Excitatory & Inhibitory Neurotransmission Flashcards
What is the typical resting membrane potential (RMP) for a neurone?
- 70mV
When the resting membrane potential increases, this is known as _______
Depolarisation (excitation)
When the resting membrane potential decreases, this is known as _______
Hyperpolarisation (inhibition)
Opening of a Na channel causes…?
Inflow of Sodium - depolarisation & excitation
Opening of a Ca channel causes…?
Inflow of Calcium - depolarisation & excitation
Opening of a Cl channel causes…?
Inflow of Chloride - hyperpolarisation & inhibition
Opening of a K channel causes…?
Outflow of Potassium - hyper polarisation & inhibition
Where does the membrane potential summate before causing an ‘all or nothing’ action potential?
Axon Hillock
What are the stages in neurotransmission?
- An AP depolarises the axon terminal.
- The depolarisation opens voltage-gated calcium channels, allowing calcium in.
- Calcium entry triggers exocytosis of synaptic vesicle contents.
- Neurotransmitter diffuses across the synaptic cleft and binds with receptors on the post-synaptic cell.
- Neurotransmitter binding initiates a response on the post-synaptic cell.
What happens to neurotransmitter molecules after they have fulfilled their purpose?
- Return to axon terminal for reuse
- Deactivation by enzymes
- Diffusion out of the synaptic cleft
Which kind of receptor is part of the ion channel molecule?
Hint: acts directly
Ionotropic receptor
Which kind of receptor acts via a G-coupled protein receptor?
(Hint: acts indirectly)
Metabotropic receptor
Which receptor (ligand-gated channel) is tetrameric?
Glutamate Receptor
NB - this is the major excitatory neurotransmitter but can have inhibitory effects at metabotropic glutamate receptors.
Which receptor (ligand-gated channels) are pentameric?
ACh, GABA, Glycine
Which receptor opens a channel permeable to Sodium, Calcium and Potassium?
NMDA receptor
The non-NMDA receptor (ionotropic) is acted upon by which molecules?
AMPA and Kainate
Which is the main inhibitory neurotransmitter in the CNS?
GABA
Which form of GABA acts on an ionotropic receptor?
GABA-a
Which form of GABA acts on a metabotropic receptor?
GABA-b
What is Excitatory Post-synaptic Potential (EPSP)?
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.
What is Inhibitory Post-synaptic Potential (IPSP)?
A negative change in RMP caused by release of an inhibitory neurotransmitter. It inhibits crossing of the threshold so no action potential is produced.
What is graded potential?
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.
Which is the main excitatory neurotransmitter int he CNS?
Glutamate
What is a quanta?
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.
