Synapses

Question 1

The synapse

Answer 1

Junction that allows 2 neurones to communicate with each other using neurotransmitters

Question 2

Pre synaptic neurone

Answer 2

The one receiving the action potential that will send it to the next one

Question 3

Post synaptic neurone

Answer 3

The neurone that receives neurotransmitter from pre synaptic neurone to stimulate the generation of a new action potential

Question 4

Where in the neurones are impulses transmitted over the synapse?

Answer 4

From the synaptic knob of pre synaptic neurone (at axon terminal end) to the dendrites of the cell body on the post synaptic neurone

Question 5

Types of synapses

Answer 5

Excitatory
Inhibitory

Question 6

Excitatory synapse

Answer 6

Stimulates the development of new action potentials at post synaptic neurone

Question 7

Neurotransmitters

Answer 7

Allows for communication of neurones over the synapse by diffusion of the neurotransmitter from one neurone to the next

Question 8

What neurotransmitter is on the specification ?

Answer 8

Acetyl choline

Question 9

Cholinergenic synapse

Answer 9

Type of synapse that communicates to next neurone using acetyl choline

Question 10

What happens when action potentials arrive at the synaptic knob of presynaptic neurone?

Answer 10

Depolarises the pre synaptic membrane

Question 11

What happens when the synaptic knob is depolarised?

Answer 11

Voltage gated Ca2+ channel proteins are triggered to open so
Ca2+ ions diffuse into synaptic knob down electrochemical gradient using channel proteins

Question 12

What happens when Ca2+ ions enter the synaptic knob?

Answer 12

Causes synaptic vesicles in synaptic knob to fuse with the presynaptic neurone membrane

Question 13

Fusion of synaptic vesicles with synaptic knob

Answer 13

The synaptic vesicles containing acetyl choline will release acetyl choline into synaptic cleft

Question 14

Once acetyl choline is in the synaptic cleft…

Answer 14

It will diffuse to the post synaptic membrane and bind to receptors on the membrane

Question 15

When acetylcholine binds to receptors on post synaptic membrane in an excitatory synapse

Answer 15

Na+ channel proteins are triggered to open (on post synaptic membrane) so Na+ ions are triggered to diffuse into the post synaptic neurone

Question 16

In an excitatory synapse, what happens when Na+ diffuses into post synaptic neurone?

Answer 16

Causes depolarisation of neurone membrane
If threshold is reached, this generates new action potentials to be sent along post synaptic neurone

Question 17

Inhibitory synapse

Answer 17

Stops the generation of new action potentials at the post synaptic membrane

Question 18

What happens in an inhibitory synapse when acetyl choline binds to receptors on post synaptic neurone?

Answer 18

Triggers opening of K+ channel proteins so K+ diffuses out of the post synaptic neurone by facilitated diffusion
Causes hyper polarisation of post synaptic neurone
So less likely to reach threshold and won’t generate an action potential

Question 19

Summation

Answer 19

Determining whether threshold will be reached thus an action potential generated in post synaptic neurone

Question 20

2 types of summation

Answer 20

Temporal
Spatial

Question 21

Temporal summation

Answer 21

A higher frequency of impulses is sent along presynaptic neurone so more neurotransmitter is released so more likely for post synaptic membrane to reach threshold and generate a new impulse

Question 22

Spatial summation

Answer 22

If a post synaptic neurone membrane is connected at the synapse to 2 or more pre synaptic neurones so will receive neurotransmitter from more than 1 neurone
More likely to trigger enough depolarisation and reach threshold to generate new impulse

Question 23

Neurone to myofibril synapse

Answer 23

Same mechanism but the post synaptic neurone is the myofibril, it’s membrane is the sarcomella and an impulse is sent along the muscle fibre not neurone