Transcript Touch, Taste, Smell - Downey Unified School District

Touch, Taste, Smell
• Chemoreceptors
– Smell and taste
• Pain receptors
– touch
• Thermoreceptors
– Taste and touch
• Mechanoreceptors
– Hearing
(proprioreceptors)
Dermal Structures
Receptors
Bare nerve endings
Meissner’s corpuscles
Pacinian corpuscles
Merkel’s Disks
Ruffini’s corpuscles
Location
Function
Pain Receptors
• Provide protection
• Do not adapt rapidly
• Stimulated by
– Changes in temperature
– Mechanical force
Smell
• Olfactory organ
– Appear as the yellowish
mass
– They are covered by a
pinkish mucous
membrane
– Nasal cavity, superior
nasal conchae, nasal
septum
– Contain the olfactory
receptor cells (400
receptors in human)
How we smell
• Olfactory receptors
– bipolar neurons surrounded by
columnar epithelial cells
– Chemoreceptor
• Gas partially dissolves
• Knobs at distal end of dendrites
covered with hair-like cilia
– Generates nerve impulse
• (travel along axon through
openings of cribriform plates of
ethmoid bone)
• fibers synapse with
neurons located in the
enlargement of the
olfactory bulbs:
– Structures that lie on
either side of the crista
galli of the ethmoid
bone.
• Sensory impulses are
analyzed within
olfactory bulbs.
Unique characteristics
• Undergo sensory adaptation rather rapidly.
– intensity of an odor drops 50% within a second
following the stimulation.
– Within a minute may become insensitive to odor.
• Only nerve cells in direct contact with the
outside environment.
– Subject to damage
– Only damaged neurons that are regularly
replaced.
Taste
• Saliva (must dissolve)
• Combination of chemicals
binding to specific
receptors on taste hair
surfaces
• Binding results in
depolarization
• Degree of change is
directly proportional to
concentration of tasted
substance
Taste
•
5 primary tastes
– Flavors results of one (or
combination of) flavor(s) on tongue
• Sweet (tip)
• Sour (margins)
• Salty (everywhere)
• Bitter (back)
• Umami (unknown)
– Different factors may influence
taste
• Temperature
• Smell
• Texture
– Burning Sensation
• Capaisin-irritant
Taste Receptors
• Gustatory/ taste cells
– Modified epithelial cells
– Function as receptors in the taste
buds.
– Each of our 10,000 taste buds
houses 50-150 taste cells.
• spherical
• Taste pore
– Located on the free surface, an
opening where projection
(microviilli) protrude
• Masticate food
• Chemicals dissolve in saliva
• Network of nerve fibers are
interwoven and wrapped
around taste cells.
– Ends of the fibers closely
contact receptor cell
membranes.
– Stimulated receptor cell
triggers an impulse on a
nearby nerve fiber.
• Facial
• Glossopharyngeal
• vagus nerves
– Then travels to the brain.
Impulses
• Medulla oblongata 
up thalamus  to
gustatory cortex
(parietal lobes for
interpretation)
• Functions for ~ 3 days
then replaced
• Exposed to external
environment but not as
high turnover as nose