5.1.3 Neuronal Communication, Synaptic Transmission

Question 1

Synapse

Answer 1

Gap between neurones

Question 2

Information transmitted by

Answer 2

Chemicals / neurostransmitters

Question 3

New action potential

Answer 3

Triggered in post synaptic neurone

Question 4

Gaps are — wide

Answer 4

20-30 nm

Question 5

Where are synapses?

Answer 5

At dendrites / axon terminal

Question 6

Stage 1 of synaptic transmission?

Answer 6

Depolarisation (knob becomes more positive), caused by incoming potential; calcium ion channels open and Ca+ ions flood into the synaptic knob

Question 7

Stage 2 of synaptic transmission?

Answer 7

Influx of Ca+ ions causes synaptic vesicles to fuse with presynaptic membrane; neurotransmitters are released into the cleft by exocytosis

Question 8

Stage 3 of synaptic transmission?

Answer 8

Neurotransmitter (acetylcholine, in cholinergic synapses) is released into the synaptic cleft; it binds to the receptor site on the sodium-ion channels on the post synaptic neurone; ion channels open

Question 9

Stage 4 of synaptic transmission?

Answer 9

Neurotransmitter binds to the receptor; causes a conformational shape change; channels open; Na+ ions flood in and cause depolarisation in the postsynaptic neurone; if depolarisation is above -55mV, action potential is passed on

Question 10

Stage 5 of synaptic transmission?

Answer 10

Hydrolytic enzyme acetylcholinesterase breaks neurotransmitters into acetyl and choline; sodium ion channels close (only NT on ion channels are broken down)

Question 11

Stage 6 of synaptic transmission?

Answer 11

Acetyl and choline diffuse back into the presynaptic neurone; ATP is used to reform them into acetylcholine; stored in vesicles

Question 12

Unidirectionality

Answer 12

Messages can only be sent from the presynaptic neurone to the postsynaptic neurone

Question 13

Summation?

Answer 13

Low level signals can be amplified

Question 14

Acclimitisation?

Answer 14

After repeated stimuli the synapse runs out of acetylcholine, cannot send any more signals

Question 15

A single stimulus can create

Answer 15

Multiple simultaneous responses in different parts of the body

Question 16

Multiple stimuli can combine to

Answer 16

Produce one single response

Question 17

Integration

Answer 17

Combination of many inputs into one signal (interpretation + coordination)

Question 18

Spatial summation

Answer 18

A number of different presynaptic neurones share the same synaptic cleft; together they can release enough NT to create an action potential

Question 19

Temporal summation

Answer 19

A single presynaptic neurone releases NT many times over a short period; if the total amount of N exceeds the threshold valued, an action potential is sent