A&P Chapter 8: Part 2

Refraction

the bending of light

Accommodation

adjustment of the eye for seeing objects at close range

Optic chiasma

the partical crossover of fibers of the optic nerves

Optic tracts

carries the nerve impulse from the eye

Optic radiation

runs to the occipital lobe of the brain

Convergence

the ability of both eyes to work together to focus on a nearby object

Emmetropia

perfect, 20/20 vision; the eye focuses images correctly on the retina

Myopia

nearsightedness

Hyperopia

farsightedness

Astigmatism

a visual defect resulting from irregularity in the lens or cornea of the eye causing the image to be out of focus

Photopupilary reflex

when the eyes are suddenly exposed to bright light, the pupils immediately constrict

Accommodation pupillary reflex

the pupil constricts reflexively when you view close objects; provides for more acute vision

Mechanoreceptors

receptors sensitive to mechanical pressures such as touch, sound, or contractions

External/outer ear

composed of the auricle and the external acoustic meatus

Auricle/pinna

the shell-shaped structure surrounding the auditory canal opening

External acoustic meatus

a short, narrow chamber carved into the temporal bone of the skull

Ceruminous glands

glands that secrete earwax

Cerumen

earwax; a waxy substance secreted by glands located throughout the external canal

Tympanic membrane

the eardrum; vibrates when sound waves hit it

Tympanic cavity/middle ear

a small, air-filled, mucosa-lined cavity within the temporal bone

Oval window

the membrane that separates the middle ear from the inner ear

Round window

equalizes pressure in the inner ear; located just below the oval window

Pharyngotympanic (auditory) tube

links the middle ear cavity with the throat

Otitis media

inflammation of the middle ear

Ossicles

the three bones of the middle ear: hammer, anvil, and stirrup

Hammer/malleus

transfers the vibration to the anvil

Anvil/incus

passes vibrations from the hammer to the stirrup; middle ear bone

Stirrup/stapes

presses on oval window of inner ear, sets fluids in motion, excites hearing receptors; third ear bone

Internal ear

houses receptors for hearing and equilibrium; a maze of bony chambers

Bony/osseous labyrinth

name for the internal ear

Cochlea

a cavity of the inner ear resembling a snail shell; houses the hearing receptor

Vestibule

subdivision of the bony labyrinth situated between the semicircular canals and the cochlea

Semicircular canals

three canals within the inner ear that contain specialized receptor cells that generate nerve impulses with body movement

Perilymph

plasmalike fluid in the bony labyrinth

Membranous labyrinth

suspended in the perilymph; system of membrane sacs that follow the shape of the bony labyrinth

Vestibular apparatus

the equilibrium receptors of the inner ear

Maculae

receptors essential to the sense of static equilibrium

Static equilibrium

balance concerned with changes in the position of the head

Otolithic hair membrane

a jelly-like material containing otoliths

Otolith

tiny stones made up of calcium salts

Vestibular nerve

nerve that conducts impulses related to maintaining balance to the brain; a division of cranial nerve VIII

Dynamic equilibrium

sense that reports on angular or rotary movements of the head in space

Crista ampullaris

a sensory organ in the inner ear that detects head movements

Cupula

a domelike structure that detects when you are spinning/twirling and directs your body back into the correct position

Organ of Corti

contains the hearing receptors; transmits sound of hearing

Hair cells

hearing receptors in the cochlear duct

Deafness

hearing loss of any degree

Otosclerosis

fusion of the ossicles

Vertigo

a sensation of spinning

Chemoreceptors

receptors sensitive to various chemicals in solution

Olfactory receptors

receptors for the sense of smell

Olfactory receptors cells

neurons equipped with olfactory hairs

Olfactory hairs

long cilia that protrude from the nasal epithelium and are continuously bathed by a layer of mucus secreted by underlying glands

Olfactory filaments

bundled axons of olfactory neurons that collectively make up the olfactory nerve

Olfactory nerve

cranial nerve I; smell

Anosmias

olfactory disorder; commonly result from head injuries, sickness, or aging

Taste buds

receptors for taste on the tongue, roof of mouth, pharynx, and larynx

Papillae

small peglike projection

Circumvallate papillae

large papillae with taste buds

Fungiform papillae

mushroom-like protuberances often containing taste buds and located on the sides and tip of the tongue

Gustatory cells

specific cells that respond to chemicals dissolved in the saliva

Gustatory hairs

long microvilli that protrude through the taste pore, and when they are stimulated, they depolarize and impulses are transmitted to the brain

Taste pore

opening in the taste bud that exposes taste cell microvilli (gustatory hairs) to oral cavity

Facial nerve

cranial nerve VII; serves the anterior part of the tongue

Glossopharyngeal nerve

cranial nerve IX; all other taste-bud areas

Vagus nerve

cranial nerve X; all other taste-bud areas

Basal cells

stem cells found in the deeper regions of the taste buds

Strabismus

"crossed eyes;" results from unequal pulls by the external eye muscles that prevent the baby from coordinating movement of the two eyes

Presbyopia

"old vision;" results from decreasing lens elasticity that accompanies aging