Synapses and the role of Neurotransmitters

Question 1

What makes up the CNS?

Answer 1

Brain and spinal cord

Question 2

What makes up the PNS?

Answer 2

Sensory neurones
Motor neurones
Autonomic nervous system (ANS)

Question 3

What makes up the ANS?

Answer 3

Sympathetic
Parasympathetic
Enteric

Question 4

What are some neuronal specialisations?

Answer 4

Dendrites
Axons
Axon terminals
Synaptic bouton

Question 5

What do dendrites do?

Answer 5

Receive input from other neurones

Question 6

What do Axons do?

Answer 6

Carry out impulse conduction

Question 7

What is the purpose of the axon terminal?

Answer 7

Release of neurotransmitter

Question 8

How are neurones classified?

Answer 8

Based on morphological criteria:

Number of processes - uni/bi/multi/pseudo
Dendrites - shape/presence or absence of spines
Connectors - motor/interneurones
Axon length - golgi type 1 / 2
Neurotransmitter

Question 9

What is a unipolar nerve cell?

Answer 9

a single axonal process

Question 10

What is a multipolar nerve cell?

Answer 10

nerve cell with multiple axonal processes

Question 11

What is a bipolar cell?

Answer 11

2 axonal processes

Question 12

What’s the fastest electrical synapse?

Answer 12

the gap junction

Question 13

What are some features of the gap junction?

Answer 13

direct transfer of ionic current (also small molecules)

-bi-directional

Question 14

Where are gap junctions found?

Answer 14

between neurones in the CNS

Question 15

What type of neurones takes information to the brain

Answer 15

Afferent

Question 16

What type of neurone takes information away from the brain?

Answer 16

Efferent

Question 17

What is a chemical synapse?

Answer 17

Unidirectional
Close association between presynaptic axon terminal and post synaptic membrane.
Release of neurotransmitters

Question 18

How does synaptic transmission work?

Answer 18

1. action potential invades the nerve terminal
2. depolarisation triggers Ca2+ channel opening causing Ca2+
3. Neurotransmitter released by exocytosis
4. Neurotransmitter diffuses across the synapse and binds to a receptor
5. post synaptic effect
6. rapid termination of signal

Question 19

How is the signal terminated?

Answer 19

• re-upatake of neurotransmitter

- enzymatic breakdown

Question 20

What is the major excitatory neurotransmitter?

Answer 20

glutamate

Question 21

What is the major inhibitory neurotransmitter?

Answer 21

GABA

Question 22

How do neurotransmitter receptors work?

Answer 22

They are membrane spanning proteins that have a structural change when neurotransmitter binds.

• each receptor is specific for a neurotransmitter
• one neurotransmitter can have several receptor subtypes

Question 23

What can act as neurotransmitters?

Answer 23

• amino acids
• monoamines
• acetylcholine
• neuroactive peptides

Question 24

What are the two types of receptor signalling mechanisms?

Answer 24

Ionotropic (receptor operated/ligand gated channels)

Metabotropic (G protein coupled)

Question 25

How does the ionotropic receptor signalling mechanism work?

Answer 25

-trasmitter binding causes a conformational change which causes a channel to open, allowing ion movement

Question 26

How does the metabotrophic receptor signalling mechanism work?

Answer 26

-transmitter binding causes a conformational change which activates a G protein which activates effector systems which has indirect effects of opening or closing ion channels, this stimulates or inhibits enzymes/secondary messenger systems

Question 27

What are some excitatory ionotropic receptors?

Answer 27

Glutamatergic receptors (AMPA/NMDA/Kainate)
Ach (nicotinic)
GABAb

Question 28

What are some inhibitory ionotropic receptors?

Answer 28

GABAa

Glycine