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MD 12.00 The Sensory System. The Eye. 1” in diameter Protected by orbital socket of skull, eyebrows, eyelashes and eyelids. The Eye. Bathed in fluid from LACRIMAL GLANDS – tears empty into nasal cavity

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the eye
The Eye
  • 1” in diameter
  • Protected by orbital socket of skull, eyebrows, eyelashes and eyelids
the eye1
The Eye
  • Bathed in fluid from LACRIMAL GLANDS – tears empty into nasal cavity
  • CONJUNCTIVA – thin membrane that lines the eyelids and covers part of the eye, secretes mucous to lubricate eye
  • Wall of the eye made up of three coats:
    • SCLERA, CHOROID COAT AND RETINA
sclera
SCLERA
  • Outer layer
  • White of the eye
  • Tough coating, helps maintain shape of eye and protects what’s inside
  • Muscles responsible for moving the eye are attached to the sclera – called EXTRINSIC MUSCLES
cornea
CORNEA
  • Front of sclera – clear part (no blood vessels)
  • Transparent so light rays can pass through
  • Gets oxygen and nutrients through lymph 
choroid coat
CHOROID COAT
  • Middle layer
  • Contains blood vessels
  • Opening in front is the PUPIL
  • Colored, muscular layer surrounding pupil is IRIS
  • INTRINSIC MUSCLES – change size of iris to control amount of light entering through the pupil. 
slide7
LENS
  • Crystalline structure located behind iris and pupil
  • Elastic, disc-shaped, biconvex
  • Situated between the anterior and posterior chambers
chambers of the eye
Chambers of the Eye
  • ANTERIOR CHAMBER filled with AQUEOUS HUMOR, a watery fluid.
  • POSTERIOR CHAMBER filled with transparent, jellylike substance – VITREOUS HUMOR
retina
RETINA
  • Innermost layer
  • Light rays focus an image on the retina
  • The image travels to the cerebral cortex via the OPTIC NERVE
  • If light rays don’t focus properly on the retina, corrective lenses can bend the light rays as required.
retina1
RETINA
  • Retina contains specialized cells – rods and cones
  • RODS – sensitive to dim light
  • CONES – sensitive to bright light and color
  • OPTIC DISC – on the retina, known as the blind spot– nerve fibers gather here to form the optic nerve, no rods or cones
slide11

Pathway of Vision

Cornea

Pupil

Lens (Where light rays are refracted)

Rods and Cones (pick up stimulus)

Retina

Occipital Lobe

Optic Nerve

slide12

Common Sensory Disorders

Disorders of the Eye

conjuctivitis
CONJUCTIVITIS
  • “Pink eye”
  • Inflammation of conjunctival membranes in front of the eye
  • Redness, pain, swelling and discharge
  • Highly contagious
  • Rx – antibiotic eye drops
glaucoma
GLAUCOMA
  • Excessive intraocular pressure causing destruction of the retina and atrophy of the optic nerve
  • Caused by overproduction of aqueous humor, lack of drainage, or aging
  • Symptoms – develop gradually – mild aching, loss of peripheral vision, halo around lights.
glaucoma1
GLAUCOMA
  • TONOMETER – measures intraocular pressure
  • Rx – drugs or laser surgery
cataracts
CATARACTS
  • Lens of eye gradually becomes cloudy
  • Frequently occurs in people over 70
  • Causes a painless, gradual blurring and loss of vision
  • Pupil turns from black to milky white
  • Rx – surgical removal of the lens
macular degeneration
MACULAR DEGENERATION
  • Eye disorder that occurs with aging
  • The macula (part of the retina responsible for sharp color vision) degenerates
  • Vision is reduced but usually doesn’t cause total blindness
detached retina
DETACHED RETINA
  • May occur with aging – accident can cause it at younger age
  • Retina detaches from choroid
  • Symptoms – loss of peripheral vision and then central vision
  • Rx – laser or freezing technique
sty hordeolum
STY (HORDEOLUM)
  • Abscess at the base of an eyelash (in sebaceous gland)
  • Symptoms – red, painful and swollen
  • Rx – warm, wet compresses
eye injuries
EYE INJURIES
  • Tears are effective in cleaning the eye
  • If glass or fragments get in eye, cover both eyes and seek medical treatment.
  • (DO NOT remove the object)
slide21
Night blindness = NYCTALOPIA – due to inactive rods
  • Color blindness – cones are affected – genetic disorder that is carried by the female and transmitted to males
vision defects
Vision Defects
  • PRESBYOPIA
  • Lens loses elasticity, can’t focus on close or distant objects
  • Usually occurs after age 40
  • Rx – Bifocals or reading glasses
  • Presby- aging -opia - eyes
hyperopia
HYPEROPIA
  • Farsighted. (Can see objects far away clearly, but close objects are blurry.
  • Focal point beyond the retina because eyeball too short
  • Convex lenses help
myopia

)(

MYOPIA
  • Nearsighted. (Objects in distance are blurry, but close objects are clear.
  • Eyeball too long.
  • Concave lenses help.
  • Most common vision defect.
amblyopia
AMBLYOPIA
  • Reduction or dimness of vision
astigmatism
ASTIGMATISM
  • Irregular curvature of the cornea or lens, causing blurred vision and eye strain
  • Rx – corrective lenses
diplopia
DIPLOPIA
  • Double vision
strabismus
STRABISMUS
  • (cross-eyes)
  • Eye muscles do not coordinate their actions
  • Usually in children
  • Rx – eye exercises or surgery
ophthalmoscope
OPHTHALMOSCOPE
  • Instrument for viewing inside the eye
snellen eye chart
SNELLEN EYE CHART
  • Chart that uses letters or symbols in calibrated heights to check for vision defects
the ear
The Ear
  • Hearing and equilibrium
  • 3 parts: Outer, middle and inner ear
outer ear
Outer Ear
  • PINNA (AURICLE) – outer ear, collects sound waves
  • EXTERNAL AUDITORY CANAL – ear canal
  • CERUMEN – earwax, protects the ear
  • TYMPANIC MEMBRANE – ear drum, separates outer and middle ear.
middle ear
Middle Ear
  • Cavity in temporal bone
  • Connects with pharynx by EUSTACHIAN TUBE – which equalizes pressure in the middle ear with outside atmosphere
middle ear1
Middle Ear

Middle Ear

Eustachian Tube

inner ear
Inner Ear
  • Contains spiral shaped organ of hearing – the COCHLEA
  • The cochlea contains a membranous tube, the cochlear duct – which is filled with fluid that vibrates when sound waves are transmitted by the stapes
inner ear1
Inner Ear
  • ORGAN OF CORTI – delicate hairlike cells that pick up vibrations of fluid and transmit them as a sensory impulse along the vestibulocochlear nerve to the brain.
inner ear2
Inner Ear
  • SEMICIRCULAR CANALS – three structures in the inner ear, contain liquid that is set in motion by head and body movements – impulses sent to cerebellum to help maintain body balance. (equilibrium)
slide40

External Auditory Canal

Ossicles (malleus, incus & stapes)

Tympanic Membrane

Vestibulocochear Nerve

Cochlea-Organ

Of Corti

Temporal lobe (hearing)

Cerebellum (for balance)

Pathway of Hearing

slide41

Common Sensory Disorders

Disorders of the Ear

loud noise and hearing loss
Loud noise and hearing loss
  • Hearing is fragile. Loud noise over a period of time can cause hearing loss.
  • Symptoms – TINNITUS (ringing in ears) and difficulty understanding what people are saying
types of hearing loss
Types of hearing loss:
  • Conductive – which sounds are prevented from reaching inner ear.
  • Sensorineural – problem with inner ear or vestibulocochlear nerve
otitis media
OTITIS MEDIA
  • Infection of the middle ear
  • Often a complication of a common cold in children
  • Rx – antibiotics
  • If chronic or if fluid builds up – MYRINGOTOMY (opening in the tympanic membrane) with tubes inserted will relieve the pressure
slide45

Malleus seen through tympanic membrane

Tympanic membrane

Myringotomy tube

otosclerosis
OTOSCLEROSIS
  • Chronic, progressive middle ear disorder
  • Stapes becomes spongy and then hardens, becoming fixed and immobile.
  • Common cause of deafness in young adults.
  • Rx – stapedectomy and total replacement of stapes
tinnitus
TINNITUS
  • Ringing in the ears from impacted wax, otitis media, otosclerosis, loud noise, blockage of normal blood supply to the cochlea, or as a side effect of certain drugs. (aspirin )
presbycusis
PRESBYCUSIS
  • Deafness due to the aging process, can be helped with the use of hearing aids.
meniere s disease
MENIERE’S DISEASE
  • Affects the semicircular canals of the inner ear causing marked VERTIGO (dizziness)
  • The vertigo is accompanied by vomiting, ringing (tinnitus) in the ears
  • Rx – bed rest during acute attack, medication to relieve symptoms
  • Cause – unknown
the nose
The Nose
  • Smell accounts for 90% of taste.
  • Tissue in the nose, olfactory epithelium, contains specialized nerve cell receptors.
  • Those receptors stimulate the OLFACTORY NERVE to the brain.
the tongue
The Tongue
  • Mass of muscle tissue.
  • Bumps on the surface arePAPILLAE, they contain theTASTE BUDS
  • Receptors in taste buds send stimuli through 3 cranial nerves to the cerebral cortex
slide53

Common Sensory Disorders

Disorders of the Nose

rhinitis
RHINITIS
  • Inflammation of the lining of the nose with nasal congestion, drainage, sneezing and itching
  • Caused by allergies, infection, fumes, odors, emotion, or drugs
  • Rx – eliminate causes, antihistamines
deviated septum
DEVIATED SEPTUM
  • Bend in cartilage of nasal septum
  • Causes breathing problems, headaches, snoring, and nose bleeds
  • Rx – surgical correction
deviated septum1
DEVIATED SEPTUM
  • Temporary RxBreathe Right nasal strips