The speed of an action potential depends on which of the following factors?

• A. The number of dendrites on the neuron
• B. The length of the neuron's cell body
• C. The diameter of the axon and the presence of myelin sheath
• D. The amount of neurotransmitter released at the synapse

Answer: (C)

Verified step by step guidance

1. Understand the concept of action potential: An action potential is the electrical signal that travels along the axon of a neuron. Its speed is influenced by certain structural and physiological factors.
2. Learn about the role of axon diameter: Larger axon diameters reduce resistance to the flow of ions, allowing the action potential to propagate faster. This is a key factor in determining the speed of signal transmission.
3. Understand the importance of the myelin sheath: The myelin sheath is a fatty layer that insulates the axon. It enables saltatory conduction, where the action potential 'jumps' between nodes of Ranvier, significantly increasing the speed of transmission.
4. Eliminate irrelevant factors: The number of dendrites, the length of the cell body, and the amount of neurotransmitter released at the synapse do not directly affect the speed of the action potential. These factors are related to other aspects of neuronal function, such as signal reception and synaptic transmission.
5. Conclude that the speed of an action potential is primarily determined by the diameter of the axon and the presence of the myelin sheath, as these factors directly influence the efficiency of signal propagation.