Special Senses

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Special Senses

• sensory receptors are within large, complex
  sensory organs in the head
• smell in olfactory organs
• taste in taste buds
• hearing and equilibrium in ears
• sight in eyes

connected
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Sense of Smell

• Olfactory Receptors
• chemoreceptors
• respond to chemicals dissolved in liquids

• Olfactory Organs
• contain olfactory receptors and supporting
  epithelial cells
• cover parts of nasal cavity, superior nasal
  conchae, and a portion of the nasal septum

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Olfactory Receptors
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Olfactory Nerve Pathways

• Once olfactory receptors are stimulated, nerve
  impulses travel through
• olfactory nerves olfactory bulbs
  olfactory tracts limbic system (for
  emotions-moms apple pie.) and olfactory cortex
  (for interpretation)

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Olfactory Stimulation

• olfactory organs located high in the nasal
  cavity above the usual pathway of inhaled air
• olfactory receptors undergo sensory adaptation
  rapidly
• sense of smell drops by 50 within a second
  after stimulation

• Olfactory Code
• hypothesis
• odor that is stimulated by a distinct set of
  receptor cells and its associated receptor
  proteins (the variety stimulated determines the
  smell)

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Sense of Taste

• Taste Buds
• organs of taste
• located on papillae of tongue, roof of mouth,
  linings of cheeks and walls of pharynx

• Taste Receptors
• chemoreceptors
• taste cells modified epithelial cells that
  function as receptors
• taste hairs microvilli that protrude from taste
  cells sensitive parts of taste cells

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Taste Receptors
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Taste Sensations

• Four Primary Taste Sensations
• sweet stimulated by carbohydrates
• sour stimulated by acids
• salty stimulated by salts
• bitter stimulated by many organic compounds

Spicy foods activate pain receptors (and sour)
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Taste Nerve Pathways

• Sensory impulses from taste receptors travel
  along
• cranial nerves to
• medulla oblongata to
• thalamus to
• gustatory cortex (for interpretation)

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Hearing
Ear organ of hearing

• Three Sections
• External
• Middle
• Inner

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External Ear

• auricle
• collects sounds waves
• external auditory meatus
• lined with ceruminous glands
• carries sound to tympanic membrane
• terminates with tympanic membrane
• tympanic membrane
• vibrates in response to sound waves

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Middle Ear

• tympanic cavity
• air-filled space in temporal bone
• auditory ossicles
• vibrate in response to tympanic membrane
• malleus, incus, and stapes
• oval window
• opening in wall of tympanic cavity
• stapes vibrates against it to move fluids in
  inner ear

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Auditory Tube

• eustachian tube
• connects middle ear to throat
• helps maintain equal pressure on both sides of
  tympanic membrane (think altitude-pop)
• usually closed by valve-like flaps in throat

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Inner Ear

• complex system of labyrinths
• osseous labyrinth
• bony canal in temporal bone
• filled with perilymph
• membranous labyrinth
• tube within osseous labyrinth
• filled with endolymph

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Inner Ear

• Three Parts of Labyrinths
• cochlea
• functions in hearing
• semicircular canals
• functions in equilibrium
• vestibule
• functions in equilibrium

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Cochlea

• Scala vestibuli
• upper compartment
• leads from oval window to apex of spiral
• part of bony labyrinth
• Scala tympani
• lower compartment
• extends from apex of the cochlea to round window
• part of bony labyrinth

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Cochlea

• Cochlear duct
• portion of membranous labyrinth in cochlea
• Vestibular membrane
• separates cochlear duct from scala vestibuli
• Basilar membrane
• separates cochlear duct from scala tympani

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Organ of Corti

• group of hearing receptor cells (hair cells)
• on upper surface of basilar membrane
• different frequencies of vibration move
  different parts of basilar membrane
• particular sound frequencies cause hairs of
  receptor cells to bend
• Ca influx causes NT release onto sensory nerve
• AP generated-to medulla-to thalamus-to auditory
  cortex (temporal)
• Some crossover occurs

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Organ of Corti
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Auditory Nerve Pathways
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Summary of the Generation of Sensory Impulses
from the Ear
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Equilibrium

• Dynamic Equilibrium
• semicircular canals
• sense rotation and movement of head and body

• Static Equilibrium
• vestibule
• sense position of head when body is not moving

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Vestibule

• Utricle
• communicates with saccule and membranous portion
  of semicircular canals
• Saccule
• communicates with cochlear duct
• Mucula
• hair cells of utricle and saccule

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Macula

• responds to changes in head position
• bending of hairs results in generation of nerve
  impulse

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Semicircular Canals

• three canals at right angles
• ampulla
• swelling of membranous labyrinth that
  communicates with the vestibule
• crista ampullaris
• sensory organ of ampulla
• hair cells and supporting cells
• rapid turns of head or body stimulate hair cells

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Crista Ampullaris