Excitatory And Inhibitory Neurotransmission In The CNS

Question 0

What is the direction of Ca2+ in the resting membrane?

Answer 0

Inwards
Depolarisation
Excitatory

Question 1

What is the direction of Na flow in a neurone at rest?

Answer 1

Influx
Depolarisation
Excitatory

Question 2

What is the direction of Cl flow in the resting membrane?

Answer 2

Inwards
Hyperpolarisation
Inhibitory

Question 3

What is the direction of K+ flow in the resting membrane?

Answer 3

Outwars
Hyperpolarisation
Inhibitory

Question 4

What is the effect of an Na channel antagonist?

Answer 4

Closes channel, stops Na ion flow, favours inhibition.

E.g. Local anaesthetics like lidocaine

Question 5

What are the 2 modes of action of neurotransmitters at the post-synaptic area?

Answer 5

Direct gating by ionotropic receptors

Indirect gating by activation of metabotropic receptors

Question 6

What is the role of glutamate in the CNS?

Answer 6

The major excitatory neurotransmitter but also has inhibitory effects via its effect on metabotropic glutamate receptors

Question 7

What happens at non-NMDA glutamate receptors?

Answer 7

The receptor binds the agonists kainate or AMPA controlling a channel permeable to Na+ and K+
Mediates fast epsp

Question 8

What happens at the NMDA glutamate receptor?

Answer 8

Controls a channel permeable to Na+ and K+ and Ca2+

Mediates slow epsp

Question 9

What is the consequence of the high permeability of NMDA glutamate receptors to Ca2+?

Answer 9

Promotes neurotoxicity

Certain anaesthetic agents e.g. Ketamine and phencyclidine are selective blockers of the channels

Question 10

What is the role of GABA in the CNS?

Answer 10

The main inhibitory neurotransmitter in the CNS
Ionotropic GABAa receptor operates a Cl- channel
Metabotropic GABAb receptor often activates a K+ channel

Question 11

What drugs act on GABA receptors?

Answer 11

Benzodiazepines: excitatory to GABAa
Barbiturates: excitatory to GABAa
Baclofen: agonist of GABAb

Question 12

What is the role of glycine in the CNS?

Answer 12

Inhibitory neurotransmitter on glycine ionotropic receptor that gates a Cl- channel.

Question 13

How is glycine released?

Answer 13

By interneurones in the spinal cord to inhibit antagonist muscles motoneurones

Question 14

Which CNS receptor is faster?

Answer 14

Ionotropic receptors are faster than metabotropic receptors

Question 15

How do metabotropic receptors trigger an action potential?

Answer 15

Modulatory synaptic actions
Act on presumptive channels to modulate transmitter release
Modulate transmitter-gated channels to regulate the size of the epsp
Modulate the resting and voltage gated ion channels in the neuronal soma

Question 16

What is graded potential?

Answer 16

The strength of the action potential affects the spread of the signal

Question 17

What is a quanta?

Answer 17

The release of neurotransmitter from a single vesicle

The number of quanta depends on the stimulus

Question 18

What is synaptic integration?

Answer 18

Summation of postsynaptic membrane potentials allows multiple synaptic inputs to be integrated