SPECIAL SENSES

The Special Senses Special Senses: Organs and sensory receptors associated with touch, vision, hearing, taste, and smell Organs include – eyes, ears, nose, tongue, and sensory receptors of the skin

The Eye

10 Facts about the Eye Video

Eye One inch in diameter sphere Protected by: Orbital socket /Skull Eye lashes and brows Lacrimal glands – produce tears which moisten and cleanse the eye Conjunctiva- mucous membrane which lines eyes and covers front of eye to provide protection and lubrication

3 layers of eye Sclera Choroid coat Retina

Anatomy of the Eye 3 Layers 1. Sclera: white of the eye Maintains the shape of the eye Extrinsic muscles - responsible for moving the eye within socket, are attached to outside of sclera

3 layers of eye (cont’d) 2. Choroid layer Middle layer of eye Vascular

3 layers of the eye (cont’d) Retina – innermost layer of the eye Many layers of nerve cells which transmit light impulses to optic nerve 2 types of special cells: rods and cones Cones – sensitive to bright light and color - responsible for color vision Rods – sensitive to dim light

Ophthalmoscope: used to examine retina

Fovea Centralis Retina viewed through ophthalmoscope, dark disc is macula . Within macula is fovea centralis which contains cones for color vision. Blind spot (optic disc) – contains no rods or cones therefore no visual reception

Optic Nerve 4. Optic Nerve - Cranial Nerve II = responsible for vision

Vitreous Humor 5. Vitreous humor – transparent, jellylike substance filling posterior chamber of eye Helps maintain eyeball’s spherical shape

Lens 6. Lens- located behind pupil/iris. Sits in between anterior and posterior chamber of eye Function is to refract or bend light as it passes through – to focus images on the retina Lens held in place by suspensory ligaments

Iris 7. Iris – colored muscular layer. Behind cornea and in front of choroid coat. Contains 2 muscles which control size of pupil and regulates amount of light entering eye 8. Intrinsic muscles – sphincter papillae (iris/pupil) And suspensory ligaments and ciliary body (lens)

Pupil 9. Pupil – opening in center of iris. Light passes into eye through pupil

Aqueous Humor 10. Aqueous humor – water fluid in anterior chamber of eye

Cornea 11. Cornea – clear, circular area on front center of sclerotic coat Has pain and touch receptors making it sensitive to foreign particles that come in contact with its surface

12. suspensory ligaments – holds lens in place 13. ciliary bodies – smooth muscle controlling shape of lens

Conjunctiva 14. Conjunctiva – thin membrane lining the eyelids and covers part of the eye (anterior portion) Secretes mucous to lubricate eye

Cow Eye Dissection Exploratorium Cow Eye Dissection

Application Identify and describe your table partner’s: pupil – how does the pupil react to light/dark iris sclera upper lid lower lid conjunctiva lacrimal duct (lacrimal canaliculus)

Review of Structures of Eye Structures of Eye Video

Application: BS&F pg 180-181 Define the following vision disorders: Presbyopia Hyperopia Myopia Amblyopia Astigmatism Diplopia Stabismus

Vision Disorders Presbyopia – lens loses elasticity resulting in decreased ability to focus on close objects – usually onset at 40 yo Hyperopia – farsightedness – eyeball shorter than normal – prescription lenses Myopia – nearsightedness – eyeball elongated-prescription lenses Amblyopia – dimness of vision in one eye, lazy eye. Tx: covering good eye to strengthen weak eye. If not tx by 8 or 9 yo blindness may occur Astigmatism – irregular curvature of cornea or lens resulting in blurred vision or eye strain – prescription lenses

Vision Disorders (cont’d) Strabismus – cross eyes – extrinsic muscles of eye don’t coordinate activity. Can be corrected by eye exercises or surgery.

Color blindness Cone cells of retina Genetic More prevalent in males than females Red-green – inability to distinguish between the two colors most common

Vision Simulations http://visionsimulations.com/

Vision Disorders Night blindness – difficult to see at night due to defect in rod cells Color blindness – inability to distinguish colors – usually heredity http://colorvisiontesting.com/ishihara.htm

Vision Testing Snellen Chart

Kindergarten eye chart

Vision Testing Illiterate Eye Chart

Vision Testing Near Vision Chart

Vision Testing Ophthalmascope

Eye Injuries Chemical or solutions – rinse eye with eye wash or water Fragments or particles – do not attempt to remove or rub eye, report to supervisor and seek medical attention

Application: Define the following disorders and S&S and Tx: Cataract Conjunctivitis Glaucoma Macular degeneration Detached retina

Eye Disorders Cataract: Lens becomes cloudy Usually as a result of aging Sometimes by trauma Leading cause of blindness in world Sx: blurred vision, gradual vision loss, yellowing of colors, halos around lights Tx: lens implant

Cataract Surgery cataract surgery video

Conjunctivitis Pink eye Highly contagious Viral or bacterial or allergic Redness, pain, itching, discharge Tx.: antibiotics

Glaucoma Increased intraocular pressure Excess aqueous humor Common after 40 2nd leading cause of blindness Sx – loss of peripheral vision, halos around lights, limited night vision Tx. – medication, surgery

Macular Degeneration Major cause of blindness Effects 10% of elderly Disease of macula – part of retina Caused by damage to blood vessels which nourish retina S&S: blurred, distorted vision Tx: currently no cure

Detached Retina Result of aging or traumatic injury Tear in the retina Loss of peripheral vision followed by loss of central vision Tx: early detection important. Laser surgery

Stye Hordeolum Tiny abscess at base of eyelash Caused by inflammation of a sebaceous gland of eyelid S&S: red, painful, swollen Tx: warm, wet compresses

Diabetic Retinopathy Damage to retina due to long term diabetes Swelling and leaking of vessels that supply blood to retina S&S: pt sees red spots Tx: Early detection – laser surgery

Vitreous Floaters Small, irregular shaped specks in vision field Caused by tiny chunks of gel-like vitreous humor breaking off and floating in aqueous humor Distracting, not a cause for alarm Sudden, multiple floaters with flashes of light can be sign of retinal detachment

Pathway of light through the eye The images in the light “hit” the cornea -> pupil ->lens The light rays are bent or refracted ->retina ->rods and cones pick up the stimulus -> optic nerve -> optic chiasm (where the two optic nerves cross) -> optic tracts -> occipital lobe of the brain for interpretation (Cornea – pupil-lens-retina-optic nerve-occipital lobe)

The Ear Special sense organ designed to pick up sound waves and send the impulses to the auditory center of the brain

3 anatomical regions of ear: External ear – outer - hearing Middle ear – tympanic membrane (eardrum) - hearing Internal ear – inner – hearing and balance

The Outer Ear Pinna- collects sound waves and directs them into the auditory canal to the eardrum or tympanic membrane, which separates the outer and middle ear The auditory canal is lined with sebaceous or ceruminous glands that secrete a waxlike substance called cerumen – cleans, protects the ear, and lubricates

Outer Ear Pinna or auricle – cartilage Collects sound waves and directs them to the auditory canal external auditory meatus or auditory canal

Pinna- collects sound waves and directs them into the auditory canal From auditory canal to the tympanic membrane (eardrum), which separates the outer and middle ear The auditory canal is lined with sebaceous glands that secrete a waxlike substance called cerumen – protects the ear (ear wax)

Sound waves enter auricle -> external auditory canal -> vibrate on tympanic membrane

The Middle Ear The middle ear- cavity in the temporal bone It connects with the pharynx (throat) by means of a tube called the Eustachian tube The tube equalizes the ear pressure in the middle ear on both sides of tympanic membrane A chain of 3 tiny bones called Ossicles is found in the middle ear Malleus (Hammer) Incus (Anvil) Stapes (Stirrup)

Malleus, Incus, Stapes – transmit and amplify sound waves

What happens when we yawn: A way to help bring pressure in the pharynx, Eustachian tube, and middle ear to same level as pressure outside the ear Involuntary – yawn before we’re born How Stuff Works: Yawning Psychological? Physiological?

Inner Ear Most complex portion of ear Separated from middle ear by membrane called oval window Vestibule – first section – acts as entrance to 2 other parts of inner ear. Cochlea – snail shell shaped – contains, delicate, hairlike cells, which make up Organ of Corti

Organ of Corti – receptor of sound waves – transmits impulses from sound waves to the auditory nerve temporal lobe interpreted as hearing Semicircular canals – located in inner ear – contain liquid and delicate, hairlike cells that bend when liquid moves with head and body movements, maintains our sense of balance and equilibrium

Pathway of Hearing Sound waves -> pinna (auricle) -> auditory canal -> tympanic membrane -> ossicles -> stimulate the receptors on the cochlea -> cochlear nerve (part of vestibulocochlear nerve) -> temporal lobe of the brain for interpretation

Ear disorders Otitis media – middle ear Infants/children Eustachian tube not developed Bacteria or virus Pain, pus, swelling, fever

External Otitis Swimmer’s ear Bacterial or fungal Caused by immersion in contaminated water S&S: pain, fever, temporary hearing loss Prevention: throughly cleaning and drying ear canal with alcohol based solution after swimming

Ear disorders Ostosclerosis a chronic, progressive disease in which the stirrup becomes spongy and then hardens results in hearing loss

Ear disorders Meniere’s disease Affects the semicircular canals of the inner ear Causes vertigo (dizziness) May cause N/V and tinnitus (ringing or buzzing in the ear) Treatments include medications for s/s

Tinnitus Ringing in ear Hair cells in Organ of Corti that stimulate the auditory nerve are damaged Normally, movement of hair cells triggered by sound waves If damaged, hair cells move randomly, generating ringing in the ear Most common cause: exposure to loud noise (including music) Common and growing disorder: 50 million

Inner Ear Infection Labyrinthitis – infection of inner ear Inflammation & swelling of inner ear Semicircular canals Vertigo (dizziness) and N&V

Ear disorders Presbycusis- deafness due to aging Hearing loss can result from exposure to loud noise, conductive loss, and sensorineural damage Hearing aids

Application: Differentiate between swimmer’s ear, middle ear infection, inner ear infection.

Swimmer’s ear – external otitis media – bacterial or fungal – pain, fever, temp hearing loss Otitis Media –middle ear infection – bacterial or viral – pain, swelling, pus – common in children bc Eustachian tube not fully developed

Application: Using your smartphone, work with your table partner to research the following: Research products OR services available for deafness or otitis media. What products and/or services are available? Discuss findings with your table partner Be prepared to share your findings with class

What is a cochlear implant? http://www.youtube.com/watch?v=zeg4qTnYOpw&feature=c4-overview-vl&list=PLtmKi6_4W4acy3H0KxLKG7lx9VEI8Jecw

Tongue (Taste) A mass muscle of tissue which has structures called papillae There are taste buds for sweet, sour, salty, and bitter that are stimulated by the flavors of foods

Tongue/Taste facts Facial, glossopharyngeal, and vagus nerves transmit taste sensations to brain Flavor is a combination of taste, smell, texture or consistency, and temperature 75%-90% of what we taste is actually due to what we smell Parietal lobe – taste/smell sensations

Lab: What is difference bw taste and flavor? Hold your nose, chew jelly bean. What flavor is jelly bean? Describe what you taste. Let go of your nose. Continue chewing jelly bean. What happens? Did you get a sudden rush of flavor? Can you better identify flavor of jelly bean? What did you learn from this simple experiment?

Tongue disorders Hairiness- over growth of the normal projections Discoloration- tongue may appear black if the person takes bismuth preparations for an upset stomach Infection- may be the result of tongue piercings Cancer- sores, lumps, discoloration, etc

Hairy tongue, smoker’s tongue, cancer of tongue

The Nose (Smell) Detects about 10,000 smells The specialized patch of tissue called the olfactory epithelium has the receptors that send stimuli to the olfactory nerve Smell accounts for about 90% of what we think of taste

Rhinitis Inflammation of mucous membranes that line nasal passages Most common cause – common cold Allergies, chemical odors, illegal drugs

Why do I get a runny nose? Inflammation of nasal membranes causes release of histamines Histamines – molecules which trigger a reaction that produces congestion and drainage Tx: removing or minimizing irritant, antihistamines (decrease production of histamines)

Nose disorders Rhinitis- inflammation of the lining of the nose Nasal polyps- growths in the naval cavity Deviated nasal septum- a bend in the cartilage structure of the septum

Touch The sense of touch is due to very sensitive neurons that respond to pressure, heat, cold, touch, and pain Each receptor perceives only one type of sense

Careers related to Special Senses Define: Audiologist Ophthalmologist Optometrist Otolaryngologist