6.2.2 Synapses

Question 1

What is A

Answer 1

Vesicle

Question 2

What is B

Answer 2

Neurotransmitter

Question 3

What is C

Answer 3

Synaptic cleft

Question 4

Describe and explain the events that occur at the cholinergic synapse

Answer 4

• Membrane of presynaptic neurone depolarised
• Calcium channels open, causing calcium ions to enter synaptic knob
• Causes synaptic vesicles to fuse with presynaptic membrane, releasing acetylcholine
• Acetylcholine diffuses across synaptic cleft
• Acetylcholine attaches to receptors on post-synaptic neurone membrane
• Sodium ions enter as membrane more permeable to sodium ions
• leading to depolarisation and action potential

Question 5

Describe the events at the cholinergic synapse in the pre-synaptic neurone

Answer 5

• Membrane of pre-synaptic neurone depolarised
• Calcium ion channels open, and calcium ions enter synaptic knob
• Causes synaptic vesicles to fuse with presynaptic membrane, releasing acetylcholine

Question 6

Describe events at cholinergic synapse at post-synaptic neurone

Answer 6

• Acetylcholine attaches to receptors on post-synaptic membrane
• Sodium ions enter as membrane more permeable to sodium ions
• Leading to depolarisation and action potential

Question 7

Describe the events at cholinergic synapse between the post and pre synaptic neurone

Answer 7

Acetylcholine diffuses across synaptic cleft

Question 8

How is a unidirectional synapse possible

Answer 8

• Neurotransmitter released only from pre-synaptic membrane
• Receptors for neurotransmitter are only on post-synaptic membrane

Question 9

Describe temporal summation

Answer 9

• Pre-synaptic membrane recieves serveral impulses in a short time
• Release of enough neurotransmitter for the threshold level to be reached in post-synaptic neurone

Question 10

Describe spatial summation

Answer 10

Many pre-synaptic membranes release enough neurotransmitter for the threshold level to be reached in post-synaptic neurone

Question 11

Describe how synapses can be inhibitory

Answer 11

• Binding of neurotransmitter causes post-synaptic membrane to become more negatively charged
• As trigger influx of negative ions
• More sodium ions requried to reach threshold level
• Threshold level not reached
• No depolarisation
• No action potential produced

Question 12

Two main similarities of cholinergic synpase and neuromnuscular junction

Answer 12

• acetylcholine diffuses across synaptic cleft
• enzymes break down neurotransmitter

Question 13

Two main differences of cholinergic synpase and neuromnuscular junction

Answer 13

• synapses always exciatatory in NMJ, but either excitatory or injibitory at cholinergic
• NMJ only links motot neuroens to mucles, but choilnergic links any two neurones