Chapter 13: The Special Senses

Vocabulary practice flashcards generated from Chapter 13 lecture notes covering the five special senses, eye and ear anatomy, visual accommodation, photo-reception, and vestibular balance systems.

Special Senses

Senses that have highly localized receptors providing specific environmental information, including smell, taste, sight, hearing, and balance.

Odorants

Airborne molecules entering the nasal cavity that interact with sensory receptors to produce the sense of smell.

Olfactory Neurons

Bipolar neurons located in the olfactory epithelium whose distal ends have olfactory hairs that respond to dissolved odorants.

Taste Buds

Sensory structures detecting taste stimuli, primarily located in the papillae epithelium on the tongue, palate, lips, and throat.

Papillae

Projections on the tongue, three types of which contain taste buds, while the fourth and most numerous type provides roughness without taste buds.

Salty Taste

One of the five basic taste sensations, elicited primarily by sodium ions.

Sour Taste

One of the five basic taste sensations, elicited by acids.

Sweet Taste

One of the five basic taste sensations, elicited by sugars, certain other carbohydrates, and some proteins.

Bitter Taste

Primary taste sensation elicited by alkaloids (bases), to which human taste buds exhibit the highest sensitivity.

Umami Taste

Primary taste sensation elicited by the amino acid glutamate and related compounds.

Facial Nerve

Cranial nerve responsible for carrying taste sensations from the anterior two-thirds of the tongue.

Glossopharyngeal Nerve

Cranial nerve responsible for transmitting taste sensations from the posterior one-third of the tongue.

Vagus Nerve

Cranial nerve responsible for carrying taste sensations from the epiglottis.

Lacrimal Apparatus

Accessory eye system consisting of the lacrimal gland, lacrimal canaliculi, and nasolacrimal duct that produces and drains tears.

Sclera

The posterior $\frac{4}{5}$ths of the fibrous layer of the eye, made of white connective tissue that maintains shape and attaches muscles.

Cornea

The transparent anterior $\frac{1}{5}$th of the fibrous layer of the eye that refracts light entering the eye.

Choroid

Pigmented, black vascular network in the vascular layer that prevents light reflection inside the eye.

Ciliary Body

Vascular layer structure containing smooth muscle that changes lens shape and ciliary processes that produce aqueous humor.

Sphincter Pupillae

Smooth muscle of the iris that constricts the pupil in response to close vision and bright light.

Dilator Pupillae

Smooth muscle of the iris that dilates the pupil in response to distant vision and dim light.

Macula

Retinal area containing the fovea centralis with the highest concentration of photoreceptors and greatest light sensitivity.

Optic Disc

The 'blind spot' of the eye where optic nerves exit and blood vessels enter, lacking photoreceptors.

Aqueous Humor

Fluid produced by ciliary processes in the anterior and posterior chambers that nourishes the cornea and drains into the scleral venous sinus.

Vitreous Humor

Fluid filling the vitreous chamber that maintains eye shape, contributes to intraocular pressure, and holds the retina in place.

Emmetropic Eye

The normal resting condition of the eye when ciliary muscles relax and the lens flattens for distant vision.

Accommodation

Process where ciliary muscles contract to increase lens sphericity, allowing focus on objects closer than $20\,\text{feet}$.

Rods

Photoreceptors responsible for non-color vision and low-illumination night vision, containing rhodopsin.

Rhodopsin

Photosensitive pigment in rods composed of the protein opsin covalently bound to retinal.

Cones

Photoreceptors responsible for color vision and visual acuity, containing iodopsin photopigments sensitive to blue, red, and green light.

Ceruminous Glands

Glands located in the external acoustic meatus that produce cerumen (earwax).

Tympanic Membrane

Thin connective tissue eardrum that vibrates in response to sound waves, separating the external and middle ear.

Auditory Ossicles

Three small middle ear bones (malleus, incus, stapes) that transmit vibrations from the eardrum to the oval window.

Auditory Tube

Canal connecting the middle ear cavity to the pharynx, equalizing pressure with external air.

Endolymph

Potassium-rich ($\text{K}^+$) fluid contained within the membranous labyrinth of the inner ear.

Perilymph

Fluid located in the space between the bony labyrinth and membranous labyrinth of the inner ear.

Cochlea

Spiral-shaped canal within the temporal bone that houses the sensory apparatus for hearing.

Spiral Organ

Structure within the cochlear duct consisting of inner and outer hair cells with stereocilia attached to the tectorial membrane.

Pitch

Sound quality determined by the frequency of sound waves.

Volume

Sound quality determined by the amplitude of sound waves.

Timbre

The resonant quality or overtones of a sound wave.

Static Balance

Sensory function of maculae in the utricle and saccule that evaluates head position relative to gravity and linear movement.

Otoliths

Protein-calcium carbonate crystals embedded in the gelatinous otolithic membrane of the maculae.

Dynamic Balance

Sensory function evaluated by the semicircular canals that detects rotational head movements.

Crista Ampullaris

Sensory structure within the ampulla of each semicircular canal containing hair cells embedded in the gelatinous cupula.