PY11.1-7 | Special Senses — Glossary

The sense of smell; detection of airborne volatile chemical molecules by receptors in the olfactory epithelium

A modified bipolar neuron in the olfactory epithelium that detects odorant molecules via G-protein coupled receptors on its cilia

The perforated bony plate of the ethmoid bone through which olfactory nerve fibres pass from the nasal cavity to the olfactory bulb

The sense of taste; detection of dissolved chemical substances by taste receptor cells in taste buds

A cluster of 50-100 taste receptor cells located mainly in the papillae of the tongue that transduce chemical stimuli into neural signals

The fifth basic taste quality elicited by L-glutamate and nucleotides, signalling protein-rich food; detected by T1R1+T1R3 receptors

The eardrum; a thin, semi-transparent membrane separating the outer ear from the middle ear that vibrates in response to sound waves

The three middle ear bones (malleus, incus, stapes) that transmit and amplify sound vibrations from the tympanic membrane to the oval window

The spiral-shaped structure of the inner ear containing the organ of Corti, responsible for converting sound vibrations into nerve impulses

The sensory receptor organ for hearing located on the basilar membrane, containing inner and outer hair cells that transduce mechanical vibrations into electrical signals

The membrane within the cochlea that vibrates in response to sound; its width and stiffness vary from base (high frequency) to apex (low frequency), creating tonotopic organisation

The potassium-rich fluid filling the scala media (cochlear duct) and the membranous labyrinth of the vestibular system; its high K+ concentration drives hair cell transduction

The portion of the inner ear (three semicircular canals, utricle, saccule) responsible for detecting head position and movement for balance and equilibrium

Three fluid-filled loops (anterior, posterior, lateral) oriented in three planes that detect angular (rotational) acceleration of the head

Hearing loss caused by damage to the cochlear hair cells or the cochlear nerve (CN VIII), characterised by Rinne-positive test and Weber lateralising to the normal ear

Hearing loss caused by impaired sound transmission through the outer or middle ear, characterised by Rinne-negative test and Weber lateralising to the affected ear

A tuning fork test comparing air conduction (AC) with bone conduction (BC); normally AC > BC (positive); in conductive deafness BC > AC (negative)

The innermost layer of the eye containing photoreceptors (rods and cones) that convert light into neural signals transmitted via the optic nerve

The visual pigment in rod photoreceptors composed of opsin protein and 11-cis retinal (derived from vitamin A); bleaches on light absorption to initiate phototransduction

The central depression of the macula containing only cones at highest density, responsible for sharp central vision and colour perception

The process by which the lens increases its refractive power (becomes more convex) to focus on near objects, achieved by contraction of the ciliary muscle and relaxation of zonular fibres

Short-sightedness; a refractive error where the eyeball is too long or the cornea too curved, causing distant images to focus in front of the retina; corrected with concave (diverging) lenses

Age-related loss of lens accommodation due to decreased lens elasticity, causing difficulty focusing on near objects; onset typically after age 40

The neural route from retina to visual cortex: optic nerve → optic chiasm (nasal fibres cross) → optic tract → lateral geniculate nucleus → optic radiation → primary visual cortex (area 17)

Deficiency in colour perception due to absence or dysfunction of one or more cone types; most commonly X-linked red-green colour blindness (protanopia or deuteranopia)