THE SPECIAL SENSES

1
THE SPECIAL SENSES

• PETER REONISTO, MD
• MOORPARK COLLEGE

2
TRADITIONAL SENSES

1. Smell
2. Taste
3. Sight
4. Hearing
5. Equilibrium

3
SPECIAL SENSES RECEPTORS

• Localized and confined to the head region
• Not free nerve endings of sensory neurons
• Distinct receptor cells

• Receptor cells neuron-like epithelial cells
  that transfer sensory information to other
  neurons in afferent pathways to the brain
• 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

4
CHEMICAL SENSES

• TASTE (Gustation)
• Taste receptors- located on
• tongue surface
• posterior palate
• Inner surface of cheek
• Posterior pharyngeal wall
• epiglottis

• SMELL (Olfaction)
• Smell receptors- called olfactory epithelium
  located on
• Superior nasal concha
• Superior nasal septum

5
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.

6
(No Transcript)
7
TASTE

• Tongue mucosa (papillae)
• 1) Fungiform papillae- scattered over the entire
  surface of the tongue.
• 2) (Circum)vallate papillae- inverted V near the
  back of the tongue

8
Taste Buds

• 10,000 taste buds in the tongue

9
(No Transcript)
10
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.

11
Lower pharynx, epiglottis
Anterior 2/3
VAGUS NERVE
Posterior 1/3, pharynx
12
THALAMIC NUCLEI
Solitary Nucleus (Medulla Oblongata)
CN VII, IX, X
Taste Buds
13
SMELL

• Odor particles drift into your nose and cause
  your smell receptors to send messages to your
  brain.

14
OLFACTORY BULB (SMELL)

• The smell part of the brain is in the limbic
  region, and is connected to feeling and memory.

Limbic Lobe
Olfactory bulb (CN I)
Olfactory epithelium
Olfactory receptor cell

• Olfactory epithelium- pseudostratified columnar
  epithelium
• Olfactory receptor cell- bipolar neurons

15
Vision

• Your eyes gather visual information, which is
  sent to your brain to be processed and
  understood.

16
(No Transcript)
17
ANATOMY OF THE EYE
1) SCLERA
2) CHOROID
Ciliary Body
Iris
Cornea
3) RETINA
CONJUNCTIVA
18
(No Transcript)
19
(No Transcript)
20
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.

21
VISUAL PATHWAY
22
Light/ Image
Aqeous Humor
Vitreous Humor
Optic Nerve
Rods or Cones (Photoreceptors)
23
(No Transcript)
24
(No Transcript)
25
RETINAL/GANGLION CELLS
OPTIC NERVE
OPTIC CHIASM
OPTIC TRACT
LATERAL GENICULATE NUCLEUS
OPTIC RADIATION
VISUAL CORTEX
26
VISUAL FIELD DEFECTS
27
Hearing

• Sound waves make your eardrum vibrate. Then, the
  small bones in your ear vibrate, and the
  vibrations go through the snail-like cochlea,
  which turns them into nerve impulses to your
  brain.

28
THE EAR HEARING AND EQUILIBRIUM

• Regions
• Outer (External) Ear
• Middle Ear
• Inner (Internal) Ear

29
EXTERNAL EAR

• Components
• a) Auricle (Pinna)
• b) External Acoustic (Auditory) canal
• c) Hair, sebaceous gland, modified apocrine
  sweat gland (ceruminous gland)
• d) Tympanic membrane

30
2/3 Temporal bone
1/3 Elastic cartilage
31
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

32
(No Transcript)
33
(No Transcript)
34
MIDDLE EAR

• Components
• Ossicles
• (1) Malleus (hammer)
• (2) Incus (anvil)
• (3) Stapes (stirrup)
• b) Skeletal muscle
• (1) Tensor tympani
• (2) Stapedius

35
Origin cartilage part of Pharyngotympanic
tube. Insertion malleus
Origin Posterior wall Middle ear Insertion
Stapes
36
INNER EAR (LABYRINTH)

• Bony labyrinth (petrous bone cavity) filled
  with perilymph
• Semicircular canals
• Vestibule
• cochlea

• Membranous labyrinth- membrane-walled sacs and
  ducts) filled with endolymph
• Semicircular ducts
• Utricle and saccule
• Cochlear duct

37
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

38
(No Transcript)
39
Ends with the vestibule
Cochlear duct
Ends at the round window

• AUDITORY PATHWAY

40
1 row of inner hair cells
Spiral Organ of Corti
3 rows of outer hair cells
41
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)
42
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
43
(No Transcript)
44
END