The amplitude of a graded potential primarily depends on the strength of the stimulus.
Understanding Graded Potentials
Graded potentials are localized changes in the membrane potential of a neuron. Unlike action potentials, they are not "all-or-nothing"; their magnitude can vary. This variability is precisely what gives them the name "graded".
According to the provided information, graded potentials "vary in amplitude depending on the strength of stimulus." This means a stronger stimulus will typically produce a larger graded potential, while a weaker stimulus will produce a smaller one.
Factors Influencing Amplitude
Beyond the initial stimulus strength, the amplitude of a graded potential is also influenced by factors related to the movement of ions across the neuron's membrane. The reference states:
- The size of the potentials varies with the number of gated ion channels open or closed.
- The size also varies with how long the gated ion channels stay open.
These factors are directly linked to the stimulus. A stronger stimulus is likely to open more ion channels or keep them open for a longer duration, leading to a greater flow of ions and thus a larger change in membrane potential (amplitude).
Key Determinants of Graded Potential Amplitude:
- Strength of the Stimulus: This is the primary factor. A larger stimulus (e.g., more neurotransmitter binding, more pressure) causes a larger change in membrane potential.
- Number of Gated Ion Channels Affected: A stronger stimulus can open or close more ion channels in the membrane. More open channels mean a greater influx or efflux of ions, leading to a larger potential change.
- Duration of Channel Opening: How long the ion channels remain open also affects the total flow of ions. Longer opening times contribute to a larger graded potential.
These factors explain why graded potentials can range in size, from a small depolarization or hyperpolarization to a larger one, depending on the intensity and duration of the triggering event.
