Biological Bases of Behavior Practice Test

Threshold is the minimum stimulation needed to trigger an action potential. When a neuron’s membrane potential reaches this level, voltage-gated ion channels open and an all-or-none spike is produced. Subthreshold stimuli don’t reach that point and fail to fire. Stronger stimuli beyond threshold don’t make the spike taller—the action potential has a consistent size; instead, they can increase the firing rate or recruit more neurons to convey stronger signals. The refractory period describes a brief recovery window after firing, not the trigger level. Aphasia is a language impairment, and the endocrine system deals with hormones, not the initiation of neural impulses.