Synapses and the Role of Neurotransmitters

Question 1

What is the relative abundance of glia with respect to neurones?

Answer 1

Glia are 10-50x more abundant than neurones.

Question 2

List 5 functions of glia.

Answer 2

1 - Guiding connecting.

2 - Physical support.

3 - Metabolic support.

4 - Electrical insulation.

5 - Signalling.

Question 3

What is the function of the axon hillock?

Answer 3

Action potential generation.

Question 4

What are the two types of synapse in the CNS?

Answer 4

1 - Electrical synapses (gap junctions).

2 - Chemical synapses.

Question 5

List 2 differences between electrical and chemical synapses.

Answer 5

1 - Electrical synapses are faster than chemical synapses.

2 - Electrical synapses allow for bi-directional communication whereas chemical synapses only allow for uni-directional communication.

Question 6

Where are gap junctions found?

Answer 6

1 - Between glia and neurones.

2 - Between glia and other glia.

3 - In cardiac myocytes.

Question 7

What 2 processes terminate a signal at a synapse?

Answer 7

1 - Enzymatic breakdown of receptor-neurotransmitter complexes.

2 - Reuptake of the neurotransmitter.

Question 8

What is the major excitatory neurotransmitter?

Answer 8

Glutamate.

Question 9

What is the major inhibitory neurotransmitter?

Answer 9

GABA.

Question 10

List 4 major chemical groups of neurotransmitters.

Answer 10

1 - Amino acids.

2 - Monoamines.

3 - Acetylcholine.

4 - Neuroactive peptides.

Question 11

List 3 amino acid neurotransmitters.

Which are excitatory and which are inhibitory?

Answer 11

1 - Glutamate (excitatory).

2 - GABA (inhibitory).

3 - Glycine (inhibitory).

Question 12

List 4 monoamine neurotransmitters.

Answer 12

1 - Noradrenaline.

2 - Adrenaline.

3 - Dopamine.

4 - Serotonin.

Question 13

List 2 types of neuroactive peptide.

Answer 13

1 - Opioid peptides.

2 - Tachykinins.

Question 14

What are the two types of receptor signalling mechanisms in chemical synapses?

Answer 14

1 - Ionotropic.

2 - Metabotropic.

Question 15

List the differences between the effects of ionotropic and metabotropic receptor signalling mechanisms.

Answer 15

1 - Ionotropic receptors have faster transmission than metabotropic receptors.

2 - Ionotropic receptors have shorter lasting effects than metabotropic receptors.

Question 16

List 4 excitatory ionotropic receptors.

Answer 16

1 - Nicotinic ACh receptor.

Some subtypes of glutamate receptor:

2 - AMPA receptor.

3 - NMDA receptor.

4 - Kainate receptor.

Question 17

What is the result of excitatory ionotropic receptor activation?

Answer 17

• Membrane depolarisation by Na+ influx.

- A small excitatory post-synaptic potential (EPSP).

Question 18

Give an example of an inhibitory ionotropic receptor.

Answer 18

The GABA-A receptor is an inhibitory ionotropic receptor.

Question 19

What is the result of inhibitory ionotropic receptor activation?

Answer 19

• Membrane hyperpolarisation (more negative) by Cl- influx.

- A small inhibitory post-synaptic potential (IPSP).

Question 20

What is the difference between GABA-A and GABA-B receptors?

Answer 20

GABA-A receptors are ionotropic whereas GABA-B receptors are metabotropic.

Question 21

List 3 metabotropic receptors.

Answer 21

1 - Muscarinic ACh receptors.

2 - GABA-B receptors.

3 - Monoamine receptors (all are metabotropic with one exception).

*Excitatory or inhibitory depending on subtype!

Question 22

Define spatial summation.

Answer 22

Spatial summation is the summation of postsynaptic potentials generated at separate synapses at the soma of a neurone.

Question 23

Define temporal summation.

Answer 23

Temporal summation is the summation of postsynaptic potentials generated at the same synapse at the soma of a neurone when the incoming action potentials are generated in rapid succession.

Question 24

How does the mechanism of ionotropic receptors differ from that of a metabotropic receptor?

Answer 24

• An ionotropic receptor functions by directly opening an ion channel.
• A metabotropic receptor functions by triggering effector systems through GPCRs.