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Canada (161,877)
HLTC22H3 (102)
Anna Walsh (49)
Chapter 7

Chapter 7
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Department
Health Studies
Course
HLTC22H3
Professor
Anna Walsh
Semester
Winter

Description
Chapter 7Aging And The Regulatory Systems y In order for the organs to function properly they must recognize changes in both the external and internal environment and be able to communicate with each other to maintain homeostasis avert dangers and manage growth y The regulatory systems that manage this communication are the sensory nervous endocrine and immune systems SENSORY SYSTEM y The sensory system is composed of five senses touch smell taste hearing and vision y Sensory organs allow the nervous system to gain information about the external environment y 71 Anatomy of the Ear y Presbycusis or hearing loss with age is the most common hearing problem y Because the shorter the hair cells that respond to high frequencies are located at the beginning of the cochlea they receive the most wear and tear thus highpitched sounds such as womens voices are usually lost first y Interestingly African American men have less haring loss even with equal exposure to loud noises suggesting that genetics plays a role in accelerating or decelerating the loss of this sense y As the ability to determine the presence of others and to hear birds singing or water running declines or disappears one may lose a sense of connection to the environment y Furthermore a decreased willingness to communicate with others or to mingle in social settings frequently accompanies diminished hearing y That is there was a linear increase in problems in physical health mental health and social functioning with each decrement in hearing ability showing that hearing loss can have a profound effect on an older adults quality of life y Tinnitus often defined as a ringing in the ears with no discernable cause is another common problem with age Vision y Figure 71 shows the anatomy of the eye y Light passes through the cornea a transparent structure that protects the eye y By contracting and dilating muscles in the iris regulate the amount of light that enters the eye y At the back of the eye is the retina which contains photoreceptors rods and cones y The lens focuses the image on the retina adjusting for the distance of the object y The photoreceptors then translate light energy into action potentials in the optic nerve y Cones are most numerous in the macula which the in the center of gaze in a direct line from the cornea rods are typically found in the more peripheral regions of the retina y The whole structure is supported by gellike substances called humors in the chambers in the eye y Aqueous watery humor not only provides support but also transports nutrients and wastes whereas the more gellike vitreous humor protects the eye against shocky The conjunctiva a clear mucus membrane inside the eyelids also provides protection y The cornea lens and vitreous humor all diminish in transparency reducing the amount of light entering the eye and also scattering the light that does come in making the eye more sensitive to glare y Yellowing of the lens also decreases its transparency and makes it difficult to differentiate blues greens and violetsy The lens loses elasticity with age making it more difficult to focus on near objects y This is called presbyopia and is the most common agerelated visual problem y The curvature of the cornea becomes more irregular resulting in astigmatisms that distort vision by doubling the edges of objects andor causing starry halos around lights y The muscles in the iris decrease in number and strength with age and its collagen stiffens reducing the ability of the pupil to enlarge y These changes in the iris also decrease the speed at which it responds to light so it stays open fractionally too long when the eye is exposed to bright light and does not expand quickly enough when the light dims y The fluids in the eye show agerelated changes y The lacrimal tear gland and conjunctiva produce less of their protective fluids which can result in inflammation and irritationy The rate at which aqueous humor is generated also declines and there might not be enough to properly maintain the shape of the cornea y Vitreous humor also decreases in size and becomes more liquid y As the vitreous humor moves about it can create tension on the retina causing flashes too much tension can cause the retina to detach causing blindness y Cones in the fovea which is in the central area of the macula are stable but the rods in the central retina are vulnerable to aging y Optic nerve fibers are also lost decreasing the quality of vision y The four most common serious diseases of the eye in late life are cataracts macular degeneration glaucoma and diabetic retinopathy y Cataracts are characterized by cloudiness or opacity of the lens this can occur at any age but is found much more frequently in later years y The main risk factors for developing cataracts besides age are exposure to UVB light and environmental pollutants topical or internal steroids diabetes smoking dehydration eye trauma and low levels of antioxidants such as vitamins A C and E
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