Central Nervous System Physiology Summary

INITIATION OF IMPULSES IN SENSE ORGANS SENSE ORGANS & RECEPTORS The term "receptor" is used in physiology to refer not only to sensory receptors but also, in a very different sense, to proteins that bind neurotransmitters, hormones, and other substances with great affinity and specificity as a first step in initiating specific physiologic responses The sensory receptor may be part of a neuron or a specialized cell that generates action potentials in neurons. The receptor is often associated with nonneural cells that surround it, forming a sense organ. The receptors in each of the sense organs are adapted to respond to one particular form of energy at a much lower threshold than other receptors respond to this form of energy. The particular form of energy to which a receptor is most sensitive is called its adequate stimulus. Receptors do respond to forms of energy other than their adequate stimulus, but the threshold for these nonspecific responses is much higher. . THE SENSES Sensory Modalities Because the sensory receptors are specialized to respond to one particular form of energy and because many variables in the environment are perceived, it follows that there must be many different types of receptors. There are