Action potentials: Tick the box next to the ONE answer you believe is TRUE.
A. compound action potentials increase in amplitude as the stimulus strength is increased.
B. ONE action potential takes in the order of 1-2 seconds to be observed.
C. generation decreases the Na+ conductance.
D. induce nerve conductance velocities that are solely determined by axon diameter.
E. can be propogated by subthreashold stimuli eliciting active voltage changes.
The true statement about action potentials is:
E. can be propagated by subthreshold stimuli eliciting active voltage changes.
Explanation:
Action potentials are rapid, transient changes in the membrane potential of a neuron. They are generated when the membrane potential reaches a threshold level, usually around -50 to -55 mV. At this threshold, voltage-gated sodium channels open, allowing an influx of sodium ions into the cell, which leads to depolarization and the initiation of an action potential.
In option E, it states that subthreshold stimuli, which are stimuli below the threshold level, can still elicit active voltage changes and propagate action potentials. This is true because if a subthreshold stimulus is strong enough and brings the membrane potential close to the threshold, it can trigger an action potential.
The other options are not true:
A. Compound action potentials do not necessarily increase in amplitude as the stimulus strength is increased. The amplitude of action potentials is typically constant once the threshold is reached.
B. The duration of an action potential is in the order of milliseconds, not seconds. It is a rapid and brief event.
C. The generation of an action potential actually increases the sodium conductance, not decreases it. This allows the influx of sodium ions and leads to depolarization.
D. Nerve conduction velocity depends on various factors, including axon diameter, myelination, and temperature. Axon diameter is one factor that affects conduction velocity, but it is not the sole determinant.