2. •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
3. •TYPES OF RECEPTORS based on Location:
1. SUPERFICIAL
2. DEEP
3. 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)
4. •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
5. 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)
6. 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
Pacinian
II. THERMORECEPTORS – for temperature
changes
III. NOCICEPTORS – noxious stimuli ( damage to
tissues)
7. 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
8. 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
10. •ACUTE PAIN
A-delta fibers
Fast
Sharp pain
Localized
•CHRONIC PAIN
C fibers
Slow
associated with
dull aching pain
diffused (difficult
to pinpoint)
ACUTE PAIN VS. CHRONIC PAIN
11. •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)
12. •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
14. GUSTATORY RECEPTORS
Located at the taste buds
Can also be found on the soft palate, pharynx
and larynx
Taste buds declines with age
Taste bud
Organs of taste
Location
a. Tongue Papillae
b. Mouth(roof)
c. Cheeks(lining)
d. Pharynx(wall)
e. Lips
15. 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
16. -most numerous in CHILDREN
-decreases with age
4.Filiform-filament-shaped
-most numerous
-no taste function
17. 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 receptors
Taste Pathway
Impulses from taste receptors → cranial
nerves97,9,10) →medulla →thalamus
↓
limbi syste,hypothalamus↓
Gustatory cortex
18. 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 muscles
3. Optic nerves (II), tracts, and pathways
19. Eyebrows- Protects eyes
1. Perspiration
2. Shade from the sun
Eyelid(PALPEBRA)-for blinking (protects the eye
from foreign objects)
-Average blinking: 25x/min
Muscles
a. Orbicularis Oculi- closes
b. 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
20. CONJUNCTIVE-mucous membrane; lines eyelid and
covers portion of eyeball
Conjunctivitis-”pink eye”
-Inflammation caused by infection
or irritation
21. Extrinsic Eye Muscles
Lateral 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 in
Inferior rectus- down and in
Superior oblique- down and out
Inferior 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
22. •Lacrimal Apparatus
Lacrimal
•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
27. Light refraction
One of the first organs transplanted
Central 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.
Sclera
Posterior portion; firm, opaque, white functions:
Protection
Muscle attachment
Shape of the eye
Iris
Anterior portion
pigmented
28. Smooth muscle
Controls light intensity
Pupil is the hole in iris
Dim light stimulates radial muscles and pupil
dilates
Bright light stimulates circular muscles and pupil
constricts
-blue eyes: decreased melanin
-black/brown: increased melanin
29.
30. •Ciliary Body
Anterior portion
Pigmented
Holds lens
Moves lens for focusing
Forms internal ring around front of eye
Ciliary processes-radiating folds
Ciliary muscles-contract and relax to move lens
•Choroid Coat
Provides blood supply
Pigments absorb extra light
31. •Retina
Contains visual receptors
Continuous with optic nerve
Macula lutea- yellowish spot in retina
Fovea centralis-center of macula lutea;produces
sharpest vision
Optic disc-blind spot; contains no visual receptors
Vitreous 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
34. •Refraction
Bending of light
Occurs when light waves pass at an oblique angle
into mediums of different densities
Convex lenses cause light waves to converge
Concave lenses cause light waves to diverge
35. •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
36. Visual Receptors
•Rods
oContain light sensitive pigment called rhodopsin
oMore sensitive to light than cones
oProvide vision in dim light
oProduce colorless vision
oProduce outlines of objects
•Cones
oShort, blunt projections
oProvide vision in bright light
oProduce sharp images
oProduce color vision
37. 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
38. Visual Pathway and Visual field cuts
Lesions:
a.Blindness in one eye
b.Bitemporal Hemianopia
c.Homonymous Hemianopia
d.Quadrantanopsia
e.Homonymous Hemianopsia
40. 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
41. External auditory meatus
•Sinus tube that leads to tympanic cavity
•Isthmus: narrowest potion of meatus
Functions:
1. Conduct sounds waves from auricle to tympanic
membrane
2. 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.
42. Auditory Ossicles:
1. Malleus: largest; handle is attached to the
center of the eardrum
2. 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.
43. Middle ear
Chorda tympani
-branch if the facial nerve carrying taste impulses
from the anterior two-thirds of the tongue
-no function in hearing
Inner ear
Bony Labyrinth:
1. Vestibule: for balance
2. Semicircular canals: for balance
3. Cochlea: for hearing
Membranous labyrinth
1. Utricle
2. Saccule
3.Semilunar ducts
4. Cochlear ducts
44. STEPS IN HEARING
1. 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.
45. 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.
46. 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
47. 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. Deafness
a. conduction- impaired conduction through the
external canal and ossicles to endolymph and
tectorial membrane
-cause:external/middle ear diseases
48. b. sensorineural/nerve- interruption of cochlear
nerve fibers from hair cells to BS
-cause: cochlear nerve/ inner nerve
VESTIBULAR SYSTEM
For maintenance of stance and body posture;
coordination of the body, head and eye movements;
and visual fixation
STATIC LABYRITH
-Stuctures involved:
1. Saccule
2. Utricle
-involved in evaluating the position of the head
relative to gravity
49. -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
50. •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 Balance
1. 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.
51. 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
52. TINNITUS
Consists of noises such as ringing, clicking,
whistling, or booming in the ears
MOTION SICKNESS
Consists 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 MEDIA
Infections of the middle ear
VERTIGO
