General and Special Senses Flashcards

Comprehensive vocabulary flashcards covering the anatomical and physiological principles of general senses, cutaneous receptors, gustation, olfaction, vision, audition, and equilibrium.

Receptor Specificity

The principle that each sensory receptor is specialized in detecting one particular type of stimulus.

Transducers

Sensory receptors that interface between the nervous system and the environment by converting physical or chemical stimuli into action potentials.

Sensation

The detection of stimuli by sensory receptors, representing the raw sensory information generated by a stimulus.

Perception

The interpretation of sensory information within cortical areas of the brain, resulting in conscious awareness.

Receptive Field

The specific area of reception monitored by a single sensory neuron; smaller fields yield precise stimulus localization, whereas larger fields make localization difficult.

Tonic Receptors

Sensory receptors that maintain a constant action potential firing frequency and do not adapt (or take a very long time to adapt), such as nociceptors and photoreceptors.

Phasic Receptors

Sensory receptors that adapt to sustained stimuli over time by decreasing action potential frequency, such as olfactory receptors and cutaneous touch receptors.

Exteroceptors

Sensory receptors that detect stimuli originating from the exterior of the body, including skin sensations (touch, temperature, pressure) and the special senses.

Interoceptors

Sensory receptors that detect stimuli originating from internal organs, such as blood vessel pressure and blood oxygen levels.

Proprioceptors

Sensory receptors that detect mechanical deformations related to body position and movement in space, such as stretch in muscles, tendons, and joints.

Tactile Discs (Merkel's Discs)

Unencapsulated tactile receptors located in the stratum basale of the epidermis that respond to light touch by releasing neurotransmitters to activate sensory neurons.

Tactile Corpuscles (Meissner's Corpuscles)

Encapsulated tactile receptors located in the papillary layer of the dermis (concentrated in fingertips, lips, nipples, and genitals) that detect discriminative touch, textures, and low-frequency vibrations.

Lamellar Corpuscles (Pacini's Corpuscles)

Encapsulated tactile receptors located deep in the dermis that are sensitive to deep pressure and high-frequency vibrations.

Bulbous Corpuscles

Encapsulated tactile receptors located deep in the dermis that respond to deep, continuous pressure.

Root Hair Plexus

Unencapsulated tactile receptors located in the dermis wrapped around hair follicles that detect the movement of hair on the body surface.

Baroreceptors

Mechanoreceptors that detect mechanical deformations caused by pressure changes (especially barometric pressure), located in structures such as the carotid sinus, aortic sinus, lungs, urinary bladder, and digestive tract.

Muscle Spindles

A type of proprioceptor that detects changes in muscle length.

Golgi Tendon Organs

Proprioceptors that detect tension within tendons produced by muscle contraction.

Nociceptors

Tonic, unencapsulated free nerve endings located throughout the body with large receptive fields that signal pain upon exposure to tissue damage or harmful stimuli.

Referred Pain

A condition in which pain is perceived in an area different from its anatomical origin due to sensory nerve fibers from both sites converging along shared central nervous system pathways.

Gustatory Cells

Specialized epithelial cells in taste buds with microvilli (gustatory hairs) that depolarize and release neurotransmitters when chemicals dissolve in saliva and bind to chemoreceptors.

Papillae

Visible bumps on the dorsal surface of the tongue containing grooves lined with microscopic taste buds.

Taste Pore

A small opening in a taste bud facing the papilla groove that permits dissolved chemical tastants in saliva to contact gustatory microvilli.

Facial Nerve (CN VII in Gustation)

The cranial nerve responsible for transmitting taste information from the anterior $\frac{2}{3}$ of the tongue to the central nervous system.

Glossopharyngeal Nerve (CN IX in Gustation)

The cranial nerve responsible for transmitting taste information from the posterior $\frac{1}{3}$ of the tongue, the palate, and the epiglottis to the central nervous system.

Olfactory Sensory Neurons

Bipolar sensory neurons within the superior nasal cavity whose dendrites detect volatile odorants and whose axons pass through the cribriform plate to synapse in the olfactory bulb.

Olfactory Nerve (CN I)

The shortest cranial nerve, formed by olfactory sensory neuron axons crossing the cribriform plate; it is the only cranial nerve directly exposed to the external environment.

Anosmia

The total loss of the sense of smell resulting from aging, head trauma, sinonasal diseases, or neurological disorders such as Alzheimer's disease.

Rod Cells

Retinal photoreceptors that are highly sensitive to low light levels and provide black-and-white vision in dim lighting.

Cone Cells

Retinal photoreceptors that detect color and provide high-resolution, sharp visual acuity primarily in bright light.

Fovea Centralis

A depression located in the center of the retinal macula that possesses the highest concentration of cone cells and provides the sharpest visual resolution.

Tarsal Glands

Sebaceous glands embedded within the tarsal plates of the eyelids that secrete an oily substance to prevent the eyelids from adhering to each other.

Conjunctiva

A continuous epithelial membrane covering the anterior sclera (bulbar conjunctiva), turning at the fornix, and lining the inner surface of the eyelids (palpebral conjunctiva) to prevent foreign debris from slipping behind the eyeball.

Nasolacrimal Duct

A passage extending from the medial lacrimal punctum into the nasal cavity through which excess lacrimal fluid drains.

Cornea

The transparent, avascular anterior portion of the fibrous tunic that accounts for approximately $70\%$ of the total refraction of light entering the eye.

Sclera

The white, dense fibrous outer layer of the eye that protects internal structures and serves as an anchoring site for extrinsic eye muscles.

Choroid

The heavily vascularized middle layer of the eye containing an extensive capillary network that nourishes the retina and dissipates heat generated by focused light.

Ciliary Body

A vascular tunic structure consisting of ciliary muscles that adjust lens shape via ciliary zonule fibers (accommodation) and epithelial cells that produce aqueous humor.

Aqueous Humor

A clear, watery fluid filtered from plasma by the ciliary body into the posterior chamber, circulating through the pupil into the anterior chamber to nourish the avascular cornea and lens.

Scleral Venous Sinus (Canal of Schlemm)

A circular drainage channel situated at the corneoscleral junction that reabsorbs aqueous humor from the anterior chamber.

Glaucoma

A pathology caused by obstructed reabsorption of aqueous humor, generating elevated intraocular pressure that damages the optic nerve and can lead to permanent blindness.

Vitreous Humor

A clear, gelatinous fluid formed during embryonic development filling the posterior cavity, maintaining eyeball geometry and holding the neural and pigmented layers of the retina in contact.

Optic Disc

The blind spot of the retina where ganglion cell axons converge to form the optic nerve (CN II) and retinal vessels enter/exit; it contains no photoreceptor cells.

Optic Chiasm

The X-shaped junction where $50\%$ of optic nerve fibers from each eye decussate to the contralateral side before continuing into the optic tracts.

Tympanic Membrane

A delicate, vibrating fibrous partition separating the external acoustic meatus from the middle ear cavity.

Auditory Ossicles

The three minute middle ear bones (Malleus, Incus, Stapes) arranged in a chain that amplify sound wave vibrations and transfer them to the oval window.

Tensor Tympani and Stapedius

Middle ear skeletal muscles that attach to the malleus and stapes, respectively, contracting to dampen ossicular vibration during loud sounds.

Auditory Tube

A passageway connecting the middle ear cavity to the nasopharynx that opens to equalize air pressure across the tympanic membrane.

Endolymph

The fluid contained entirely within the interior of the membranous labyrinth of the inner ear.

Perilymph

The fluid occupying the space between the outer bony labyrinth and the inner membranous labyrinth that cushions the membranous structures.

Spiral Organ (Organ of Corti)

The sensory receptor structure for hearing located within the cochlear duct, housing hair cells that convert perilymph and endolymph vibrations into action potentials.

Helicotrema

The narrow communication channel at the apex of the cochlea connecting the scala vestibuli with the scala tympani.

Utricle

A horizontally oriented sac within the vestibule containing otoliths and hair cells that detects linear acceleration along the horizontal plane (back-and-forth movement).

Saccule

A vertically oriented sac within the vestibule containing otoliths and hair cells that detects vertical linear acceleration (up-and-down movement) and gravitational pull.

Otoliths

Microscopic calcium carbonate mineral granules situated atop the gelatinous otolithic membrane in the vestibule whose inertial movement bends the underlying hair cell stereocilia.

Semicircular Canals

Three fluid-filled canals (anterior, posterior, lateral) positioned along orthogonal spatial planes (X, Y, Z) that detect rotational head acceleration through endolymph displacement.

Vestibular Ganglion

The peripheral ganglion containing the cell bodies of bipolar sensory neurons whose dendrites receive balance signals from vestibular hair cells and whose axons form the vestibular branch of CN VIII.