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BALANCE & AGING
24 January 2014
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How do we maintain balance?Cerebellum monitors and controls balance.
It receives input from four main sources:Maculae (vestibule of inner ear)Crista ampullaris (semicircular canals of inner
ear)Photoreceptors (eyes)Proprioceptors (receptors in muscles, tendons, and joints that detect tension)
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Static vs. Dynamic EquilibriumStatic equilibrium has to do with our position or straight-line changes in speed
e.g. upside down, tilted to the left, slowing down, etc.
Sensed by the maculae of the vestibule
Dynamic equilibrium has do to with angular acceleration
E.g. spinning, roller coasters, boat rides
Sensed by the crista ampullaris of the semicircular canals
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Static EquilibriumThe macula contains hair cells surrounded by
an otolithic membrane (a jelly-like material) that contains otoliths (tiny calcium stones)
The otolithic membrane slides due to gravity or linear acceleration, bending the hairs
When the hairs are bent, the hair cell generates a nerve impulse
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Dynamic Equilibrium3 canals, oriented in the three planes of space
At the base of each is a receptor region called the crista ampullaris, which consists of hair cells covered with a gelatinous cap called the cupula.
During angular / rotational movements, the endolymph in one or more canals will move, pushing against the hair cells
When the hair cells are bent, they generate a nerve impulse.
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Types of Sensory ReceptorsWhat senses / sensory receptors have we discussed?
What have we not yet covered?
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Sense Type of Sensor
Name Location
Vision Photoreceptor Rods & cones Retina of eye
Hearing Mechanoreceptor
Hair cells ( on organ of Corti)
Cochlea of ear
Balance Mechanoreceptor
macula
Hair cells (on crista ampullaris)
Proprioceptors
Vestibule of ear
Semicircular canals of ear
Tendons, muscles, joints
Smell Chemoreceptor
Olfactory receptor Top of nasal cavity
Taste Chemoreceptor
Taste buds Papillae of tongue
Pain nocioreceptor nocioreceptors Skin, muscles, bladder, digestive system, mucus membranes, cornea
Temp thermoreceptor
Thermoreceptors Skin
Pressure
mechanoreceptor
Pacinian corpuscle Skin & internal organs
Touch mechanoreceptor
Meissner’s corpuscle Skin
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Senses and AgingVisionDevelops slowly in babies
Kids are far-sighted until around 6 because the eye needs to grow
In old ageLens loses elasticity, causing presbyopia – an inability
to accommodate and focus on near itemsOther factors which reduce visual acuity include
discolored lens, inability to fully dilate pupil, loss of photoreceptors
Many diseases more common with age: cataracts, glaucoma, macular degeneration, etc.
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Senses and AgingHearingPresbycusis –
a loss of hearing, especially speech sounds and high pitches – due to damage to the organ of Corti
A type of sensorineural hearing lossAssociated with age and noise exposure
Conductive hearing loss - Anything that prevents sound from getting to
the inner ear, including fusion of ossicles
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Senses and AgingSmell & TasteVery sharp at birthDeclines starting around age 40Most people over 80 have poor taste
sensation and almost no ability to smell
Balance, Touch, PainBegin to decline around age 50Leads to increased risk of fallsInability to recognize injury
Babies’ senses Elderly senses
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ClosureWhat were our objectives, and what did you
learn about them.
What was our learner profile trait and how did we exemplify it?
How does what we did today address our unit question?