What is the range of the speed of a nerve impulse?
0.5m/s-1 to 120m/s-1
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What are three factors acceting the speed of a nerve impulse?
- Myelin sheath - Diameter of the axon - Temperature
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How does the presence of a myelin sheath affect the speed of a nerve impulse?
It prevents the formation of an action potential as it is an electrical insulator but myelinated axons use saltatory conduction for the transmission of a nerve impulse hence it increases the speed of a nerve impulse
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What is the effect of the diameter of an axon on the speed of a nerve impulse
The greater the axon diameter the faster the speed of a nerve impulse because there is less leakage of ions (leakage makes membrane potential harder to maintain)
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What is the effect of temperature on the speed of a nerve impulse?
The higher the temperature the faster the speed of an impulse because the sodium-potassium pump uses active transport which uses ATP from respiration. The sodium-potassium pump like respiration relys on enzyme activity which have optimum temperatures
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What is the all-or-nothing principl in relation to nerve impulses?
If a value below the threshold value is produced by a stimulus then no action potential hence nerve impulse is created. If it exceeds to threshold value there is an action potential and nerve impulse generated
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Why can the strength of the stimulus not be detected by the size of the stimulus?
All action potentials are more or less the same size
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What two mechanisms can help an organism perceive the size of the stimulus?
- The larger the stimulus the more impulses that are generated in a given time - By having different neurones with different threshold values the brain can interpret the number and type of neurones to generate a determination of its size
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During the refractory period- what ions are prevented from moving?
Na+ ions
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What prevents the Na+ ions movement during the refractory period?
The closing of voltage-gated sodium channels
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What are the three purposes of the refractory period?
- It ensures that action potentials are propagated in only one direction - It produces discrete impulses - It limits the number of action potentials
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How does the refractory period ensure that action potential only travel in one direction?
Action potential can only pass from an active region to a resting region, hence action potentials can't be propagated ina region that is refractory
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How does the refractory period produce discrete impulses?
A new action potential cannot be propagated immediately behind the first one due to the refractory period so action potentials are separated from each other
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How does the refractory period limit the number of action potentials?
As action potentials cannot be propagated in a region during the refractory period which prevents continuous action potentials being produced
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Other cards in this set
Card 2
Front
What are three factors acceting the speed of a nerve impulse?
Back
- Myelin sheath - Diameter of the axon - Temperature
Card 3
Front
How does the presence of a myelin sheath affect the speed of a nerve impulse?
Back
Card 4
Front
What is the effect of the diameter of an axon on the speed of a nerve impulse
Back
Card 5
Front
What is the effect of temperature on the speed of a nerve impulse?
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