ST110 Concorde Career College, Portland. Define the term sense. Describe the functions of the sensory system.

ST110Concorde Career College, Portland

Define the term sense.

Describe the functions of the sensory system.

List and identify the structures of the sensory system and describe the function of each.

Describe the mechanism by which the sensory system helps to maintain homeostasis.

Describe common diseases, disorders, and conditions of the sensory system including signs and symptoms, diagnosis, and available treatment options.

Demonstrate knowledge of medical terminology related to the sensory system verbally and in the written form.

Sense

The terms sense is defined as the perception of any stimulus.

From the Latin: sentio - to feel or perceive

Special senses - localized in a special sense organ Vision Hearing and Equilibrium Gustation Olfaction

General senses - widely distributed throughout the body Touch, pressure, temperature, proprioception,

pain

Nervous system component that detects a stimulus that results in experience of a sensation. May be a/an: Free dendrite of a sensory neuron (pain

receptor) End-organ (modified ending) found on the end

of an afferent neuron (touch and temperature receptors)

Special cell associated with an afferent neuron (rods and cones of the eye)

Sensory Thermoreceptors (temperature - skin) Photoreceptors (light - retina) Chemoreceptors (chemicals - tongue,

nose)Mechanical - respond to movement

Stretch (skin, muscle - proprioception) Pressure (skin) Vibration (hearing, balance)

OrbitEyelidsEyelashes and eyebrowConjunctivaLacrimal apparatus

Frontal Sphenoid Ethmoid Maxilla Malar (zygoma) Lacrimal Palate

Protect the anterior one third of the eyeball Blinking -

lubrication▪ Levator palpebrae

▪ Blephar/o

Help keep foreign matter out of the eyes

Thin membrane that lines the eyelid and covers the anterior portion of the eyeball

Tears lubricate the eye and wash away foreign objects

Tears contain an enzyme that protects the eye from infection

Tunics (coats) of the Eye

Outer - sclera Middle - choroid Inner - retina

Pathway of Light Rays and Refraction

Cornea Aqueous humor Lens Vitreous humor

Fovea centralis Sharpest vision

Optic disk or “blind spot” No receptors

Rods - function in dim light (dark adaptation)

Cones - function in bright light (color and sharp images) Three types - red,

green, blue

The color blindness test consists of a set of five charts. Each chart shows a number in one color on a different background color. People with normal color vision will have no problem seeing the numbers on the charts, but people with color blindness will see only random colored dots. Seventy-five percent of color blind people have poor green perception. Of the remaining, 24% have poor red perception, and 1% are affected by a rare tritan type.

Superior oblique Inferior oblique Superior rectus Inferior rectus Lateral rectus Medial rectus (not

shown)

Iris Ciliary Body

Accommodation Adaptation of the lense to facilitate focus

Convergence/Divergence

Emmetropia

20/20

Snellen Chart

1st number-distance from the chart (20ft)

2nd number- deviation from the norm based on ability to read chart

Myopia - nearsightedness

Hyperopia - farsightedness

A. Papilledema

B. Deep retinal hemorrhages

C. Neovascularization

D. Cotton wool spots

Increase IOP

Loss of vision/blindness

Dry eye

Keratitis

Iritis

Conjunctivitis

Corneal transplant

“cross eyed”“wall eyed”

External Middle Inner

Pinna (auricle) Meatus External auditory

canal (contains ceruminous glands)

Tympanic membrane

Tympanic membrane Ossicles

Malleus (hammer) Incus (anvil) Stapes (stirrup)

Oval window Eustachian tube Mastoid sinus

Bony labyrinth - contains perilymph Vestibule Semicircular canals Cochlea

Membranous labyrinth - contains endolymph

Air Conduction- sound waves enter the ear through the pinna and travel down the auditory canal and strike the TM between the outer and middle ear

Bone Conduction- bones vibrate and send

Sensorineural Conduction- sound vibrations reach inner ear

Organ of Corti Cochlear branch of the vestibulocochlear nerve

Vestibular apparatus

Vestibular branch of the vestibulocochlear nerve

Impacted cerumen

Otalgia

Otitis

Otorrhagia

Eustachitis

Mastoiditis

Myringitis

Otosclerosis

Otitis Media

Otitis Media

Labryinthitis

Meniere’s Syndrome

Tinnitus

Vertigo

Otoplasty

Mastoidectomy

Myringotomy

Stapedectomy

Deafness

Conductive Hearing Loss

Noise-Induced Hearing Loss

Sensorineural Loss

Presbycusis

Tongue Taste buds Fissures

Sweet (c) Sour (d) Salty (e) Bitter (f)

Cranial nerves VII (facial) and IX (glossopharyngeal)

Taste bud-modified epithelial cells that function as receptors

Contain microvilli

Smell Olfactory epithelium Olfactory bulb Olfactory nerve Temporal lobe

Taste is affected by olfaction

Chemoreceptors-sense smells and taste Nociceptors-pain Thermoreceptors-temperature MechanoreceptorsChanges in pressure/movement Photoreceptors- in eyes, respond to light

energy

Sensations- Feelings that occur when the brain receives sensory impulse from PNS.

Perceptions-conscious awareness of sensation after interpretation.

Involve the receptors associated with skin, muscles, joints and visceral organs.

Touch- tactile receptors located in the skin or just beneath it.

Pressure- stimulation of receptors in deeper tissue

Touch and Pressure Free ends of sensory nerve fibers Meissner’s corpuscles Pacinian corpuscles

Touch

Tactile corpuscles Dermis Lips Tip of tongue

Receptors for deep touch Located subcutaneously, near the joints,

muscles, and other deep tissues Are active even when the skin is

anesthetized resulting in a consciousness of pressure sensation

Thermal- perceptions of degrees of warmth and coolness

Temperature- free nerve endings located beneath skin Heat receptors Cold receptors

Receptors are free nerve endings in the skin

Separate receptors for heat and coldHypothalamus initiates internal

responses according to the temperature of the blood passing through the brain

Pain- free nerve endings that are stimulated when tissues are damaged.

Acute

Chronic

Occurs very rapidly

Not felt in deeper tissues

Sharp/stabbing pain

Slower onset

Builds slowly in intensity (sec. or min.)

AKA referred pain

Pg 194 fig 9-1

Sensations of lengthening and stretching muscles

Golgi tendon organs

Muscle spindles

Position

Receptors located in muscles, tendons, and joints

Relay information concerning location of body parts to one another

Information processed in the cerebellum