Final answer:
The characterization of an action potential as fast or slow is determined by the speed of the depolarization phase. Other key differences between fast and slow action potentials include the stability of resting membrane potential, duration of the action potential, and the presence of a plateau phase.
Step-by-step explanation:
Characterization of an action potential as a fast or slow response depends on the speed of the depolarization phase of its action potential. A fast action potential is typically associated with cardiomyocytes or skeletal muscle cells, while a slow action potential is commonly seen in pacemaker cells of the heart.
Three other differences in the action potentials of fast and slow response cells include:
- Resting Membrane Potential: Fast response cells have a stable resting membrane potential, while slow response cells have a less stable resting membrane potential due to spontaneous depolarization.
- Duration of Action Potentials: Fast response cells generally have shorter action potentials (1-5 ms) compared to slow response cells, which can have action potentials lasting up to a few hundred milliseconds.
- Presence of Plateau Phase: Fast response cells display a distinct plateau phase due to the opening of Ca2+ channels, which is not present in the action potentials of slow response cells.
The speed at which the membrane depolarizes significantly impacts whether an action potential is categorized as fast or slow, with the aforementioned differences contributing to their functional distinctions.