Special senses
Lecture 1
Lecture 2
Special Senses
Senses allow body to react to the environment
See, hear, taste, smell, and to maintain balance
Body structures receive sensation, nerves carry to brain, brain interprets and responds to message
Eye
Sense of sight
Light rays transmitted to the optic nerve
Optic nerve relays information to brain
Eye is well protected
Bony socket - protection
Eyelids and eyelashes- help keep dirt and pathogens out
Lacrimal glands- make tears and keep eye clean and moistened
Conjunctiva- mucous membrane lines the eyelids and covers the eye to protect and lubricate
Layers of the eye
Sclera—outer it is the white of the eye helps to maintain shape of the eye
Choroid coat—middle interlaced with many blood vessels to feed the eye
Retina—innermost has many layers of nerve cells, which transmit the light impulses to the optic nerves
Cones- sensitive to color and mainly to see when its lights. Cones are located in a depression on the back of the surface of retina called fovea centralis (gives sharpest vision)
Rods- are used when it is dark or dim
Other Special Structures
Iris- colored portion of eye
Pupil- the opening of the center of the eye it regulates the amount of light
Lens-circular structure behind the pupil it refracts or bends the light rays so its is focused on the retina
Aqueous humor- a clear watery fluid that fills the space between the cornea and iris
Vitreous humor- jelly like substance behind the lens, it helps to maintain shape
Muscles- provide for movement of the eye
Diseases and Abnormal Conditions
Amblyopia—lazy eye occurs in early childhood treatment includes covering the good eye to strengthen muscles
Astigmatism- curvature of the cornea that causes blurred vision at a distance. Light rays focus on multiple areas of the retinal Corrective lenses, LASIK or PRK
Cataract-clear lens becomes cloudy as a result of aging or trauma. Leading cause of blindness.S/SX blurred vision, halos around lights, gradual vision loss and a milky white pupil.TX- surgical removal of lens/implanted intraocular lens/ glasses.
Conjunctivitis—pink eye- highly contagious, redness, gritty sensation of the eye, pain and itching. Discharge from one or both eyes forms crust. TX- antibiotics
Glaucoma- an increase in intraocular pressure d/t aqueous humor. Common after the age of 40. Loss of peripheral vision, halos around lights, limited night vision and mild aching. Controlled with medications or laser therapy to open clogged drainage canals
Hyperopia—farsightedness (objects far away are seen clearly but objects close up are blurry.Image focuses behind the retina. Use convex lenses LASIK or PRK
Myopia—nearsightedness image focuses in front of retina. Glasses and LASIK or PRK Macular degeneration death of the macula the most sensitive portion of the retina. Age related disorder damage to blood vessels that nourish the eye. Most common one is dry macular degeneration.Fatty deposits decrease blood supply. They lose central vision but peripheral vision not affected. Wet Mac Degen is caused by leakage of blood from an abnormal blood vessels. Laser treatment out there looking at bionic eye or artificial retinal
Presbyopia- farsightedness caused by loss of lens elasticity. Normal aging glasses, or LASIK
Strabismus- eyes do not move or focus together , can move in, out, up, or down. Can appear crosseyed TX- Aides in helping muscles get stronger. Botox can be used q 3-4 months
Ear
Controls hearing and balance
Sound waves transmitted to the auditory nerve
Auditory nerve relays information to the brain for interpretation
Consists of the outer ear, middle ear, and inner ear
Outer Ear
Pinna or auricle
Auditory canal
Tympanic membrane
Middle Ear
Malleus- one of the three ossicles in middle ear. It receives vibrations from the tympanic membrane and transmits this to the incus
Incus(anvil)-receives vibrations from the malleus and transmits these to the stapes
Stapes-smallest bone in the body. Transmits sound vibrations from the incus.
Eustachian tube- how the middle ear is connected to the pharynx. It allows air to enter the middle ear and help equalize air pressure on both sides of the tympanic membrane.
Inner Ear
Oval window- part of middle ear which helps to transmit the motion of the eardrum to the inner ear. This increases the pressure on the connective tissue of the oval window. This pressure is transmitted through the stapes, which eventually with go to the cochlea
Vestibule- is the entrance to the parts of the inner ear.
Cochlea- shaped like a snail, contains hair like cells (organ of Corti
Organ of Corti- this is the receptor of sound waves and transmits the impulses from sound waves to the auditory nerve.
Semicircular canals- contain liquid and delicate hair like cells that bend when the liquid moves with the head and body movements- helps with balance
Diseases and abnormal conditions
Hearing loss
Conductive- sound waves cant get to inner ear. Causes wax, plug object
Sensory – damage to inner ear or auditory nerve cannot be corrected, cochlear implants
Otitis externa (swimmer’s ear)- Infection of the external auditory canal.
Otitis media- infection of the middle ear
Otosclerosis- inherited bony overgrowth of the footplate of the stapes. Causing the stapes to become immobile causing conductive hearing loss
correction- treatment and artificial stapes
Meniere’s disease
A collection of fluid in the labyrinth of the inner ear and a degeneration of the hair cells in the cochlea. S/SX vertigo, tinnitus, N/V ; loss of balance, and a tendancy to fall. TX- medications to reduce fluid, anti nausea and motion sickness medication , draining of the fluid, and antihistamines. Severe cases, surgery to destro cochlea but causes permanent deafness
Sense of Taste
Taste receptors located on the tongue
Four main tastes
Sweet
Salty
Sour
Bitter
5th taste umani- detects meaty or savory sensations
Taste is influenced by smell.
Sense of Smell
Nose is the organ of smell
Olfactory receptors in nasal cavity located in the upper part of the nasal cavity. Impulses carried from the olfactory nerve to the brain for interpretation
Humans can detect over 6,000 smells
Sense of taste and smell related but the sense of smell is more sensitive
Skin and General Senses
General sense receptors for pressure, heat, cold, touch, and pain located in the skin and connective tissue.
Each receptor perceives only one typed of sense
Allows the human body to respond to its environment
Help body react to conditions that could cause injury