Excitatory & Inhibitory Neurotransmission in CNS

Question 1

Entry of + ions (Na,Ca,K) or exit of - ions (Cl)

Answer 1

Positive change (Depolarisation or excitation)

Question 2

Exit of + ions (Na,Ca,K) or entry of - ions (Cl)

Answer 2

Negative change (Hyperpolarisation or inhibition)

Question 3

Resting membrane potential

Answer 3

-70mV

Question 4

Extracellular concentration

Answer 4

Na - 145
K - 4
Cl - 123
Ca - 1.5

Question 5

Intracellular concentration

Answer 5

Na - 12
K - 155
Cl - 4
Ca - 10

Question 6

Na channels

Answer 6

Flows inwards (depolarisation, excitatory)

Question 7

Ca channels

Answer 7

Flows inwards (depolarisation, excitatory)

Question 8

Cl channels

Answer 8

Flows inwards (hyperpolarisation, inhibitory)

Question 9

K channels

Answer 9

Flows outwards (hyperpolarisation, inhibitory)

Question 10

Direct gating

Answer 10

Ionotropic receptors.
(The receptor is an integral component of the molecule that forms the channel it controls. Ionotropic receptor is itself a channel).

Question 11

Indirect gating

Answer 11

Mediated by activation of metabotropic receptors.
(Receptor and channel it controls are distinct. Metabotropic receptors are a signalling structure. Works by sending molecules/signals that affect a channel).

Question 12

GABA, Gylcine and ACh (nicotinic) receptors

Answer 12

Pentamers

Question 13

Glutmate receptors

Answer 13

Tetramers

Question 14

Glutamate

Answer 14

Major excitatory neurotransmitter.

May also have inhibitory effects via its response at Metabotropic Glutamate Receptors.

Question 15

GABA

Answer 15

Main inhibitory neurotransmitter in CNS

Question 16

GABA acts on:

Answer 16

Ionotropic GABAa receptor that operates a Cl- channel

GABAb metabotropic receptor, activates potassium channel.

Question 17

Ionotropic Glutamate Receptors

Answer 17

Non-NMDA - mediate fast excitatory synaptic transmission, AMPA or kainate agonist controlling channel permeable to Na and K.

NMDA - slow component, controls channels permeable to Na, Ca, K

Question 18

Benzodiazepines

Answer 18

Positive allosteric modulator of GABAa receptor (enhance Cl- entry).

Question 19

Barbiturates

Answer 19

Similar to benzodiazepines, potentiate GABA effect at GABAa.

Question 20

Baclofen

Answer 20

GABAb receptor agonist, enhances K current (increases inhibition)

Question 21

Fast EPSP

Answer 21

Due to activation of nicotinic (ionotropic) ACh receptors.

Channels conduct Na and K.

Question 22

Slow EPSP

Answer 22

Activation of muscarinic (GPCR) ACh receptors.

ACh closes a K+ channel (M-type).

Question 23

EPSP

Answer 23

Excitatory postsynaptic potential: depolarising change in rmp caused by the actions of excitatory neurotransmission. Large or multiple EPSPs can cause rmp to cross threshold and result in an AP.

Question 24

IPSP

Answer 24

Inhibitors postsynaptic potential: negative change in rmp by release of an inhibitory neurotransmitter. Inhibits crossing of threshold and inhibits AP.

Question 25

Glutamate (summary)

Answer 25

Major excitatory neurotransmitter.

Acts on iontropic receptors to allow Na, Ca into cell and allow K out of the cell. Result is EPSP.

Question 26

GABA (summary)

Answer 26

Major inhibitory neurotransmitter.

Acts on ionotropic receptors to allow Cl into cell. Result is IPSP.

Question 27

Interneurone

Answer 27

Locally acting neurone, typically releases GABA.

Function is local processing of information.

Question 28

Projection neurone

Answer 28

Neurone responsible for conveying signals to other parts of the brain, typically releasing Glutamate.

Question 29

Spatial Summation

Answer 29

EPSPs and IPSPs are spatially distributed but timed together.

Question 30

Temporal Summation

Answer 30

EPSPs occur in temporal sequence such that threshold is triggered.

Question 31

Quanta

Answer 31

Discrete packages of neurotransmitter from single vesicle.