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Senses
Cassidy McCombs
Claire Johnson
Siobhan O’Shea
Kevin Su
Basic Definitions
• General Senses: Receptors are widely distributed
through out the body (Skin/Organs/Joints)
• Specialized Senses: Specialized receptors confined to
the structures of the head
• Sensation: Raw form in which receptors send
information to the brain
• Perception: The way the brain interprets a received
sensation
• Projection: What the brain sends back to the projection
source (allows person to pinpoint the region)
Receptor Types
• Chemoreceptors: Changes in concentration of
chemical substances (Senses of smell and taste;
changes in blood such as oxygen, hydrogen, glucose)
• Pain Receptors: Respond to tissue damage (exposure
to electrical, chemical, thermal, and mechanical energy)
• Thermo Receptors: Temperature Change
• Photoreceptors: Detects light energy intensity (found in
eyes)
• Mechanoreceptors: changes that deform receptors
– Proprioceptors: Muscles and Tendons
– Baroreceptors: Certain blood vessels and blood pressure
– Stretch Receptors: Lungs (by degree of inflation)
Apple Example
Hearing
• Sound Pathway:
• Auricle → External Acoustic Meatus → Tympanic Membrane →
Ossicles → Oval Window → Scala Vestibuli → Vestibular
Membrane → Cochlear Duct → Hair Cells → Sensory Neurons →
Temporal Lobe
External Ear
• Auricle: Cone shaped,
collects sound
• External Auditory
Meatus: Lined with
ceruminous glands,
transfers sound to
tympanic membrane
• Tympanic Membrane:
Vibrates as a result of
sound vibrates ossicles
Middle Ear
• Tympanic Cavity: air-filled
space in the temporal bone
• Ossicles: Vibrates from
contact from the tympanic
membrane, malleus, incus,
stapes
• Oval Window: Small cavity
in the tympanic cavity,
stapes vibrates against it to
move fluids in inner ear
Eustachian (Auditory) Tube
• Eustachian tube
• Part of Middle Ear
• 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
Inner Ear
• Contains two labyrinths
• Osseous Labryinth: bony
canal, filled with perilymph
• Membranous Labyrinth: tube
within Osseous Labyrinth, filled
with endolymph
• Three parts of the Labyrinth:
Cochlea, Semicircular
Canals, Vestibule
• But we’ll focus on the Cochlea
for now because the other two
are not in the sound pathway
Cochlea
From the stapes in the middle
ear, vibrations enter the oval
window and transfer to the scala
vestibuli. Different pitched
sounds travel different distances
along the length of the scala
vestibuli. The vibrations take a
u-turn then enter the vestibular
membrane and pass through
the membranous labyrinth.
Here, the sounds are processed
and sent to the brain. The
sounds then pass through the
Basilar membrane, then back
down the cochlea through the
scala tympani to be absorbed
by the round window.
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
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
Equilibrium
Static Equilibrium
• uses vestibule
• sense position of
head when body is
not moving
Dynamic Equilibrium
• uses semicircular canals
• sense rotation and
movement of head and
body
Vestibule
• Utricle
• communicates with
saccule and
membranous portion of
semicircular canals
• Saccule
• communicates with
cochlear duct
• Mucula
• hair cells of utricle and
saccule
Macula
Static eq.
• responds to
changes in head
position
• bending of hairs
results in
generation of nerve
impulse
Crista Ampullaris
Dynamic Eq
Smell
• Smell works closely with taste to aid in food
selection
▫ We smell food the same time we taste it
▫ 75%-80% of flavor derives from the sense of smell
• Olfactory receptors
▫ used to sense smell
▫ Similar to chemoreceptors and taste
Olfactory Receptor Cells
• Bipolar neurons surrounded by columnar
epithelial cells
• Neurons have knobs at the distal ends of
their dendrites and are the sensitive portion
of the receptors
• Odorant molecules stimulate olfactory
receptors
• Main interpreting areas for olfactory impulses
are located deep within the temporal lobes
and at the bases of the frontal lobes
Olfactory Organs
• Contain the olfactory receptors and epithelial
supporting cells
• Appear as yellowish brown masses surrounded
by pinkish mucous membrane
• Cover upper parts of the naval cavity, the
superior nasal conchae and a portion of the
nasal septum
Odorant molecules
• Enter the nasal cavity as gases
• Must dissolve at least partially in the watery
fluids that surround the cilia before they can
be detected by bonding to receptor proteins
on the cilia
• Bind to about 500 types of olfactory
receptors, depolarizing the olfactory receptor
cells, therefore generating nerve impulses
• Signaling proteins inside the receptor cells
translate the chemical signals into the electro
chemical language of the nervous system
Receptors
• Sensory receptors
▫ respond to sensory stimuli
• Membrane receptors
▫ Molecules such as proteins and glycoproteins
▫ Allow cells to respond to specific molecules
• Olfactory receptors
▫ Respond to specific molecules and chemical
stimuli
Olfactory Nerve Pathways
• When stimulated nerve impulses travel along
their axons through tiny opening in the
cribriformplates of the ethmoid bone
• These fibers synapse with neurons located in
the enlargements of the olfactory bulbs
• Within the olfactory bulbs the sensory impulses
are analyzed and additional impulses travel
along the olfactory tracts to portions of the limbic
system
Olfactory Stimulation
• Biologists not certain how stimulated receptors
encode specific cells
• Leading hypothesis is that each odor likely
stimulates a distinct set of receptor cells that in
turn have distinct sets of receptor proteins
• The brain then recognizes the particular
combination as an olfactory code
Olfactory Adaptation
• The sense of smell drops about 50% within a
second following stimulation
• Within a minute the receptors may become
almost insensitive to a given odor
• Olfactory receptor neurons are the only nerve
cells in direct contact to the outside
environment
▫ Basal cells along the basement membrane of the
olfactory epithelium regularly divide and yield
differentiated cells that replace lost neurons
Taste Receptors
• The sense of taste derives from combinations of
chemicals binding specific receptors on taste
hair surfaces
• This binding alters membrane polarization and
generates sensory impulses on nearby nerve
fibers
• The degree of change is directly proportional to
the concentration of the stimulating substance
Taste Sensations
• Five primary taste sensations are sweet, sour,
salty, bitter, and umami
▫ Each of the flavors we experience results from
one of the primary sensations or from a
combination of two or more of them
▫ The way we experience flavors may also reflect
the concentration of chemicals as well as the
sensations of smell, texture, and temperature
Taste Nerve Pathways
• Cranial nerves conduct the impulses into the
medulla oblongata
• From there the impulses ascend to the thalamus
and are directed to the gustatory cortex of the
cerebrum, located in the parietal lobe along a
deep portion of the lateral sulcus
Anatomy of the Eye
•From outermost to innermost:
•Sclera, Cornea, Aqueous humor, Iris, Pupil, Lens,
Vitreous humor, Retina, Choroid coat, optic nerve
The Outer Tunic of the Eye
•The outer tunic consists of the sclera, cornea, and
optic nerve. The sclera is the white of the eye. The
cornea is the “window of the eye” where light enters,
it helps focus light into the eye. The optic nerve
transports stimuli from the eye to the brain.
The Middle Tunic of the Eye
•Also called the vascular tunic. Includes the chortoid
coat, the ciliary body, and the iris. The ciliary body
is the thickest part. Suspensatory ligaments extend
from the back of it and connect to the lens.
The Inner Tunic of the Eye
•Contains the retina. The retina has several parts:
the fovea centralis (where vision is best), the optic
disc – which becomes the optic nerve, and the
vitreous humor. The vitreous humor supports the
internal structure of the eye and helps it maintain
its shape.
Refraction and Focus
Refraction occurs when light enters the eye and bends in order to focus. Images
appear upside down when they reach the retina, but are perceived as right side
up by the brain.
If the lens is normal, the light always focuses on the retina. In myopia and
hyperopia the shape if the eye is slightly deformed. In myopia the eye is too long
and the light focuses too far in front of the retina. It is corrected using glasses
with concave lenses. In hyperopia the eye is too short and light focuses to far
behind the retina, it is corrected using a convex lens.
Visual Pigments
Rods and cones contain pigments that decompose when they absorb light. Rhodopsin is
found in rods, which see shapes and are not very acute. In darkness, more rods are
used, and when going from darkness to somewhere light, the rhodopsin decomposes.
Too little vitamin A reduces the amount of rhodopsin, causing a condition called
“nightblindness”.
Cones contain idopsins , which see color and vision is acute.
Stereoscopic Vision and Visual
nerve Pathways
Stereoscopic vision perceives depth, height, and width. It depends on having two
eyes.
Visual nerve pathways: the optic nerves in the eyes split into two, sending
messages to both sides of the brain.
Bibliography
• "Gustatory Receptor Cells." - WolfWikis. Web.
03 Apr. 2012.
<http://wikis.lib.ncsu.edu/index.php/Gustatory_re
ceptor_cells>.
• Shier, David. Hole's Human Anatomy &
Physiology. Student Ed. Eleventh ed. [S.l.]:
McGraw, 2007. Print.
• "Please Pass The Salt." Basal Science Clarified.
14 Aug. 2011. Web. 03 Apr. 2012.
<http://bsclarified.wordpress.com/2011/08/14/ple
ase-pass-the-salt/>.
• Haas’s Previous Slideshows