The smell of an apple

The taste of an apple

The sight of an apple

Biting into an apple

Chemoreceptors in internal organs detect changes in the blood concentrations of substances, including oxygen, hydrogen ions, and glucose.

2. Tissue damage. Tissue damage stimulates pain receptors (nociceptors). Triggering factors include exposure to excess mechanical, electrical, thermal, or chemical energy.

3. Temperature change. Receptors sensitive to temperature change are called thermoreceptors (ther"mo-re-sep'torz).

4. Mechanical forces. A number of sensory receptors sense mechanical forces, such as changes in the pressure or movement of fluids. As a rule, these mechanoreceptors (mek"ah-no re-sep'torz) detect changes that deform the receptors. For example, proprioceptors (pro"pre-o-sep'torz) sense changes in the tensions of muscles and tendons, whereas baroreceptors (pressoreceptors) in certain blood vessels can detect changes in blood pressure. Similarly, stretch receptors in the lungs sense degree of inflation.

5. Light intensity. Light receptors, or photoreceptors (fo"to-re-sep'torz), are only in the eyes. They respond to light energy of sufficient intensity.

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.

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