Chapter 12

Vocabulary flashcards covering the general and special senses, receptor types, anatomy of the ear and eye, and common sensory disorders based on the Chapter 12 lecture notes.

General senses

Receptors that are widely distributed throughout the body, including the skin, various organs, and joints.

Special senses

Specialized receptors confined to structures in the head, such as the eyes, ears, nose, and mouth.

Sensory receptors

Specialized cells or multicellular structures that collect information from the environment and relay it to the CNS on sensory neurons.

Transduction

The process where a stimulus is converted into graded receptor potentials.

Transmission

The conduction of action potentials along sensory neurons to the CNS.

Chemoreceptors

Sensory receptors that respond to changes in chemical concentrations, such as smell, taste, and oxygen concentration.

Pain receptors (nociceptors)

Sensory receptors that respond to tissue damage caused by mechanical, electrical, or thermal energy.

Thermoreceptors

Sensory receptors that respond to moderate changes in temperature.

Mechanoreceptors

Sensory receptors that respond to mechanical forces that distort the receptor, such as touch, tension, blood pressure, and stretch.

Photoreceptors

Sensory receptors in the eyes that respond to light.

Sensation

Occurs when action potentials make the brain aware of a sensory event, such as the awareness of pain.

Perception

Occurs when the brain interprets sensory impulses, such as realizing pain is from stepping on a tack.

Projection

The process in which the cerebral cortex interprets sensation as being derived from certain receptors, allowing a person to locate the region of stimulation.

Sensory Adaptation

The ability to ignore unimportant or continuous stimuli, involving a decreased response from receptors or along CNS pathways.

Exteroceptive senses

General senses associated with the body surface, such as touch, pressure, temperature, and pain.

Interoceptive (visceroceptive) senses

General senses associated with changes in the viscera, such as blood pressure stretching blood vessels.

Proprioceptive senses

General senses associated with changes in muscles, tendons, joints, and body position.

Free nerve endings

The simplest receptors, common in epithelial tissues, that sense itching and other sensations.

Tactile (Meissner’s) corpuscles

Receptors abundant in hairless portions of skin and lips that detect fine touch, texture, and distinguish between 2 points.

Lamellated (Pacinian) corpuscles

Nerve endings encased in large ellipsoidal structures that detect heavy pressure and vibrations in deeper tissues.

Warm receptors

Thermoreceptors sensitive to temperatures above $25^{\circ}C$ ($77^{\circ}F$) and unresponsive above $45^{\circ}C$ ($113^{\circ}F$).

Cold receptors

Thermoreceptors sensitive to temperatures between $10^{\circ}C$ ($50^{\circ}F$) and $20^{\circ}C$ ($68^{\circ}F$).

Referred pain

Visceral pain that feels as if it is coming from some other part of the body due to common nerve pathways.

Fast pain (A-delta) fibers

Myelinated axons that conduct impulses rapidly (up to $30\,m/sec$) and are associated with sharp, acute pain in localized skin.

Slow pain (C) fibers

Unmyelinated axons that conduct impulses slowly (up to $2\,m/sec$) and are associated with dull, aching, chronic pain.

Muscle spindles

Stretch receptors in skeletal muscles that initiate stretch reflexes causing muscle contraction.

Golgi tendon organs

Stretch receptors in tendons that stimulate reflexes opposing stretch reflexes to protect muscle attachments.

Synesthesia

A condition caused by genetic mutation where the brain interprets a stimulus for one sense as coming from another.

Olfaction

The sense of smell, provided by chemoreceptors that respond to chemicals dissolved in liquids.

Gustation

The sense of taste, occurring in taste buds located on papillae of the tongue and other oral areas.

Auricle (Pinna)

The funnel-shaped part of the outer ear that collects sound waves.

Tympanic membrane (Eardrum)

A membrane that vibrates in response to sound waves at the end of the external acoustic meatus.

Auditory ossicles

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

Tympanic Reflex

Muscle contractions involving the tensor tympani and stapedius that occur during loud sounds to prevent hearing receptor damage.

Auditory (eustachian) tube

A tube connecting the middle ear to the throat that helps maintain equal air pressure on both sides of the tympanic membrane.

Osseous (bony) labyrinth

The bony canal in the temporal bone filled with perilymph.

Membranous labyrinth

A tube lying within the osseous labyrinth filled with endolymph.

Spiral Organ (Organ of Corti)

The receptor organ for hearing located in the cochlear duct, containing hair cells with stereovilli.

Static equilibrium

The sense of head position when the body is not moving, managed by receptors in the vestibule.

Dynamic Equilibrium

The sense of rotation and movement of the head and body, managed by receptors in the semicircular canals.

Macula

The organ of static equilibrium consisting of hair cells embedded in gelatinous material with otoliths on the surface.

Crista ampullaris

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

Lacrimal apparatus

An accessory organ of the eye consisting of the lacrimal gland, canaliculi, lacrimal sac, and nasolacrimal duct for tear production.

Cornea

The transparent anterior one-sixth of the outer tunic that helps focus light rays.

Sclera

The white, opaque, tough posterior five-sixths of the outer tunic that protects the eye.

Accommodation

A change in the shape of the lens (thickening or thinning) to view objects at different distances.

Aqueous Humor

The watery fluid in the anterior cavity that provides nutrients and maintains the shape of the front of the eye.

Vitreous humor

A thick gel in the posterior cavity that holds the retina flat against the choroid coat.

Rods

Photoreceptors with long, thin projections containing rhodopsin that provide vision in dim light without color.

Cones

Photoreceptors with short, blunt projections containing iodopsins that provide sharp color vision in bright light.

Fovea centralis

A small depression in the center of the macula lutea that contains only cones and produces the sharpest vision.

Optic disc

The blind spot of the retina where nerve fibers leave the eye to become the optic nerve, containing no photoreceptors.

Refraction

The bending of light which occurs when light waves pass at an angle between mediums of different densities.

Myopia

Nearsightedness caused by an eyeball that is too long, resulting in light focusing in front of the retina.

Hyperopia

Farsightedness caused by an eyeball that is too short, resulting in light focusing behind the retina.

Astigmatism

A defect in the curvature of the cornea or lens causing some parts of an image to be out of focus.

Presbyopia

The farsightedness of age caused by the loss of elasticity in the lens capsule, making accommodation difficult.