Temperature Senses

Temperature receptors (thermoreceptors) include two groups of free nerve endings located in the skin. Those that respond to warmer temperatures are called warm receptors, and those that respond to colder temperatures are called cold receptors. The warm receptors are most sensitive to temperatures above 25° C (77° F) and become unresponsive at temperatures above 45° C (113° F). As 45° C is approached, pain receptors are also triggered, producing a burning sensation.

Cold receptors are most sensitive to temperatures between 10° C (50° F) and 20° C (68° F). If the temperature drops below 10° C, pain receptors are stimulated, and the person feels a freezing sensation.

Figure

(a) Light micrograph of a Meissner's corpuscle from the skin of the palm (250x). (b) Light micrograph of a Pacinian corpuscle (25x enlarged to 100x).

At intermediate temperatures, the brain interprets sensory input from different combinations of these receptors as a particular temperature sensation. Both warm and cold receptors rapidly adapt, so that within about a minute of continuous stimulation, the sensation of warm or cold begins to fade. Imagine stepping into a bathtub containing "hot" water that soon feels pleasantly warm or diving into a "freezing" pool of water that soon becomes refreshingly cool. These are familiar temperature adaptations.

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

Get My Free Ebook


Post a comment