Nervous System IV: Special Senses

Comprehensive vocabulary flashcards covering the anatomy, function, and pathways of the eye, ear, nose, and tongue as discussed in the Special Senses lecture.

Vision (Sight)

The capability of the eye(s) to focus and detect images of visible light on photoreceptors in the retina of each eye that generates electrical nerve impulses.

Audition

The sense of sound perception; also known as hearing.

Olfaction

The chemical sense of smell where odour molecules excite specific receptors to create signals perceived by the brain.

Mechanoreception

A perception resulting from activation of neural receptors generally in the skin, hair follicles, tongue, throat, and mucosa; also known as touch or somatosensory.

Tarsal glands

Modified sebaceous glands associated with the eyelid edges that produce an oily secretion to lubricate the eye.

Conjunctiva

A delicate membrane that lines the eyelids and covers part of the outer surface of the eyeball, ending at the edge of the cornea.

Lacrimal apparatus

Consists of the lacrimal gland and a number of ducts that drain lacrimal secretions into the nasal cavity.

Lacrimal canaliculi

Small ducts where tears flush medially across the eyeball before entering the lacrimal sac and nasolacrimal duct.

Extrinsic eye muscles

Six muscles attached to the outer surface of the eye including the lateral rectus, medial rectus, superior rectus, inferior rectus, inferior oblique, and superior oblique.

Sclera

Thick, glistening, white connective tissue forming the outermost fibrous layer, visible as the 'white of the eye'.

Cornea

The crystal clear central anterior portion of the fibrous layer through which light enters the eye.

Choroid

A blood-rich layer in the vascular region of the eye that prevents light from scattering inside the eye.

Iris

The pigmented part of the vascular layer with a rounded opening called the pupil through which light passes.

Neural layer of the Retina

The inner layer of the retina consisting of photoreceptors, which are the light-detecting cells of the eye.

Fovea centralis

A depression within the macula that has a high concentration of light-detecting cells and is responsible for high acuity vision.

Optic disc

The site where the optic nerve enters the retina; it contains no light-detecting cells and is known as the blind spot.

Aqueous humor

A clear, watery fluid in the anterior segment of the eye that helps maintain intraocular pressure.

Vitreous humor

A gel-like substance in the posterior segment of the eye also known as the vitreous body that helps prevent the eyeball from collapsing.

Glaucoma

A condition resulting from the obstructed drainage of aqueous humor, leading to increased pressure inside the eye.

Photopupillary reflex

A protective reflex where the pupils immediately constrict when exposed to bright light to prevent damage to photoreceptors.

Accommodation pupillary reflex

Automatic eye adjustment for near vision involving pupillary constriction, lens thickening, and eye convergence.

Diabetic retinopathy

A complication of diabetes caused by high blood sugar levels damaging the retina, which can lead to blindness.

Papilloedema

Swelling of the optic disc occurring secondary to raised intracranial pressure, which may be caused by meningitis or hydrocephalus.

Pinna

The shell-shape structure surrounding the auditory canal opening; also called the auricle.

Cerumen

Waxy, yellow earwax secreted by glands in the external acoustic meatus to provide a sticky trap for foreign bodies.

Tympanic membrane

Commonly called the eardrum, it separates the external from the middle ear and vibrates when hit by sound waves.

Pharyngotympanic tube

A tube running obliquely downward to link the middle ear cavity with the pharynx.

Ossicles

The three smallest bones in the body (hammer/malleus, anvil/incus, and stirrup/stapes) that transmit vibratory motion to the inner ear.

Cochlea

The subdivision of the bony labyrinth that houses the auditory part of the inner ear, specifically the organ of Corti.

Organ of Corti

The structure within the cochlea that contains hearing receptors, or hair cells.

Semicircular canals

Three canals in the inner ear responsible for maintaining balance.

Nasal conchae

Three bony structures located on the lateral wall of the nasal cavity.

Olfactory filaments

Bundled axons of olfactory neurons that collectively make up the olfactory nerve (CN I).

Sulcus terminalis

A V-shaped group that divides the dorsum of the tongue into a posterior third and an anterior two-thirds.

Gustation

The sensation produced when substances react with taste receptor cells.

Primary tastes

The five sensations of bitter, salty, sour, sweet, and umami (savory).

Cranial Nerve VII (Facial)

The nerve responsible for the innervation of taste for the anterior two-thirds of the tongue.

Cranial Nerve IX (Glossopharyngeal)

The nerve responsible for the innervation of taste for the posterior third of the tongue.