Download Sensory System

L.
Sensory System
1H12.01
Explain the structure of the eye.
A. Eye
1. 1” in diameter
2. Protected by orbital cavity, eyebrows, eyelashes, eyelids
3. Lacrimal glands – tears empty into nasal cavity
4. Conjunctiva – thin membrane lines eyelids
5. Wall of eye made up of three coats
B. Sclera
1. Outer layer
2. White of the eye
3. Tough coating, helps maintain shape of eye
4. Muscles responsible for moving eye attached to sclera = extrinsic
muscles
C. Cornea
1. Front of sclera (clear part) no blood vessels
2. Transparent so light rays can pass through
D. Choroid coat
1. Middle layer, contains blood vessels
2. Opening in front is pupil
3. Colored, muscular layer surrounding pupil is iris
4. Intrinsic muscles – change size of iris to control amount of light entering
through pupil
E. Lens
1. Crystalline structure located behind iris and pupil
2. Elastic, disc-shaped, biconvex
3. Situated between the anterior and posterior chambers
F. Anterior Chamber – filled with aqueous humor
G. Posterior Chamber – filled with vitreous humor
H. Retina
1. Innermost layer
2. Light rays focus image on retina
3. Image travels to the cerebral cortex via optic nerve
4. Rods – sensitive to dim light
5. Cones – sensitive to bright light and color
6. Optic disc – on retina, known as blind spot, nerve fibers that form optic
nerve
1H12.02
Analyze the function of the eye.
A. Eye
1. Protected by orbit, eyebrows, eyelashes, eyelids
2. Lacrimal glands – tears empty into nasal cavity and clean the eyes
3. Conjunctiva – secretes mucous to lubricate eyes
B. Sclera
1. Tough coating, helps maintain shape of eye
2. Extrinsic muscles - responsible for moving eye attached to sclera
C. Cornea - Transparent so light rays can pass through
Summer 2005 L.1
D. Choroid coat
1. Middle layer, contains blood vessels
2. Intrinsic muscles – change size of iris to control amount of light entering
through pupil
3. Pupil constricts – gets smaller – in bright light
4. Pupil dilates – gets larger – in dark light
E. Lens
1. Where light rays are refracted
2. Accommodation – change in the shape of the lens to allow for near and
distant vision
F. Retina
1. Light rays focus image on retina
2. Image travels to the cerebral cortex via optic nerve
3. Rods – sensitive to dim light
4. Cones – sensitive to bright light and color
5. Optic disc – on retina, known as blind spot, nerve fibers that form optic
nerve
G. Pathway of vision - Image travels through cornea, then pupil, through lens,
hits retina, picked up by rods and cones and carried to optic nerve where the
brain interprets image
1H12.03
Explain the structure and function of the ear, nose, and tongue.
A. Outer ear
1. Pinna (auricle)
a. Visible ear
b. Collects sound waves
2. External auditory canal – ear canal
3. Cerumen – ear wax, protects the ear
4. Tympanic membrane – ear drum, separates outer and middle ear
B. Middle ear
1. Cavity in temporal bone
2. Connects with pharynx by Eustachian tube - which equalizes pressure in
the middle ear with outside atmosphere
3. Bones - transmit sound waves from ear drum to inner ear
a. Malleus (hammer)
b. Incus (anvil)
c. Stapes (stirrup)
C. Inner ear
1. Cochlea - spiral shaped organ of hearing, contains a membranous tube,
the cochlear duct – which is filled with fluid that vibrates when sound
waves are transmitted by the stapes
2. Organ of Corti – delicate hairlike cells that pick up vibrations of fluid and
transmit them as a sensory impulse along the auditory nerve to the brain
3. Semicircular canals – three structures in inner ear that contain liquid set
in motion by head and body movements
4. Impulses sent to cerebellum to help maintain body balance (equilibrium)
D. Pathway of hearing – ear to external auditory canal to tympanic membrane to
ossicles (malleus, incus and stapes) to cochlea to auditory nerve to brain
E. Nose
1. Smell accounts for 90% of taste
2. Tissue in the nose, olfactory epithelium, contains specialized nerve cell
receptors
3. Those receptors stimulate the olfactory nerve to the brain
Summer 2005 L.2
F. Tongue
1. Mass of muscle tissue
2. Bumps on surface are papillae, they contain taste buds
3. Receptors in taste buds send stimuli through 3 cranial nerves to cerebral
cortex
1H12.04
Discuss characteristics and treatment of common sensory
disorders.
A. Disorders of the eye
1. Conjunctivitis (Pink eye)
a. Inflammation of conjunctival membranes in front of eye
b. Redness, pain, swelling and discharge
c. Highly contagious
d. Rx – antibiotic eye drops
2. Glaucoma
a. Excessive intraocular pressure causing destruction of the retina and
atrophy of the optic nerve
b. Caused by the overproduction of aqueous humor, lack of drainage,
or aging
c. Symps – develop gradually, mild aching, loss of peripheral vision,
halo around light
d. Tonometer – measures intraocular pressure
e. Rx – drugs or laser surgery
3. Cataracts
a. Lens of eye gradually becomes cloudy
b. Frequently occurs in people over 70
c. Causes painful, gradual blurring and loss of vision
d. Rx – surgical removal of the lens
4. Sty (hordeolum)
a. Abscess at the base of an eyelash in sebaceous gland
b, Symps – red, painful, swollen
c. Rx – warm, wet compresses
5. Eye injury - Glass or fragment in eye – cover eye and seek medical help,
do not remove the object
6. Color blindness
a. Cones affected
b. Genetic disorder that is carried by female and transmitted to males
B. Vision defects
1. Presbyopia
a. Lens loses elasticity, can’t focus on close or distant objects
b. Usually after age 40
c. Rx – bifocals
2. Hyperopia
a. Farsighted
b. Focal point beyond retina, eyeball too short
c. Convex lenses help
3. Myopia
a. Nearsighted
b. Eyeball too long
c. Concave lenses help
4. Astigmatism
a.. Irregular curvature of the cornea or lens, causing blurred vision or
eye strain
b. Rx – corrective lenses
Summer 2005 L.3
5. Diplopia – double vision
6. Strabismus (cross-eyed)
a. Eye muscles to not coordinate their actions
b. Usually in children
c. Rx – eye exercises or surgery
7. Ophthalmoscope – instrument for viewing inside the eye
8. Snellen eye chart – chart that uses letters or symbols in calibrated
heights to check for vision defects
C. Disorders of the ear
1. Hearing loss
a. Hearing is fragile, loud noise over period of time can cause hearing
loss
b. Symps – tinnitus (ringing in ears) and difficulty understanding what
people are saying
2. Otitis Media
a. Infection of middle ear
b. Often complication of common cold in children
c. Rx – antibiotics
d. Myringotomy – tubes inserted through tympanic membrane to relieve
pressure
3. Otosclerosis
a. Chronic , progressive middle ear disorder
b. Stapes becomes spongy and then hardens, becoming fixed and
immobile
c. Rx – stapedectomy and total replacement of stapes
4. Tinnitus – ringing of ears from impacted wax, otitis media, loud noise,
etc.
5. Types of hearing loss
a. Conductive – sounds prevented from reaching inner ear
b. Sensorineural – problem with inner ear and auditory nerve
D. Disorders of the nose
1. Rhinitis
a. Inflammation of lining of nose with congestion, drainage
b. Cause – allergies, drugs, infection, odors, etc.
c. Rx – eliminate cause, antihistamine
Summer 2005 L.4
Unit L: Sensory System
Terminology List
Eye
Ear
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
auricle
cerumen
cochlea
Eustachian tube
external auditory canal
incus
malleus
organ of Corti
pathway of hearing
pinna
semicircular canals
stapes
13. tympanic membrane
accommodation
anterior chamber
aqueous humor
choroid coat
cones
conjunctiva
constrict
cornea
dilate
extrinsic muscles
intrinsic muscles
iris
lacrimal glands
lens
optic disc
optic nerve
orbital cavity
posterior chamber
pupil
retina
rods
22. sclera
23. vitreous humor
Nose/Tongue
1.
2.
3.
olfactory nerve
papillae
taste buds
Disorders and Related Terminology
1. astigmatism
2. cataracts
3. color blindness
4. conductive hearing loss
5. conjunctivitis
6. deafness
7. epistaxis
8. glaucoma
9. hordeolum
10. hyperopia
11. myopia
12. ophthalmoscope
13. otitis media
14. presbyopia
15. rhinitis
16. sensorineural hearing loss
17. Snellen eye chart
18. sty
19. vertigo
Summer 2005 L.5
The Eye
 1” in diameter
 Protected by orbital socket of
skull, eyebrows, eyelashes
and eyelids
 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
 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
Summer 2005 L.6
CORNEA
 Front of sclera – clear part (no blood vessels)
 Transparent so light rays can pass through
 Gets O2 and nutrients through lymph
CHOROID COAT
 Middle layer
 Contains blood vessels
 Opening in front is the PUPIL
 Colored, muscular layer surrounding pupil is
IRIS
Summer 2005 L.7
 INTRINSIC MUSCLES – change size of iris to
control amount of light entering through the
pupil
LENS
 Crystalline structure located behind iris and
pupil
 Elastic, disc-shaped, biconvex
 Situated between the anterior and posterior
chambers
 ACCOMMODATION – change in the shape of
the lens to allow for near and distant vision
 ANTERIOR CHAMBER filled with AQUEOUS
HUMOR, a watery fluid.
 POSTERIOR CHAMBER filled with
transparent, jellylike substance – VITREOUS
HUMOR
RETINA
 Innermost layer
 Light rays focus an image on the retina
 The image travels to the cerebral cortex via
the OPTIC NERVE
Summer 2005 L.8
 If light rays don’t focus properly on the retina,
corrective lenses can bend the light rays as
required.
 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
Pathway of Vision
Cornea
Pupil
Retina
RR
Lens (Where light
rays are refracted)
Rods and Cones
(pick up stimulus)
Summer 2005 L.9
The Ear
Hearing and equilibrium
3 parts: Outer, middle and inner 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
Summer 2005 L.10
Middle Ear
 Cavity in temporal bone
 Connects with pharynx by EUSTACHIAN
TUBE – which equalizes pressure in the
middle ear with outside
atmosphere
 Bones in middle ear that
transmit sound waves from
ear drum to inner ear
1. MALLEUS (hammer)
2. INCUS (anvil)
3. STAPES (stirrup)
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
ORGAN OF CORTI – delicate hairlike cells
that pick up vibrations of fluid and transmit them
as a sensory impulse along the auditory nerve to
the brain
SEMICIRCULAR CANALS – three structures
in the inner ear, contain liquid that is set in motion


Summer 2005 L.11
by head and body movements – impulses sent to
cerebellum to help maintain body balance
(equilibrium).
Pathway of Hearing
External
Auditory Canal
Ossicles (malleus,
incus & stapes)
Auditory
nerve
Summer 2005 L.12
Tympanic
Membrane
Cochlea
RR
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



to the cerebral cortex
Summer 2005 L.13
Mass of muscle
tissue
Bumps on the
surface are
PAPILLAE,
they contain
the TASTE
BUDS
Receptors in
taste buds
send stimuli
through 3
cranial nerves
Disorders of the Eye
CONJUCTIVITIS
 Pink eye
 Inflammation of conjunctival membranes in
front of the eye
 Redness, pain, swelling and discharge
 Highly contagious
 Rx – antibiotic eye drops
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
 Symps – develop gradually – mild aching, loss
of peripheral vision, halo around the light
 TONOMETER – measures intraocular
pressure
 Rx – drugs or laser surgery
Summer 2005 L.14
CATARACTS
 Lens of eye gradually becomes cloudy
 Frequently occurs in people over 70
 Causes a painful, gradual blurring and loss of
vision
 Pupil turns from black to milky white
 Rx – surgical removal of the lens
STY (HORDEOLUM)
 Abscess at the base of an eyelash (in
sebaceous gland)
 Symps – red, painful and swollen
 Rx – warm, wet compresses
Vision Defects
PRESBYOPIA
 Lens loses elasticity, can’t focus on close or
distant objects
 Usually occurs after age 40
 Rx - Bifocals
HYPEROPIA
 Farsighted
 Focal point beyond the retina because eyeball
too short
 Convex lenses help
Summer 2005 L.15
MYOPIA
 Nearsighted
 Eyeball too long
 Concave lenses help
ASTIGMATISM
 Irregular curvature of the cornea or lens,
causing blurred vision and eye strain
 Rx – corrective lenses
OPHTHALMOSCOPE – instrument for viewing
inside the eye
SNELLEN EYE CHART – chart that uses letters
or symbols in calibrated heights to check for
vision defects
Summer 2005 L.16
Disorders of the Ear
Loud noise and hearing loss – hearing is fragile.
Loud noise over a period of time can cause
hearing loss. (Deafness)
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
Disorders of the Nose
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
Summer 2005 L.17