Topic 6 Nerve Impulse Flashcards
What is the definition of resting potential?
What is voltage?
Resting potential is difference in electrical charge between outside and inside neurone when impulse isn’t being conducted about
-70mv
How is resting potential maintained?
Gives details of Na+ and K+
Resting potential maintained by sodium potassium pump which Involves active transport so needs ATP
3Na+ outside neurone and 2K+ inside neurone
Why is their a difference in distribution of Na+ and K+ when there is a resting potential?
At resting potential there is 3Na+ outside neurone and 2K+ inside neurone.
This is due K+ ions diffuse out as K+ is more permeable then Na+ entering
How is action potential created in nerve impulses?
Impulse received from receptors and voltage gated Na+ channel open Na+ ions enter neurone causing depolarisation so charge become positive.
If depolarisation reaches threshold potential causes voltage gated Na+ to be activated leading to a higher influx of Na+ causing action potential.
After action potential is caused in nerve impulses what happens?
After action potential reached voltage gated Na+ channels close while voltage gated K+ channels open so repolorisation occurs as K+ leave neurone
When most K+ leave the neuron causes hyper-polarisation so voltage gated K+ channel close
Sodium-Potassium pump returns neurone back to its resting potential
What kind of response is action potentials in nerve impulses?
How is this caused?
Action potentials In nerve impulses are All or nothing response.
Caused when threshold potential reached, action potential depolarises axon to same voltage by voltage-gated Na+ channel.
What does all or nothing response cause?
Same voltage is reached every time important in maintaining rate of impulse.
What is refractory period?
Period in action potential when axon cant be depolarised to initiate another action potential.
What is the purpose of refractory period?
Limits frequency of action potential.
Ensures action potential travel in one direction (discrete)
How is action potential transmitted in Non-Myelinated Neurone?
When depolarisation occurs voltage gated Na+ channel open further down axon by the time depolarisation spread part of neurone has already been polarised.,
Depolarisation occurs along whole length of lamellae/axon
How is action potential transmitted in Myelinated Neurone?
What is the advantage?
What is it called?
Action potential only occurs at nodes of Ranvier
(Action potential jumps from node to node)
The advantage is its quicker.
Called saltatory conduction.
How does the structure of Myelinated Neurone advantageous when transmitting action potential?
Myelination provides insulation which increases the speed as saltatory conduction occurs.
Myelination also provides insulation which increases temperature.
What are the factors that affect speed of impulse?
1.Myelination increase speed as saltatory conduction occurs.
2.Axon diameter (wider axon=faster impulse)
3.Temperature (increase temperature=increase speed of impulse)
