Chapter 4: Action Potential Flashcards
What are the four phases of an action potential?
Rising phase, overshoot, falling phase, return to resting potential.
How is the generation of an action potential initiated in skin nerve fibers?
By the opening of sodium channels when stretched, allowing Na+ to enter and depolarize the membrane.
What does the frequency of action potentials reflect?
The intensity of the depolarizing current: minimal current for low frequency and increased current for higher frequency.
What is the role of the voltage-gated sodium channel in an action potential?
It allows Na+ to pass through the neuron’s membrane, opening when the membrane depolarizes and closing when it repolarizes.
How do voltage-gated potassium channels contribute to the falling phase of an action potential?
They open in response to depolarization, allowing K+ to exit the cell and helping return the membrane potential to its resting state.
What ensures the one-way travel of an action potential along an axon?
The refractory period of the just-activated membrane segment prevents backward movement.
What factors influence action potential conduction velocity?
Axonal diameter and the presence of myelin; larger diameters and myelination increase velocity.
Describe the process of saltatory conduction in myelinated axons.
The action potential ‘jumps’ from node to node, significantly increasing conduction velocity compared to unmyelinated axons.
Why do action potentials predominantly occur in axons?
Due to the presence of voltage-gated sodium channels necessary for their generation.
What is the significance of the axon hillock in action potential initiation?
It often serves as the spike-initiation zone due to its concentration of voltage-gated sodium channels.
What is K+
Potassium
What is Na+
Sodium
What is the resting potential inside the neuronal membrane?
Around -70mv
What does “Orthodromic” mean in regards to an action potential?
The action potential travels in one direction (Down the axon to the axon terminal)
