Senses

Sensory Receptor

Specialized cell or nerve ending that detects a stimulus and converts it into a nerve impulse.

General Senses

Touch, pressure, pain, temperature, vibration, and proprioception; found throughout the body.

Special Senses

Vision, hearing, taste, smell, and equilibrium; located in specialized organs.

Mechanoreceptors

Detect touch, pressure, vibration, stretch, and sound.

Thermoreceptors

Detect changes in temperature (heat and cold).

Nociceptors

Detect pain caused by tissue damage.

Chemoreceptors

Detect chemicals involved in taste and smell.

Photoreceptors

Detect light; rods and cones in the retina.

Adaptation

Decreased awareness of a constant stimulus over time.

Referred Pain

Pain perceived in a different location than where it actually originates.

Taste Buds

Sensory organs that contain taste receptor cells and detect dissolved chemicals in food.

Lingual Papillae

Small bumps on the tongue that contain most taste buds.

Five Basic Tastes

Sweet, sour, salty, bitter, and umami.

Olfactory Receptors

Sensory receptors located in the roof of the nasal cavity that detect airborne chemicals.

Taste Receptors

Sensory receptors located in taste buds that detect dissolved chemicals in food.

Taste vs. Smell

Taste detects dissolved chemicals on the tongue; smell detects airborne chemicals in the nasal cavity.

External Ear

Collects and directs sound waves into the ear.

Auricle (Pinna)

Funnel-shaped outer ear that collects sound waves.

External Acoustic Meatus

Ear canal that carries sound to the tympanic membrane.

Middle Ear

Air-filled chamber that amplifies sound vibrations.

Tympanic Membrane

Eardrum that vibrates when struck by sound waves.

Tympanic Cavity

Air-filled space in the middle ear.

Auditory Tube

Connects the middle ear to the throat to equalize air pressure.

Auditory Ossicles

Three tiny bones (malleus, incus, stapes) that transmit and amplify sound.

Malleus

Hammer-shaped bone attached to the tympanic membrane.

Incus

Anvil-shaped bone between the malleus and stapes.

Stapes

Stirrup-shaped bone that transmits vibrations to the oval window.

Internal Ear

Contains structures responsible for hearing and balance.

Cochlea

Spiral-shaped organ that converts sound vibrations into nerve impulses.

Scala Vestibuli

Upper chamber of the cochlea filled with perilymph.

Scala Tympani

Lower chamber of the cochlea filled with perilymph.

Perilymph

Fluid that surrounds the cochlear duct in the cochlea.

Cochlear Duct

Middle chamber of the cochlea containing the Organ of Corti and hair cells.

Hair Cells

Sensory receptors that convert sound vibrations into nerve impulses.

Hearing Pathway

Auricle → External Acoustic Meatus → Tympanic Membrane → Malleus → Incus → Stapes → Oval Window → Cochlea → Hair Cells → Auditory Nerve → Brain.

Equilibrium

The ability to maintain balance and body position.

Static Equilibrium

Detects head position, gravity, and straight-line movement.

Vestibule

Inner ear structure responsible for static equilibrium.

Macula

Sensory receptor in the vestibule that detects gravity and linear acceleration.

Dynamic Equilibrium

Detects rotational (angular) movement of the head.

Semicircular Canals

Three canals that detect rotational head movement.

Ampulla

Enlarged base of each semicircular canal containing the crista ampullaris.

Crista Ampullaris

Sensory receptor inside the ampulla that detects rotational movement.

Eye

Organ responsible for vision.

Fibrous Layer

Outer layer of the eye containing the sclera and cornea.

Sclera

White, protective outer layer of the eye.

Cornea

Transparent front of the eye that bends (refracts) light.

Vascular Layer

Middle layer containing the choroid, ciliary body, iris, and pupil.

Choroid

Vascular layer that nourishes the retina.

Ciliary Body/Ciliary Muscles

Change the shape of the lens for focusing.

Iris

Colored part of the eye that controls pupil size.

Pupil

Opening in the iris that allows light into the eye.

Inner Layer (Retina)

Light-sensitive layer containing rods and cones.

Rods

Photoreceptors responsible for night vision, black-and-white vision, and peripheral vision.

Cones

Photoreceptors responsible for color vision and sharp detail.

Macula

Central area of the retina responsible for detailed central vision.

Fovea Centralis

Center of the macula with the sharpest vision and highest concentration of cones.

Optic Disc

Blind spot where the optic nerve leaves the eye; contains no photoreceptors.

Anterior Cavity

Front chamber of the eye filled with aqueous humor.

Posterior Cavity

Large chamber behind the lens filled with vitreous humor.

Optic Chiasma

Location where optic nerve fibers partially cross.

Optic Tracts

Nerve pathways carrying visual information from the optic chiasma to the brain.

Vision Pathway

Cornea → Anterior Chamber → Pupil → Lens → Posterior Cavity → Retina → Optic Nerve → Optic Chiasma → Optic Tracts → Visual Cortex.

Accommodation

Process of changing the lens shape to focus on near or distant objects.

Near Vision

Ciliary muscles contract, causing the lens to become thicker (rounder).

Far Vision

Ciliary muscles relax, causing the lens to become thinner (flatter).