BALANCE & AGING

24 January 2014

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)

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

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

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.

Types of Sensory ReceptorsWhat senses / sensory receptors have we discussed?

What have we not yet covered?

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

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.

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

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

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?