13.10 Sliding filament model Flashcards

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1
Q

what happens to the I-band when contraction occurs?

A

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2
Q

what happens to the A-band when contraction occurs?

A

it stays the same

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3
Q

what happens to the Z-lines when contraction occurs?

A

move closer together

so sarcomere becomes smaller

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4
Q

what happens to the H-zone when contraction occurs?

A

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5
Q

relaxed vs contracted sarcomere

A
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6
Q

what is the structure of myosin?

A

have globular heads which can bind to ATP

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7
Q

what is the structure of actin?

A

have:
troponin
tropomyosin
actin-myosin binding site

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8
Q

what does troponin do?

A

holds tropomyosin over the binding site

releases tropomyosin when a Ca2+ ion binds to it

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9
Q

what happens at neuromuscular junction?

A

SAME AS AT SYNAPSE!!!!

acetylcholine is the neurotransmitter released

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10
Q

what happens when the sarcolemma is depolarised?

A

it causes the sarcoplasmic reticulum to open Ca2+ channels which causes Ca2+ ions to diffuse into the sarcoplasm

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11
Q

what do the Ca2+ ions from the sarcoplasmic reticulum do?

A

they bind to troponin on the actin molecules

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12
Q

what does the binding of Ca2+ ions to the troponin do?

A

causes change in troponin shape which leads to tropomyosin detaching which exposes the myosin-actin binding site

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13
Q

what is formed between the myosin head and the binding site?

A

a cross bridge

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14
Q

how does the myosin head pull the actin?

A

by flexing

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15
Q

how is the myosin head detached from the actin?

A

ADP molecule releases from the head and reacts with P to form ATP

ATP binds to the myosin head which causes the myosin head to detach by breaking the cross bridges

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16
Q

how does the myosin head return to normal position?

A

ATPase hydrolyses the ATP into ADP + P which releases energy which returns the head back to its normal position

17
Q

what does the myosin head do once it returns to it’s normal position?

A

it binds to a binding site further along the actin filament

cycle is then repeated

18
Q

how does the actin filament return to it’s resting position?

A

Ca2+ ions leave their binding sites and tropomyosin returns to cover the binding site

the actin filaments slide back to their relaxed positions

19
Q

what ways is ATP generated for muscle contraction to occur?

A

aerobic respiration
anaerobic respiration
phosphocreatine

20
Q

what is aerobic respiration in muscles used for?

A

long periods of low-intensity exercise

21
Q

what causes muscle fatigue?

A

the build up of lactate in muscles due to anaerobic respiration

22
Q

what is anaerobic respiration in muscles used for?

A

short periods of high-intensity exercise

23
Q

what is aerobic respiration in muscles used for?

A

long periods of low-intensity exercise

24
Q

what does phosphocreatine do?

A

provides a reserve supply of phosphate which can combine with ADP to produce ATP