Human Anatomy and Physiology: The Special Senses

Comprehensive vocabulary flashcards covering the anatomy, physiology, and pathology of the special senses (smell, taste, vision, hearing, and balance) based on Chapter 15 of Human Anatomy and Physiology, Third Edition.

Special Senses

Senses that convey specific stimuli from specialized sensory organs in discrete locations in the head, including smell (olfaction), taste (gustation), vision, hearing (audition), and vestibular sensation (balance).

Transduction

The process where a physical or chemical stimulus is converted into an action potential that can be interpreted by the brain.

Olfactory Neurons

Modified bipolar neurons and chemoreceptors that detect chemical substances perceived as odors; their axons form the Olfactory Nerve.

Basal Cells (Olfactory)

Stem cells located in the olfactory epithelium that replace olfactory neurons, which have a lifespan of only $30–60$ days.

Anosmia

The inability to detect smells; it is an early symptom of COVID-19 caused by the $S A R S-CoV-2$ virus.

Mitral Cells

Cells in the olfactory bulb whose dendrites synapse with the axon terminals of olfactory neurons.

Gustation

The sense of taste, which involves the stimulation of specialized receptor cells in taste buds.

Vallate (Circumvallate) Papillae

Large dome-shaped projections on the tongue that contain hundreds of taste buds.

Filiform Papillae

Long, thin cylinders scattered across the tongue that lack taste buds but detect the texture and temperature of food.

Gustatory (Taste) Cells

Specialized epithelial cells with microvilli that detect different tastes and have a lifespan of about $10–14$ days.

Umami

A savory taste sensation produced by glutamate or other amino acids.

Tarsal Plate

A stiffening structure in the eyelids made of dense regular collagenous connective tissue containing Tarsal Glands that secrete oil.

Conjunctiva

A thin epithelial membrane where the palpebral portion lines the posterior eyelids and the bulbar portion covers the anterior surface of the eye.

Lacrimal Apparatus

A group of structures that produces tears and drains them from the eye, including the lacrimal gland, puncta, canaliculi, sac, and nasolacrimal duct.

Diplopia

Blurred or double vision that occurs when the eyes cannot move together.

Sclera

The white part of the eye's fibrous layer made of irregularly arranged collagen fibers that resist deformation to maintain the shape of the eyeball.

Cornea

The translucent anterior one-sixth of the eyeball that allows light into the eye and lacks blood vessels.

Ciliary Body

A structure in the vascular layer containing a ring of smooth muscle that changes the shape of the lens to focus light on the retina.

Pupillary Sphincter Muscle

The muscle that constricts the pupil to reduce the amount of light entering the eye in response to the parasympathetic nervous system.

Rods

Photoreceptors responsible for black and white vision in low light levels and peripheral vision; they are more concentrated away from the fovea.

Cones

Photoreceptors responsible for high-acuity color vision in higher light levels; they are highly concentrated in the fovea centralis.

Fovea Centralis

An indented area within the macula lutea containing tightly packed cones that allows for extremely detailed vision.

Optic Disc

The portion of the retina where axons of the optic nerve gather and there are no photoreceptors; also known as the blind spot.

Vitreous Humor

A gelatinous material in the posterior cavity consisting of water, collagen fibers, and hyaluronic acids that helps maintain the shape of the eyeball.

Aqueous Humor

A fluid secreted by the ciliary body that fills the anterior cavity and drains into the Scleral Venous Sinus.

Cataract

A clouded lens often caused by trauma, aging, UV radiation, or diabetes, leading to blindness.

Glaucoma

A condition where aqueous humor cannot drain, raising intraocular pressure and leading to compression of the retina and optic nerve.

Photon

The basic unit of light that stimulates the photoreceptors in the retina.

Refraction

The bending of light rays as they pass through a translucent object.

Accommodation

The process where the lens 'rounds up' into a spherical shape to refract light from nearby objects onto the retina.

Emmetropic State

The relaxed state of the eye where the lens is flattened to focus on distant objects ($20$ feet or more).

Presbyopia

A condition where the lens gradually stiffens with age, making it difficult to focus on objects requiring close vision.

Hyperopia

A condition where the eyeball is too short or the cornea is too flat, resulting in difficulty focusing on near objects (farsightedness).

Myopia

A condition where the distance between the cornea and retina is too long or the cornea curves too much, resulting in nearsightedness.

Rhodopsin

A pigment found in the discs of rods made of the protein opsin and the pigment retinal.

Iodopsin

A pigment found in the discs of cones made of the protein photopsin and the pigment retinal.

Tympanic Membrane

A thin sheet of epithelium and connective tissue that separates the outer ear from the middle ear; also called the eardrum.

Pharyngotympanic (Auditory) Tube

A tube connecting the middle ear to the nasopharynx that equalizes pressure on both sides of the tympanic membrane.

Auditory Ossicles

The three smallest bones in the body (malleus, incus, and stapes) that amplify and concentrate sound vibrations onto the oval window.

Endolymph

Fluid filling the membranous labyrinth with a higher concentration of potassium ions than sodium ions.

Perilymph

Fluid found between the bony and membranous labyrinths with a higher concentration of sodium ions than potassium ions.

Spiral Organ (Organ of Corti)

The structure in the cochlear duct that contains the hair cell receptors for hearing.

Tinnitus

The sensation of hearing noise, such as ringing or buzzing, in the absence of actual external sound.

Conduction Hearing Loss

Hearing loss due to problems in the outer or middle ear that prevent sound waves from reaching the inner ear.

Otis Media

Inflammation of the middle ear cavity, common in children due to shorter, more horizontal pharyngotympanic tubes.

Otoliths

Calcium carbonate crystals found in the otolithic membrane of the utricle and saccule that assist in maintaining static equilibrium.

Cristae Ampullaris

Clusters of hair cells located in the ampullae of the semicircular ducts that detect rotational movement of the head.

Cupula

A gelatinous mass in the cristae ampullaris where the stereocilia and kinocilia of rotational-detecting hair cells are embedded.