Concepts of Human Anatomy & Physiology   5/e   Van De Graaff/Fox
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I. Characteristics of Sensory Receptors

Concept: Each type of sensory receptor responds to a particular modality of environmental stimulus by causing the production of action potentials in a sensory neuron. These impulses are conducted to parts of the brain that provide the proper interpretation of the sensory information when that particular neural pathway is activated.

II. Somatic Senses

Concept: The somatic senses arise in cutaneous receptors and proprioceptors. There are several types of sensory receptors in the skin, each of which is specialized to be maximally sensitive to one modality of sensation. Proprioceptors provide sensory information about muscles, joints, and tendons.

III. Taste and Smell

Concept: The receptors for taste and smell respond to molecules that are dissolved in fluid; hence, they are classified as chemoreceptors. Although there are only four basic modalities of taste, they combine in various ways and are influenced by the sense of smell, thus allowing for a wide variety of sensory experiences.

IV. Vestibular Apparatus and Equilibrium

Concept: The sense of equilibrium is provided by structures in the inner ear, collectively known as the vestibular apparatus. Movements of the head cause fluid within these structures to bend extensions of sensory hair cells, and this mechanical bending results in the production of action potentials.

V. The Ears and Hearing

Concept: Sound causes vibrations of the tympanic membrane. These vibrations, in turn, produce movements of the auditory ossicles, which press against the oval window. Movements of the oval window produce pressure waves within the fluid of the cochlea, which in turn cause movements of the basilar membrane. Sensory hair cells are located on the basilar membrane, and the movements of this membrane in response to sound results in the bending of hair cell processes. This stimulates action potentials in sensory fibers that are transmitted to the brain and interpreted as sound.

VI. Development of the Ear

VII. The Eyes and Vision

Concept: Light from an observed object is focused by the cornea and lens onto the photoreceptive retina at the back of the eye. The focus is maintained on the retina at different distances between the eyes and the object by muscular contractions that change the thickness and degree of curvature of the lens.

VIII. Development of the Eye

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