Synaptic Transmission

Question 1

What is a synapse?

Answer 1

A chemically gated cell that initiates either an exhibitory or excitatory response

Question 2

Synaptic transmission stage 1

Answer 2

Action potential reached nerve terminal hence Ca2+ enter from the ECF into the nerve terminal through VGC
Cells maintain ICF calcium levels very low and ECF very high
Ca2+ triggers some synaptic vesicles to be transported up nerve terminal causing membrane to join together and contents discharged

Question 3

Synaptic transmission stage 2

Answer 3

depolarisation (if reaches threshold) or inhibitory postsynaptic transmission (if chloride channels open)

Question 4

Synaptic transmission stage 3

Answer 4

ACh diffuses across synaptic cleft, binds to ACh gated sodium ion channels and produces a graded depolarisation

Question 5

Synaptic transmission stage 4

Answer 5

Depolarisation ends as ACh is broken down into acetate and choline by AChE

Question 6

Synaptic transmission stage 5

Answer 6

The axon terminal reabsorbing choline from the synaptic cleft and uses it to synthesis new molecules of ACh

Question 7

What is an electrical synapse?

Answer 7

Where pre and post synaptic membranes are joined by gap junctions and depolarisation from presynaptic cell passes directly to post synaptic cell

Question 8

Nerve to nerve muscle synapses

Answer 8

Synapses are tiny
AP in an individual neuron will rarely bring the partner to threshold
Inputs may be excitatory or inhibitory, many transmitters used

Question 9

Nerve to skeletal muscle synapses

Answer 9

Synapses are huge
AP in a neuron very likely to bring muscle fibre to threshold
Only excitatory inputs, only ACh used