15.5 synapses

Question 1

synapse

Answer 1

point where one neurone communicates with an effector

Question 2

neurotransmitters

Answer 2

chemicals that are transferred from one neurone to another(transmit information)

Question 3

presynaptic neurone

Answer 3

neurone that releases the neurotransmitter

Question 4

synaptic cleft

Answer 4

small gap that seperated neurones

Question 5

synaptic knob

Answer 5

end of the axon of the neurone

Question 6

Function of synaptic knob

Answer 6

lots of mitochondrion and endoplasmic reticulum to manufacture neurotransmitters

Question 7

synaptic vesicles

Answer 7

where neurotransmitter is stored

Question 8

postsynaptic neuron

Answer 8

the neurone where the neurotransmitter diffuses across to

Question 9

Postsynaptic neuron feature

Answer 9

has specific receptor proteins on membrane to receive neurotransmitters

Question 10

unidirectionality

Answer 10

only passes information in one direction from pre-post synaptic neurones
- like valves

Question 11

spatial summation

Answer 11

number of different presynaptic neurones release enough neurotransmitters together to exceed threshold value of postsynaptic neurone

-trigger new action potential

Question 12

temporal summation

Answer 12

single presynaptic neurone releases neurotransmitter many times over short period

conc of neurotransmitter exceeds threshold value, new action pt stimulated

Question 13

inhibition

Answer 13

• presynaptic neurones releases neurotransmitter that binds to chloride ion protein channels on postsynaptic neurone
• neurotransmitter cause Cl- ions protein channels to open
• binding neurotransmitter causes opening of nearby K+ channels
• K ions diffuse out of postsynaptic neurone into synapse
• inside of postsynaptic membrane more negative and outside more positive

-hyperpolarisation means it makes it less likely new action potential will be created(larger influx of Na+ ions needed to be produced)

Question 14

Function of synapse

Answer 14

allow single impulse along one neurone to initiate new impulses in number of different neurones at a synapse(single stimuli create number of responses)

number of impulses to be combined at a synapse(nerve impulses from receptors react to different stimuli to create single response)

Question 15

cholinergic synapse

Answer 15

occur in CNS and neuromuscular junctions

neurotransmitter is made of acetylcholine

Question 16

Transmission across synapse

Answer 16

1. action pt at end of presynaptic neurone causes Ca+ protein channels to open and Ca+ enter the synaptic knob
2. influx of Ca+ into presynaptic neurone causes synaptic vesicles to fuse with presynaptic membrane, releasing neurotransmitter into synaptic cleft
3. neurotransmitter diffuse across synaptic cleft very quickly because diffusion pathway is short
4. neurotransmitter binds to receptor sites on Na+ protein channels in membrane of postsynaptic neurone
5. Na+ protein channels open and Na+ diffuse rapidly along conc gradient and influx causes a new action potential

Question 17

Recycling acetylcholine

Answer 17

acetylecholinterase hydrolyses acetylcholine into choline and ethanoic acid, which diffuses back across synaptic cleft to presynaptic neurone

Prevent acetylcholine to continuously generate new action potential in postsynaptic neurone

Na+ protein channels close in absense of acetylecholine in receptor sites of postsynaptic neurone

ATP released by mitochondria recombines to reform aceytylcholine in presynaptic neurone

Question 18

excitatory synapses

Answer 18

synapses that produce new action potentials