HES 319 Lecture Notes - Collagen, Muscle Contraction, Alpha Motor Neuron
Document Summary
The input signal (a receptor or synaptic potential) is graded in amplitude, proportional to the amplitude and duration of the stimulus. The trigger zone integrates the input signal the receptor potential in sensory neurons, or synaptic potential in motor neurons into a trigger action that produces action potentials that will be propagated along the axon. An action potential is generated only if the input signal is greater than a certain spike threshold. Once the input signal surpasses this threshold, any further increase in amplitude of the input signal increases the frequency with which the action potentials are generated, not their amplitude. The duration of the input signal determines the number of action potentials. Thus, the graded nature of input signals is translated into a frequency code of action potentials at the trigger zone. Every action potential has the same amplitude and duration, and thus the same wave form on an oscilloscope.