Action Potentials Flashcards
In the peripheral nervous system, what cells produce myelin sheath?
Schwann Cells
In the CNS, what cells produce myelin sheat?
Oligodendrocytes
In a resting membrane potential, which is more negatively charged - the inside or outside of a cell?
The inside of the cell
What is the resting membrane potential?
-70mV
What is the threshold that must be reached for a cell to depolarise?
-55mV
During repolarisation, are the voltage-sensitive K+ channels open or closed and are the Na+ gates open or closed?
voltage K+ channels open.
Na+ channels close
During the depolarising phase, what happens to increase the membrane potential and what does the membrane increase to?
Voltage-gated Na+ channels open which causes an influx of sodium into the cell. membrane potential increases from -55mV to +30/40mV
During repolarisation what channel opens?
Voltage-gated K+ channels open allowing postassium to move out of the cell.
What would happen if the level of extracellular K+ ions was to increase?
The resting potential becomes less negative so it won’t be able to repolarise and create new APs so muscle contraction ceases and causes death.
What is the term given to an AP that travels down a myelinated axon?
Saltatory Conduction
Name 3 things that can affect axon conduction velocity.
1) Axon Diameter
2) Myelination
3) Temperature
What type of nerve fibres have the largest diameter?
A fibres (largest is A-alpha fibres)
Name a drug that prolongs inactivated state of Na+ channels and absolute refractory periods and state what it is used for.
Carbamaxepine.
Used for managing epilepsy and nerve pain.
What is the substance found in pufferfish that is lethal if consumed and how does it work?
Tetrodotoxin (TTX)
blocks fast voltage-gated sodium channels so blocks action potentials. victim dies of respiratory paralysis
How do local anaesthetics work?
block voltage-gated sodium channels, preventing transmission of APs within a local region
