Somatic and Special Senses

Sensation

Conscious or subconscious awareness of changes in the external or internal environment.

Perception

Conscious awareness and interpretation of sensations and is primarily a function of the cerebral cortex.

Stimulus

Something that causes a response or reaction.

Receptor

A specialized cell or structure that detects and responds to a specific stimulus.

Nerve impulses

Electrical signals transmitted by nerve cells.

Sensory pathway

The route that nerve impulses take from the receptors to the brain.

Adaptation

A decrease in the strength of sensation during prolonged stimulus due to a decrease in responsiveness of receptors.

Mechanoreceptors

Receptors that respond to mechanical stimuli such as touch or pressure.

Thermoreceptors

Receptors that respond to changes in temperature.

Nociceptors

Receptors that respond to pain.

Photoreceptors

Receptors that respond to light.

Chemoreceptors

Receptors that respond to chemical stimuli.

Tactile receptors

Receptors that respond to touch.

Corpuscles of touch

Cutaneous mechanoreceptors that detect light touch.

Lamellated corpuscles

Receptors that detect pressure and vibration.

Itch

Sensation caused by the stimulation of free nerve endings by chemicals.

Tickling

Sensation caused by the stimulation of free nerve endings when someone else touches you.

Thermal receptors

Receptors that respond to changes in temperature.

Pain receptors

Receptors that respond to pain.

Fast pain

Rapid, acute, sharp or pricking pain that is felt immediately after a stimulus.

Slow pain

Pain that increases in intensity over a period of time and may be chronic, burning, aching, or throbbing.

Referred pain

Pain felt in a different location than the actual source of the pain.

Proprioceptive sensations

Sensations that allow us to know the position and movement of our body parts.

Olfaction

Sense of smell.

Olfactory receptors

Cells in the olfactory epithelium that detect odors.

Supporting cells

Cells in the olfactory epithelium that provide structural support.

Basal cells

Cells in the olfactory epithelium that can differentiate into new olfactory receptor cells.

Adaptation

Decreasing sensitivity to odors that occurs rapidly with olfaction.

Olfaction

The sense of smell.

Gustation

The sense of taste.

Nasal mucosa

The lining of the nasal cavity.

Olfactory receptors

Receptors in the nasal mucosa that detect odors.

Olfactory nerve

The nerve that carries signals from the olfactory receptors to the brain.

Cribriform plate

A bony structure in the skull through which the olfactory nerve fibers pass.

Olfactory bulb

A structure at the base of the brain where the olfactory nerve fibers terminate.

Olfactory tract

A bundle of nerve fibers that carries signals from the olfactory bulb to other parts of the brain.

Primary olfactory area

The region in the temporal lobe of the brain where smell signals are processed.

Taste buds

Structures on the tongue that contain gustatory receptor cells.

Saliva

The fluid in the mouth that dissolves substances for tasting.

Salty

One of the five primary tastes, characterized by a taste of salt.

Sweet

One of the five primary tastes, characterized by a taste of sugar.

Sour

One of the five primary tastes, characterized by a taste of acidity.

Bitter

One of the five primary tastes, characterized by a taste of bitterness.

Umami

One of the five primary tastes, characterized by a taste of savory or meaty flavors.

Tongue papillae

Small bumps on the tongue that contain taste buds.

Vallate papillae

Large papillae at the back of the tongue that contain taste buds.

Fungiform papillae

Mushroom-shaped papillae scattered over the tongue that contain taste buds.

Foliate papillae

Papillae located in lateral trenches of the tongue that contain taste buds.

Filiform papillae

Papillae that cover the entire surface of the tongue, but do not contain taste buds.

Tastant

A substance that can be tasted.

Neurotransmitter

A chemical messenger that transmits signals between nerve cells.

Facial nerve

The seventh cranial nerve that carries taste signals from the front two-thirds of the tongue.

Glossopharyngeal nerve

The ninth cranial nerve that carries taste signals from the back third of the tongue.

Vagus nerve

The tenth cranial nerve that carries taste signals from the throat and epiglottis.

Medulla oblongata

The part of the brainstem that controls basic functions, including taste.

Limbic system

A group of brain structures involved in emotion and memory.

Hypothalamus

A region of the brain that regulates various bodily functions, including appetite and thirst.

Thalamus

A relay station in the brain that processes and relays sensory information, including taste.

Eyebrows

The hair above the eye that helps protect the eye from sweat and debris.

Eyelids

The movable folds of skin that cover and protect the eye.

Eyelashes

The hairs on the edge of the eyelids that help protect the eye from debris.

Lacrimal apparatus

The system that produces and drains tears.

Extrinsic eye muscles

Muscles that control the movement of the eyeball.

Palpebral muscles

Muscles that control the movement of the eyelids.

Conjunctiva

A thin, protective membrane that lines the eyelids and covers the sclera.

Tarsal plate

A fold of connective tissue that gives form to the eyelids.

Lacrimal glands

Glands that produce tears.

Lacrimal ducts

Ducts that carry tears from the lacrimal glands to the surface of the eye.

Lacrimal puncta

Small openings on the edge of the eyelids that drain tears into the lacrimal canaliculi.

Lacrimal canaliculi

Small channels that carry tears from the lacrimal puncta to the lacrimal sac.

Retina

The inner coat of the eyeball that contains photoreceptor cells.

Optic nerve

The nerve that carries visual signals from the retina to the brain.

Fovea

A small depression in the retina that contains a high concentration of cones for sharp central vision.

Rods

Photoreceptor cells in the retina that are sensitive to dim light and shades of gray.

Cones

Photoreceptor cells in the retina that are responsible for color vision and visual acuity.

Photoreceptors

Cells in the retina that convert light into electrical signals.

Anterior chamber

The front part of the eye between the cornea and the iris.

Posterior chamber

The back part of the eye between the iris and the lens.

Aqueous humor

A clear, watery fluid that fills the anterior and posterior chambers of the eye.

Posterior cavity

The space behind the lens of the eye that is filled with vitreous humor.

Vitreous humor

A transparent, gelatinous substance that fills the posterior cavity of the eye.

Fibrous tunic

The outer coat of the eyeball, consisting of the cornea and sclera.

Cornea

The transparent front part of the eye that refracts light.

Sclera

The white, tough outer layer of the eyeball.

Vascular tunic

The middle coat of the eyeball, consisting of the choroid, ciliary body, and iris.

Choroid

The vascular layer of the eye that supplies blood to the retina.

Ciliary body

The part of the eye that produces aqueous humor and controls the shape of the lens.

Iris

The colored part of the eye that controls the size of the pupil.

Color Blindness

A condition in which a person is unable to perceive colors or has difficulty distinguishing between certain colors.

Hearing Ear

The organ responsible for hearing, consisting of the external ear, middle ear, and inner ear.

External Ear

The outer part of the ear that includes the auricle (pinna), external auditory canal, and eardrum.

Middle Ear

The part of the ear between the eardrum and the inner ear, consisting of the auditory (eustachian) tube, ossicles (malleus, incus, and stapes), and oval window.

Internal Ear

The innermost part of the ear, also known as the labyrinth, which contains the bony labyrinth and membranous labyrinth.

Auricle

The visible part of the external ear, also known as the pinna.

External Auditory Canal

The tube-like structure that connects the auricle to the eardrum.

Tympanic Membrane

Also known as the eardrum, it vibrates in response to sound waves.

Cerumen

Earwax secreted by the ceruminous glands in the external auditory canal to protect the canal and eardrum.

Auditory Ossicles

The three smallest bones in the body located in the middle ear:malleus, incus, and stapes.

Oval Window

A membrane-covered opening in the middle ear that transmits sound vibrations from the ossicles to the inner ear.

Eustachian Tube

A tube that connects the middle ear to the nasopharynx, helping to regulate air pressure in the middle ear.