5th Semester → CNS → Physiology →

Sensory receptors & coding of sensory information

  1. Function of Receptors:
    • Receptors convert one form of energy (mechanical, thermal, chemical, etc.) into nerve impulses — this process is called transduction.
    • They are the first step in sensation.
  3. Definition of Adequate Stimulus:
    • The adequate stimulus is the type of energy to which a receptor is most sensitive, i.e., it can activate the receptor with the lowest intensity.
    • Example: Light is the adequate stimulus for photoreceptors in the eye.
  5. Definition of Generator Potential:
    • A local change in membrane potential that occurs in a receptor when it is stimulated.
    • It is a graded potential, meaning its size varies with stimulus intensity, and it is not all-or-none.
  7. Properties of Generator Potential:
    • Graded in amplitude → increases as stimulus intensity increases.
    • Local → does not propagate along the nerve fiber.
    • Not all-or-none → varies in size.
    • Can summate (temporal or spatial).
    • When it reaches threshold, it triggers action potentials in the sensory neuron.