View
217
Download
1
Category
Tags:
Preview:
Citation preview
Anatomy and Physiology 2
The Special SensesSmellTasteSightHearingThese allow us to
experience and interpret the world around us
Anatomy of the EyeA sphere that is
about 1in in diameter
Only about 1/6 of the eye is seen and rest is protected
The eye is protected by bone, eyelids and eyelashes
Anatomy of the EyeThere are several
glands and ducts around the eyeTarsal glands:
lubricate the eyeLacrimal gland:
produce tearsNasolacrimal duct:
empties tears into the nasal cavity
Anatomy of the EyeEye muscles
Lateral rectus: moves laterally
Medial rectus: moves medially
Superior rectus: elevates Inferior rectus:
depressesInferior oblique: elevates
and turns laterallySuperior oblique :
depresses and turns laterally
Anatomy of the EyeStructures:
Sclera: the “white of the eye:
Cornea: where light enters
Lens: focuses the light that enters through the cornea
Iris: the pigmented part of the eye
Pupil: controls the amount of light that enters the eye
Retina: responds to the light
Anatomy of the EyeStructure:
Retina continued: Contains rods and
cones which are called photoreceptors
Cones allow us to see colors
Rods allow us to see in dim light and use our peripheral vision
Optic nerve: transfers information to the optic cortex of the brain
How we seeWhen light passes
through cornea and lens the light is bent or refracted as they move through the aqueous humor
The image is then projected on the retina upside down
That information is then carried to the optic nerve and process by the brain
Eye ProblemsMyopic eye (nearsighted):
distant objects appear blurry, results of an eyeball that is too long
Hyperopic eye (farsighted): close objects appear blurry, results from a too short eye
Astigmatism: the cornea has an unusual curve to it
Conjunctivitis: bacteria or viral infection of the conjunctive (membrane that covers the eye)
Anatomy of the EarOuter ear:
Pinna or auricle what is typically called the ear
External acoustic meatus: a narrow chamber carved into the temporal bone Lined with
ceruminous glands that produce earwax or cerumen
Anatomy of the EarMiddle Ear
Ear drum: vibrates in response to sound waves
Ossicles: the three smallest bones in the body Incus (anvil), malleus
(hammer) and stapes (stirrup)
Vibrations trigger the coordinated movements of these bones
Anatomy of the EarInner Ear
Bony labyrinth Cochlea Vestibule Semicircular canals
Vestibular apparatus (responsible for equilibrium)
Equilibrium Static equilibrium
Static = at restProvides information on
which way is up or down
Helps maintain posture and balance when standing upright
Dynamic equilibriumProvides information for
angular movements (e.g. twirling, spinning. Etc.)
How We HearThe auricle works to
capture as much sound waves as possible
The waves travel through the ear until they reach the cochlear duct
Hair follicles move in response to the vibrations
Once the follicles are triggered they send the impulse to the cochlear nerve
Hearing and Equilibrium Deficits
Deafness is defined as hearing loss of any degreeConduction deafness =
problems in the earSensorineural deafness =
problems in the cochlear nerve or brain
Vertigo is the sense of falling or spinningUsually result in nausea
and difficulty in maintaining balance
Chemical Senses: SmellThe nose contains
thousands of olfactory receptors that can respond to thousands of different smells
The olfactory receptors lead to the olfactory nerve, which leads to the olfactory cortex in the brain (here the smells are “identified”)
Chemical Senses: SmellThe olfactory cortex
of the brain is tied to the emotional part of the brain, thus many smells with trigger memories and emotions
The receptors are quickly triggered, but also quickly adapt to smells
Chemical Senses: TasteTaste buds are the
receptors for tasteThe tongue contains
about 10,000 taste budsThe small peg like
projections on the tongue are called papillae
The papillae contain tiny hairs that are linked to 3 nerves that carry the information to the brain
Chemical Senses: Taste5 basic taste sensations:
Sweet = responds to sugars, saccharine and certain amino acids
Sour: responds to acidsBitter: responds to
alkaloidsSalty: responds to
metal ionsUmami: recently
discovered to respond to food additives
Chemical Senses: TasteHistorically, each taste
on the tongue had “it’s own part”, but only slight differences have been found between the parts
Typically, cravings are linked to deficits in the body, but like smell the taste part of the brain is close to the emotionally part of the brain
Developmental AspectsAll special senses are
functional at birth; however, vision is the only one not fully functional
Newborns see only in gray tones and cannot see much further that a foot in front of them
It takes until about 5 years of age to have fully functioning vision
The lens will continue to grow throughout life causing “old vision”
Hearing is very important to language development
Smell and taste also developmentally important
Recommended