how nerves work 5

Question 1

neuromuscular junction

Answer 1

1-action potential reaches pre-synaptic terminal
2- this opens voltage-gated ca 2+ channels and causes ca 2+ to diffuse into cell
3-this leads to vesicles containing Ach to fuse with pre-syanptic membrane and diffuse across the synapse
4-ach binds to receptors on the post-synaptic terminal and causes ligand-gated Na+ channels to open
5- this leads to depolarisation of adjacent membrane which if reaches AP causes muscle to contract
6-ach is broken down by acetlycholinesterase. otherwise would continue to depolarise cell.

Question 2

how is the CNS synapse different

Answer 2

1- many different neurotransmitters-not just Ach
2- can be monosynaptic or polysynaptic
3-the neurotransmitter can be released onto different parts of the neurone (axon-somatic, axo-dendritic and axon-axonal)
4- can have a fast, slow EPSPs and IPSPs. NMJ only has end-plate potential
5- can have synaptic integration

Question 3

convergence, divergence and feedback-inhibition

Answer 3

convergence: multiple cells synapse onto 1 cell
divergence: one cell synapses onto many
feed-back inhibition: after the cell has fired an action potential it prevents it from firing another one straight away to allow separate electrical impulses to be fired.