Synapses

Question 1

What is a synapse?

Answer 1

a junction between a neurone and another neurone or neurone and effector cell

Question 2

What happens when action potential reaches synaptic knob?

Answer 2

presynaptic membrane depolarises causing calcium ion channels to open and the Ca+ ions diffuse into presynaptic knob. This causes vesicles containing neurotransmitters to fuse with pre synaptic membrane and are released into synaptic cleft via exocytosis

Question 3

What happens to neurotransmitter in synaptic cleft?

Answer 3

it binds to receptors on postsynaptic membrane

Question 4

What happens in postsynaptic neurone after neurotransmitter has bound to receptors?

Answer 4

sodium ion channels open and sodium ions diffuse in causing an action potential on other side of synapse

Question 5

What happens after action potential is triggered in postsynaptic neurone?

Answer 5

enzymes release neurotransmitter from receptors and breaks it down and returns it to presynaptic knob. This prevents response happening again and again

Question 6

What are the roles of synapses?

Answer 6

ensuring impulses are unidirectional, allows an impulse to be transmitted from one neurone to a number of neurones and a number of neurones can transmit impulses into a single neurone.

Question 7

What is summation?

Answer 7

The sum total of lots of smaller impulses triggers an action potential as neurotransmitter builds up so that threshold value it met

Question 8

What are the two types of summation?

Answer 8

spatial - multiple presynaptic neurones connect to one postsynaptic neurones
temporal - a single presynaptic neurone releases lots of neurotransmitter as a result of several action potentials action potentials arriving in quick succession

Question 9

What are the two types of neurotransmitter?

Answer 9

excitatory and inhibitory

Question 10

What does an inhibitory neurotransmitter do?

Answer 10

causes hyperpolarisation of post synaptic neurone which prevents an action potential