Human Biology: Chapter 15 - The Senses

Vocabulary practice flashcards covering sensory receptors, somatic senses, taste, smell, vision, and hearing based on Chapter 15 of Human Biology (16th Edition).

Sensory Receptors

Specialized dendrites that detect specific internal physiological states or external environmental stimuli.

Chemoreceptors

Sensory receptors that respond to chemical stimuli, including taste cells, olfactory cells, and nociceptors.

Nociceptors

Pain receptors that function as chemoreceptors by responding to chemicals released by damaged tissues.

Photoreceptors

Sensory receptors located in the retina, specifically rods and cones, that respond to light energy.

Mechanoreceptors

Sensory receptors that detect mechanical forces such as pressure, sound waves, motion, and gravity.

Thermoreceptors

Sensory receptors situated in the skin that are stimulated by changes in temperature.

Sensation

The event that occurs when a sensory receptor interacts with and is altered by a stimulus, triggering a nervous signal to the central nervous system.

Perception

The conscious interpretation of sensory stimuli by the brain's cortex.

Sensory Adaptation

A reduction in receptor responsiveness to repetitive, stable, and unchanging stimuli, preventing the nervous system from wasting processing capacity.

Cutaneous Receptors

Diverse mechanoreceptors, chemoreceptors, and thermoreceptors located in the dermis that enable the skin to sense touch, pressure, pain, and temperature.

Proprioceptors

Mechanoreceptors located within joints and muscles that monitor stretch and position to maintain muscle tone, body posture, and equilibrium through reflex circuits.

Taste Buds

Sensory structures on the tongue containing chemoreceptive taste cells that detect sweet, sour, salty, bitter, and umami tastes.

Olfactory Receptors

Chemoreceptive sensory neurons, numbering approximately $10\text{ to }20\text{ million}$, situated in the roof of the nasal cavity that bind inhaled airborne chemicals.

Special Senses

Complex senses, specifically vision and hearing, that require specialized intermediate tissues and structures to focus and channel environmental stimuli toward sensory receptor cells.

Cornea

The transparent, protective outer layer at the front of the eye that allows light to pass through toward the retina.

Visual Accommodation

The adjustment in the shape of the flexible lens facilitated by ciliary muscles to focus incoming light directly onto the retina for varying distances.

Rods

Retinal photoreceptors sensitive to all wavelengths of visible light, essential for peripheral vision and low-light night vision, requiring Vitamin A for proper function.

Cones

Retinal photoreceptors containing red, green, or blue pigments that respond to specific wavelengths of light, allowing color perception and high-detail vision.

Optic Nerve

The bundle of sensory nerve fibers composed of ganglion cell axons that exits the retina to convey visual signals to the brain.

Blind Spot

The area on the retina where ganglion axons gather to exit as the optic nerve, containing no photoreceptors.

Color Blindness

A genetic condition, primarily affecting males, characterized by an inability to differentiate certain colors (typically red and green) due to missing or defective cone photoreceptors.

Cataract

An abnormality of the eye marked by the clouding of the normally clear lens.

Glaucoma

An eye condition characterized by abnormally high fluid pressure within the ocular chambers, resulting in retinal damage and potential vision loss.

Astigmatism

A refractive error where an uneven curvature of the cornea or lens prevents light rays from focusing evenly on the retina.

Nearsightedness

A condition in which the eyeball is abnormally long, causing light rays from distant objects to focus in front of the retina rather than directly on it.

Farsightedness

A condition in which the eyeball is abnormally short, causing light rays from close objects to focus behind the retina.

Pinna

The external ear flap composed of cartilage and skin that collects and directs sound waves into the auditory canal.

Auditory Canal

A tubular pathway lined with fine hairs and modified sweat glands that secrete cerumen (earwax) to trap debris while directing sound to the eardrum.

Tympanic Membrane

The eardrum; a thin membrane separating the outer and middle ear that vibrates upon contact with sound waves to transfer acoustic energy to the ossicles.

Ossicles

Three tiny middle-ear bones—the malleus, incus, and stapes—that mechanically amplify and transmit vibrations to the inner ear's oval window.

Auditory Tube

Also called the Eustachian canal; a duct connecting the middle ear cavity to the throat to equalize air pressure across the tympanic membrane.

Cochlea

A snail-shell-shaped, fluid-filled organ of the inner ear that converts fluid vibrations into nerve impulses for hearing.

Spiral Organ

Also known as the organ of Corti; the functional unit within the cochlea consisting of hair cells whose stereocilia bend against the tectorial membrane to initiate action potentials.

Vestibular System

The sensory apparatus of the inner ear, consisting of the vestibule and semicircular canals, that monitors head movement and gravitational orientation to maintain balance.

Hereditary Sensory Autonomic Neuropathy

A very rare genetic disorder (HSAN) that prevents individuals from perceiving physical pain, eliminating a crucial protective warning mechanism against tissue damage.