9.2.5 - Nervous Transmission Flashcards
In unmyelinated neourones, how are nerve impulses transmitted?
as a self-propagating wave of depolarisation
At resting potential are there more potassium ions inside or outside the axon?
Inside
What are localised electric currents?
Where ions are entering the axon at one point.
Where does a flow of current get set up in myleninated neurons?
Nodes of ranvier
When action potentials leap between nodes of ranvier, what is this called?
Saltatory conduction
Does saltatory conduction speed up or slow down the speed of propagation?
Speed up
How does the diameter of an axon effect the speed of impulses?
A wider diameter = faster impulses.
Why does an increase in temperature increase the conduction speed?
The propagation of an impulse involves the diffusion of ions.
Rate of diffusion increases at high temperatures.
Temperature also affects the enzymes involved in active transport in resting potential.
What happens to nerve conduction at VERY high temperatures?
Enzymes will denature.
Resulting in lower speeds.
What does a stronger stimulus mean in terms of the frequency of action potentials?
Higher frequency of action potentials.
Describe the refractory period in regions of an axon that has just transmitted an action potential.
There is a short period of time which that region of the axon cannot transmit another action potential.
What are 3 things the refractory period can help with/prevent?
Ensures the action potential can only travel in one direction.
Prevents the overlap of action potentials.
Limits the action potentials in a time period.
Inside an unmyelinated axon what happens when a stimulus is detected?
The action potential propagates down the axon.
What causes action potentials to be transmitted much more rapidly in myelinated axons than in unmyelinated axons?
Saltatory conduction.
In a mylenitated axon, the local electrical circuits are much longer so the action potentials don’t have to pass down the whole axon.
Other than the speed of transmission of action potentials, what is another benefit of saltatory conduction?
repolarisation requires ATP.
Due to saltatory conduction, less ATP is used to repolarise the axon.
