BALANCE & AGING January 14-15 2016

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 Equilibrium Static 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 Equilibrium The 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 Equilibrium 3 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 Receptors What 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 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 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 Meissner’s corpuscle

Senses and Aging Vision Develops slowly in babies Kids are far-sighted until around 6 because the eye needs to grow In old age Lens loses elasticity, causing presbyopia – an inability to accommodate and focus on near items Other 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 Aging Hearing Presbycusis – Conductive hearing loss - a loss of hearing, especially speech sounds and high pitches – due to damage to the organ of Corti A type of sensorineural hearing loss Associated with age and noise exposure Conductive hearing loss - Anything that prevents sound from getting to the inner ear, including fusion of ossicles

Senses and Aging Smell & Taste Very sharp at birth Declines starting around age 40 Most people over 80 have poor taste sensation and almost no ability to smell Balance, Touch, Pain Begin to decline around age 50 Leads to increased risk of falls Inability to recognize injury Babies’ senses Elderly senses

Closure What 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?