Special Senses – Chapter 17 Vocabulary Review

A comprehensive set of 100 vocabulary flashcards covering olfaction, gustation, vision, and hearing topics from Chapter 17 lecture material.

Olfactory glands

Glands that coat the olfactory epithelium with a pigmented, mucus-based secretion to trap odorants.

Olfactory bulb

Brain structure where axons of olfactory receptor cells first synapse after passing through the cribriform plate.

Cribriform plate

Perforated region of the ethmoid bone through which olfactory receptor axons travel to the olfactory bulb.

Olfactory epithelium

Specialized sensory epithelium inside the nasal cavity that contains olfactory receptor cells, supporting cells, and basal (stem) cells.

Olfactory discrimination

Ability to distinguish thousands of odors; declines with age as olfactory receptors decrease.

Olfactory cortex

Region of the cerebrum that receives primary olfactory information without passing through the thalamus first.

Limbic system connection

Neural link between olfaction and emotion/memory, explaining why smells often evoke vivid memories.

Olfactory stem cells

Basal cells in the olfactory epithelium capable of dividing to replace damaged olfactory receptors.

Odorant

Airborne chemical that binds to receptor proteins on olfactory cilia to initiate smell perception.

cAMP (in olfaction)

Second messenger that opens sodium channels in olfactory receptor membranes, depolarizing the cell.

Olfactory tract

Bundle of axons that carries olfactory information from the olfactory bulb to the brain.

Gustatory receptors

Taste receptors located primarily on the tongue’s taste buds that detect dissolved chemicals.

Lingual papillae

Epithelial projections on the tongue surface that house taste buds and provide texture.

Fungiform papillae

Mushroom-shaped lingual papillae scattered over the tongue; contain several taste buds each.

Circumvallate papillae

Large, dome-shaped papillae forming a V at the back of the tongue; each houses hundreds of taste buds.

Filiform papillae

Slender, threadlike papillae that create tongue friction; they contain no taste buds.

Glossopharyngeal nerve (IX)

Cranial nerve carrying taste sensations (especially sour and bitter) from the posterior one-third of the tongue.

Facial nerve (VII)

Cranial nerve that conveys taste from the anterior two-thirds of the tongue.

Vagus nerve (X)

Cranial nerve transmitting taste sensations from the epiglottis and parts of the pharynx.

Trigeminal nerve (V)

Cranial nerve whose nociceptors convey spicy, peppery, and painful oral sensations.

Nociceptors (trigeminal)

Pain receptors in the trigeminal nerve that detect chemical irritants like capsaicin, producing a peppery-hot sensation.

Primary taste sensations

Basic taste categories: sweet, salty, sour, bitter, umami, and water.

Umami

Savory taste sensation triggered by amino acids such as glutamate.

Lacrimal gland

Gland in the superior-lateral orbit that secretes watery, slightly alkaline tears containing lysozyme.

Lysozyme

Antibacterial enzyme within tears that helps prevent ocular infection.

Fibrous tunic

Outer layer of the eyeball consisting of sclera, cornea, and limbus; provides support and focusing power.

Sclera

Opaque, white portion of the fibrous tunic that protects the eye and serves as muscle attachment site.

Cornea

Transparent anterior part of the fibrous tunic where most light refraction occurs.

Limbus

Border region between the cornea and the sclera.

Vascular tunic (uvea)

Middle eye layer containing the iris, ciliary body, and choroid; supplies blood and controls light entry.

Iris

Colored part of the eye with pupillary muscles that regulate the pupil diameter.

Ciliary body

Thickened ring of tissue containing ciliary muscles and processes that adjust lens shape and produce aqueous humor.

Choroid

Highly vascular layer between sclera and retina, supplying oxygen and nutrients to the eye.

Neural tunic (retina)

Innermost layer containing photoreceptors, bipolar cells, ganglion cells, and supporting neurons.

Palpebrae (eyelids)

Protective coverings for the eye; lined with conjunctiva and equipped with tarsal glands.

Tarsal glands

Sebaceous glands along eyelid margins that secrete lipid-rich fluid preventing eyelids from sticking.

Lacrimal caruncle

Fleshy mass at the medial canthus containing glands that produce gritty eye sleep deposits.

Conjunctiva

Transparent mucous membrane covering inner eyelids and anterior sclera (not cornea).

Canthus

Medial or lateral corner where the upper and lower eyelids meet.

Anterior chamber

Space between cornea and iris filled with aqueous humor.

Posterior chamber

Narrow space between iris/ciliary body and the lens containing aqueous humor.

Vitreous body

Gelatinous mass filling the posterior cavity; stabilizes eye shape and presses retina against choroid.

Aqueous humor

Clear fluid produced by the ciliary body that fills anterior and posterior chambers; drains via canal of Schlemm.

Canal of Schlemm

Scleral venous sinus through which aqueous humor is reabsorbed into venous circulation.

Lens accommodation

Process of changing lens shape to focus on near or distant objects.

Ciliary muscle

Smooth muscle that contracts to reduce tension on suspensory ligaments, rounding the lens for near vision.

Pupillary constrictor (sphincter)

Circular muscle fibers in the iris that constrict the pupil under parasympathetic control.

Pupillary dilator (radial)

Radial muscle fibers in the iris that dilate the pupil under sympathetic control.

Myopia

Nearsightedness; condition in which the eyeball is too long or cornea too curved, focusing images in front of the retina.

Fovea

Central pit within the macula lutea containing only cones; site of highest visual acuity.

Optic disc

Blind spot on the retina where optic nerve exits; lacks photoreceptors.

Photoreceptors

Specialized retinal cells—rods and cones—that detect light.

Rods

Retinal photoreceptors highly sensitive to dim light; provide black-and-white vision.

Cones

Photoreceptors responsible for color vision and sharp detail; three types sensitive to red, green, or blue light.

Rhodopsin

Visual pigment in rods composed of opsin and retinal; also called visual purple.

Opsin

Protein component of visual pigments that determines the wavelength sensitivity of the photoreceptor.

Retinal

Vitamin A-derived molecule that changes shape (11-cis to 11-trans) when it absorbs a photon.

Bleaching

Process in which rhodopsin splits into opsin and trans-retinal after light exposure, temporarily inactivating the photoreceptor.

Phototransduction

Conversion of light into an electrical signal in photoreceptors through changes in cGMP and membrane potential.

Dark adaptation

Increase in retinal sensitivity after moving from bright to dim light as rhodopsin regenerates.

Light adaptation

Decrease in retinal sensitivity after moving into bright light as photopigments bleach.

Transducin

G-protein activated by opsin in photoreceptors; initiates phosphodiesterase activity to reduce cGMP.

cGMP (in vision)

Second messenger that keeps sodium channels open in dark; its breakdown closes channels during light exposure.

Basilar membrane

Flexible membrane inside the cochlea that moves with pressure waves, supporting the organ of Corti.

Tectorial membrane

Gelatinous structure overlying hair cells in the organ of Corti; stereocilia bend against it during sound transduction.

Organ of Corti

Sensory structure on the basilar membrane containing hair cells responsible for hearing.

Cochlea

Spiral portion of the bony labyrinth housing the cochlear duct and auditory receptors.

Vestibule

Central part of the bony labyrinth containing the utricle and saccule for gravity/linear acceleration.

Semicircular canals

Three looped structures oriented in different planes that detect rotational (dynamic) movements.

Ampulla

Expanded region at each semicircular canal base containing the crista ampullaris.

Crista ampullaris

Receptor structure within the ampulla for rotational equilibrium; hair cells project into the cupula.

Maculae

Patch of hair cells in utricle and saccule that detect gravity and linear acceleration.

Otoliths

Calcium carbonate crystals embedded in the otolithic membrane, adding weight to detect head position.

Utricle

Macula-containing chamber sensitive to horizontal acceleration and head tilt.

Saccule

Macula-containing chamber sensitive to vertical acceleration.

Otolithic membrane

Gel layer in the vestibule embedding otoliths and stereocilia of macular hair cells.

Auditory ossicles

Chain of three tiny bones—malleus, incus, stapes—that transmit tympanic vibrations to the inner ear.

Malleus

Hammer-shaped ossicle attached to the tympanic membrane; articulates with the incus.

Incus

Anvil-shaped middle ossicle linking malleus to stapes.

Stapes

Stirrup-shaped ossicle whose footplate covers the oval window, transmitting vibrations to inner ear fluids.

Tympanic membrane

Eardrum; thin membrane that converts sound waves into mechanical movements of ossicles.

Oval window

Membrane-covered opening where stapes transfers vibrations into the perilymph of the inner ear.

Round window

Membrane at the end of the cochlear duct that bulges to dissipate pressure waves in perilymph.

External acoustic meatus

Ear canal leading from the auricle to the tympanic membrane, conveying sound waves.

Auditory tube (Eustachian)

Canal connecting middle ear to nasopharynx; equalizes air pressure across the tympanic membrane.

Perilymph

Fluid in spaces of the bony labyrinth surrounding the membranous labyrinth.

Endolymph

Potassium-rich fluid inside the membranous labyrinth bathing the hair cell stereocilia.

Bony labyrinth

Hard outer structure of the inner ear containing perilymph and the membranous labyrinth.

Membranous labyrinth

Soft duct system within the bony labyrinth filled with endolymph and housing sensory receptors.

Hair cells

Mechanoreceptor cells in cochlea and vestibular system whose stereocilia detect movement of endolymph or membranes.

Stereocilia

Long microvilli on hair cells; bending them alters transmembrane potential and neurotransmitter release.

Frequency (pitch)

Perceived tone of sound determined by which portion of basilar membrane is stimulated.

Amplitude (loudness)

Perceived volume determined by how much the basilar membrane moves.

Spiral ganglion

Cluster of sensory neuron cell bodies that innervate cochlear hair cells and form the cochlear nerve.

Vestibular nuclei

Brainstem nuclei integrating balance information and relaying it to spinal cord, cerebellum, and cortex.

Accommodation (near vision)

Lens rounding that occurs when viewing objects closer than 20 ft to increase refraction of divergent light rays.

20/15 vision

Visual acuity where a person sees at 20 ft what a normal eye must approach to 15 ft to see clearly.

Sty

Inflammation or blockage of a tarsal or sebaceous gland on the eyelid edge.

Glaucoma

Eye disorder caused by excessive aqueous humor or poor drainage, leading to increased intraocular pressure.

Presbyopia

Age-related decline in lens elasticity that reduces accommodation for near objects.