T8L3 Synapses

Question 1

Explain how an action potential is passed between two neurones at a synapse

Answer 1

Action potential reaches synapse
Voltage gated calcium ion channels open
Calcium ions flood into cell
This causes synaptic vesicles containing neurotransmitter to fuse with membrane
Neurotransmitter released by exocytosis
Neurotransmitter diffuses across synaptic cleft
Neurotransmitter binds with neuroreceptors in post synaptic
Causes Sodium channels to open
Sodium ions diffuse into post synaptic which can initiate an action potential

Neurotransmitter broken down and products reabsorbed to re-synthesise neurotransmitter

Question 2

What enzyme breaks down acetylcholine

Answer 2

acetylcholinesterase

Question 3

Why are there so many mitochondria in the presynaptic neurone

Answer 3

Generate energy to resynthesise neurotransmitter

Question 4

Name 4 roles of the synapse

Answer 4

• one direction
• integration: can reach several post synaptic
• Spatial and temporal summation
• filtering out

Question 5

Name two types of synapse

Answer 5

Excitatory and inhibitory

Question 6

What are the neuroreceptors in excitatory synapses

Answer 6

Na+
Na ions diffuse in to initiate action potential

Question 7

What are the neuroreceptors in inhibitory synapses

Answer 7

Cl-
Cause hyperopolarisation to occur making the action potential unlikely