Senses Review: General Senses, Taste, Smell, Hearing, Equilibrium, and Vision

Vocabulary-style flashcards covering receptor properties, senses, taste, smell, hearing, equilibrium, and vision based on lecture notes.

Receptor

A structure specialized to detect a stimulus; may be bare nerve endings or true sense organs.

Sense organ

A structure of nerve tissue surrounded by other tissues that enhances response to a stimulus.

Transduction

Conversion of stimulus energy into nerve signals.

Receptor potential

A small local electrical change on a receptor cell caused by a stimulus that can lead to neurotransmitter release or action potentials.

Sensation

Subjective awareness of a stimulus; many signals do not reach consciousness.

Modality

Type of stimulus or sensation (vision, hearing, taste, etc.).

Labeled line code

Each nerve pathway is labeled to indicate its modality, helping the brain interpret the signal.

Receptive field

Area within which a sensory neuron detects stimuli.

Phasic receptor

Receptors that adapt rapidly, generating a burst of signals at first stimulation and then diminishing.

Tonic receptor

Receptors that adapt slowly, maintaining signals during the stimulus.

Unencapsulated nerve endings

Nerve endings without connective tissue wrapping (free nerve endings, tactile discs, hair receptors).

Free nerve endings

Unencapsulated endings for pain and temperature.

Tactile disc

Unencapsulated endings associated with Merkel cells for light touch.

Hair receptor

Unencapsulated ending that wraps around a hair follicle to monitor movement.

Encapsulated nerve endings

Nerve endings wrapped by glial cells or connective tissue to enhance response.

Meissner corpuscles

Encapsulated endings for light touch and texture in the dermal papillae.

Krause end bulbs

Encapsulated tactile endings in mucous membranes.

Lamellar (Pacinian) corpuscles

Encapsulated receptors for deep pressure, vibration; phasic response.

Bulbous (Ruffini) corpuscles

Encapsulated receptors for heavy touch and skin stretch; tonic response.

Nociceptors

Pain receptors that detect tissue injury or potentially damaging stimuli.

Fast pain

Sharp, well-localized pain carried by myelinated fibers.

Slow pain

Dull, diffuse pain carried by unmyelinated fibers.

Somatic pain

Pain from skin, muscles, and joints.

Visceral pain

Pain from internal organs; often poorly localized.

Pain projection pathways

First-, second-, and third-order neurons; include spinothalamic and spinoreticular tracts.

Referred pain

Pain from viscera perceived at a distant, usually cutaneous, site due to CNS convergence.

Analgesic mechanisms

CNS processes that relieve pain, including endogenous opioids.

Endogenous opioids

Internally produced analgesic peptides such as enkephalins, endorphins, and dynorphins.

Spinal gating

Descending signals from the brainstem modulate or block pain transmission in the spinal cord.

Gustation (taste)

Sensation produced by chemical stimulants on taste buds.

Taste buds

Clusters of taste cells, supporting cells, and basal cells with a taste pore and hairs.

Lingual papillae

Tongue structures: filiform (no taste buds), fungiform, foliate, vallate.

Taste cells

Chemosensory cells with apical microvilli that detect tastants and release neurotransmitters.

Taste pore

Opening into a taste bud through which taste hairs project.

Basal cells (taste)

Stem cells that replace taste cells every 7–10 days.

Supporting cells (taste)

Cells resembling taste cells but without sensory role.

Cranial nerves for taste

CN VII (facial) anterior 2/3, CN IX (glossopharyngeal) posterior 1/3, CN X (vagus) palate/pharynx/epiglottis.

Olfaction

Sense of smell triggered by odorants acting on olfactory receptor neurons.

Olfactory mucosa

Mucous membrane containing olfactory receptors and supporting/basal cells.

Cranial nerve I

Olfactory nerve that transmits smell information to the brain.

Olfactory bulb

Structure where olfactory receptor neurons synapse; contains mitral and tufted cells.

Glomerulus (olfactory)

Spherical cluster where olfactory axons converge on mitral/tufted cells.

Primary olfactory cortex

Temporal lobe region where olfactory information is initially processed.

Olfactory adaptation

Decreased sensitivity to odors with continued exposure.

Hearing (audition)

Perception of sound; involves outer, middle, and inner ear.

Outer ear

Pinna and external acoustic meatus; funnels sound to the eardrum.

Middle ear

Air-filled cavity with the tympanic membrane and ossicles that transmit vibrations to the inner ear.

Ossicles

Malleus, incus, and stapes; amplify and transmit vibrations to the oval window.

Tympanic reflex

Protective contraction of middle-ear muscles to dampen loud sounds.

Inner ear

cochlea and vestibular apparatus; converts vibrations to nerve signals and senses balance.

Cochlea

Spiral organ of hearing with three fluid-filled compartments.

Organ of Corti

Acoustic organ in the cochlea containing hair cells that transduce sound.

Hair cells

Inner hair cells for hearing and outer hair cells for sensitivity and amplification.

Stereocilia and kinocilium

Hair-like projections on hair cells involved in mechanotransduction; tip links regulate channels.

Basilar membrane

Membrane where different regions respond to different frequencies (tonotopy).

Tectorial membrane

Gelatinous membrane above hair cells that interacts with stereocilia.

Auditory pathway

Cochlear nuclei → superior olivary nucleus → inferior colliculus → thalamus (medial geniculate) → primary auditory cortex.

Pitch

Perceived frequency of a sound, encoded by which part of the basilar membrane is stimulated.

Loudness

Perceived sound energy; correlated with amplitude and firing rate of neurons.

Basilar membrane tonotopy

High frequencies near the base; low frequencies near the apex.

Cataracts

Clouding of the lens causing blurred vision; can be treated by lens replacement.

Glaucoma

Elevated intraocular pressure from poor drainage of aqueous humor; can damage retina.

Refraction

Bending of light as it passes between media; cornea is the primary refractor.

Near response

Convergence, pupillary constriction, and lens accommodation for near vision.

Emmetropia

Eye focus where distant objects are seen without effort; relaxed state.

Myopia vsHyperopia

Myopia: nearsightedness; Hyperopia: farsightedness.

Color vision

Trichromatic vision using S, M, and L cones with different absorption peaks.

Color blindness

Most commonly red-green; due to lacking or altered L or M cones.

Dual visual system

Rods mediate night vision while cones mediate day vision; separate pathways.

Fovea centralis

Central retina region with high cone density and high visual acuity.

Visual projection pathway

Optic nerve → optic chiasm → optic tract → lateral geniculate nucleus → optic radiations → primary visual cortex.

Stereopsis

Depth perception from binocular vision and slight differences between the two eyes.

Macula lutea

Region of the retina with high acuity; contains the fovea at its center.

Rods vs cones (pigments)

Rods use rhodopsin for night vision; cones use photopsin for color/day vision.

Ocular tunics

Three layers of the eye: fibrous (sclera, cornea), vascular (choroid, ciliary body, iris), neural (retina).

Aqueous humor flow

Secreted by the ciliary body into the posterior chamber, through the pupil to the anterior chamber, and reabsorbed via the scleral venous sinus.