Excitatory And Inhibitory Neurotransmission In The CNS Flashcards
(19 cards)
What is the direction of Ca2+ in the resting membrane?
Inwards
Depolarisation
Excitatory
What is the direction of Na flow in a neurone at rest?
Influx
Depolarisation
Excitatory
What is the direction of Cl flow in the resting membrane?
Inwards
Hyperpolarisation
Inhibitory
What is the direction of K+ flow in the resting membrane?
Outwars
Hyperpolarisation
Inhibitory
What is the effect of an Na channel antagonist?
Closes channel, stops Na ion flow, favours inhibition.
E.g. Local anaesthetics like lidocaine
What are the 2 modes of action of neurotransmitters at the post-synaptic area?
Direct gating by ionotropic receptors
Indirect gating by activation of metabotropic receptors
What is the role of glutamate in the CNS?
The major excitatory neurotransmitter but also has inhibitory effects via its effect on metabotropic glutamate receptors
What happens at non-NMDA glutamate receptors?
The receptor binds the agonists kainate or AMPA controlling a channel permeable to Na+ and K+
Mediates fast epsp
What happens at the NMDA glutamate receptor?
Controls a channel permeable to Na+ and K+ and Ca2+
Mediates slow epsp
What is the consequence of the high permeability of NMDA glutamate receptors to Ca2+?
Promotes neurotoxicity
Certain anaesthetic agents e.g. Ketamine and phencyclidine are selective blockers of the channels
What is the role of GABA in the CNS?
The main inhibitory neurotransmitter in the CNS
Ionotropic GABAa receptor operates a Cl- channel
Metabotropic GABAb receptor often activates a K+ channel
What drugs act on GABA receptors?
Benzodiazepines: excitatory to GABAa
Barbiturates: excitatory to GABAa
Baclofen: agonist of GABAb
What is the role of glycine in the CNS?
Inhibitory neurotransmitter on glycine ionotropic receptor that gates a Cl- channel.
How is glycine released?
By interneurones in the spinal cord to inhibit antagonist muscles motoneurones
Which CNS receptor is faster?
Ionotropic receptors are faster than metabotropic receptors
How do metabotropic receptors trigger an action potential?
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
What is graded potential?
The strength of the action potential affects the spread of the signal
What is a quanta?
The release of neurotransmitter from a single vesicle
The number of quanta depends on the stimulus
What is synaptic integration?
Summation of postsynaptic membrane potentials allows multiple synaptic inputs to be integrated
