Synaptic Transmission

Question 1

Define synaptic transmission.

Answer 1

Synaptic transmission is the process by which a nerve impulse passes across the synaptic cleft from one neurone (presynaptic neurone) to another (postsynaptic neurone).

Question 2

1. What is transmission of nerve impulses across the synapse and how long does it take?

Answer 2

It is chemical and takes a fraction of a second.

Question 3

2. What are stored at the end of axons and what do they contain?

Answer 3

Sacs (synaptic vesicles) containing chemical messengers (neurotransmitters)

Question 4

3. As the action potential travels down the axon to the axon terminal, what does it do?

Answer 4

It stimulates the vesicles to release neurotransmitter molecules into the synapse.

Question 5

4. What happens to the neurotransmitter which is released?

Answer 5

It diffuses across the gap over to the postsynaptic membrane of the next neurone and binds to specialised receptors that are activated by that particular neurotransmitter.

Question 6

5. Wheat does the whole process produce?

Answer 6

Either excitatory or inhibitory effects on the postsynaptic terminal.

Question 7

What happens if the neurotransmitter is excitatory?

Answer 7

The post synaptic neurone is more likely to fire an impulse.

Question 8

What happens if the neurotransmitter is inhibitory?

Answer 8

The post-synaptic neurone is less likely to fire.

Question 9

What happens after synaptic transmission?

Answer 9

The neurotransmitter is released back into the synaptic space and is then cleared from the synaptic cleft by the process of:
- Diffusion: some of the neurotransmitter drifts away
- Break-Down: some of the neurotransmitter is broken down by enzymes
- Re-Uptake: some of it is taken back up to the presynaptic neurone, repackaged and stored for later use

Question 10

What does an ecxhitatory neurotransmitter do and what is an example of one?

Answer 10

Excitatory synaptic connections increase neural activation in the CNS
E.g) Noradrenaline

Question 11

What happens when an excitatory neurotransmitter binds with a postsynaptic receptor?

Answer 11

It causes an electrical change in the cell membrane which results in an excitatory postsynaptic potential (EPSP) making the postsynaptic neurone more likely to fire.

Question 12

What do inhibitory synaptic connections do and give an example of one?

Answer 12

Inhibitory synaptic connections decreased neural activation in the CNS
E.g) GABA

Question 13

What happens when an inhibitory neurotransmitter binds with a postsynaptic receptor?

Answer 13

It results in an inhibitory postsynaptic potential (IPSP) making the postsynaptic cell less likely to fire.