5.1 Synapses

Question 1

what is a synapse?

Answer 1

the junction between two neurones

Question 2

how does information pass across the synaptic cleft?

Answer 2

chemicals called NEUROTRANSMITTERS

Question 3

what is the presynaptic neurone?

Answer 3

the neurone along which the impulse arrives

Question 4

what is the synaptic knob and what does it contain?

Answer 4

swollen end of the presynaptic neurone containing many mitochondria and large amounts of ER to make neurotransmitters

Question 5

what are synaptic vesicles? what do they do?

Answer 5

vesicles containing neurotransmitters

fuse with the membrane to release neurotransmitters

Question 6

what is the synaptic cleft?

Answer 6

the gap separating the axon of one neurone from the dendrite of the next

Question 7

what are receptor sites?

Answer 7

receptor molecules which the neurotransmitter binds to on the postsynaptic neurones membrane

Question 8

what do synapses ensure about impulses?

Answer 8

they are UNIDIRECTIONAL

Question 9

which two ways can an impulse be transmitted?

Answer 9

• to a number of neurones at multiple synapses resulting in a number of simultaneous responses
• a number of neurones can feed into the same synapse with a single postsynaptic neurone

Question 10

1. neurones are not in direct contact, what separates them?

Answer 10

the synaptic cleft

Question 11

2. when an action potential arrives at the end of a presynaptic neurone what does it cause to open?

Answer 11

calcium channels resulting in calcium flooding in to the axon

Question 12

3. what does increased levels of calcium stimulate?

Answer 12

synaptic vesicles to move toward membrane of presynaptic neurone.

Question 13

3. what neurotransmitter do the vesicles contain?

Answer 13

acetylcholine

Question 14

4. vesicles fuse with the membrane and acetylcholine is released into the synaptic cleft by what process?

Answer 14

exocytosis

Question 15

5. how does acetylcholine move across the synaptic cleft?

Answer 15

diffusion

Question 16

5. what does acetylcholine do when it reaches the post synaptic neurone and what does this result in?

Answer 16

binds to receptors on sodium ion channels, results in the channels opening allowing sodium to flood in

Question 17

6. what does the flooding in of sodium do to the postsynaptic membrane?

Answer 17

depolarizes it and if the threshold value is reached an action potential is generated

Question 18

7. what is acetylcholine broken down into?

Answer 18

ethanoic acid and choline

Question 19

7. what enzyme breaks down acetylcholine?

Answer 19

acetylcholinesterase

Question 20

7. where is acetylcholinesterase found?

Answer 20

in the synaptic cleft

Question 21

8. what do choline and ethanoic acid do?

Answer 21

diffuse back into the presynaptic neurone

Question 22

8. when choline and ethanoic acid diffuse back into the presynaptic neurone what happens?

Answer 22

ATP from the mitochondria used to recombine them back to acetylcholine

Question 23

which sort of synapses use the neurotransmitter acetylcholine?

Answer 23

cholinergic synapses

Question 24

where are cholinergic synapses found?

Answer 24

in the CNS of invertebrates at neuromuscular junctions

Question 25

why is the amount of neurotransmitter from a single impulse not enough to trigger an action potential in postsynaptic neurone?

Answer 25

threshold value not reached

Question 26

what does a stimulatory drug do?

Answer 26

creates more action potentials resulting in enhanced response

Question 27

what does an inhibitory drug do?

Answer 27

creates fewer action potentials resulting in reduced response

Question 28

what sort of drug is alcohol? what does it do?

Answer 28

inhibitory

binds to GABA receptors

Question 29

what does GABA do?

Answer 29

decreases activity of brain by preventing nervous transmission

Question 30

what does Prozac block? what does this do?

Answer 30

the reuptake of serotonin

more action potentials generated increasing serotonin levels

Question 31

what is Prozac used to treat?

Answer 31

depression

Question 32

what is temporal stimulation?

Answer 32

action potentials from one neurone arrive in rapid succession

Question 33

what is spatial stimulation?

Answer 33

several action potentials from different neurones arrive at post synaptic membrane at same time