Chapter 8 Study notes

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8 Feb 2011
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Chapter 7- Aging and The Regulatory System
SENSORY SYSTEM
5 senses
Allows nervous system to gain information about the extrernal environment
Age Related Changes
Touch
Skin is a sense organ
Age related changes in: touch receptors (Meissners corpuscles) and pressure
receptors (Pacinian corpuscles)
Both decrease with age and in number and sensitivity
Decreased ability to locate, identify and manipulate objects
Smell
Only about 10% decline
Sensory neurons decrease in nasal lining and olfactory pathways
Smoking causes most severe degradation
May cause decrease in appetite, increases risk of food borne illnesses
Taste
Aging may cause minor decrease in sensitivity neurons
Loss in taste occurs because of smoking, periodontal disease, illness and medications
May lead to anorexia and increases mortality
Hearings
Changes affect both hearing and balance
Sound goes from outer ear ear canal middle ear through vibrations in the
eardrum
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Middle ear: 3 ossicles/little bones that pass vibrations to oval window
(hammer, anvil, and stirrup)
Oval window: flexible membrane at beginning of inner ear
Inner ear puts pressure on cochlea snail shell organ
Inner e3ar is lined with the basilar membrane which has rows of neurons
(thousands)
Neurons make up the organ of Corti (hair cells contact nerve fibers and
transmit acoustic signals to CNS
Vestibule
Complex structure in inner ear
Allows organisms to sense gravity and head rotation
Has 2 small gelatine filled sacs that have mineral particles and sensors
Minerals press down on sensors and transmit information to brain
With age: ear wax build up decreases hearing sensitivity
Organ of Corti affected by wear and tear and otoxic medications
Vestibule degrades leading to dizziness and falls
Presbycusis
hearing loss with age
Men lose 80% by age 90, women lose only 30%
Unable to hear high pitch sounds because of damage to shorter hair cells
close to cochlea
African men have less hearing loss genetic factor
Tinnitus
Ringing in the ears without a cause
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May be due to ear infection high blood pressure, diabetes and tumours,
arthrosclerosis, medications and toxins
Vision
Light passes through cornea transparent, protects the eye
Muscles in the iris control amount of light that enters the eye
Retina back of the eye; has photoreceptors with rods and cones
Rods: transmit black and white information; found in peripheral regions of
retina
Cones: transmit colour; numerous in macula; centre of gaze
Whole eye structure is supported by humours (gel like substance) which also
transports nutrients and waste
Conjunctiva is a clear mucus membrane inside eyelids that also provides protection
with age, cornea, lens and vitreous humour diminish in transparency, making
the eye sensitive to glare
lens becomes yellow and decreases ability to differentiate between colours
also loses elasticity, making it difficult to focus on objects
makes driving problemtic
4main eye diseases:
1.Cataracts
Cloudiness and opacity of the lens
Interferes with vision and especially in bright sun or at night
Leading causes of blindness and treated with curgery
2.Glaucoma
Causes by increased buildup of aqueous humour in eye
Resultys in increased intraocular pressure and damage to retina and optic
nerve results in blindness
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