Speed of The Nerve Impulse Flashcards
What is a nerve impulse?
The transmission of an action potential along the axon of a neurone
How does an action potential move along the axon?
It propagates as a wave of depolarisation, stimulating the next section of the axon while the previous section repolarises
What are the three factors that affect the speed at which action potentials pass along the axon?
- The myelin sheath
- Diameter of the axon
- Temperature
What is the role of the myelin sheath in nerve impulse transmission?
It acts as an electrical insulator, preventing action potentials in the myelinated regions of the axon
How does the action potential travel in a myelinated neurone?
It jumps from one node of Ranvier to another in a process called saltatory conduction
How does myelination affect the speed of an action potential?
Increases the speed of conductance
How does the diameter of the axon affect the speed of nerve impulse conduction?
A larger axon diameter increases the speed of conductance
Why does a larger axon diameter increase conduction speed?
This is because there is less ion leakage, making it easier to maintain membrane potentials
How does temperature affect the speed of nerve impulses?
Higher temperatures increase diffusion rates, speeding up nerve impulses
Why does higher temperature increase nerve impulse speed?
This is because ion diffusion rates increase and enzymes controlling respiration and the sodium - potassium pump work faster
What happens to nerve impulses conduction at very high tempertaures?
Enzymes and plasma membrane proteins denature, stopping impulse transmission
Besides nerve impulse speed, what else does temperature affect?
The speed and strength of muscle contractions
What is meant by the “all-or-nothing” principle of nerve impulses?
An action potential only occurs if the stimulus reaches the threshold value; if it does not, no action potential is generated
What happens if a stimulus is below the threshold value?
No, action potential is generated, so no nerve impulse is transmitted
What happens if a stimulus is above the threshold value?
An action potential is generated and a nerve impulse travels along the neurone
How does the strength of a stimulus affect the size of an action potential?
It does not affect the size; all action potentials are the same size once triggered
If all action potentials are the same size, how can an organism perceive the strength of a stimulus?
Through the number of impulses per second and the type of neurons activated
How does the frequency of nerve impulses indicate stimulus strength?
A larger stimulus generates more impulses per second
How does having different neurones with different threshold values help detect stimulus strength?
Stronger stimuli activate neurons with higher threshold values, allowing the brain to interpret the intensity of the stimulus
