Transmission of nerve impulses Flashcards
What is a resting neuron?
A neuron that is not carrying an impulse
What is a threshold?
The minimum stimulus needed to cause an impulse to be carried in a neuron
What is the ‘all or nothing’ law?
This states that if the threshold is reached an impulse is carried, but if the threshold is not reached no impulse is carried
How does an impulse move along a neuron?
6 points
Once the threshold is reached the axon or dendrite changes its permeability to ions
This allows for the transmission of an impulse
An impulse will cause a section of a neuron to change its permeability to ions
This will cause the next section to change its permeability and the impulse will ‘jump’ to that section
Once the impulse has moved along, the area behind is restored to the original state
This pattern of movement of ions continues along the entire length of the neuron
What is the refractory period?
This is a short time span after a neuron has carried an impulse during which a stimulus fails to cause a response.
What does the speed at which an electrical impulse travels along a neuron depend on?
Whether myelin is present or absent around the neuron
When myelin is present how does an electrical impulse move?
The impulse ‘jumps’ from one node of Ranvier to the next i.e. it moves very fast
When myelin is not present how does an electrical impulse move?
The impulse must travel along the entire length of the neuron i.e. the impulse moves slowly
Besides the presence or absence of myelin what affects the speed at which an impulse travels?
The diameter of the dendrite or axon i.e. the larger the diameter the faster the impulse travels
What happens to an axon or dendrite when the threshold is reached?
Its permeability to ions changes to allow for the transmission of an impulse
What causes a section of a neuron to change its permeability to ions?
An impulse
