeletal (2)

Answer 1

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Question 2

What’s T-tubule?

Answer 2

Invaginated sarcolemma

Question 3

What’s a triad?

Answer 3

T-tubule sandwiched be two SR (the full thing)

Question 4

What’s the thick and what’s the thin filament?

Answer 4

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Question 5

What’s a motor unit?

Answer 5

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Question 6

The number of fibres innervated by motor units indicates what?

Answer 6

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Question 7

What does
Excitation (3)
Contraction (3)
Relaxation (2)
involve?

Answer 7

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Question 8

What’s the excitation process at NMJ?

Answer 8

AP reaches end of motor neurone, which causes Ca++ entry into nerve terminal

Synaptic vesicles release Ach, which diffuses into synaptic cleft (motor neuron close to fibre bc limits to diffu distances)

Ach stimulates ACH RECEPTORS IN FIBRE

DEPOLARISATION of muscle SARCOLEMMA, initiating AP

Question 9

When AP travels over sarcolemma and ______, it triggers the release of _____ from ______

Answer 9

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Question 10

When Ca++ diffuses to myofilaments, what does it trigger?

Answer 10

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Question 11

What’s the four steps to contraction

Answer 11

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Question 12

What’s involved in relaxation? (6)

Answer 12

1. REPOLARISATION of sarcolemma
2. Ca++ REUPTAKE into SR (no Ca++ being released)
3. Reduced AFFINITY of Ca++ with troponin
4. Actin and myosin bound but not enough to initiate new cross bridges so
5. ATP binds to myosin to UNCOUPLE
6. Fibre returns to RESTING STATE