15.5+15.6: Synapses

Question 1

Synapse

Answer 1

the point where one neurone communicates with another or an effector

Question 2

How do synapses transmit information

Answer 2

by means of chemicals called neurotransmitters

Question 3

Synaptic cleft

Answer 3

small gap (20-30nm wide) that separates neurones

Question 4

Presynaptic neurone

Answer 4

The neurone that releases neurotransmitter

Question 5

Synaptic knob

Answer 5

The axon of the presynaptic neurone ends in a swollen portion.

Question 6

What does the synaptic knob contain

Answer 6

lots of mitochondria and ER which required for manufacturing the neurotransmitter which occurs in the axon

Question 7

Synaptic vesicles

Answer 7

store the neurotransmitter

Question 8

What happens once the neurotransmitter is released from the vesicles

Answer 8

it diffuses across to the postsynaptic neurone, which possesses specific receptor proteins on its membrane to receive it

Question 9

Two features of synapses

Answer 9

unidirectionality

summation

Question 10

Unidirectionality

Answer 10

Can only pass information in one direction from the presynaptic neurone to the postsynaptic neurone

Question 11

What feature of synapses means that they act like valves?

Answer 11

unidirectionality

Question 12

Summation

Answer 12

Rapid build up of neurotransmitter in the synapse

Question 13

What process allows low frequency action potentials to trigger an action potential in the postsynaptic neurone

Answer 13

summation

Question 14

Why are low frequency action potentials unable to trigger a new action potential in the postsynaptic neurone

Answer 14

they lead to the release of insufficient concentrations of neurotransmitter to trigger a new action potential

Question 15

Two types of summation

Answer 15

spatial and temporal

Question 16

Spatial summation

Answer 16

A number of different presynaptic neurones together release enough neurotransmitter to exceed the threshold value of the postsynaptic neurone, triggering an action potential.

Question 17

Temporal summation

Answer 17

A single presynaptic neurone releases neurotransmitter many times over a short period, if the concentration of neurotransmitter exceeds the postsynaptic neurone’s threshold value, an action potential will be triggered

Question 18

Inhibitory synapses

Answer 18

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

Question 19

Which two ion channels are involved in the process of operation of inhibitory synapses

Answer 19

Cl- and K+

Question 20

What do synapses act as

Answer 20

junctions

Question 21

Functions of synapses

2

Answer 21

1. a single impulse along one neurone to initiate new impulses in a number of different neurones at a synapse-number of simultaneous responses
2. a number of impulses to be combined at a synapse (allows nerve impulses from receptors reacting to diff. stimuli to contribute one response

Question 22

Where are neurotransmitters made

Answer 22

only in the presynaptic neurone

Question 23

Where is the neurotransmitter stored

Answer 23

stored in synaptic vesicles

Question 24

How is neurotransmitter released from the synaptic vesicles

Answer 24

when an action potential reaches the synaptic knob, the synaptic vesicles fuse with the pre-synaptic membrane to release the neurotransmitter

Question 25

What happens when neurotransmitter is release from the synaptic vesicles and fuses with the pre-synaptic membrane

Answer 25

the neurotransmitter diffuses across the synaptic cleft to bind to specific receptor proteins which are found only on the postsynaptic neurone

Question 26

What happens when the neurotransmitter binds with receptors on the postsynaptic neurone

Answer 26

it leads to a new action potential in the postsynaptic neurone, synapses that produce action potentials in this way = excitatory synapses

Question 27

Cholinergic synapse

Answer 27

One in which the neurotransmitter is a chemical called acetylcholine

Question 28

What is acetylcholine made up of?

Answer 28

acetyl and choline

Question 29

Where are cholinergic synapses found

Answer 29

common in vertebrates where they occur in the CNS and at neuromuscular junctions

Question 30

Neuromuscular junctions

Answer 30

junctions between neurones and muscles