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THE SPECIAL SENSES
PETER REONISTO, MD
MOORPARK COLLEGE
TRADITIONAL SENSES
1)
2)
3)
4)
5)
Smell
Taste
Sight
Hearing
Equilibrium
SPECIAL SENSES RECEPTORS
• Localized and confined •
•
•
Receptor cells – neuron-like
epithelial cells that transfer
to the head region
sensory information to other
Not free nerve endings
neurons in afferent pathways to
of sensory neurons
the brain
Distinct receptor cells • Sensory receptor cells are housed
in complex sensory organs (eye
or ear) or in distinctive epithelial
structures (taste buds or olfactory
epithelium)
• Sensory information travels via
cranial nerves
CHEMICAL SENSES
TASTE (Gustation)
Taste receptors- located
on
1) tongue surface
2) posterior palate
3) Inner surface of
cheek
4) Posterior pharyngeal
wall
5) epiglottis
SMELL (Olfaction)
Smell receptors- called
olfactory epithelium;
located on
1) Superior nasal
concha
2) Superior nasal
septum
Taste
• 10,000 taste buds
in your mouth
• Sweet and salty
are least
sensitive
• Bitter ones are
most sensitive
Your tongue picks
up four types of
taste: sweet,
sour, bitter, and
salty.
Tongue mucosa
(papillae):
1) Fungiform
papillaescattered over
the entire
surface of the
tongue.
2) (Circum)vallate
papillaeinverted V near
the back of the
tongue
TASTE
Taste Buds
10,000 taste
buds in the
tongue
Tastebuds closeup
Molecules of
food
stimulate
the taste
cells to
send
messages to
your brain.
The sweet
and salty
buds are
the least
sensitive
and the
bitter ones
are the
most
sensitive.
Lower pharynx,
epiglottis
VAGUS
NERVE
Posterior 1/3,
pharynx
Anterior 2/3
THALAMIC NUCLEI
Solitary
Nucleus
(Medulla
Oblongata)
Taste
Buds
CN VII,
IX, X
SMELL
Odor particles
drift into
your nose
and cause
your smell
receptors to
send
messages to
your brain.
OLFACTORY BULB (SMELL)
Limbic Lobe
Olfactory bulb (CN I)
The smell
part of the
brain is in
the limbic
region, and
is
connected
to feeling
and
memory.
Olfactory epithelium
Olfactory receptor cell
• Olfactory epithelium- pseudostratified columnar epithelium
• Olfactory receptor cell- bipolar neurons
Vision
Your eyes
gather
visual
information
, which is
sent to your
brain to be
processed
and
understood.
ANATOMY OF THE EYE
1) SCLERA
2) CHOROID
Ciliary Body
Iris
Cornea
3) RETINA
CONJUNCTIVA
Vision (retina)
Vision: Retina
• Rods sense
brightness
• Cones sense color
The retina, in the back
of your eye, has cells
that are sensitive to
light. They connect
directly to your
brain.
VISUAL PATHWAY
Light/
Image
Aqeous
Humor
Vitreous
Humor
Rods or Cones
(Photoreceptors)
Optic
Nerve
RETINAL/GANGLION CELLS
OPTIC NERVE
OPTIC CHIASM
OPTIC TRACT
LATERAL GENICULATE NUCLEUS
OPTIC RADIATION
VISUAL CORTEX
VISUAL FIELD DEFECTS
Hearing
Sound waves
make your
eardrum
vibrate.
Then, the
small bones
in your ear
vibrate, and
the
vibrations
go through
the snaillike cochlea,
which turns
them into
nerve
impulses to
your brain.
THE EAR: HEARING AND EQUILIBRIUM
• Regions:
1) Outer (External) Ear
2) Middle Ear
3) Inner (Internal) Ear
EXTERNAL EAR
Components:
a) Auricle (Pinna)
b) External Acoustic (Auditory) canal
c) Hair, sebaceous gland, modified apocrine
sweat gland (ceruminous gland)
d) Tympanic membrane
2/3 Temporal bone
1/3 Elastic cartilage
MIDDLE EAR
Boundaries: Petrous part of temporal bone
a) Medial boundary
(1) superior oval window (vestibular)
(2) inferior round window (cochlear)
b) Lateral boundary
(1) Tympanic membrane
c) Superior boundary
(1) Petrous bone
d) Posterior wall
(1) Mastoid antrum- leadsto the mastoid air cells
e) Anterior wall
(1) Pharyngotympanic tube- leads to the pharynx
f) Inferior boundary
(1) thin bony floor where the internal jugular vein lies
MIDDLE
EAR
Components:
a) Ossicles
(1) Malleus
(hammer)
(2) Incus (anvil)
(3) Stapes (stirrup)
b) Skeletal muscle
(1) Tensor tympani
(2) Stapedius
Origin: cartilage part of
Pharyngotympanic tube.
Insertion: malleus
Origin: Posterior wall
Middle ear
Insertion: Stapes
INNER EAR (LABYRINTH)
Bony labyrinth: (petrous
bone cavity); filled
with perilymph
1) Semicircular canals
2) Vestibule
3) cochlea
Membranous labyrinthmembrane-walled
sacs and ducts); filled
with endolymph
1) Semicircular ducts
2) Utricle and saccule
3) Cochlear duct
COCHLEA
• Spiraling chamber
• Coils for about 2 ½ turns around a pillar
called modiolus
• Consist of coiled part of the membranous
labyrinth called cochlear duct (scala media)
which contains the receptors for hearing
• Cochlear nerve runs through the core of the
modiolus
Ends with the
vestibule
Cochlear duct
Ends at the round
window
AUDITORY PATHWAY
Reissner’s
membrane
Scala
vestibuli
Scala
media
Scala
tympani
Tectorial membrane
1 row of inner hair cells
Auditory
nerve
Outer
hair cell
Basilar
membrane
Spiral
Organ of
Corti
Inner hair cell
3 rows of outer hair cells
AUDITORY
PATHWAY
Acoustic area (temporal lobe cortex)
Medial geniculate body
Brachium of inferior colliculi
Inferior colliculi (midbrain)
Lateral Lemniscus
Nuclei of lateral lemniscus
Cochlear nuclei (medulla)
Cochlear division CN VIII
Spiral ganglion
Hair cells (Organ of corti)
SEMICIRCULAR CANAL
AND VESTIBULE
Handles EQUILIBRIUM PATHWAY:
1) Cupula (semicircular canals)
2) Macula (Vestibule)
Cupula and Macula
Vestibular nerve
Reflex centers
Vestibular
Nuclei in
medulla
Vestibular
Nuclei in
cerebellum
END