specail senses ana. physio
TRANSCRIPT
SPECIAL SENSES
•General senses – all throughout the body.
•Special senses – confined in the head, eyes and ears ( hearing and balance, sight, taste, smell) - conveyed by
cranial nerves
•TYPES OF RECEPTORS based on Location:1. SUPERFICIAL2. DEEP3. CORTICAL (combination of superficial and deep) Info: ↓ ↓ Exteroreceptors Proprioceptors - pain, temp., light
touch, pressure-from OUTSIDE the body
-position sense, kinesthesia, vibration-- from inside the body (muscle spindle, tendons, ligaments)
•Visceral Sensation – relayed by the autonomic efferent fibers - hunger, nausea, visceral pain - visceral pain receptors are only in
the viscera and respond differently to stimulation not localized
Referred pain – as if coming from other parts of the body
Ex: liver and gall bladder problem may be referred to the right shoulder
I. MECHANORECEPTORS Respond to mechanical deformation of
receptors A. CUTANEOUS SENSORY RECEPTORS Free nerve ending – pain and temp Merkel’s disk - two-pt discrimination,
localization of touch Ruffini – warmth (above 25 deg C) Krause end bulb – cold (100-200 deg C)
Meissner’s – discriminative touch (texture recognition)
Pacinian – deep touch and vibration B. DEEP/JOINT RECEPTORS Muscle Spindle – velocity of movement GTO- monitors tension Free nerve endings- pain and temp PacinianII. THERMORECEPTORS – for temperature
changesIII. NOCICEPTORS – noxious stimuli ( damage to
tissues)
III. ELECTROMAGNETIC RECEPTORS – respond to light (rods and cones)
IV. CHEMORECEPTORS – respond to chemical substance
A. Taste- receptors of taste buds B. Smell - receptors of olfactory nerves in
olfactory epithelium C. Arterial O2- receptors of Aortic and
carotid bodies D. Osmolality - neurons of supraoptic
nuclei
E. Blood CO2 - receptors in or on surface of medulla and in aortic and carotid bodies F. Blood Glucose, amino acid and fatty acids - receptors in hypothalamus Projection – the brain projects sensation back to the source - person pinpoints region of
stimulation
Pathways From Sensation to Perception (Example of an Apple)
•ACUTE PAIN
A-delta fibers Fast
Sharp pain Localized
•CHRONIC PAINC fibers
Slowassociated with dull aching pain
diffused (difficult to pinpoint)
ACUTE PAIN VS. CHRONIC PAIN
•OLFACTION - sense of smell, occurs in response to odors that stimulate sensory receptors
- receptors located in the extreme superior region of the nasal cavity, called the olfactory recess
PATHWAY:Once olfactory receptors are stimulated, nerve impulses travel through olfactory nerves → olfactory bulbs → olfactory tracts →limbic system (for emotions) olfactory cortex (for interpretation)
•olfactory receptors undergo sensory adaptation rapidly•sense of smell drops by 50% within a second after stimulation
•Mechanism of olfactory discrimination- unknown-wide variety of detectable (4000) smells actually combinations of a smaller number of primary odors
7 primary scents•Camphor•Musk•Floral•Peppermint•Ether•Pungent•Putrid GUSTATION/Taste
- a chemical sense that requires dissolving substance before it can be tasted.
GUSTATORY RECEPTORSLocated at the taste budsCan also be found on the soft palate, pharynx
and larynxTaste buds declines with ageTaste budOrgans of tasteLocation
a. Tongue Papillaeb. Mouth(roof)c. Cheeks(lining)d. Pharynx(wall)e. Lips
Taste receptors• Chemoreceptors• Taste cells-function as receptors• Taste hairs- microvilli that protude from taste
cells;sensitive parts of taste cells
4 major types of Papillae according to shape:1. Vallate- largest; V-shaped
-between anterior and posterior border of tongue
2. Fungiform-mushroom-shaped-contains most sensitive to taste
buds-folds on the sides of the tongue
-most numerous in CHILDREN-decreases with age
4.Filiform-filament-shaped-most numerous-no taste function
Five Primary Sensations• Sweet- stimulated by carbohydrates• Sour- stimulated by acids• Salty- stimulated by salts• Bitter- stimulated by many organic compounds•Umami
Spicy foods activate pain receptorsTaste PathwayImpulses from taste receptors → cranial nerves97,9,10) →medulla →thalamus
↓limbi syste,hypothalamus↓
Gustatory cortex
Visual System
oComponents
1.Eyes- respond to light and initiate afferent action potentials.
2. Accessory structures- help protect the eyes from direct sunlight and damaging particles
-includes:eyebrows, eyelids, eyelashes, lacrimal apparatus,conjunctiva, extrinsic eye muscles3. Optic nerves (II), tracts, and pathways
Eyebrows- Protects eyes1. Perspiration2. Shade from the sun
Eyelid(PALPEBRA)-for blinking (protects the eye from foreign objects)
-Average blinking: 25x/min Muscles
a. Orbicularis Oculi- closesb. Levator Palperbrae Superiosis- opens
• Canthi: angels where the eyelids join at the medial and lateral margins of the eye
• Caruncle: small reddish, on the medial canthi; contains modified sabaceous and sweat galnds
CONJUNCTIVE-mucous membrane; lines eyelid and covers portion of eyeballConjunctivitis-”pink eye”
- Inflammation caused by infection or irritation
Extrinsic Eye MusclesLateral rectus- outward; paralysis of both lateral will cause eyes to deviate inward (internal strabismus)Medial rectus- inward; paralysis of both medial will cause eyes to deviate outward (external strabismus)Superior rectus- up and inInferior rectus- down and inSuperior oblique- down and outInferior oblique- up and out
EYELASHES-double or triple row of hairs to the free edges of the eyelids-lubricates lids and restrains tears from flowing over the margin of the eyelids; openings behind the lashes
•Lacrimal ApparatusLacrimal• Lateral to eye• Secretes tears
Canaliculi• Collect tears
Lacrimal Sac• Collects from canaliculi
Punctum•Opening of each lacrimal canaliculis
Nasolacrimal Duct• Collects from lacrimal sac• Empties tears into nasal cavity
Optical Components:
•LAYERS/TUNICS:1. Outer Fibrous Tunis Sclera
Cornea
2. Middle/Vascular Tunic ChoroidCiliary BodyIris
3.Inner RetinaCorneaAnterior portionAVASCULARTransparentLight permission
Light refractionOne of the first organs transplantedCentral part of the cornea receives oxygen from
the outside air.soft plastic contact lenses worn for periods must
be permeable to air to reach the cornea.ScleraPosterior portion; firm, opaque, white functions:ProtectionMuscle attachmentShape of the eye
IrisAnterior portionpigmented
Smooth muscleControls light intensityPupil is the hole in irisDim light stimulates radial muscles and pupil
dilatesBright light stimulates circular muscles and pupil
constricts-blue eyes: decreased melanin-black/brown: increased melanin
•Ciliary BodyAnterior portionPigmentedHolds lensMoves lens for focusingForms internal ring around front of eyeCiliary processes-radiating foldsCiliary muscles-contract and relax to move lens
•Choroid CoatProvides blood supplyPigments absorb extra light
•RetinaContains visual receptorsContinuous with optic nerveMacula lutea- yellowish spot in retinaFovea centralis-center of macula lutea;produces
sharpest visionOptic disc-blind spot; contains no visual receptorsVitreous humor- thick gel that holds retina flat
against choroid coat fluid in anterior cavity of eye
•Aqueous Humor Fluid in the anterior cavity; provides nutrients Maintains shape of anterior portion of eye
•LensTransparentBiconvexLies behind irisHeld in place by suspensory ligaments of ciliary
body
Accomodation Changing of lens shape to view objects
•RefractionBending of lightOccurs when light waves pass at an oblique angle
into mediums of different densitiesConvex lenses cause light waves to convergeConcave lenses cause light waves to diverge
•Focusing on retina As light enters eye, it is refracted by
Convex surface of cornea Convex surface of lens
Image focused on retina is upside down and reversed from left to right
Visual Receptors•RodsoContain light sensitive pigment called rhodopsinoMore sensitive to light than conesoProvide vision in dim lightoProduce colorless visionoProduce outlines of objects•ConesoShort, blunt projectionsoProvide vision in bright lightoProduce sharp imagesoProduce color vision
Clinical Correlation•Myopia-nearsightedness, too ↑ refraction•Hyperopia- farsightedness, ↓ refraction•Astigmatism- curvature of either lens or cornes is
greater in 1 axis or meridian• Scotomas- abnormal blind spot in visual fields
Visual Pathway and Visual field cuts
Lesions:a.Blindness in one eyeb.Bitemporal Hemianopiac.Homonymous Hemianopiad.Quadrantanopsiae.Homonymous Hemianopsia
HEARING AND BALANCEEAR
External ear• Consists of: auricle and external auditory meatus• Function: hearing only
Middle Ear/Tympanic Cavity• Consist of: air-filled CAVITY within the temporal
bone, and auditory ossicles• Function in both hearing balance
Auricle/Pinna:• Fleshy part of the external ear on the outside of
the head• Shape helps to collect sound waves and direct
them toward the external auditory meatus• Elastic cartilage covered with skin, extrinsic and
intrinsic mm
External auditory meatus• Sinus tube that leads to tympanic cavity• Isthmus: narrowest potion of meatus
Functions:1. Conduct sounds waves from auricle to tympanic
membrane2. Prevents foreign objects from reaching the
delicate eardrum thru the lined hairs and ceremonous glands, which produce cerumen(earwax)
o Tympanic Membrane/Eardrum Thin, semitransparent, nearly oval Separates the external ear from the middle ear.
Auditory Ossicles:1. Malleus: largest; handle is attached to the
center of the eardrum2. Incus: attached to the other side of malleus
:Whenever malleus moves, incus moves with it.
3. Stapes: attatched to opposite end of incus- Lies against the membranous labyrinth in
the opening of oval window where sound waves are conducted into inner ear.
Middle earChorda tympani
-branch if the facial nerve carrying taste impulses from the anterior two-thirds of the tongue-no function in hearing
Inner earBony Labyrinth:
1. Vestibule: for balance2. Semicircular canals: for balance3. Cochlea: for hearing
Membranous labyrinth1. Utricle2. Saccule
3.Semilunar ducts4. Cochlear ducts
STEPS IN HEARING1. The auricle collects sound waves that are then
conducted through the external auditory meatus to the tympanic membrane, causing it to vibrate.
2. The vibrating tympanic membrane causes the malleus, incus, and stapes to vibrate.
3. Vibration of the stapes produces vibration in the perilymph of the scala vestibuli.
4. The vibration of the perilymph produces simultaneous vibration of the vestibular membrane and the endolymph causes in the cochlear duct.
5. Vibration of the endolymph causes the basilar membrane to vibrate.
6. As the basilar membrane vibrates, the hair cells attached to the membrane move relative to the tectorial membrane, which remains stationary.7. The hair cell microvilli, embedded in the tectorial membrane, become bent.8. Bending of the microvilli causes depolarization of the hair cells.9. The hair cells induce action potentials in the cochlear neurons.10. The action potentials generated in the cochlear neurons are conducted to the CNS.11. The action potentials ate translated in the cerebral cortex and are perceived as sound.
Auditory Pathway:Sensory axons from the cochlear
↓Ganglion terminate in the cochlear nucleus in the brainstem
↓Superior olivary nucleus or to the inferior colliculus
↓Medial geniculate nucleus of the thalamus
↓Auditory cortex
↓Neurons in the superior olivary
Neurons in the superior olivary nucleus send axons to the inferior colliculus, back to the inner ear, or to motor nuclei in the brainstem that send efferent fibers to the middle ear muscles.Clinical correlation:1. Tinnitus- ringing, buzzing, roaring or “paper
crushing” noises in the ear, frequently an early sign of peripheral cochlear disease
2. Deafnessa. conduction- impaired conduction through the
external canal and ossicles to endolymph and tectorial membrane
-cause:external/middle ear diseases
b. sensorineural/nerve- interruption of cochlear nerve fibers from hair cells to BS
-cause: cochlear nerve/ inner nerve
VESTIBULAR SYSTEMFor maintenance of stance and body posture; coordination of the body, head and eye movements; and visual fixationSTATIC LABYRITH
-Stuctures involved:1. Saccule2. Utricle
-involved in evaluating the position of the head relative to gravity
-responds to linear acceleration deceleration, such as when a person is in a car that is increasing or decreasing speed
•Macula of the Utricllie: determines person’s head position w/ respect to gravitational force when person is in upright position•Macula of the saccule: equilibrium in lying down
OTOLITHS/OTOCONIA: small Ca Carbohydrates crystals in saccule and utricle
-displaces the hair cells and excites the saccule and utricle in response to Vertical and Horizontal acceleration
•KINETIC LABYRITH- Detects head rotation: Angular Rotation- When head begins to rotate-endolymph in S.D.
remain stationary while S.D moves w/ the head direction-cause flow to flow into ampula, bending cupula to side
- From hair cells- vestibular nerve to apprise the N.S of change in the rate of direction
-Pathway For Balance1. Sensory axons from the vestibular ganglion
pass through the vestibular nerves to the vestibular nucleus, which also receives input from several other sources, such as proprioception from the legs.
2. Vestibular neurons send axons to the cerebellum, which influences postural muscles, and to the motor nuclei (oculomotor, trochlear, andabducents), which control extrinsic eye muscles.3. Vestibular neurons also send axons to the posterior ventral nucleus of the thalamus. 4. Thalamic neurons project to the vestibular area
of the cortex. OTOSCLEROSIS
-Is an ear disorder in which spongy bone grows over the oval window and immobilizes the stapes, leading to progressive loss of hearing
TINNITUSConsists of noises such as ringing, clicking, whistling, or booming in the ears
MOTION SICKNESSConsists of nausea, weakness and other dysfuntions caused by stimulation of the semicircular canals during motion, such as is boat, automobile, airplane, swing or amusement park ride
OTITIS MEDIAInfections of the middle ear
VERTIGO