Special Senses

includes

smell, taste, sight, hearing, equilibrium

not touch (mix of pain and pressure receptors)

eye

contains 70% of all sensory receptors

accessory structures of the eye

eyebrows, eyelids, conjunctiva, lacrimal apparatus, extrinsic eye muscles

eyelids

meet at commisures-corners of eye

eyelashes

tarsal/oil and ciliary/sweat glands

conjunctiva

mucous membrane that lines the eyelids and outer surface of the eyeball

lacrimal apparatus

lacrimal gland and ducts

cannalicali

ducts drainign tears medially

nasolacrimal duct

drains to nasal cavity

extrinsic eye muscles

palpebral fissure

layers of eye

Fibrous (sclera, cornea), vascular (choroid, ciliary body, iris), sensory (retina).

cornea

the transparent layer forming the front of the eye.

-only human tissue that can be transplanted, no blood vessels

collagen and modified skin

choroid

nutrients and pigment so no light scatters and is between retina and sclera

ciliary body

ring of tissue behind the peripheral iris that is composed of ciliary muscle and ciliary processes

-smooth muscle attached to lens

iris (w/pupil)

gives eye color and controls light entering eye

retina

outer pigmented layer and inner neural cells

inner neural cells

1 rod for 3 cones

gray vs color vision

neuron chain of photoreceptors

bipolar neurons and ganglion cells

optic disc

Region at the back of the eye where the optic nerve meets the retina. It is the blind spot of the eye because it contains only nerve fibers, no rods or cones, and is thus insensitive to light.

color blindness

lack of one cone type

cones

blue, green, red

lens

Focuses light onto retina

cataracts

clouding of the lens

two chambers of eye

Anterior Chamber - filled with aqueous humor (clear watery fluid). Posterior Chamber - filled with transparent jelly like substance that gives shape to eyeball. Does not continuously get replaced.

opthalmoscope

instrument used to examine the interior of the eye

pathway of light

cornea, aqueous humor, pupil, lens, vitreous humor, retina

optic chiasma

the crossing of the optic nerves from the two eyes at the base of the brain

optic tracts

the continuation of the optic nerve fibers beyond the optic chiasma

real image formed on retina

reverse, left to right, and smaller than actual object

accomodation

lens change shape ot focuso n clsoer objects

set for distance vision of abotu 20 ft away

eye reflexes

Internal muscles are controlled by the autonomic nervous system

eye internal reflexes

briht light causing pupil constriction and accomodatio nfor clsoer objects

external eye reflexes

convergence, eyes mroe medially

glaucoma

increased intraocular pressure results in damage to the retina and optic nerve with loss of vision

hemianopia

blindness in one-half of the visual field

emmetropia

normal vision

myopia

nearsightedness

hyperopia

farsightedness

astigmatism

defective curvature of the cornea or lens of the eye

night blindness

inhibited rod function

ear

hearing and balance

mechanoreceptors

3 areas of ear

external, middle, inner

external ear

hearing only, pinna and auditory canal with ear wax

middle ear

tympanic, ari filled, hearing

auditory tube connecting to throat ot equalize pressure

bones:malleus, incus, stapes- function virbations from eardrum move ot inner ear

inner ear

hearing and balance sense organs

bony labrinyth

filled with perilymph

bony chambers (cochlea, vestibule, semicicrular canals)

static equilibrium

the perception of the orientation of the head when the body is stationary

-maculae-position of head, vestibular nerve

=anatomy with hair cells and otoliths

dynamic equilibrium

Result of diffusion where there is continuous movement of particles but no overall change in concentration

-angular/rotary movements

what sense dynamic equilibrium

crista ampullaris in semicircular canals

=cupula drags against endolymph when head moves and vestibular nerve to cerebellum and virtgo

conduction deafness

hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea

sensorineural deafness

deafness that usually results from damage to the inner ear or to the auditory nerve

hearing aids rely on

conduction thro bone

round and oval window

Only spot of non dense bone in the bony labyrinth

round: thin membrane spans the opening and separates the perilymph and the air in the middle ear

oval: attached to base of stapes

sound eventually vibrates the stapes, and receptors in the cochlear duct allow us to hear it

olfaction

receptors in roof of nasal cavity

dissolved in mucus for detection

olfaction and tase

chemorecptors

taste buds house

receptor organs

location of taste buds

tongue, soft palate, cheeks

tongue

covered with projections called papillae

1. filiform: sharp w/no taste buds

2. fungiform: rounded with taste buds

3. circumvallate: large with taste buds

gustatory cells are

receptors

long microvilli hair stimulated by chemicals dissolved in saliva

taste sensations

sweet, sour, salty, bitter, umami

sweet receptors

sugars, saccharine, some amino acids

sour receptors

acids

bitter receptors

alkaloids

salty receptors

metal ions

taste has how many types of receptors

4

umami=glutamate, savory

developmental aspects of special sense

formed early in embyronic development

eyes are outgrowths of the brain

all special sense are functional at birth

tarsal glands secrete

lipids

lacrimal glands secrete

saline, immune components (IgA and lysozyme)

Melanocytes in the iris

lens is a ---structure made of--

crystalline structure

common proteins

scleral venous sinus (canal of Schlema)

drainign lfuid

-glaucoma is excessive fluid pressure

ciliary muscles change shape of lens

close up objects-convex

distance-concave (flatter)

retinal

vitamin A

opsins: proteins to transduce light into impulse

retina bleaching

fovea centralis

area consisting of a small depression in the retina containing cones and where vision is most acute

sumary of pathway of light

optic nerve, optic chiasma, optic tract, thalamus, optic radiation, visual cortext in occipital lobe of brain

organ of corti

Center part of the cochlea, containing hair cells, canals, and membranes

olfactory nerves are

among few that can regenerate