Communication Between Excitable Cells

Question 1

Name X3 examples of where axon synapses can terminate.

Answer 1

Axo-dendritic synapses (axon to dendrite)
Axo-axonic synapses (axon to axon)
Axo-somatic synapses (axon to cell body)

Question 2

Explain the steps in synaptic transmission, starting with a pre-synaptic action potential and ensuring to mention the role of calcium.

Stop after the neurotransmitter is released.

Answer 2

1) pre-synaptic action potential travels down the axon
2) the synaptic terminal depolarises
3) this opens voltage-gated calcium channels which are responsible for causing fusion of neurotransmitter containing vesicles with the membrane
4) neurotransmitter is released

Question 3

What does 5-HT stand for?

What is its other name?

Answer 3

5-hydroxytryptamine OR serotonin

Question 4

How does L-dopa work?

Is it an agonist or antagonist?

How does it work in the normal synaptic transmission pathway?

Answer 4

It is an agonist which works by serving as a neurotransmitter precursor.

It acts by being converted to dopamine.

Question 5

How does botulinum toxin work?

Is it an agonist or antagonist?

What is it used to treat!

Answer 5

It is an antagonist which inhibits neurotransmitter release by degrading SNAP25.

It is used to treat overactive bladder by targeting muscarinic receptors in this area.

Question 6

How do nicotine and muscarine work?

Are they agonists or antagonists?

Answer 6

They are agonists which stimulate post-synaptic receptors.

Question 7

How do curae and atropine work?

Are they agonists or antagonists?

Answer 7

They are antagonists which block post-synaptic receptors

Question 8

What X3 things can reduce vesicle release from the synapse?

Answer 8

1) low calcium
2) high magnesium
3) curare

Question 9

What do EPSP and IPSP stand for?

What do each of these mean?

What causes each of these?

Answer 9

Excitatory post-synaptic potential
= a post-synaptic potential that brings the membrane potential closer to the threshold potential and therefore makes it more likely to fire.
= a small local depolarisation
= caused by open Na channels

Inhibitory post-synaptic potential
= a post-synaptic potential that brings the membrane potential further away from the threshold potential and therefore makes it less likely to fire.
= a small local hyperpolarisation
= caused by open K or Cl channels