Excitatory & Inhibitory Neurotransmission

Question 1

What is the typical resting membrane potential (RMP) for a neurone?

Answer 1

• 70mV

Question 2

When the resting membrane potential increases, this is known as _______

Answer 2

Depolarisation (excitation)

Question 3

When the resting membrane potential decreases, this is known as _______

Answer 3

Hyperpolarisation (inhibition)

Question 4

Opening of a Na channel causes…?

Answer 4

Inflow of Sodium - depolarisation & excitation

Question 5

Opening of a Ca channel causes…?

Answer 5

Inflow of Calcium - depolarisation & excitation

Question 6

Opening of a Cl channel causes…?

Answer 6

Inflow of Chloride - hyperpolarisation & inhibition

Question 7

Opening of a K channel causes…?

Answer 7

Outflow of Potassium - hyper polarisation & inhibition

Question 8

Where does the membrane potential summate before causing an ‘all or nothing’ action potential?

Answer 8

Axon Hillock

Question 9

What are the stages in neurotransmission?

Answer 9

1. An AP depolarises the axon terminal.
2. The depolarisation opens voltage-gated calcium channels, allowing calcium in.
3. Calcium entry triggers exocytosis of synaptic vesicle contents.
4. Neurotransmitter diffuses across the synaptic cleft and binds with receptors on the post-synaptic cell.
5. Neurotransmitter binding initiates a response on the post-synaptic cell.

Question 10

What happens to neurotransmitter molecules after they have fulfilled their purpose?

Answer 10

1. Return to axon terminal for reuse
2. Deactivation by enzymes
3. Diffusion out of the synaptic cleft

Question 11

Which kind of receptor is part of the ion channel molecule?

Hint: acts directly

Answer 11

Ionotropic receptor

Question 12

Which kind of receptor acts via a G-coupled protein receptor?

(Hint: acts indirectly)

Answer 12

Metabotropic receptor

Question 13

Which receptor (ligand-gated channel) is tetrameric?

Answer 13

Glutamate Receptor

NB - this is the major excitatory neurotransmitter but can have inhibitory effects at metabotropic glutamate receptors.

Question 14

Which receptor (ligand-gated channels) are pentameric?

Answer 14

ACh, GABA, Glycine

Question 15

Which receptor opens a channel permeable to Sodium, Calcium and Potassium?

Answer 15

NMDA receptor

Question 16

The non-NMDA receptor (ionotropic) is acted upon by which molecules?

Answer 16

AMPA and Kainate

Question 17

Which is the main inhibitory neurotransmitter in the CNS?

Answer 17

GABA

Question 18

Which form of GABA acts on an ionotropic receptor?

Answer 18

GABA-a

Question 19

Which form of GABA acts on a metabotropic receptor?

Answer 19

GABA-b

Question 20

What is Excitatory Post-synaptic Potential (EPSP)?

Answer 20

A depolarising change in RMP caused by the actions of excitatory neurotransmission.

NB - Multiple EPSPs, or very large EPSPs can cause the RMP to cross the threshold, producing an action potential.

Question 21

What is Inhibitory Post-synaptic Potential (IPSP)?

Answer 21

A negative change in RMP caused by release of an inhibitory neurotransmitter. It inhibits crossing of the threshold so no action potential is produced.

Question 22

What is graded potential?

Answer 22

A change in the RMP caused by EPSP or IPSP that is not of a magnitude large enough to cross threshold and produce and AP.

Question 23

Which is the main excitatory neurotransmitter int he CNS?

Answer 23

Glutamate

Question 24

What is a quanta?

Answer 24

A specific quantity of neurotransmitter released from a single vesicle.

NB the number of quanta released is various with neurone type and the stimulus, although the actual amount in the quanta is constant.