nerve impulses and synapses

Question 1

Describe the sequence of events involved in transmission across a cholinergic synapse (5)

Answer 1

1. Depolarisation/AP of presynaptic membrane;
2. Calcium channels open and calcium ions enter (synaptic knob);
3. (Calcium ions cause) synaptic vesicles move to/fuse with presynaptic membrane and release acetylcholine
4. Acetylcholine/neurotransmitter diffuses across (synaptic cleft);
5. (Acetylcholine attaches) to receptors on the postsynaptic membrane;
6. Sodium ions enter (postsynaptic neurone) leading to depolarisation;

Question 2

following release of acetylcholine into a neuromuscular junction, a muscle contraction occurs.

describe the sequence of events following the release of acetylcholine that leads to stimulation of this contraction (4)

Answer 2

1. Acetylcholine diffuses across synaptic cleft
   2. Acetylcholine attaches to receptors on post synaptic membrane
   3. Sodium ions enter leading to depolarisation
2. Calcium ions released by endoplasmic reticulum