Tri A - Action Potentials Flashcards
What causes an Action Potential to be produced?
Produced when the membrane depolarises in excitable cells
What is the function of Action Poteintals?
To code information into the nervous system
What 2 ways can information be coded?
- Frequency of APs
- Duration of APs
What is required for an AP to be generated?
The threshold needs to be reached
Describe the All or none law?
Once APs are generated, they are always the same size no matter the stimulus strength
When can a 2nd AP be produced? and what is this called?
Only when the 2 stimuli are separated by a sufficient time interval
This is called the refractory period
Describe the Absolute refractory period
A period of time when the neuron is not able to send additional action potentials
Describe the Relative refractory period
The interval of time during which a second action potential can be initiated
Describe Propagation
APs travelling from one end of the nerve to the other
Describe the process of Propagation
The current flows through the membrane in front of the depolarised region
This stimulates the region in front
Depolarises the next region
What is the name of the material on axons and what cells produce this?
Myelin
Schwann cells
Name the gaps produced by the myelin sheath
Nodes of Ranvier
Explain Saltatory Conduction
The myelin sheath has gaps. APs can only be produced here, so appear to jump from one to the next
Describe autoimmune diseases
The body attacks and destroys its own myelin sheath, and therefore there is less conduction velocity
Describe the relationship between diameter of the axon and the speed of conduction velocity
Larger diameter = faster conduction velocity
Small diameter = slower conduction velocity
