PPT13Chapter13SensorySystem
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Transcript PPT13Chapter13SensorySystem
Sensory System
CHAPTER 13
JOE PISTACK MS/ED
Allows us to experience the world.
Sensory
System
Senses:
Seeing
We experience the world through
our senses.
Hearing
Feeling
Tasting
Allows us to keep track of what is
happening in our bodies.
Acts as a danger signal when we
come in contact with a harmful
stimulus.
Five types of sensory receptors:
Cells that
detect stimuli
Receptor-a
specialized area of a
sensory neuron that
detects a specific
stimulus.
Chemoreceptors-stimulated by
changes in chemicals such as H+,
calcium and food. Ex. Taste and
smell.
Pain receptors or nociceptors Ex. Receptors in the
eye respond to light.
Ex. Receptors in the
tongue respond to
chemicals in food.
stimulated by tissue damage or
distention. Ex. Pain.
Thermoreceptors -receptors
stimulated by changes in
temperature. Ex. Heat and cold
Mechanoreceptors-receptors
Receptors
(continued)
stimulated by changes in pressure
or movement of body fluids.
Ex. Hearing and equilibrium.
Photoreceptors-receptors
stimulated by light.
Ex. Sight.
Four components of a sensation:
Sensation
The conscious
awareness of
incoming
sensory
information.
Ex. “Ouch”indicates that
you are aware
of a painful
stimulus.
(1) Stimulus-light will stimulate
sight. Absence of light, you
cannot see.
(2) Receptor-light waves
stimulate photoreceptors in the
eye producing a nerve impulse.
(3) Sensory nerve-the nerve
impulse is conducted to the
occipital lobe of the brain.
Sensation
(continued)
Two
characteristic
s of sensation
are:
Projection
Adaptation
Projection-the process by which
the brain, after receiving a
sensation, refers that sensation
back to its source. Ex. Pain
Adaptation-adapting to the
stimulus. Ex. When you enter a
room with a strong odor, it may
be overwhelming at first and then
become less noticeable. Sensory
receptors adapt.
Two Groups of Senses
General senses: called
general or somatic.
Widely distributed
throughout the body.
Special senses:
Localized within a
particular organ in the
head.
Include:
Include:
Pain
Taste
Touch
Smell
Pressure
Sight
Temperature
Hearing
Proprioception
Balance
Five Special Senses
Five special senses:
Smell
Taste
Sight
Hearing
balance
Pain
Pain-receptors for pain,
called nociceptors consist
of free nerve endings that
are stimulated by tissue
damage.
Pain receptors are widely
distributed throughout
the skin, the visceral
organs, and other
internal tissues.
Serves a protective function, it
Pain
motivates the person to remove
its cause.
Patient’s with diminished pain
response are at risk .
Diabetic patients have a
decreased pain sensation due to
nerve damage. They are unable to
feel pain in lower extremities.
They require meticulous foot care.
Referred Pain
Referred Pain-when pain
feels as if it is coming
from an area other than
the site where it
originates.
Ex. Heart pain radiates
down arm.
Analgesics-drugs to
relieve pain.
Three pain triggers:
Pain Triggers
(1) Tissue injury promotes the
release of certain chemicals that
stimulate pain receptors.
(2) A deficiency of oxygen
stimulates pain receptors.
(3) Pain may be experienced
when tissues are stretched or
deformed.
Mechanoreceptors
Touch receptors or tactile
receptors are found mostly
in the skin.
They allow us to feel.
Particularly numerous in
the lips, fingers, toes,
tongue, and external
genitalia.
Located in the skin,
subcutaneous tissue, and
deep tissue.
Thermoreceptors
Two types of thermoreceptors
are heat and cold.
Found in free nerve endings,
and specialized sensory cells
beneath the skin.
Cold receptors are stimulated
between 50 and 76 degrees F
and heat receptors are
stimulated between 76 and
112 degrees F.
Proprioception
Sense of orientation or
position.
Allows you to locate your
body part without
looking at it.
Plays an important role
in maintaining posture
and coordinating body
movement.
Proprioception
The receptors for
proprioception are located
in muscles, tendons, and
joints.
Proprioceptors are also
found in the inner ear,
where they function in
equilibrium.
The cerebellum receives
sensory information from
these receptors.
Sense of Smell
Olfaction-sense of smell,
associated with the
sensory structures
located in the upper
nose.
Classified as
chemoreceptors,
stimulated by chemicals
that dissolve in the
moisture of the nasal
tissue.
Sense of Smell
The olfactory receptors
are stimulated , the
sensory impulses travel
along the olfactory nerve
(CN I).
The sensory information
is eventually interpreted
as smell within the
olfactory area of the
temporal lobe.
Sense of Taste
The sense of taste is also
called the gustatory
sense or gustation.
The taste buds are the
special organs of taste.
Taste receptors are
located in the tongue and
are classified as
chemoreceptors.
Sense of Taste
Four basic taste
sensations:
Sweet-tip of the tongue.
Salty-near the tip of the
tongue.
Sour-located in the middle
of the tongue.
Bitter-back of the tongue.
Sense of Sight
Vision is one of the most
cherished senses.
The eyes are the organs
of vision.
Visual accessory organs
assist with function and
protecting the eye from
injury.
Visual Accessory Organs
Visual accessory
organs include the:
Eyebrows
Eyelids
Conjunctiva
Eyelashes
Lacrimal apparatus
Extrinsic eye muscles
Visual Accessory Organs
The eyebrows:
Patches of hair located
above the eyes.
Perform a protective
role.
Keep perspiration out of
eyes and shade eyes from
glaring sunlight.
Participate in facial
expression as in the
“raised eyebrow look”.
Visual Accessory Organs
Eyelids:
Also called palpebrae.
Protect the eyes.
Prevent the entrance of
foreign objects.
Wash tears over the
surface of the eye.
The medial inner canthus
and the lateral outer
canthus are the corners of
the eye where the upper
and lower eyelids meet.
Visual Accessory Organs
Skeletal muscle opens
and closes the eyelids.
The muscle that opens
the eyelid is called the
levator palpebrae
superioris,
(levator means to raise,
like an elevator).
The muscle that closes
the eyelid is the
obicularis oculi.
Visual Accessory Organs
Conjunctiva-thin mucous
membrane that lines the
inner surface of the
eyelid.
The conjunctiva also
folds back to cover a
portion of the sclera
(discussed later) on the
anterior surface of the
eyeball and is called the
white of the eye.
Visual Accessory Organs
The conjunctiva secretes
a substance that
moistens the surface of
the eye.
The anterior surface of
the eye must be kept
moist or it will ulcerate
and scar.
The conjunctiva is very
vascular.
Visual Accessory Organs
The “Bloodshot”
appearance of the eyes is
caused when the blood
vessels dilate.
Eye drops that get the
red out, cause the blood
vessels of the conjunctiva
to constrict.
Conjunctivitis-”pink eye”
inflammation of the
conjunctiva caused by a
bacterial infection.
Visual Accessory Organs
Eyelashes:
Line the edges of the
eyelid and help to trap
dust.
Touching the eyelash
stimulates blinking.
Sty or hordeolum -
infection of the hair
follicle caused by staph.
Visual Accessory Organs
Lacrimal Apparatus:
Composed of the lacrimal
gland and a series of
ducts called tear ducts.
The lacrimal gland is
located in the upper
lateral part of the orbit
and secretes tears which
flow across the surface
toward the nose.
Visual Accessory Organs
Tears drain through
small openings called
lacrimal puncta and then
into the lacrimal sac and
nasolacrimal ducts.
The nasolacrimal ducts
eventually empty into the
nasal cavity.
Visual Accessory Organs
Normal tears flow to the back
of the throat and are
swallowed.
Increase in tears, as in crying,
nose begins to run.
Tears perform several
functions, moisten, lubricate
and cleanse the surface of the
eye.
Tears contain losozyme which
helps destroy pathogens and
prevent infection
The Eyeball
Has a spherical shape and
is approximately ¾ to 1
inch in diameter.
Most of the eyeball sits
within the bony orbital
cavity of the skull,
partially surrounded by a
layer of orbital fat.
Composed of three layers:
sclera, choroid, and the
retina.
The Sclera
The outermost layer.
Made up of tough, fibrous,
connective tissue that
covers most of the eyeball.
Helps contain the
contents of the eye.
Shapes the eye and is the
site of attachment for
extrinsic muscles.
The Cornea
Cornea-transparent
extension of the sclera.
Covers the area over the
iris.
Cornea is avascular and
transparent, light rays can
go through this structure.
Called the window of the
eye
The Cornea
The cornea has a rich
supply of nerve fibers ,
sensitive to touch.
Corneal reflex-protective
function, if the surface of
the cornea is touched
lightly, causes blinking.
The Choroid
The Choroid is the middle
layer of the eye located
between the retina and the
sclera.
Highly vascular.
Attached to the innermost
layer of the retina.
Extends toward the front of
the eyeball to form the ciliary
body.
The Choroid
The ciliary body secretes
a fluid called the aqueous
humor.
Gives rise to the ciliary
muscles.
Iris-most anterior
portion of the choroid,
the colored portion of the
eye.
The Pupil
Pupil-opening or hole in
the middle of the iris.
Pupil size is regulated by
two sets of intrinsic
muscles located in the
iris.
Iris regulates the amount
of light entering the eye.
The Retina
Innermost layer of the
eyeball.
Nervous layer containing
visual receptors which
are sensitive to light,
called photoreceptors.
Two types of
photoreceptors are rods
and cones.
The Retina
Rods, scattered
throughout but most
abundant along
periphery.
Cones, most abundant in
the central portion of the
retina.
Fovea centralis area that
contains the highest
concentration of cones.
The Retina
The Optic Nerve forms
where the neurons of the
retina converge in a small
circular area in the back of
the eye called the optic disc.
Because there are no
photoreceptors there,
images formed there are not
seen by the brain. This area
is called the “Blind Spot”
The Eye
Cavities of the Eye
Anterior Cavity
Posterior Cavity
Located between the
Larger and located
Lens and Cornea
Filled with Aqueous
Humor
Aqueous Humor helps
maintain shape of
anterior eye and
nourishes the cornea
between the Lens and
Retina
Filled with Vitreous
Humor
Vitreous Humor pushes
on the retina creating
good contact with the
Choroid ensuring a rich
supply of oxygenated
blood
Eye Muscles
Extrinsic eye muscles:
Skeletal muscles.
Located outside the eye.
Move the eyeball in
various directions.
Eyes move together in a
coordinated way.
Seeing
Light waves enter your
eye, are refracted and
focused on the
photoreceptors of the
retina.
Photoreceptors of the
retina translate light
impulses, to a nerve
impulse, which is then
transmitted from the
retina, along the optic
nerve to the occipital lobe
of the brain.
Muscles of the Eye
Strabismus:
Also called cross-eyed.
Eyeballs are not
aligned, do not focus
on a desired point.
Muscles of the Iris
Iris contains two muscles:
Radial muscle
Circular muscle
Contraction of the radial
muscle causes the pupil to
dilate.
Contraction of the circular
muscle causes pupil to
constrict.
Mydriasis-sympathetic nerve
Mydriasis
stimulation that causes pupillary
dilation.
Mydriatic agents-drugs that cause
the pupils to dilate.
The Eye
Night vision
Rods respond to dim
light.
Provide us with black
and white vision.
Deficiency of vitamin A
can cause night
blindness.
Day vision
Image produced by the
stimulation of cones.
Three types of cones that
produce different colors,
green, blue and red.
Stimulation of
combinations of these
colors produces different
colors.
The Eye
Seeing
Not seeing
Light waves enter your
Defect along the
eye.
Photoreceptors translate
light signal to nerve
impulses and then
transmitted from retina,
along optic nerve to
occipital lobe.
pathway from the
cornea to the brain can
interfere with vision.
Ex. Scarred cornea or
cloudy lens may block
light.
Conditions of the Eye
Glaucoma-increased
intraocular pressure may
squeeze the blood vessels
of the choroid, depriving
the retina of adequate
blood supply.
Can lead to blindness.
Conditions of the Eye
Detached retina-retina
falls away from the
choroid and it’s blood
supply.
Macular Degeneration
Abilities of the Eye
Accommodation- the ability of the lens to change
shape in order to focus on close objects
Presbyopia- the inability of the lens to change shape
in order to focus on close objects
Convergence- movement of the eye medially (toward
the nose) to stay focused on an object
Photopupillary Reflex- When the pupil of the eye
changes size to either limit or increase the amount of
light entering the eye
Refraction- the bending of light rays
Consensually- what one pupil does…so does the other
Conditions of the Eye
Diabetic retinopathy-
damage of the retinal
blood vessels of diabetic
patients.
Vessels may develop
micro aneurysms which
rupture and cause
bleeding and scar
formation throughout
the retina.
The Ear
Ear is divided into three
parts:
(1) external ear
(2)middle ear
(3)inner ear
External Ear
Part of the ear you can
see.
Composed of the auricle
and the external auditory
canal.
Auricle or pinna-
composed of cartilage
covered by a layer of
loose fitting skin.
The Ear
Auricle opens into the
external auditory canal.
Canal provides a
passageway for sound
waves to enter the ear.
External auditory is
hollowed out of the
temporal bone.
The Ear
External auditory canal
is about 1 inch long and
½ inch wide and extends
to the eardrum
(tympanic membrane).
Tympanic membrane
separates the external
ear from the middle ear.
The Ear
External auditory ear
canal is lined with tiny
hairs and glands that
secrete cerumen.
Hairs help prevent dust
and foreign objects from
entering the ear.
Objects inserted to
remove cerumen may
damage the tympanic
membrane.
Middle Ear
Small air-filled chamber
located between the
tympanic membrane at
one end and a bony wall
at the other end.
Contains:
Tympanic membrane
Three tiny bones
The eustachian tube
Middle Ear
Tympanic membrane is
composed of connective
tissue and has a rich
supply of nerves and
blood vessels.
Tympanic membrane
vibrates in response to
sound waves that enter
the ear through the
external auditory canal.
Vibration is passed on to
tiny bones.
Middle Ear
Middle ear contains the
three tiniest bones in the
body:
(1)malleus (hammer)
(2)Incus (anvil)
(3)Stapes (stirrup)
The Ear
If pressure becomes
unequal, tympanic
membrane bulges.
Membrane streches
causing pain. Ex. Pain
and pressure in an
airplane.
Inner Ear
Consists of an intricate
system of tubes hollowed
out of the temporal bone
called the bony labyrinth.
Inner ear has three parts:
(1) vestibule
(2) semicircular canals
(3) cochlea
Inner Ear
Cochlea-snail shaped
part of the bony
labyrinth.
Inside the cochlea are the
receptors for hearing,
they are tiny cells that
contain tiny hairs and
are called the organ of
corti.
Hearing
Hearing:
Sound waves travel
through the external
auditory canal and hit
the tympanic membrane.
Vibration causes malleus,
incus and stapes to
vibrate.
Stapes causes the fluid in
the inner ear to move.
This causes the hairs to
bend.
Hearing
The bending of the hairs
triggers the nerve
impulse carried by the
cochlear branch of the
vestibulocochlear nerve,
(CN VIII) to the brain.
Temporal lobe of the
cerebrum interprets the
impulse as sound.
Equilibrium
Receptors for balance are
mechanoreceptors.
Vestibule contains the
receptors that provide
information about the
position of the head at
rest.
Semicircular canalas
provide information
about the position of the
body as it moves.
Equilibrium
Receptors sense
changing positions of the
head.
When position changes
the hairs are bent.
Receptor cells send
nerve impulses to the
brain.
Brain sends the signal to
restore balance.