Transmission between neurons

Question 1

What is a synapse?

Answer 1

The small gap between neurons.

Question 2

Define: neurotransmitter

Answer 2

A chemical that carries information across the synapse between two neurons.

Question 3

The presynaptic neuron’s terminal/bouton contains neurotransmitters in the…?

Answer 3

Vesicles.

Question 4

The postsynaptic neuron has receptors that are…

Answer 4

Specific to a neurotransmitter.

Question 5

When the AP arrives in the bouton of the presynaptic cell, …?

Answer 5

Ca2+ channels open and calcium floods into the bouton.

Question 6

Calcium in the presynaptic bouton causes…?

Answer 6

The vesicles to fuse with the presynaptic membrane and release the neurotransmitter across the synaptic cleft.

Question 7

What is exocytosis?

Answer 7

The fusion of the vesicles with the cell membrane.

Question 8

The neurotransmitter diffuses across the cleft and…?

Answer 8

Binds onto post-synaptic neuron receptors.

Question 9

The neurotransmitter binding with receptors triggers…?

Answer 9

A new AP (or something different depending on the neurotransmitter).

Question 10

After release, neurotransmitters can be removed from the cleft by:

Answer 10

• Re-uptake (transporter molecules use energy to take it back into the presynaptic neuron)
• Diffusion
• Deactivation

Question 11

How are neurotransmitters in the synaptic cleft deactivated?

Answer 11

An enzyme breaks it down into parts.

E.g. Acetylcholinesterase breaks up acetylcholine into acetate and choline.

Question 12

Define: neuromuscular junction

Answer 12

Where a neuron joins a muscle to stimulate it.

Question 13

What is curare?

Answer 13

A substance used in poison darts which blocks the action of acetylcholine and paralyses prey.

Question 14

Name 5 neurotransmitters.

Answer 14

Acetylcholine (ACh)
Serotonin
GABA
Glutamate
Dopamine

Question 15

What is ACh?

Answer 15

A neurotransmitter, found in both neuromuscular junctions and the brain, binds to nicotinic receptors which opens ion channels. Ions cross the cell membrane and initiate a second AP. At nicotinic receptors it’s fast (ionotropic) and excitatory.

Question 16

What is serotonin?

Answer 16

A neurotransmitter found only in the brain which binds to receptors triggering G-protein. This activates a second messenger within the cell which opens the ion channels. It can also activate genes, change the synapse and cause learning. It’s slow (metabotropic) and excitatory.
Prozac increases its impact.

Question 17

What is GABA?

Answer 17

Gamma-aminobutyric acid, a nt found throughout the brain. Binds to both fast and slow GABA receptors, which open the channels causing Cl- to cross the membrane, inhibiting the neurons.

Question 18

Can neurons have multiple neurotransmitters, or multiple receptor types?

Answer 18

Receptor types - each neuron releases only one transmitter.

Question 19

Is glutamate metabotropic or ionotrpic, and is it excitatory or inhibitory?

Answer 19

Ionotropic excitatory.

Question 20

Is dopamine metabotropic or ionotrpic, and is it excitatory or inhibitory?

Answer 20

Metabotropic excitatory.

Question 21

What do excitatory neurotransmitters actually do?

Answer 21

Sodium and calcium enter the cell, excitatory post-synaptic potential (EPSP), increases the membrane potential from -70mV making AP more likely.

Question 22

What do inhibitory neurotransmitters actually do?

Answer 22

Potassium leaves the cell and chloride enters, inhibitory post-synaptic potential (IPSP), causes membrane potential to decrease making AP less likely.

Question 23

How does a post-synaptic neuron ‘decide’ whether to send an AP?

Answer 23

It integrates its inputs (PSPs) and fires an AP if the membrane potential exceeds -55mV.