Somatic and Special Senses Chapter 10 Mr. Wright, 2011
Transcript
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Somatic and Special Senses Chapter 10 Mr. Wright, 2011
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INTRODUCTION Section 10.1
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Sensory Receptors Sensory receptors detect environmental
changes and trigger nerve impulses. The CNS then processes and
interprets the impulse. Finally, the body reacts to the sensory
impulse.
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Sensory Receptors 2 main categories: Somatic Senses touch,
temperature, and pain Special Senses performed by complex sensory
organs; things like taste, smell, sight, etc.
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RECEPTORS AND SENSATIONS Section 10.2
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Types of Receptors Chemoreceptors stimulated by changes in
chemical concentration Pain receptors stimulated by tissue damage
Thermoreceptors stimulated by changes in temperature
Mechanoreceptors stimulated by changes in pressure or movement
Photoreceptors stimulated by light
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Sensations Sensation a feeling that occurs when the brain
interprets a sensory impulse What you feel is based on which region
of the brain receives the impulse. Projection your brains analysis
of where the feeling comes from
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Sensory Adaptation When receptors are continuously stimulated
many of them undergo sensory adaptation. Receptors will stop
sending impulses to stop sensation. Examples: You dont feel your
clothes you are wearing Garbagemen dont notice the smell anymore
Water feels hot when you get into a hot tub, but only for a little
while.
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SOMATIC SENSES Section 10.3
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Somatic Senses Somatic senses - touch, pressure, temperature,
and pain.
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Touch and Pressure 3 kinds of receptors: Sensory Nerve Fibers
free nerves between epithelial cells Meissners Corpuscles found in
hairless portions of skin, respond to motion and light touch. Made
of CT. Pacinian Corpuscles found deep in skin and in muscles and
joints, sense heavy deep pressure. Made of CT.
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Temperature Two types of receptors: warm and cold. Warm are
most sensitive from 77 -113 degrees F. Cold are most sensitive from
50 68 degrees F. Once you go below 50 or above 113, pain receptors
are triggered. Sensory adaptation does take place!
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Pain Pain receptors are stimulated by tissue damage. Have
little to no sensory adaptation. A pain receptor may send several
impulses so pain can persist. How exactly pain receptors are
stimulated is poorly understood. Chemical?
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Visceral Pain Viscera your guts Pain receptors in the viscera
are the only receptors that produce sensation. You dont feel
temperature or pressure, but you sure as heck feel pain.
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Visceral Pain Visceral pain may be referred pain. Referred pain
felt in a different part of the body than the place of stimulation.
For example, people having heart attacks generally feel a sharp
pain in their left shoulder. Caused by common nerve pathways and
mistakes by the cerebral cortex.
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Types of Pain Fibers Acute conduct nerve impulses rapidly, you
feel a sharp pain. Chronic conduct impulses slowly, you feel a
dull, aching pain. An event that stimulates pain receptors usually
stimulates both first you feel a sharp pain, followed by a dull
ache.
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SENSE OF SMELL Section 10.5
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Olfactory Receptors Olfactory smell Olfactory receptors are
chemoreceptors. Very closely associated with taste.
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Olfactory Organs Olfactory Organs yellowish-brown masses in the
upper nasal cavity. Dendrites from nerve cells stick out of
epithelium and are covered with cilia. Odors dissolve into liquids
in the nose and bind to these receptors.
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Olfactory Nerve Pathways Stimulated olfactory receptors send
impulse to the brain olfactory bulbs
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Olfactory Stimulation There are many, many different olfactory
receptors. The combination of which receptors are stimulated
determines what you smell. For example: 3, 4, and 8 together might
smell like chicken, while 1, 5, and 10 together might smell like
chocolate.
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Olfaction Lab Get Ya Stank On, Yo Create a table like the
following on a piece of paper: You will pick five different objects
from around the room (you may use items of your own if you have
something). Smell them and fill out the table: Name of item what
are you sampling? Describe the smell what does it smell like? Is it
strong? Weak? Does it burn? Sensory imprinting - sometimes, a smell
is tied closely to a certain though or memory. Does the smell bring
anything to mind? Does it make you taste something in your mouth?
Sensory Adaptation Give yourself a minute or so to forget the
smell. Then, start smelling it again, but this time keep breathing
it in. Time how long it takes before you no longer notice the
smell. NameDescriptionImprinting?Adaptation?
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SENSE OF TASTE Section 10.6
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Sense of Taste Taste Buds special organs of taste Located on
the tongue on tiny elevations called papillae. Also found on the
roof and walls of the mouth.
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Taste Receptors Each taste bud contains 50 150 taste cells, and
each cell is replace every 3 days. These cells are found within a
taste pore, and have small taste hairs that stick out. Taste hairs
are stimulated by liquids in the mouth and send impulse to the
brain.
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Taste Sensations 4 primary tastes: Sweet Sour Salty Bitter The
combination of these tastes that a food brings about is what causes
its unique taste. Pain receptors can also be stimulated.
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SENSE OF HEARING Section 10.7
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The Ear 3 main parts: External Ear Middle Ear Inner Ear
Functions in hearing and equilibrium.
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External Ear 2 parts: Auricle the outer ear (also called the
pinna) External Auditory Meatus your earhole which goes about 2 cm
deep The auricle of the ear funnels sound vibrations into the
meatus, inside the head.
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Middle Ear Vibrations from the meatus hit the eardrum, causes
it to vibrate. This then causes the auditory ossicles (bones) to
vibrate, in order: Malleus (the hammer) Incus (the anvil) Stapes
(the stirrups) The stapes is connected to a membrane called the
oval window, causes it to vibrate.
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Auditory Tube There is a small tube that connects the middle
ear to the throat auditory (eustachian) tube Conducts air into the
middle ear to maintain pressure necessary for vibrations. Causes
ears to pop!
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Inner Ear We are going to simplify the heck out of this,
because it looks something like this and is very complex:
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Inner Ear The Basics Vibrations hit the oval window. This
causes liquid within the inner ear to start to vibrate. Vibrations
travel through several canals, and will stimulate receptor cells
which signal the brain.
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Inner Ear The Basics Different receptor cells have slightly
different sensitivities. Some sound frequencies will stimulate
certain receptors but not others.
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SENSE OF EQUILIBRIUM Section 10.8
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Sense of Equilibrium 2 types of equilibrium Static balance when
the head and body are still Dynamic balance when the head and body
are in movement.
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Static Equilibrium Vestibule organ of static equilibrium, found
between semicircular canals and cochlea The vestibule is filled
with tiny hairs called macula and crystals called otoliths. As you
move your head, the otoliths roll around and press against the
macula. The macula then signal the brain, informing it of the heads
new position.
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Dynamic Equilibrium Organs of dynamic equilibrium semicircular
canals. Each canal corresponds to a different anatomical
plane.
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Dynamic Equilibrium As you move your head in a direction, hairs
in the canals move the opposite direction as fluids pass over them.
The combination of these hairs movements tells the brain how you
are moving and about your position.
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Dynamic Equilibrium Other sensory structure also aid with
dynamic equilibrium: Joints in the neck transfer information about
position of the body to the brain. Your eyes also detect changes in
posture and signal the brain.
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SENSE OF SIGHT VISUAL ACCESSORIES Section 10.9
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Accessory Organs - Eyelid Each eyelid is 4 layers: Skin
(thinnest in the body) Muscle Connective Tissue Conjunctiva mucus
membrane that lines the inner surface of the eyelid, secretes
mucus
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Accessory Organs Lacrimal Gland Lacrimal gland secretes tears
There are a series of ducts that also carry tears into the nasal
cavity. This is why you might get a runny nose when you cry. Tears
are ALWAYS being produced, even when youre not crying they moisten
the eye and protect against infection. Antibacterial
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Accessory Organs Tarsal Glands The eye also has structures
called tarsal glands, which secrete oil to help lubricate the
eye.
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Accessory Organs - Muscles There are 6 different muscles that
move the eye. They work together to move certain ways. Orbicularis
Oculi controls your blinking.
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SENSE OF SIGHT STRUCTURE OF THE EYE Section 10.9
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Structure of the Eye The eye is a hollow sphere about 2.5cm in
diameter. 3 distinct layers: Outer Tunic Middle Tunic Inner Tunic
Filled with fluids.
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Outer Tunic 2 main parts: Sclera the whites of your eyes, makes
up 5/6 of the outer tunic. Protects the eye and attaches to
muscles. Cornea The front 1/6 of the eye, transparent window Helps
focus light into the eye
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Middle Tunic Choroid Coat posterior 5/6 of the middle tunic,
absorbs light and nourishes. Ciliary Body anterior 1/6 of the
middle tunic, ligaments attach to hold the lens
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Middle Tunic Lens Elastic (can change shape) Allows the eye to
focus on an object Accommodation the ability of the lens to change
shape to focus
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Middle Tunic Iris The colored portion of the eye Divides the
space between cornea and lens into two chambers (posterior and
anterior) Pupil opening in the center of the eye Aqueous humor
liquid that fills these two chambers
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Inner Tunic Retina Back of the eye Contains photoreceptors
Joins to the optic nerve Optic Disc Where the nerves of the eye
join the optic nerve No photoreceptors = blind spot Vitreous Humor
jellylike fluid filling the eye
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SENSE OF SIGHT HOW IT WORKS Section 10.9
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Light Refraction Light from the outside enters the eye and is
refracted (bent) by the lens This focuses the light onto the retina
for viewing. The image is upside down and backwards, but your brain
interprets it in the right position.