5.1 Neuromuscular junctions Flashcards Preview

A Level Biology > 5.1 Neuromuscular junctions > Flashcards

Flashcards in 5.1 Neuromuscular junctions Deck (27):
1

when does the muscle contract?

when it receives a nerve impulse

2

1. where is a nerve impulse conducted?

along the motor neurone

3

2. when a nerve impulse reaches the neuromuscular junction what does it stimulate to open?

voltage gated Ca2+ channels

4

2. as the Ca2+ floods in to the synaptic knob what does it cause?

the vesicles to fuse with the membrane

5

2. as the vesicles fuse with the membrane, what does it release and by what process?

releases acetylcholine by exocytosis

6

3. what does the acetylcholine now do?

diffuses across the cleft and binds with receptor molecules on the post synaptic membrane

7

what is another term for the post synaptic membrane on a motor neurone?

sarcolemma

8

4. as the acetylcholine binds what does it cause to open?

chemical gated sodium ion channels

9

4. the opening of the sodium channels makes the membrane more permeable to what?

sodium

10

4. as sodium flood into the sarcolemma what happens to the membrane?

depolarizes, initiating action potential

11

5. acetylcholine is broken down by what?

acetylcholinesterase

12

5. what is acetylcholine broken down into?

choline and ethanoic acid

13

5. what does the breakdown of acetylcholine prevent?

muscle being overstimulated

14

6. where does depolarization spread?

through the t tubules

15

6. what are the t tubules in contact with?

the sarcoplasmic reticulum

16

6. what does the sarcoplasmic reticulum contain?

stored Ca2+

17

7. action potentials stimulate what to open?

Ca2+ channels

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7. as channels open what does the Ca2+ do?

diffuses down the concentration gradient flooding the sarcoplasm with Ca2+

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8. as the Ca2+ floods into the sarcoplasm what does it cause?

muscle contraction

20

(sliding filament theory)
1. nerve impulses stimulate the release of what?

Ca2+ from the sarcoplasmic reticulum

21

(sliding filament theory)
2. Ca2+ attach to what?

the troponin molecule

22

(sliding filament theory)
3. what happens to the troponin when bound to Ca2+ and what effect does this have?

changes shape pulling tropomyosin upwards exposing myosin binding site

23

(sliding filament theory)
4. what does the bulbous head of the myosin filament do?

attaches to the exposed binding site forming a cross bridge

24

(sliding filament theory)
5. what is activated when the head attaches to the binding site? and what does this do?

Myosin ATPase
ATP is hydrolysed this releases enough energy for the angle of the head to change

25

(sliding filament theory)
6. where does the actin filament slide?

closer to the centre of the sarcomere

26

(sliding filament theory)
7. what attaches to the myosin head?

a new ATP

27

(sliding filament theory)
8. what does the myosin head leave and what does the actin do?

myosin head leaves binding site
Actin filament moves back to original position

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