Speed of Conductance Flashcards
What three factors affect the speed of conductance/an action potential?
- myelination and saltatory conduction
- axon diameter
- temperature
What is an axon?
a long, conductive fibre that carries the nervous impulse along the motor neuron
What forms the myelin sheath?
Schwann cells
What about the Schwann cells makes them insulators?
they are lipids
What is saltatory conduction?
the action potential jumping/moving from node to node
why does the myelin sheath speed up conductance?
as action potentials only have to be generated in a limited number of spaces, not along the whole length of the axon
How does a wider diameter impact the speed of conductance?
will make it faster
Why does a wider diameter speed up conductance?
it means that there is less leakage of ions
Why does a higher temperature increase speed of conductance?
- rate of diffusion increases
-enzymes involved in respiration act faster so more ATP for co-transport
Why would no myelin sheaths lead to slower responses?
- cannot ‘jump’ from node to node
- more depolarisation over a greater length
How does the myelin sheath impact speed of conductance?
- myelin sheath increases speed of conductance
- schwann cells cause insulation around an area of the axon
- depolarisation cannot occur in insulated areas, only in the nodes of Ranvier
- saltatory conduction
How does temperature impact speed of conductance?
- high temperature increases speed of action potentials
- higher temperature increases diffusion up until a point
- enzymes involved in respiration
- above a certain point enzymes/proteins denature and APs cease
What is the All or Nothing principle?
- threshold value (-55mV)
- below the threshold, no AP regardless of strength
- stimulus above threshold will generate an action potential
- all action potentials are the same size
Why might damage to the myelin sheath of neurones cause muscular paralysis?
- no saltatory conduction/Depolarisation occurs along whole length
- impulses slowed/stopped
- do not reach/take longer to reach neuromuscular junction