Action potential and muscle contraction

Question 1

Step 1

Answer 1

Muscles under nervous control. Contraction is initiated at the neuromuscular junction.

Question 2

Step 2

Answer 2

An action potential arriving at the motor neurone causes calcium channels to open and Ca2+ ions flood into the cell

Question 3

Step 3

Answer 3

Increased concentration of Ca2+ in the cell stimulates the vesicles which contain neurotransmitter acetylcholine. These move towards the presynaptic membrane and fuse with it

Question 4

Step 4

Answer 4

Acetylcholine diffuses across the synaptic cleft. It binds to the receptors on the postsynaptic membrane. Then sodium channels opening and Na* flooding into muscle cell

Question 5

Step 5

Answer 5

The postsynaptic membrane depolarizes. If the threshold is reached an action potential is generated - this travels along the muscle cell membrane and into special structures called t-tubules

Question 6

Step 6

Answer 6

The T-tubules channel the action potential into the cell, towards the sarcoplasmic reticulum. This organelle releases stored Ca2+ ions into the cell cytoplasm in response to the depolarization

Question 7

Step 7

Answer 7

This increase in the concentration of Ca2+ in the muscle cell cytoplasm that causes the cell to contract
The acetylcholine is recycled by enzyme action and returned to the neurone