HSA- Sensory Systems Information

This is only the information you must learn and memorize, I have a seperate set for Sensory Systems abbreviations , word parts, and terms

Five major senses

Taste, smell, touch, hearing, and sight

Balance

A commonly forgotten sense not included in the traditional five

Touch

Can be subdivided into pressure, vibration, stretch, and hair-follicle position

Mechanoreceptors

Receptors that perceive touch sensations such as pressure, vibration, stretch, and hair-follicle position

Thermoreceptors

Receptors that perceive temperature

Nociceptors

Receptors that perceive pain

General sense

A sense distributed throughout the body with receptor cells within the structures of other organs

Mechanoreceptors in the skin, muscles, or walls of blood vessels

Examples of receptors for general senses

General senses

Contribute to touch, proprioception, kinesthesia, and visceral sense

Visceral sense

Sense related to internal organ activity important to autonomic functions

Proprioception

Sense of body position or awareness of where body parts are

Kinesthesia

Sense of body movement

Special sense

A sense with a specific organ devoted to it (eye, inner ear, tongue, or nose)

Gustation

The special sense associated with the tongue

Tongue epithelium

Lined by stratified squamous epithelium

Papillae

Raised bumps on the tongue that contain structures for gustatory transduction

Circumvallate papillae

One of the four types of papillae based on appearance

Foliate papillae

One of the four types of papillae based on appearance

Filiform papillae

One of the four types of papillae based on appearance

Fungiform papillae

One of the four types of papillae based on appearance

Taste buds

Structures within papillae that contain gustatory receptor cells

Gustatory receptor cells

Specialized cells that perform transduction of taste stimuli

Transduction (taste)

Process by which gustatory cells convert chemical stimuli from food into neural signals

Neurotransmitters (in taste)

Chemicals that are made by nerve cells and used to communicate with other cells, including other nerve cells and muscle cells. Released by gustatory cells based on the chemical amount in food

Cranial nerves involved in taste

Facial, glossopharyngeal, and vagus nerves

Four primary tastes

Sweet, salty, sour, and bitter

Umami

Fifth taste, recognized in the mid-1980s, meaning “savory”

Possible sixth taste

Taste for fats or lipids suggested by recent research

Olfaction

The special sense of smell, responsive to chemical stimuli

Olfactory receptor neurons

Located in a small region within the superior nasal cavity

Nasal epithelium

Contains olfactory receptor cells; can be damaged by airborne toxic chemicals

Olfactory bulb

Structure where olfactory receptor neurons send signals

Olfactory tract

Pathway that carries signals from the olfactory bulb to the brain

Primary olfactory cortex

Located in the inferior and medial temporal lobe; processes smell

Hypothalamus (smell)

Receives olfactory signals; associates smells with long-term memory and emotional response

Odor detection

Humans can detect over 10,000 different odors

Audition (Hearing)

Transduction of sound waves into neural signals via the ear

External Ear

Auricle (pinna), ear canal, tympanic membrane

Auricle (Pinna)

C-shaped curves direct sound waves toward auditory canal

Auditory Canal

Enters skull through external auditory meatus of temporal bone

Tympanic Membrane

Vibrates when struck by sound waves

Middle Ear

Ossicles, oval window, tympanic membrane

Ossicles (Malleus, Incus, Stapes)

Malleus (hammer) attaches to tympanic membrane, connects to incus (anvil), which connects to stapes (stirrup)

Stapes

Attached to inner ear; transmits vibrations through oval window

Oval Window

Vibrations move inner ear fluid; frequency of fluid waves matches sound waves

Eustachian Tube

Connects middle ear to the pharynx; equalizes air pressure across tympanic membrane

Inner Ear (Bony Labyrinth)

Series of canals in temporal bone

Cochlea

Responsible for hearing; spiral-shaped, contains organs of Corti and basilar membrane

Vestibule

Responsible for balance

Vestibulocochlear Nerve

Carries neural signals from cochlea and vestibule to brainstem

Spiral Ganglia

Sensory neurons within the cochlea

Cochlear Duct

Contains organs of Corti, transduces fluid wave motion into neural signals

Basilar Membrane

Hair cells sensitive to frequency; high frequencies at base, low frequencies at apex

Cochlea Frequency Range

Encodes sounds between 20 Hz and 20,000 Hz (20 kHz)

Hertz (Hz)

Measures frequency of sound waves in cycles per second

Low Frequencies

Detected by hair cells at apex (tip) of cochlea

High Frequencies

Detected by hair cells at base of cochlea, near round and oval windows

Auditory Stimuli

Usually a mixture of frequencies and intensities (amplitude)

Frequency Separation

Hair cells along cochlear duct respond to specific frequencies, allowing the cochlea to separate sounds by frequency, like a prism separates light

Equilibrium (Balance)

The inner ear’s function of encoding information about head position, movement, and body motion

Vestibule

Region of the inner ear that contains cells for sensing head position and motion

Otolith Organs

Sense head position

Semicircular Canals

Sense head movement

Vestibular Ganglion

Generates neural signals for balance that travel to the brainstem and cerebellum

Vestibulocochlear Nerve

Transmits equilibrium signals from inner ear to brain

Somatosensation (Touch)

A general sense encompassing modalities associated with touch, proprioception, and interoception

Sensory Modalities

Include pressure, vibration, light touch, tickle, itch, temperature, pain, proprioception, and kinesthesia

Receptors

Located throughout the body in skin, muscles, tendons, joint capsules, ligaments, and visceral organs

Free Nerve Endings

Transduce pain and temperature signals

Thermoreceptors

Sensitive to temperature changes; some detect cold, others heat

Nociception

Sensation of potentially damaging stimuli

Capsaicin

Active molecule in hot peppers that binds to nociceptor ion channels sensitive to temperatures above 37°C (98.6°F)

Topical Analgesic

Products like Icy Hot™ that reduce pain by interacting with nociceptors

Aging

Leads to loss of sensory receptor cells, including those detecting pain and temperature

Vision (Sight)

Vision is the special sense of sight that is based on the transduction of light stimuli received through the eyes

Orbit

Bony cavities in the skull that surround the eyeballs, protecting them and anchoring soft tissues

Eyelids

Protect the eye from abrasions; eyelashes block particles from landing on the surface of the eye

Palpebral Conjunctiva

Thin membrane lining the inner surface of each eyelid; conjunctiva extends over the sclera, connecting eyelids to the eyeball

Tears

Produced by the lacrimal gland beneath the lateral edges of the nose; flow through lacrimal ducts to the medial corner and wash over conjunctiva

Extraocular Muscles

Six muscles that move the eye within the orbit; four of them are arranged at the cardinal points: superior rectus, medial rectus, inferior rectus, lateral rectus

Superior Rectus

Contracts to rotate the eye upward

Medial Rectus

Contracts to rotate the eye toward the midline

Inferior Rectus

Contracts to rotate the eye downward

Lateral Rectus

Contracts to rotate the eye laterally (away from midline)

Fibrous Tunic

Outermost layer of the eye; composed of sclera (white of the eye) and cornea (transparent anterior tip that allows light in)

Sclera

Accounts for five-sixths of the eye’s surface; dense fibrous tissue providing structure and protection

Cornea

Transparent tissue covering the anterior tip; allows light to enter the eye

Vascular Tunic

Middle layer of the eye; mostly composed of choroid, ciliary body, and iris

Choroid

Highly vascularized connective tissue that provides blood supply to the eyeball; located posterior to ciliary body

Ciliary Body

Muscular structure attached to the lens by zonule fibers; bends the lens to focus light on the retina

Iris

Colored part of the eye; smooth muscle that constricts the pupil in bright light and dilates it in dim light

Pupil

Hole at the center of the iris that allows light to enter the eye

Neural Tunic (Retina)

Innermost layer of the eye; contains nervous tissue responsible for photoreception

Anterior Cavity

The space between the cornea and lens, including the iris and ciliary body; filled with aqueous humor

Posterior Cavity

The space behind the lens that extends to the posterior side of the eyeball; filled with vitreous humor

Retina

Innermost layer of the eye; composed of several layers with specialized cells for initial visual processing

Photoreceptors

Rods and cones in the retina; change membrane potential when stimulated by light, altering neurotransmitter release onto bipolar cells

Bipolar Cells

Connect photoreceptors to retinal ganglion cells (RGCs) in the retina; relay visual signals

Amacrine Cells

Contribute to retinal processing before an action potential is produced by RGCs

Retinal Ganglion Cells (RGCs)

Innermost retinal cells; their axons collect at the optic disc and leave the eye as the optic nerve