Sense Organs 04/02/13

1. Sense Organs
Mr. Hunter
04-01-13
Kennedy High School

2. Anatomy and Physiology
04/04/2013
• Objective(s)
• SWBAT
• Compare and Contrast general and specialized sense organs
• Describe the structure and functions of various parts of the
eye?
• Bell Ringer: What causes an optic disc (blind spot) to occur?
Pg. 212 text.

3. • Besides the eyes, ears, nose and
Sense Organs taste buds, millions of other sense
organs are located throughout the
body in our skin, internal organs and
muscles.
• Many receptors allow us to respond
to internal and external stimuli. The
receptors are located on the tips of
dendrites of sensory neurons.
• Our ability to sense changes in our
environment is a requirement for
maintaining homeostasis.

4. • General sense organs are
Classification microscopic receptors widely
distributed throughout the body in
the skin, muscle, tendons joints and
other internal organs.
• They are responsible for
pain, temperature, touch and
pressure.
• Special sense organs such as those
responsible for
smell, taste, vision, hearing and
equilibrium are grouped into
localized areas.
• Classification of individual receptor
cells can be (1) encapsulated or
unencapsulated and (2) types of
stimuli that activate them.
• All sense organs must be able to
detect changes in the environment.

5. • Various receptors are found and they
General Sense Organs do not all respond to the same type
of stimulus.
• Mechanoreceptors – activated by
mechanical stimuli that distort or
change the position of the receptors.
• Ex. Lamellar (Pacini) corpuscle
senses deep pressure.
• Free nerve endings associated with
light touch:
a. Hair root plexus – basketlike nerve
endings that encircle hair follicles.
b. Merkel disks – attached to nerve
endings of the epidermis.

6. • Proprioceptors – near junction
General Sense Organs between tendons and muscles.
• They provide information about the
position or movement of different
parts of the body as well as the
length and extent of contraction
along with muscle tension. Ex. Golgi
tendon organs.

7. Review 04/02/2013 Anatomy and Physiology
1. What two classes of stimuli does our sense organs allow us to respond
to?
2. Where are sensory receptors located?
3. Where are general sense organs located?
4. What is a requirement for maintaining homeostasis?
5. What types of sensory information are general sense organs
responsible for?
6. What type of sensory information are specialized sense organs
responsible for?
7. What are the two classifications of individual receptor cells?
8. How are mechanoreceptors activated?
9. Describe two free nerve endings associated with light touch.
10. What are the functions of proprioceptors?

8. • When you view a person’s eye, you
The Eye are only able to see a small portion
of the whole eye.
• Three layers of tissue form the
eyeball.
• A. sclera
• B. choroid
• C. retina
• The outer portion of the sclera
consists of tough fibrous connective
tissue.
• The “white” of the eye is part of the
front surface of the sclera.
• The other part of the front surface is
called the cornea.

9. • The cornea lacks blood and lymph
The Eye vessels which contributes to its
transparency.
• Inflammation of the cornea is called
keratitis.
• The cornea, at first glance, does not
appear to be transparent because it
lies over the colored, muscular
portion of the eye, the irs.
• The conjunctiva is a mucous
membrane that lines the eyelid and
covers the sclera in front.
Inflammation of the conjunctiva is
called conjunctivitis.

10. • The middle layer of the eyeball is the
The Eye choroid. It contains a dark pigment
to prevent scattering of light rays.
• Two involuntary muscles make up
the front part of the choroid.
• A. Iris
• B. Ciliary muscle
• The black center of the iris is called
the pupil. It is a hole in the
doughnut-shaped muscular iris.
• When certain fibers of the iris
contract , the pupils will
dialate, allowing more light to enter.
• Other fibers contract, letting fewer
light rays enter.

11. • The lens of the eye is directly behind
The Eye the pupil. It is held in place by a
ligament attached to the ciliary
muscle.
• When we look at distant objects, the
ciliary muscle is relaxed, and the lens
has only a slight curved shape.
• To focus on near objects, the ciliary
muscle must contract.
• As it contracts, it pulls the choroid
coat towards the lens, causing the
lens to bulge and curve to bring the
object into focus.
• Presbtopia is a condition where the
lens lose some of their elasticity and
cannot bulge to focus objects.

12. • When over exposure to UV radiation
occurs, the lens of the eye can be
The Eye
hard and lose its transparency. The
result is a milky film that
permanently covers the lens.
• This condition is known as cataracts.
• It can occur in one or both eyes.
• It tends to be progressive and could
eventually lead to blindness.
• The retina is the innermost layer of
the eye. It contains photoreceptor
cells called rods and cones.
• Dim light can stimulate the rods and
bright light can stimulate the cones.
• There are three kinds of cones
sensitive to red, blue or green light

13. • Yellowish area near the center of the retina
is called the macula lutea.
The Eye
• It surrounds a small depression called the
fovea centralis. This location contains the
greatest concentration of cones of any area
of the retina.
• Fluids fill the hollow inside of the eyeball.
They maintain the normal shape of the
eyeball and help to refract light rays – they
bend light rays and help them to focus on
the retina.
• Aqueous humor is the fluid in the anterior
chamber.
• This fluid is drained and replaced constantly.
If there is a build up of this fluid pressure,
glaucoma can occur.
• Vitreous humor is the jelly-like fluid located
in the posterior chamber behind the lens.

14. • Light enters the pupil and is refracted
The Eye so that it is focused on the retina.
• The rods and cones respond to a light
stimulus by producing a nerve impulse.
• Nerve signals leave the eye via the
optic nerve located on the posterior
surface of the eyeball. No rods or cones
are located in this area where the optic
nerve exits. This is the blind spot
known as the optic disc.
• The optic nerve exits and enters the
occipital lobe in the visual cortex.

15. • In addition to the function of
The Ear hearing, the ear also helps to
maintain equilibrium and balance.
• Physical forces that involve sound
vibrations and fluid movements are
responsible for initiating nerve
impulses eventually perceived as
sound as balance.
• The ear is divided into anatomical
areas.
• External Ear
• Middle Ear
• Inner Ear (internal ear)

16. • The external ear has two parts:
The Ear
• Auricle (pinna)
• External auditory canal
• The auricle is the appendage on the
side of the head surrounding the
external auditory canal.
• The canal is a curved tube,
approximately 1 inch in length. It
extends into the temporal bone and
ends at the tympanic membrane
(eardrum) – partition between
external and middle ear.

17. • The outer third of the skin of the
The Ear auditory canal contains numerous
short hairs and ceruminous glands.
• These glands produce a waxy
substance called cerumen that may
collect in the canal and impair
hearing by absorbing or blocking the
passage of sound waves.
• Normally sound waves travel
through the external auditory canal
and strike the tympanic membrane
causing it to vibrate.

18. • The middle ear is a tiny, thin epithelium
lined cavity hollowed out of the temporal
The Ear
bone.
• It contains three very small bones called
ossicles.
• Malleus
• Incus
• Stapes
• The oval window separates
• the middle ear from the inner ear.
• Movement of the stapes against the oval
window causes movement of fluid in the
inner ear.
• Sound waves cause the eardrum to vibrate,
the movement is transmitted and amplified
by the ossicles.

19. • The eustachian (auditory) tube
The Ear connects the throat with the middle
ear.
• The epithelial lining of the auditory
tubes of the middle ear and the
throat is made of one continuous
membrane.
• A sore throat can spread to produce
a middle ear infection – ottis media.
• The activation of specialized
mechanoreceptors in the inner ear
generates nervous impulses that
result in hearing and equilibrium.

20. Review 04/02/2013
Anatomy and Physiology
1. Name the three layers of tissue that form the eyeball.
2. What two structures are located on the front part of the sclera?
3. What two physiological factors contribute to the cornea being
transparent?
4. What is inflammation of the cornea called?
5. Where is the conjunctiva located and what does it cover?
6. What is inflammation of the conjunctiva called?
7. What is the middle layer of the eyeball called? What does it contain to
prevent the scattering of light rays?
8. Name the two involuntary muscles that make of the front part of the
choroid.
9. What is the name of the center of the iris?
10. What causes the pupil to dilate and constrict?
11. Where is the lens located and what holds it in place?
12. What happens to the lens when we look at near and far objects?