13.5 Synapses

Question 1

what is a synapse?

Answer 1

the junction between two neurones

Question 2

what is a cholinergic synapse?

Answer 2

synapse between a motor neurone and an effector

Question 3

what chemicals are used to transmit an impulse across a synapse?

Answer 3

neurotransmitters

Question 4

what is the synaptic cleft?

Answer 4

gap between the axon of one neurone and the dendrite of the other neurone

Question 5

what is the presynaptic neurone?

Answer 5

neurone which carries the impulse to the synapse

Question 6

what is the postsynaptic neurone?

Answer 6

neurone which recieves the impulse from the synapse

Question 7

what is the synaptic knob?

Answer 7

swollen end of presynaptic neurone which contains mitochondria and ER in order to produce neurotransmitters

Question 8

what are the synaptic vesicles?

Answer 8

vesicles which contain neurotransmitters which fuse with the presynaptic membrane and undergo exocytosis

Question 9

what two types of neurotransmitters are there?

Answer 9

excitatory
inhibitory

Question 10

what are excitatory neurotransmitters?

Answer 10

cause the depolarisation of the postsynaptic neurone and cause an action potential to be generated once a threshold is passed

Question 11

what is an example of an excitatory neurotransmitter?

Answer 11

acetylcholine

Question 12

what are inhibtory neurotransmitters?

Answer 12

cause the hyperpolarisation of the postsynaptic membrane which prevents an action potential from being generated

Question 13

what is an example of a inhibitory neurone?

Answer 13

GABA

Question 14

how does an action potential cross a synapse?

Answer 14

action potential reaches the end of the presynaptic knob

depolarisation of the presynaptic membrane causes Ca2+ channels to open

Ca2+ ions diffuse in which causes vesicles containing the neurotransmitter to fuse with the membrane and release the neurotransmitter by exocytosis

the neurotransmitter diffuse across the synaptic cleft and bind to receptors on the postsynaptic membrane causing Na+ channels to open

Na+ ions diffuse in to the postsynaptic neurone which triggers the action potential

Question 15

what happens to the neurotransmitters left in the receptors?

Answer 15

enzymes break them down and they are taken back to the presynaptic knob

Question 16

why is it important to remove the neurotransmitters from the receptors?

Answer 16

prevents the action potential being generated again

Question 17

what enzyme breaks down acetylcholine?

Answer 17

acetylcholinesterase

Question 18

what does acetylcholinesterase break acetylcholine into?

Answer 18

ethanoic acid and choline

Question 19

what is summation?

Answer 19

when an action potential is generated once the threshold is passed

Question 20

what are the types of summation?

Answer 20

temporal
spatial

Question 21

what is spatial summation?

Answer 21

when many neurones go into one neurone in order to pass the threshold and generate an action potential

Question 22

what is temporal summation?

Answer 22

when one neurone produces more neurotransmitters over a short period of time in order to pass the threshold and generate an action potential

Question 23

what is the role of synapses

Answer 23

ensure impulses are unidirectional

allow for an impulse from one neurone to reach multiple neurones

allow for multiple impulses from multiple neurones to reach a neurone

Question 24

why do synapses ensure unidirectional flow?

Answer 24

neurotransmitter receptors are only found in the postsynaptic membrane so an impulse can only travel from the presynaptic to the postsynaptic