Q4: Neurotransmitters and Synapses

Question 1

Synapses transmit

Answer 1

Information

Question 2

Where and how do synapses transmit information

Answer 2

From one neurone to another by means of chemicals called neurotransmitters

Question 3

Synaptic cleft

Answer 3

Small gap which separates neurones.

Question 4

Presynaptic neurone

Answer 4

Neurone that releases the neurotransmitter

Question 5

Synaptic knob

Answer 5

A swollen portion at end the of the presynaptic neurone which the axon ends in.

Question 6

What does the synaptic knob possess

And why

Answer 6

Many mitochondria and large amounts of endoplasmic reticulum.
Required in the manufacture of neurotransmitter which takes place in the axon?

Question 7

Where does manufacturing of neurotransmitter occur

Answer 7

In the axon

Question 8

Where is neurotransmitter stored?

Answer 8

Synaptic vesicles

Question 9

What happens once the neurotransmitter is released from the synaptic vesicles?

Answer 9

It diffuses across to the post-synaptic neurone, which possesses very specific receptor proteins on its membrane to receive it.

Question 10

Features of synapses

Answer 10

Unidirectionality

Summation

Question 11

Unidirectionality

Answer 11

Synapses can only pass information in one direction- from the presynaptic neurone to the post synaptic neurone, in this way they act like valves.

Question 12

Two types of summation

Answer 12

Spatial

Temporal

Question 13

Summation

Answer 13

Rapid build up of neurotransmitter in the synapse to trigger an action potential.

Question 14

Spatial summation

Answer 14

A number of different presynaptic neurones together release enough neurotransmitter to exceed the postsynaptic neurone’s threshold value.
Together they trigger a new action potential.

Question 15

Temporal summation

Answer 15

A single presynaptic neurone releases neurotransmitter many times over a very short period.

Question 16

How is a new action potential generated at a postsynaptic neurone?

Answer 16

The concentration of neurotransmitter exceeds the threshold value of the postsynaptic neurone.

Question 17

Inhibitory synapses

Answer 17

Synapses that make it less likely that a new action potential will be created on the postsynaptic neurone.

Question 18

Synapses act as

Answer 18

junctions

Question 19

A single impulse along one neurone can ….. at a synapse

Answer 19

initiate new impulses in a number of different neurones at a synapse.
Allowing a single stimulus to create a number of simultaneous responses.

Question 20

A number of impulses ….. at a synapse

Answer 20

can be combined at a synapse.

This allows impulses reacting to different stimuli to contribute to a single response.

Question 21

Cholinergic synapse

Answer 21

A synapse whose neurotransmitter is acetylcholine.

Question 22

Acetylcholine

made up of?

Answer 22

made up of acetyl (ethanoic acid)

and choline

Question 23

Where are cholinergic synapses found?

Answer 23

in vertebrates
in the central nervous system
at neuromuscular junctions

Question 24

Neuromuscular junctions

Answer 24

junctions between neurones and muscles

Question 25

Which enzyme hydrolyses acetylcholine?

Answer 25

acetylcholinesterase

Question 26

What causes sodium ion protein channels to open?

Answer 26

binding of acetylcholine to receptor sites on sodium ion protein channels in the membrane of the postsynaptic neurone

Question 27

What causes calcium ion protein channels to open?

Answer 27

the arrival of an action potential at the end of the presynaptic neurone

Question 28

How do calcium ions enter the synaptic knob?

Answer 28

facilitated diffusion

Question 29

What generates a new action potential in the postsynaptic neurone?

Answer 29

influx of sodium ions

Question 30

What is ATP from mitochondria used for in the presynaptic neurone?

Answer 30

recombining acetyl and choline to form acetylcholine