L3 - Synapses

Question 1

An action potential arrives at a synapse, what effect does it have on channels there?

Answer 1

The depolarisation causes Ca2+ channels to open and Ca2+ to enter the cell and triggers the fusion of ACh vesicles with the presynaptic membrane.

Question 2

ACh diffuses across the synaptic cleft, what does it bind to and what effect does this have?

Answer 2

It binds to receptors on the post synaptic membrane. This activates the receptors causing them to open chemical gates cation (positive) channels.

This causes depolarisation of the post synaptic membrane causes another AP to fire and the AP to carry on

Question 3

What is special about synapses in squid?

Answer 3

Squid have a giant synapse - the stellate ganglion (looks like a star)

These are large enough to put a glass receptor in and therefore measure things

The pre synaptic potential regulates how much neurotransmitter is released, which determines the size of the post synaptic potential

Question 4

How have jellyfish been used to prove neurotransmitter release?

Answer 4

A protein that glows blue in the presence of Ca2+ is taken from jellyfish and used to show that Ca2+ enters the presynaptic terminal

Question 5

Do neurones in the retina spike?

Answer 5

Most of them are non-spiking neurones.

Spikes aren’t needed for neurones to communicate with each other, what is needed is electrical excitement to open Ca2+ channels

Question 6

What type of synapse is found between motor neurons and muscles?

Answer 6

Always excitory synapses
- the motor end plates always respond to ACh by depolarising the Post synaptic membrane

• synapses between neurones aren’t always excitory

Question 7

What is the difference between excitory and inhibitory neurons?

Answer 7

Excitory - if the post synaptic neurones response to neurotransmitter is depolarisation

Inhibitory - if the post synaptic neurones response to neurotransmitter is hyperpolarisation