Special Senses - 15 (PDF)

SENSATION  SENSORY RECEPTORS GENERAL SENSES SPECIAL SENSES OLFACTION TASTE VISION The anterior and posterior chambers are filled with aqueous humor (watery fluid), which helps maintain pressure within the eye, refracts light, and provid...

SENSATION  SENSORY RECEPTORS GENERAL SENSES SPECIAL SENSES OLFACTION TASTE VISION The anterior and posterior chambers are filled with aqueous humor (watery fluid), which helps maintain pressure within the eye, refracts light, and provides nutrients to the inner surface of the eye. Aqueous humor is produced by the ciliary body as a blood filtrate and is returned to the circulation through a venous ring that surrounds the cornea. The presence of aqueous humor keeps the eye inflated, much like the air in a basketball. If flow of the aqueous humor from the eye through The vitreous chamber of the eye is filled with a transparent, jellylike substance called vitreous humor. The vitreous humor helps maintain pressure within the eye and holds the lens and the retina in place. It also refracts light. Unlike the aqueous humor, the vitreous humor does not circulate through the lens; if the surface is convex, they converge. As the light rays converge, they finally reach a point at which they cross. The crossing point is called the focal point (FP) (figure 9.15), and causing light to converge is called focusing. The focal point in the eye occurs just anterior to the retina, and the tiny image that is focused on the retina is inverted compared to the actual object. HEARING & BALANCE EFFECTS OF AGING ON THE SENSES As a person ages, both the general and the special sensory functions gradually decline. Among the general senses, free nerve endings and hair follicle receptors in the skin remain largely unchanged. However, the numbers of Meissner corpuscles and pacinian corpuscles decrease with age, and those that remain are often structurally distorted and less functional. As a result, elderly people are less conscious of something touching or pressing the skin, The sense of two-point discrimination decreases, and the elderly have a more difficult time identifying objects by touch. A loss of pacinian corpuscles also decreases their awareness of limb and joint positions, which can affect balance and coordination. The functions of receptors for proprioception also decline with age, which decreases information on the position, tension, and length of tendons and muscles. This can further Among the special senses, elderly people experience only a slight loss in the ability to detect odors. However, their ability to correctly identify specific odors decreases, especially in men over age 70. In general, the sense of taste decreases as people age. The number of sensory receptors decreases, and the brain’s ability to interpret taste sensations declines THANK YOU!