Physiol 3 Synaptic transmission Flashcards
(20 cards)
What are action potentials (APs) initiated?
At the axon hillock/initial segment
APs are crucial for the transmission of electrical signals in neurons.
What role do voltage-gated Na+ channels play in action potentials?
They open in response to depolarizing local potentials, driving further depolarization.
What happens when sufficient Na+ channels open at the axon hillock?
Depolarization reaches a point where large numbers of channels open, causing a sudden large increase in Na+ influx.
What are the main events driving the change of membrane potential that characterizes an action potential?
- Na+ channel opening
- Na+ current
- Na+ channel closing
- K+ channel opening
- K+ current
- K+ channel closing
What is the absolute refractory period?
A period during which no matter how large the stimulus, another AP cannot be generated because VG Na channels are inactivated.
What is the relative refractory period?
A period during which an AP can be generated, but only in response to a very large stimulus due to high K permeability.
What is the consequence of the refractory periods?
They prevent action potentials from propagating ‘backwards’.
How does increasing the diameter of an axon affect conduction speed?
It reduces resistance to flow along the axon, increasing AP conduction velocity.
What is the effect of myelination on action potential conduction?
Myelination increases conduction speed more than diameter by reducing membrane capacitance and leak.
What term describes the conduction of action potentials in myelinated axons?
Saltatory conduction
This term refers to the ‘jumping’ of action potentials from node to node.
What happens during electrotonic spread of current in myelinated axons?
It occurs very fast along the internodal region.
How does demyelination affect axons?
It can lead to conditions such as Guillain-Barré syndrome and multiple sclerosis.
What are ionotropic receptors?
Receptors that are also ion channels, closed when the ligand is not bound.
What are metabotropic receptors?
G-protein coupled receptors that can excite or inhibit post-synaptic cells and involve biochemical pathways.
What is the role of chemical neurotransmission?
It allows for more sophisticated processing in the nervous system.
Name one target for therapeutic drug action related to neurotransmission.
- Serotonin uptake blockers in depression
- AChesterase inhibitors in myasthenia gravis
What are examples of small molecule neurotransmitters?
- Acetylcholine
- Glutamate
- GABA
- Glycine
What are biogenic amines?
- Adrenaline
- Noradrenaline
- Dopamine
- Serotonin
- Histamine
What are some examples of neuropeptides?
- Neuropeptide Y
- β-endorphin
- Substance P
Fill in the blank: The main events driving the change of membrane potential in an action potential include Na+ channel opening, Na+ current, ________, K+ channel opening, K+ current, K+ channel closing.
Na+ channel closing
