Download Class 19 - 20 sensory

SPECIAL SENSES
“Bad men live that they may eat and
drink, whereas good men eat and drink
that they may live.”
Socrates
CHAPTER 11
Sensory Receptors
Distribution of sense receptors
 Special senses in sense
organ
• Vision
• Hearing
• Equilibrium
• Taste
• Smell
 General senses throughout
body
• Pressure, temperature,
pain, touch
• Sense of position

Sensory receptors
• Chemoreceptorsrespond to chemicals
• Photoreceptors-respond
to light
• Thermoreceptorsrespond to heat
• Mechanoreceptorsrespond to movement
EYE PROTECTION STRUCTURES





Eye cavity bones
Eyelids
Eyelashes and eyebrow
Conjunctiva
Lacrimal glands
ANATOMY OF THE EYE






SPHERE OF 1 INCH IN DIAMETER
RESTS WITHIN A BONY ORBIT
CUSHIONED BY FAT
MEDIAL & LATERAL CANTHUS
MEIBOMIAN GLAND – OIL TO
LUBRICATE EYELASHES
LYZOSYMES IN TEARS
The eye.
Note the three
tunics, the
refractive parts
of the eye
(cornea,
aqueous humor,
lens, vitreous
body), and
other structures
involved in
vision.
Light Pathway Structures




Cornea – transparent, clear; avascular;
main area of refraction
Aqueous humor – watery fluid supporting
cornea; gives it a curved look
Lens – biconvex; changes shape with
eye focusing
Vitreous humor – gel like fluid; maintains
shape of eyeball; aids in refraction
Structure of the Eyeball



Sclera (fibrous) – white of the eye; many
nerve sensors for pain reception
Choroid (vascular) – dark brown
pigmented layer; becomes ciliary body
anteriorly
Retina (sensory) – light receptors
• Rods
• Cones
Function of the Retina
Pigmented layer
Sensitive to light
Rods
Function in dim light
Shades of gray
Blurred images
Cones
Function in bright light
Color sensitive
Sharp images
Connecting neurons
Structure of the
retina. Rods
and cones
form a deep
layer of the
retina, near
the choroid.
Connecting
neurons carry
visual
impulses
toward the
optic nerve.
COLORS

3 TYPES OF CONES

ABSENSE OF CONES = TOTAL COLOR
BLINDNESS
MOST COMMON IS BLUE OR GREEN
X-LINKED TRAIT= SEEN IN MEN


• RED
• BLUE
• GREEN
PATHWAY OF LIGHT

LIGHT COMES THROUGH PUPIL
(cornea) TO LENS WHICH REFRACTS
IT. LIGHT HITS PHOTORECEPTORS
IN RETINA; RECEPTORS TRANSMIT
ELECTRICAL SIGNALS VIA BIPOLAR
CELLS TO GANGLION CELLS TO
OPTIC NERVE TO VISION CENTER IN
OCCIPITAL LOBE
MUSCLES OF THE EYE


6 EXTERNAL/EXTRINSIC MUSCLES
Used for convergence
•
RECTUS MUSCLES
•
OBLIQUE MUSCLES
• SUPERIOR
• MEDIAL
• LATERAL
• INFERIOR
• SUPERIOR
• INFERIOR
Extrinsic muscles of the eye. The medial rectus is not shown.
• What characteristics are used in naming the extrinsic eye muscles?
Intrinsic Muscles

Used for accomodation
Iris – 2 muscles around pupil

Ciliary Muscle – holds the lens suspends

• Circular muscle contracts = constriction
• Radial muscle contracts = dilation
by suspensory ligaments
The ciliary muscle
and lens
(posterior view).
Contraction of the
ciliary muscle
relaxes tension
on the
suspensory
ligaments,
allowing the lens
to become more
round for near
vision.
• What structures
hold the lens in
place?
TERMS






OPTIC DISC – BLIND SPOT
FOVEA CENTRALIS – ONLY CONES
LENS – BICONVEX CRYSTAL-LIKE
AQUEOUS HUMOR
VITREOUS HUMOR
SCLERAL VENOUS SINUS (CANAL OF
SCHLEMM)
IMBALANCES


CATARACTS – LENS BECOMES
HARDER AND OPAQUE
GLAUCOMA – INCREASED
PRESSURE IN FRONT OF LENS
CAUSES PRESSURE TO INCREASE
AGAINST RETINA AND NERVE
LEADING TO BLINDNESS
VISUAL FIELDS & PATHWAYS




OPTIC NERVE ENTERS BRAIN FROM
EACH EYE
MEET AT OPTIC CHIASMA
MEDIAL FIBERS CROSS TO
OPPOSITE PATHWAYS WHICH
BECOME THE OPTIC TRACT
SYNAPSE AT HYPOTHALMUS TO
FORM OPTIC RADIATION TO VISION
CENTER
Nerve Supply to the Eye





Optic nerve (cranial nerve II)
Ophthalmic branch of trigeminal nerve
(cranial nerve V)
Oculomotor nerve (cranial nerve III)
Trochlear (cranial nerve IV)
Abducens (cranial nerve VI)
Nerves of
the eye.
• Which of
the
nerves
shown
moves
the eye?
Errors of Refraction and Other Eye
Disorders





Hyperopia
Myopia
Astigmatism
Strabismus
• Convergent
• Divergent
• Amblyopia
Infections
• Conjunctivitis
• Inclusion conjunctivitis
• Ophthalmia neonatorum




Injuries
Cataract
Glaucoma
Disorders involving the
retina
• Diabetic retinopathy
• Macular degeneration
The ear. Structures in the outer, middle, and inner divisions are
shown.
HEARING AND BALANCE

OUTER EAR
• PINNA/ AURICLE
• EXTERNAL AUDITORY MEATUS
• CERUMINOUS GLANDS
• TYMPANIC MEMBRANE (EARDRUM)
MIDDLE EAR



TYMPANIC CAVITY FROM EARDRUM
LATERALLY TO OVAL WINDOW AND
ROUND WINDOW MEDIALLY
PHARYNGOTYMPANIC TUBE ( ALSO
KNOWN AS EUSTACHIAN TUBE)
3 BONES – OSSICLES
• MALLEUS
• INCUS
• STAPES
IMBALANCES


OTITIS MEDIA – MIDDLE EAR
INFECTION RESULTING FROM
BACTERIA IN SORE THROAT
TRAVELING UP THE CANAL
MYRINGOTOMY – PLACING TUBES IN
TYMPANIC MEMBRANE TO EQUALIZE
THE PRESSURES BETWEEN MIDDLE
AND OUTER EAR
INNER EAR

OSSEOUS LABYRINTH
• VESTIBULE
• COCHLEA
• SEMICIRCULAR CANALS
• PERILYMPH FILLS THE BONY LABYRINTHS

MEMBRANOUS LABYRINTH
• VESTIBULE
• SEMICIRCULAR CANALS
• COCHLEA
• ENDOLYMPH FLUID
The inner ear. The vestibule, semicircular canals, and
cochlea are made of a bony shell (labyrinth) with an
interior membranous labyrinth. Endolymph fills the
membranous labyrinth and perilymph is around it in
the bony labyrinth.
STATIC EQUILIBRIUM



MACULAE ARE SENSORY HAIRS
EMBEDDED IN A BONY MEMBRANE WITHIN
THE VESTIBULE
AS YOUR HEAD MOVES, THE OTOLITHS
ROLL WITH GRAVITY, BENDING THE HAIRS
HAIR CELLS SEND AN IMPULSE DOWN THE
NERVE TO BRAIN RELATING YOUR
POSITION IN THE SPACE AROUND YOU
Action of the receptors (maculae) for static equilibrium. As the head
moves, the thick fluid above the receptor cells, weighted with
otoliths, pulls on the cilia of the cells, generating a nerve impulse.
What happens to the cilia on the receptor cells when the fluid around them moves?
DYNAMIC EQUILIBRIUM




RECEPTORS IN SEMICIRCULAR CANALS
THAT RESPOND TO ROTATIONAL OR
ANGLED MOVES
3 D PLANES IN SPACE
RECEPTOR REGION IS CRISTAE
AMPULLARIS (HAIR CELLS IN A GEL LIKE
CUPOLA {CAP})
BALANCE OCCURS ALONG WITH SIGHT &
PROPRIOCEPTORS OF MUSCLES
Action of the receptors (cristae) for dynamic equilibrium.
As the body spins or moves in different directions, the
cilia bend as the head changes position, generating
nerve impulses.
Cochlea and the
organ of Corti.
The arrows show the
direction of sound
waves in the
cochlea.
HEARING


COCHLEAR DUCT IS FILLED WITH AN
ENDOLYMPH- CONTAINING MEMBRANOUS
LABYRINTH WHERE THE ORGANS OF
CORTI ARE FOUND
ORGAN OF CORTI CONTAINS A BASILAR
MEMBRANE WHERE THE HAIR CELLS
(HEARING RECEPTORS) ARE POSITIONED
FOLLOW THE SOUND WAVE!!!





SOUND WAVE ENTERS THE EAR CANAL
THE WAVE VIBRATES THE TYMPANIC
MEMBRANE (EAR DRUM)
VIBRATION MOVES THE OSSICLES IN A
LEVER FASHION, TRANSMITTING THE
SOUND WAVE TO THE OVAL WINDOW
AGITATION OF THE WINDOW SETS FLUID
IN INNER EAR INTO MOTION
CAUSES A PRESSURE WAVE ACROSS
BASILAR MEMBRANE BENDING HAIRS
CONTINUED



THE HAIR CELLS IN ORGAN OF CORTI
MOVE WITH THE WAVE WHICH CAUSES
STIMULATION/ IMPULSE UP TO THE
COCHLEAR NERVE THEN TO AUDITORY
CENTER IN TEMPORAL LOBE
LENGTH OF HAIR CELLS DETERMINES
FREQUENCY HEARD
SHORT = HIGH & LONG = LOW
ADAPTIONS



CONTINUED INPUT LEADS TO “TUNING
OUT”
****** HEARING IS THE LAST SENSE TO
LEAVE OUR AWARENESS WHEN WE
FALL ASLEEP, RECEIVE ANESTHESIA
OR DIE******
BE CAREFUL WHAT YOU SAY!!!!
DEFICITS




DEAFNESS – HEARING LOSS OF ANY
DEGREE
CONDUCTION- CONDUCTON IS BLOCKED/
INTERUPTED
SENSORINEURAL – DAMAGE TO
RECEPTORS, NERVE OR AUDITORY
CORTEX
MENIERE’S DISEASE
TASTE




10,000+ TASTE BUDS (RECEPTORS)
IN ORAL CAVITY- MOST ON TONGUE
CHEMICALS DISSOLVE IN SALIVA
BATHE THE PAPILLAE WHERE THE
GUSTATORY CELLS/ HAIRS ARE
FOUND
TRANSMIT IMPULSE TO BRAIN
Sense of Taste


Taste receptors (buds) on
tongue
• Stimulated by substance
in solution
Basic tastes
• Sweet
• Salty
• Sour
• Bitter


Other tastes
• Water
• Alkaline
• Metallic
• Umami
Cranial nerves
• Facial (VII)
• Glossopharyngeal (IX)
UMAMI
Special senses that respond to chemicals.
(A) Organs of taste (gustation) and smell (olfaction).
(B) A taste map of the tongue.
5 TYPES OF TASTE





SWEET – RESPONDS TO OH- GROUPS
SOUR – RESPONDS TO H+
BITTER – ALKALOIDS
SALTY – METALS
UMAMI - GLUTAMATES
Sense of Smell

Smell receptors in nasal cavity
• Stimulated by substances in solution in nasal
•

fluids
Smells stimulate appetite and flow of digestive
juices
Olfactory nerve (cranial nerve I)
OLFACTORY


OLFACTORY RECEPTORS IN ROOF OF
NOSE
CHEMICALS DISSOLVED IN THE FLUID/
MUCUS STIMULATE THE OLFACTORY
HAIRS AND THEN OLFACTORY RECEPTOR
CELLS (NEURONS) SEND IMPULSE UP
OLFACTORY NERVE TO CORTEX IN BRAIN
ADAPTIONS



FREQUENT INPUT OF AROMA
CAUSES “TUNING OUT”
ANOSMIAS – LOSS OF SMELL
OLFACTORY AURAS
FACTORS AFFECTING TASTE






SMELL AND TASTE CLOSELY RELATED
TEMPERATURE
TEXTURE
ODOR
SPICINESS
APPEARANCE
SENSORY IMBALANCES



STRABISMUS
PRESBYOPIA
PRESBYCUSIS
Sense of Position
Proprioceptors (position receptors)
 Are located in muscles, tendons, joints
 Relay impulses of body parts in relation
to each other
 Send impulses to the cerebellum for
coordination
 Help maintain equilibrium
Questions, anyone?