Ch. 12 - Sense Organs ALL KEY TERMS

key terms only

Accommodation

The process by which the curvature of the lens changes so the eye can focus on a near object

Adaptation

The diminishing of a sensation that occurs after continuous exposure to a stimulus

Analgesic

Drug used to relieve pain

Anterior cavity

Space between the lens and cornea of the eye; further divided into an anterior and posterior chamber

Aqueous humor

Clear, watery fluid that fills the anterior cavity of the eye

Astigmatism

Asymmetrical or uneven curvature of the cornea, causing light to be focused unevenly

Auditory canal

Tube running from the outer ear to the middle ear

Auditory ossicles

Three small bones (the malleus, the incus, and the stapes) that connect the eardrum to the inner ear

Auricle

Visible part of the ear; also called the pinna

Bony labyrinth

Complicated system of passageways within the temporal bone that contains the inner ear

Canal of Schlemm

Vessel that collects aqueous humor from the anterior chamber of the eye and delivers it to surrounding blood vessels

Chemoreceptors

Receptors that react to various chemicals, including odors, tastes, and the concentration of various chemicals in the body

Choroid

Highly vascular layer of tissue in the eye that supplies oxygen and nutrients to the sclera and retina

Ciliary body

Thickened extension of the choroid that secretes aqueous humor

Cochlea

Snail-like structure in inner ear that contains the structures for hearing

Cones

Photoreceptors in the retina responsible for color vision

Conjunctiva

Transparent mucous membrane that lines the eyelids and covers the anterior surface of the eyeball (except for the cornea)

Convergence

The process by which the eyes move (often toward each other) so that light rays fall on corresponding spots on each retina

Cornea

Transparent extension of sclera that sits over the iris and admits light into the eye

Depth perception

The ability to judge the distance of objects and the spatial relationship of objects at different distances

Emmetropia

When light rays focus on the retina without the need for a corrective lens; normal vision

Endolymph

Fluid occupying the inside of the membranous labyrinth

Equilibrium

The state of physical balance

Eustachian tube

Passageway from middle ear to nasopharynx

External acoustic meatus

Opening of the auditory canal to the outside of the body

Fast pain fibers

Produce sharp, localized, stabbing-type pain at the time of injury; abundant in the skin and mucous membranes

Fovea centralis

Depressed area in the middle of the macula lutea that contains only cones; it is the area of sharpest vision

Frequency

The number of sound waves that occur during a specific time frame; determines the pitch of a sound

Gustation

Sense of taste

Hyperopia

When light rays focus at a point behind the retina; farsightedness

Iris

Ring of colored muscle in the middle layer of the eye; regulates the diameter of the pupil

Lacrimal apparatus

Structure consisting of the lacrimal gland and a series of tear ducts

Lacrimal gland

Small gland that secretes tears

Lacrimal punctum

Tiny pore at the end of each lacrimal canal that drains tears into the lacrimal canals

Macula lutea

Center point of the retina

Mechanoreceptors

Receptors that respond to factors that change the position of a receptor

Membranous labyrinth

Lines the inside of the bony labyrinth

Myopia

When light rays focus in front of the retina; nearsightedness

Nasolacrimal duct

Passageway that carries tears into the nasal cavity

Nociceptors

Pain receptors that respond to tissue damage from trauma as well as from heat, chemicals, pressure, or a lack of oxygen

Olfaction

Sense of smell

Olfactory bulbs

Pair of structures residing underneath the brain’s frontal lobe

Optic chiasm

Point in the brain where half the optic nerve fibers cross to the opposite side of the brain

Optic disc

Spot where nerve fibers leave the retina, converging to become the optic nerve

Optic nerve

Nerve exiting from the posterior portion of the eyeball; transmits signals to the brain

Organ of Corti

Hearing sense organ

Oval window

Opening that leads from the middle ear to the vestibule of the inner ear

Palpebral fissure

The opening between the eyelids

Papillae

Protrusions on the tongue on which taste buds are located

Perilymph

Fluid that cushions the space between the bony and membranous labyrinth

Photopupillary reflex

Reflex that causes the pupils to constrict automatically when exposed to bright light

Photoreceptors

Receptors in the eyes that respond to light

Posterior cavity

Large cavity in the eye lying posterior to the lens and the anterior cavity

Presbyopia

When light rays focus behind the retina, creating difficulty focusing on objects up close

Proprioceptor

Receptor found in skeletal muscle, joints, and tendons that provide information about body movement, muscle stretch, and the general orientation of the body

Pupillary constrictor

Muscle encircling the pupil that works to narrow the pupil

Pupillary dilator

Muscle within the iris that works to widen the pupil

Receptors

Structures specialized at detecting a stimulus

Referred pain

Pain originating in a deep organ that is sensed as if it’s originating from the body’s surface

Refraction

Bending of light rays so they focus on the retina

Retina

Innermost layer of the eye that contains receptors for vision

Rods

Photoreceptors in the retina active in dim light

Sclera

Outermost layer of the eye; formed from dense connective tissue

Semicircular canals

Three fluid-filled bony channels in the inner ear

Slow pain fibers

Produce a dull, aching pain; found on deep body organs and structures

Tarsal glands

Glands along the thickened area at the edge of the eye that secrete oil to slow the evaporation of tears

Thermoreceptors

Receptors activated by a change in temperature

Tympanic membrane

Membrane separating outer ear from middle ear that vibrates in response to sound waves; eardrum

Vestibule

Structure at the entrance of the bony and membranous labyrinths; contains organs necessary for sense of balance

Visual acuity

The sharpness of visual perception

Vitreous humor

Jelly-like substance that fills the posterior cavity of the eye