Chapter 15: Special Senses - Eye, Vision, Hearing, and Equilibrium

Comprehensive vocabulary flashcards covering the anatomy and physiology of the special senses, focusing on the eye and ear as detailed in the Chapter 15 study guide.

Special senses

A category of senses including smell, taste, sight, hearing, and equilibrium.

Receptor potential

A graded potential produced in special sense receptors in response to a stimulus.

Action potential

The electrical signal that must be triggered by a receptor potential for a message to reach the brain.

Medial and lateral commissure

The corners of the eye where the upper and lower eyelids meet; also called the canthus.

Tarsal glands

Glands that produce an oily secretion to lubricate the eye.

Conjunctiva

A membrane lining the eyelids and eyeball that secretes mucus to keep the eye moist.

Lacrimal apparatus

A system consisting of the lacrimal gland and ducts that produce and drain tears.

Lacrimal fluid

Commonly known as tears, this fluid contains salt, mucus, antibodies, and lysozyme to protect against infection.

Extrinsic eye muscles

Six muscles responsible for creating gross movement of the eyeball.

Fibrous layer

The outermost layer of the eye consisting of the sclera and the cornea.

Sclera

The 'white of the eye' that forms part of the fibrous layer.

Cornea

The transparent front portion of the eye that allows light to enter.

Vascular layer

The middle layer of the eye consisting of the choroid, ciliary body, and iris.

Choroid

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

Ciliary body

A smooth muscle structure in the vascular layer involved in controlling the shape of the lens.

Iris

The colored part of the eye that acts as a diaphragm to regulate the amount of light entering through the pupil.

Retina

The sensory layer of the eye containing photoreceptor cells.

Rods

Photoreceptors that work in dim light, provide peripheral vision, and detect gray tones.

Cones

Photoreceptors used for color vision and sharp detail; most concentrated in the center of the retina.

Optic disc

The 'blind spot' of the eye where the optic nerve exits and no photoreceptors are present.

Fovea centralis

An area of the retina containing only cones that serves as the point of sharpest vision.

Lens

A flexible, biconvex structure that helps focus light on the retina.

Aqueous humor

A watery fluid in the anterior segment that nourishes the cornea and lens while maintaining intraocular pressure.

Vitreous humor

A gel-like fluid in the posterior segment that prevents the eye from collapsing and maintains intraocular pressure.

Accommodation

The process by which the lens changes shape to focus on near objects.

Binocular vision

The overlapping of visual fields from each eye that allows for depth perception and 3D vision.

Auricle (pinna)

The visible part of the outer ear that collects and directs sound waves into the auditory canal.

Tympanic membrane

Also known as the eardrum, it vibrates in response to sound waves and separates the outer ear from the middle ear.

Pharyngotympanic tube

A tube connecting the middle ear to the throat that equalizes pressure so the eardrum can vibrate normally.

Ossicles

Three tiny bones in the middle ear (malleus, incus, and stapes) that transmit and amplify sound vibrations.

Bony labyrinth

The portion of the inner ear consisting of the cochlea, vestibule, and semicircular canals, filled with perilymph.

Static equilibrium

The sense of head position relative to gravity, detected by maculae in the vestibule.

Otoliths

Tiny stones embedded in a gel-like membrane that shift with gravity to bend hair cells during head movement.

Dynamic equilibrium

The detection of angular or rotational movement of the head.

Crista ampullaris

The receptor for dynamic equilibrium located in the ampulla of each semicircular canal.

Cupula

A gelatinous cap over the hair cells in the crista ampullaris that drags against endolymph to detect rotation.

Spiral organ of Corti

The specific receptor organ for hearing located within the cochlear duct.

Basilar membrane

The membrane in the cochlea that vibrates to stimulate hair cells; its fibers vary in length and stiffness to detect pitch.

Tectorial membrane

The gel-like membrane that hair cells bend against to trigger an impulse for hearing.

Visual Pathway

The route of signals: Retina → Optic nerve → Optic chiasma → Optic tract → Thalamus → Optic radiation → Occipital lobe.