CH. 15 THE SPECIAL SENSES
I. SENSES - info to brain about environment
A. GENERAL - Somatic & Visceral (Tab.14.1, p. 472)
B. SPECIAL *KNOW (Tab.14.1, p. 472)
1. 5 Types: a. Smell
b. Taste
c. Sight
d. Hearing
e. Balance
2. Detect 1 type of stimuli only
3. Highly specific/modified receptors
4. Types: a. CHEMORECEPTOR - Smell & Taste
b. PHOTORECEPTOR - Sight
c. MECHANORECEPTOR - Hearing: Sound waves
- Balance: Gravity & move.
II. OLFACTION - SMELL (Fig. 15.1, p. 510)
A. OLFACTORY EPITHELIUM - receptors, superior nasal cavity
1. OLFACTORY NEURONS - 10 mill., 7-50 primary odors, 4,000 total
2. SUPPORTING CELLS
3. BASAL CELLS - replace OLFACTORY N. every 60 days
B. NEURONAL PATHWAYS
OLFACTORY BULB w/ MITRAL/TUFTED/GRANULE CELLS
è to & from brain via OLF. TRACT
èOLFACTORY CORTEX - Cerebrum (Fig. 15.3, p. 512)
- Conscious perception of smell
- Bypasses Thalamus - no “filtering” (National Geographic)
- Adjacent to Limbic system
a. MEDIAL - Visceral & emotional response to smell
b. INTERMEDIATE – Modulation & accommodation
III. GUSTATION - TASTE
A. TASTE BUDS - 10,000; on PAPILLAE on tongue (palate, lips & throat too)
B. 4 TYPES OF PAPILLAE (Fig. 15.4, p. 513)
1. VALLATE - 8-12, largest, least numerous, V-shaped
2. FUNGIFORM - scattered, red dots, dorsal
3. FOLIATE - leaf-shaped, side of tongue
4. FILIFORM - most numerous, mechanical, NO TASTE BUDS
C. 2 CELL TYPES - on taste buds, specialized epithelium (Fig. 15.5, p. 514)
1. GUSTATORY/TASTE CELLS a. “Hairs” - microvilli - receptors
b. 50 per taste bud
c. 10 day lifespan
2. SUPPORTING CELLS
3. 5 tastes: SWEET, SALT, SOUR, BITTER & UMAMI (savory!) - amino acids
D. NEURONAL PATHWAYS (Fig. 15.7, p. 516)
1. VII FACIAL - anterior 2/3 of tongue, CHORDA TYMPANI
2. IX GLOSSOPHARYNGEAL - posterior 1/3 of tongue
3. X VAGUS - Tongue root & epiglottis
4. V TRIGEMINAL - tactile sensation anterior 2/3 of tongue
5. All synapse TRACTUS SOLITARIUS of MEDULLAèTHALAMUS
è TASTE CORTEX
E. OLFACTION tied in closely.
IV. VISION - EYE & ACCESSORY STRUCTURES
A. ACCESSORY STRUCTURES (Fig. 15.8 & 15.9, p. 517 & 518)
1. EYEBROWS - keep sweat out, shade
2. EYELIDS - 2, protect eyes
a. CANTHI - corners
b. CARUNCLE - mound in medial canthus
c. 5 TISSUE LAYERS
i. SKIN
ii. AREOLAR
iii. SKELETAL MUSCLE
iv. TARSAL PLATE - dense C.T.
v. CONJUNCTIVA 1. PALPEBRAL - inside eyelid
2. BULBAR - over ant. sclera
3. FORNIX - where 1 & 2 meet
4. Continuous over lid & eye
d. EYELASHES - protection/shade/reprod “bat eyelashes”
i. CILIARY GLANDS - lubricate hairs - STY
ii. MEIBOMIAN GLANDS - lubricates eyelids
3. LACRIMAL APPARATUS – Constantly secrete tears (Fig. 15.10 p. 518)
a. LAC. GLANDSè Tears; Lubricate & kill bacteria (LYSOZYME)
b. LAC. DUCTSè to eyes
c. PUNCTAè opening to LAC. CANALICULI
d. LAC. CANALICULI è drain eyes to LAC. SAC
e. LAC. SAC è to NASOLAC. DUCT, “Nose runs when cry”
f. CRYING - removes foreign bodies
- “Washes out” Prostaglandin-like substances
(mediator of pain & inflammation)
4. EXTRINSIC EYE MUSCLES - 6, in lab (Fig. 15.11, p. 519)
EYE ANATOMY
B. LAYERS or TUNICS - 3
1. FIBROUS (Fig. 15.13, p. 520)
a. SCLERA - “White”, supports eye, hi H2O content
b. CORNEA - Clear, low H2O content
i. C.T., avascular, helps focus light
ii. Lo Immun. activity, easy to transplant
2. VASCULAR (Fig. 15.14, p. 522)
a. Blood Vessels
b. CHOROID - dark, MELANIN pigment
c. CILIARY BODY i. CILIARY MUSCLE/RING - D lens shape
ii. CILIARY PROCESSES. - prod AQ. HUMOR
d. IRIS i. PIGMENTED - Genetics
ii. PUPIL = Opening in Iris
iii. SPHINCTER PUPILLAE - close pupil, PARA
iv. DILATOR PUPILLAE - open pupil, SYMPA.
3. NERVOUS = RETINA
a. Posterior 4/5
b. MACULA LUTEA - Yellow disk (Fig. 15.15, p. 523)
c. FOVEA CENTRALIS - center of M.L., pit focusing, HI acuity
d. OPTIC DISC = “BLIND SPOT”, no rods/cones, nerv.
C. 3 CHAMBERS (Fig. 15.14, p. 522)
1. ANTERIOR CHAMBER – Cornea è Iris, w/ AQUEOUS HUMOR
2. POSTERIOR CHAMBER – Iris è Lens, w/ AQUEOUS HUMOR
a. AQ. HUMOR prod in POST. CHAMBER by CILIARY PROCESS
of CILIARY BODYèThrough PupilèANT. CHAMBER
èCANAL OF SCHLEMMèbloodstream (like C.S.F.)
b. GLAUCOMA = épressure in Ant. chamb, é Intraocular pres.
3. VITREOUS/POSTREMAL CHAMBER – post. lens,
a. VITREOUS HUMOR - gel
b. Maintains eye shape & intraocular press., bends light
c. Slow replacement
D. LENS - focus light
1. TRANSPARENT & BICONVEX
2. ANTERIOR -1 layer Cuboid Epith.
3. POSTERIOR - Enucleated Lens fibers-crystal. proteins
4. ELASTIC CAPSULE
5. SUSPENSORY LIGAMENTS attach to lens to ciliary body
E. FUNCTION OF COMPLETE EYE - 2
1. LIGHT REFRACTION - Bending
AIR èCORNEA èAQ. HUM.èLENS èVITR. HUM.èRETINA
a. Greatest Refraction: Air èCornea
b. Next Greatest: Lens èVitreous Humor
2. IMAGE FOCUSING - Adjusting lens shape; fine focusing
(Fig. 15.17, p. 525)
a. FAR POINT NEAR POINT
Distance > 20’ < 20’
Ciliary muscle RELAXED CONTRACTED
Suspensory ligaments TENSED RELAXED
Lens shape FLATTENED SPHERICAL
Name EMMETROPIA ACCOMMODATION
& Pupil constrict
& Convergence
b. NEAR POINT of VISION
i. Children 2-3”
ii. 20 y.o. 4-6”
iii. >45 y.o. 20”
c. PRESBYOPIA - loss of accomm w/ age, lens ê elasticity
F. STRUCTURE & FUNCTION OF RETINA (Fig. 15.18, p. 526)
1. PIGMENTED LAYER - 1 Cell layer, é Acuity
2. NEURAL or SENSORY LAYER - Photoreceptors & transmitters
3. RODS (Fig. 15.19, p. 527)
a. 20X more than cones, except in Fovea - no rods
b. Lo light/night/peripheral vision
c. No color
d. RHODOPSIN = RETINAL + OPSIN = VISUAL PURPLE
(Fig. 15.29, p. 528) (Vit. A-pigment) (Protein)
RHODOPSIN
ATP LIGHT
(bleaching)
RETINAL + OPSIN
ê
Hyperpolarization of Rods & Bipolar cells (Fig 15.21, p. 529)
ê
A.P. by Ganglionic cells è Optic nerve
e. DARK ACCOMM. - making more Rhodopsin, takes longer
f. LIGHT ACCOMM. - Rhodopsin bleached, rapid
4. CONES
a. Concentrated in Fovea - 35,000.
b. Bright light & visual acuity
c. Color vision
d. IODOPSIN = RETINAL + PHOTOPSIN
3 types: RED, BLUE & GREEN in various combos.
5. RETINAL PATHWAYS (Fig. 15.18, p. 533)
RODS CONES
Many synapse w/ 1 Bipolar N. 1 synapse w/1 Bipolar N.
ê Acuity, ê Detail é Acuity, é Detail
é Perception @ Lo Light ê Perception @ Lo Light
G. NEURONAL PATHWAYS
1. VISUAL FIELDS (Fig. 15.23, p. 533) - Overhead
a. Nasal fields project to Temporal retina
- NO crossing over @ Chiasma èbrain
b. Temporal fields project to Nasal retina
- Crossing over @ Chiasma èbrain
2. OPTIC TRACT è2 possible paths:
a. MOST: THALAMUS (Lateral Geniculate Body) èOPTIC
RADIATIONS èVISUAL CORTEX in OCCIPITAL LOBE
b. SUPERIOR COLLICULI (visual reflexes) bypass thalamus
èthen via OPTIC RADIATIONS èVISUAL CORTEX
3. Images UPSIDE DOWN & BACKWARDS, Brain corrects
H. KNOW EYE DISORDERS (p.534-535)
V. HEARING & BALANCE – EAR
A. PARTS - 3 (Fig. 15.24, p. 537)
1. EXTERNAL/OUTER: AURICLE/PINNA èTYMPANUM
a. EXTERNAL AUDITORY MEATUS/CANAL
i. Hair
ii. Ceruminous glands èearwax, CERUMEN
2. MIDDLE: TYMPANUM èOVAL WINDOW
a. OSSICLES: MALLEUS, INCUS & STAPES
i. é Force/Energy of Sound, AMPLIFIES sound 20X
b. AUDITORY CANAL/EUSTACHIAN TUBE
i. Connects middle ear to Pharynx, equal. press.
3. INNER: In Temporal bone (Fig. 15.27, p. 538)
- BONY LABYRINTH - filled w/ PERILYMPH, like CSF
- MEMBRANOUS LABY. - filled w/ ENDOLYMPH, Hi K+, lo Na+
a. SEMICIRCULAR CANALS - Balance
b. VESTIBULE - Balance
c. COCHLEA - Hearing
B. HEARING - COCHLEA (Fig. 15.28, p. 539)
1. Structure - Overhead T-76, T-77
a. SCALA VESTIBULI - perilymph
b. SCALA TYMPANI - perilymph
c. COCHLEAR DUCT – endolymph w/spiral organ or organ of Corti
d. Hair cells w/ microvilli embedded in gel-like TECTORIAL MEMB.
2. Physiology - ***KNOW Figure 15.33, p. 543)
- Trace PATHWAY of Sound Waves
a. Hi Freq. @ Oval Window, Base (Fig. 15.34, p. 545)
b. Lo Freq. @ HELICOTREMA, Apex
c. Sound waves èROUND WINDOW, Dampens
d. Bending of Hair cell stereocilia è stretches gating spring è
opens K+ channel èA.P. (Fig. 15.30-31, p. 541)
3. Neuronal Pathway (Fig. 15.35, p. 546)
AUDITORY N.èSUPERIOR OLIVARY NUCLEUS (Integrate &
Eval.)èINFERIOR COLLICULI èTHALAMUS è AUDITORY
CORTEX in TEMPORAL LOBE . . . also. . . è
Back to ear to modulate/suppress all but strongest A.P.
C. BALANCE
1. VESTIBULE - Static Labyrinth
- Head position relative to GRAVITY
- Acceleration & Deceleration
a. UTRICLE - Horizontal
UTRICULAR MACULA (Fig. 15.36, p. 547)
b. SACCULE - Vertical
SACCULAR MACULA (Fig. 15.36, p. 547)
c. How they work (Fig. 15.37, p. 548)
2. SEMICIRCULAR CANALS - Kinetic Labyrinth, "gyroscope"
- Head movements & motion
a. 3: TRANSVERSE, CORONAL, SAGITTAL
b. Contain endolymph
c. AMPULLA @ base of each canal (Fig. 15.38-39, p. 549)
d. CRISTA AMPULLARIS w/hair cells embedded in CUPULA
e. Physiology
3. Neural Pathway (Fig. 15.40, p. 550)
VIII èMEDULLA è a. CEREBELLUM
b. THALAMUS èVESTIBULAR CORTEX
c. SPINAL CORD
d. EXTRINSIC EYE MUSCLES
4. * KNOW Ear Disorders on p. 551-553