Neurotransmitters

Question 1

Describe process of action potential leading to cellular response

Answer 1

1. Action potential (nerve impulse/wave of depolarisation) reaches the nerve terminal
2. Causes the synaptic vesicles to fuse with the plasma membrane
3. Vesicles release their neurotransmitter contents by exocytosis –> process is Ca2+ dependent
4. Neurotransmitter diffuses across synaptic cleft
5. Binds to specific post-synaptic receptors
6. Initiates cellular response

Question 2

What are neurotransmitters?

Answer 2

Chemical messengers of the nervous system

Question 3

What are monoamines?

Answer 3

Group of neurotransmitters –> Noradrenaline, Adrenaline, Dopamine, Histamine, Serotonin

Question 4

What amino acids are neurotransmitters?

Answer 4

Glutamate, aspartate, glycine, GABA

Question 5

Where are neurotransmitters synthesised?

Answer 5

In the nerve terminal

Question 6

Where are neurotransmitters stored?

Answer 6

In synaptic vesicles within nerve terminals

Question 7

Where are neurotransmitters released? What happens after?

Answer 7

Into the synaptic cleft from pre-synaptic vesicles by exocytosis (Ca2+ dependent) in response to action potential

They diffuse across synaptic cleft and act on specific receptors located on the post-synaptic cell

Question 8

How are neurotransmitters inactivated?

Answer 8

Action is short-lived due to enzyme metabolism and/or re-uptake into pre-synaptic nerve terminal

Question 9

What are the 2 distinct types of depressive syndrome?

Answer 9

1. Unipolar depression

2. Bipolar affective disorder

Question 10

Why is depression an ‘affective disorder’?

Answer 10

Disorders of mood rather than disturbance of thought/cognition

Question 11

What is unipolar depression?

Answer 11

Mood swings are always in the same direction

Question 12

What is role of antidepressants?

Answer 12

To increase monoaminergic transmission within the synaptic cleft –> Monoamine reuptake inhibitors

Question 13

What are 3 examples of monoamine reuptake inhibitors?

Answer 13

1. TCAs - tricyclic antidepressants
2. SSRIs - selective serotonin reuptake inhibitors
3. SNRIs - serotonin/noradrenaline reuptake inhibitors

Question 14

How are monoamines involve in termination of signalling?

Answer 14

Reuptake of monoamine neurotransmitters from the synaptic cleft by monoamine transporters is a key process in the termination of monoaminergic signalling and the maintenance of presynaptic monoamine storage levels

Question 15

How do monoamine reuptake inhibitors enhance transmission?

Answer 15

Bind to pre-synaptic nerve terminal monoamine transporters –> inhibiting reuptake and raising neurotransmitter levels in the synaptic cleft

Question 16

What are monoamine oxidases (MAOs)?

Answer 16

Family of enzymes that catalyse the oxidative deamination (breakdown) of monoamine in the presynaptic nerve terminal

Question 17

How do monoamine oxidase inhibitors (MAOIs) enhancing transmission?

Answer 17

Prevent breakdown of monoamine within the nerve terminal –> more monoamine neurotransmitters available for release

Question 18

What is ACh?

Answer 18

Neurotransmitter

• Chief neurotransmitter of the parasympathetic nervous system
• Contracts smooth muscles, dilates blood vessels, increases bodily secretions, slows heart rate

Question 19

What is noradrenaline?

Answer 19

Neurotransmitter

• Increases heart rate and blood pressure, widening of pupils, narrowing of blood vessels in non-essential organs

Question 20

What are gasotransmitters?

Answer 20

• Gaseous molecules synthesised in the body (NO, CO, H2S)

- Can also be environmental pollutants or toxic gases