This document discusses sensory receptors and how they function during the Christmas holiday season. It provides examples of how sensory receptors detect stimuli like hunger cues from cookies left out for Santa, different moods conveyed through Christmas versus Halloween songs, and sensations like pain experienced by characters in Christmas movies. The document then explores the anatomy and physiology of various sensory receptors, including their location, structure, and role in senses like smell, taste, hearing, vision, balance and proprioception.

1. Does that Make Sense?

2. Why do we leave cookies out for Santa? The
answer is that he feels hungry after traveling the
world and through the chimney. He senses this
hunger with his sensory receptors.
Why are Christmas songs different than
Halloween songs? The music sets a tone that
affects the way people feel. Without hearing it
would be hard to understand the different moods.
These are just a few examples of how sensory receptors are used
during the Christmas holiday. Let’s explore what they are and what
else they do.

3. Sensory receptors-
•· Include our “special senses
(vision, hearing, balance, taste, and smell)” (2).
•· Have receptor potential which is what causes a
reflex (2). It is like a tea pot that heats and once it hits a
certain point causes the whistling sound. Once the potential
is at its climax, it causes the body to react.
•· Allows the brain to interpret sensations with the
special senses (registering heat, cold) (2).
•· Receptors adapt after a period of time. An example
from Anthony’s Textbook of Anatomy and Physiology 17th
Edition is how when a person first puts on clothes he can
feel the material but after a while does not sense it at all.

4. Distribution
•· Receptors are not distributed equally throughout
the body.
•· Receptors in the general source organs produce
somatic senses (2).
•· The two-point discrimination test proves that
there are more receptors in some areas of the body than
others (receptors in finger tips > receptors of skin on
the back) (2).

5. Location
1.Exteroceptors
•· Superficial or near the surface.
•· React to stimuli from outside of the body (2).
Examples: receptors that sense the heat from picking up
a hot cookie sheet, the cold from licking an ice sickle, a
paper cut from opening a holiday card, and the pressure
from the inside a plane during take-off or landing while
visiting family.
 (18 ©)

6. 4.Visceroceptors
•· Internal and “within body organs” (2).
•· Internal stimuli cause a reaction (2).
Examples: receptors that sense the craving of
gingerbread men, wanting eggnog, and realizing you
can’t eat anymore cookies or drink anymore apple
cider.
 3. Proprioceptors
•· Are a type of visceroceptors.
•· Located in “skeletal muscle, joint capsules,
and tendons” (2).
•· Identify body movement.
Examples: Help us to realize when we walk, when we
raise our hands, sit still, and stand tall.

7. Stimulus Detected
1.Mechanoreceptors
•· Activate or start the receptor potential (2).
•· Caused by a change of location of receptor (2).
Examples: While exercising our muscles and skin are being stretched
and causes a shift in the receptors positions.
2. Chemoreceptors
•· Depends on chemical concentration (2).
 Examples: The differences between certain smells and tastes. It is
a reaction of the different chemical make-up of what is being smelt
and tasted (vegetables vs. candy).
 (19 ©).

8. 3. Thermoreceptors
•· “Activated by change in temperature” (2).
Examples: Why we wear jackets in the winter and shorts in the
summer, and why Santa has long sleeves, long pants, snow
boots, and a hat. His cheeks are always rosy because the
winds in the air whip against his cheeks as he flies over
neighborhoods.
4. Nociceptors
•· Senses pain (2).
Examples: What Tim Allen experienced after falling of the roof
trying to tie up Frosty in Christmas with the Kranks.
5. Photoreceptors
•· “Found only in the eye” (2).
•· “Responds to light” (2).
Examples: When your eyes adjust on Christmas morning after
being in the dark to waking up in the bright early morning.

9. Structure
 Free nerve ending: Simplest, most common, and most
widely distributed sensory receptors. Located both on the
surface of the body and in the deep visceral organs. (1)
 (12 ©)
 Root hair plexuses: Delicate, web-like arrangements of
free nerve endings that surround hair follicles and detect
variations of free nerve endings called merkel discs. (1)
 (13 ©)

10.  Merkel discs: Responsible for mediating sensations of light
or discriminative touch. Delicate mechanoreceptors that
are more easily “deformed” than pacinian corpuscles and
thus are capable of generating an action potential when
exposed to minimal stimulation. (1)
 (14 ©)
 Meissner Corpuscle: Numerous in hairless skin areas, such
as nipples, fingertips and lips. These structures are large
and superficially placed ovoid or egg shaped
mechanoreceptors. (1)
 (15 ©)

11.  Pacinian Corpuscles: Large mechanoreceptors
that show thick laminated connective tissue
capsules. Found in the deep dermis of the
skin, mainly in the hands and feet. Respond
quickly to sensations of deep pressure, high
frequency, and stretch. They are sensitive and
quick to respond, adapt quickly, and the
sensations they evoke seldom last long. (1)
 (16 ©)
 Muscle Spindles: Consist of a discrete grouping
of about 5 to 10 modified muscle fibers called
intrafusal fibers. Found lying between and
parallel to the regular muscle fibers. Both ends
of spindle are connected or anchored to
connective tissue elements within the muscle
mass. (1)
 (17 ©)
 Golgi tendon Organs: Operate to provide the
body with information concerning muscle length
and the strength of muscle contraction. (1)
 (18 ©)

12. Smell
 The olfactory receptors are embedded in a specialized (20 ©) patch
of yellow-tinted mucous membrane in the roof of the nasal cavity. The
olfactory receptor neurons are chemoreceptors. Receptor potentials
are generated in olfactory receptor neurons when gas molecules or
chemicals are dissolved in mucus covering the nasal epithelium.
 The Olfactory Pathways; the Olfactory Bulb, the Olfactory Tract,
Olfactory Recess, and the Nasal cavity are a few of the Olfactory
Pathways. These pathways basically are the ways that help you
breathe in and out of our nose (2).

13. Taste
 Taste Buds are the sense organs that respond to
gustatory, or taste, stimuli. They are located in the lining
of the mouth and on the soft palate, most are on the
small elevated projections of the tongue called papillae.
As chemoreceptors, the taste buds, like olfactory
receptors, tend to be quite sensitive but fatigue easily.
 Neural Pathway connects one part of the nervous system
with another and usually consists of bundles of
elongated, myelin-insulated neurons. Neural pathways
serve to connect relatively distant areas of the brain or
nervous system. Nervous impulses generated in the
anterior two thirds of the tongue travel over the facial
nerve (2).

14. Hearing
 The Pressure Wave:
 The sound waves we hear travel through air just like the waves
travel through the slinky. The above illustration shows the relative
conformations of air molecules as they transmit a sound wave
downward. Soud travels through the air and along the outer and
middle ear as a series of compressions (crests) and rarefractions
(troughs) of air molecules. These patterns of molecules stimulate
parts of the ear as described below to create the perception of
sound.
 How the Ear Perceives Sound:
 The audirory canal (a.k.a. the outer auditory meatus) brings what
you hear from the outside of the ear to the middle ear. At the end
of the auditory canal, there is a thin layer of skin called the
tympanic membrane (more commonly called the ear drum). The
waves of sound hit the ear drum, and get further transferred onto
the three small bones in the middle ear collectively known as the
auditory ossicles: incus (anvil), stapes (stirrup), and malleus
(hammer).

15.  These structures act as a chain, which lead through an
opening in the bone between the middle and the inner ears.
The middle ear is filled with air, and the inner ear is filled
with fluid, so this opening is covered by a thin membrane to
keep them separate. This membrane allows the sound waves
to be transmitted into the inner ear, and finally to a bundle of
30,000 nerve fibers each representing a different frequency.
Noise is filtered out of this signal and the brain interprets the
signal.
 The brain’s interpretation of sound gives it an added
property: pitch. This is basically how the brain interprets the
frequency. The higher the frequency, the higer the pitch.
Since frequency is the inverse of the period, the longer the
wavelength, the lower the pitch. The amplitude of the wave
translates into how loud the brain takes the sound to be.
 Wave addition contributes to the rich complex sounds the we
hear each day. A voice is just the addition of many simpler
waves to give a unique sound. If two waves are added
together, and they happen to have the same amplitude, the
compressions of one are in the same position as the
rarefractions of the other (and vice versa) the end result is
no sound. This is how your noise cancelling headphones
work. They take in sounds from the outside, and emit a wave
that has just the right properties to cancel them out.

16. Inner Ear
(20 ©)
Middle Ear
(20 ©)
(20 ©)

17. (21 ©)
Balance:
• Proprioception — from Latin proprius, meaning "one's
own," and perception — is one of the human senses.
There are between nine and 21 in all, depending on
which sense researcher you ask. Rather than sensing
external reality, proprioception is the sense of the
orientation of one's limbs in space. This is distinct
from the sense of balance, which derives from the
fluids in the inner ear, and is called equilibrioception.
Proprioception is what police officers test when they
pull someone over and suspect drunkenness. Without
proprioception, we'd need to consciously watch our
feet to make sure that we stay upright while walking.
(21)

18. • Proprioception doesn't come from any specific organ, but
from the nervous system as a whole. Its input comes
from sensory receptors distinct from tactile receptors —
nerves from inside the body rather than on the surface.
Proprioceptive ability can be trained, as can any motor
activity. (21)
 Without proprioception, drivers would be unable to keep
their eyes on the road while driving, as they would need
to pay attention to the position of their arms and legs
while working the pedals and steering wheel. And I
would not be able to type this article without staring at
the keys. If you happen to be snacking while reading
this article, you would be unable to put food into your
mouth without taking breaks to judge the position and
orientation of your hands. (21)

19. VISION: THE EYE
 The eye is the body’s sensory organ for vision. This
organ converts the energy of light into electrical nerve
impulses that are interpreted by the brain.
Approximately five sixths of the eyeball is hidden in the
socket. There are three layers of tissue in the eye. The
three layers of tissue are the sclera, the choroid, and the
retina (2).
 The anterior layer of the sclera is called the cornea and
lies over the iris, the colored part of the eye. The
middle or choroid part of the eye contains many blood
vessels and large amounts of pigment. The iris or the
colored part of the eye, consists of circular and radial
smooth muscle fibers arranged to form a doughnut
shaped structure. The hole in the middle is called the
pupil. The iris attaches to the ciliary body (2).

20.  The retina is the innermost coat of the eyeball. Three
layers of neurons make up the major portion of the
retina; the photoreceptor, bipolar neurons, and ganglion
neurons. Rods and cones are our visual receptors (2).
(16 ©)

21. Process of seeing
Formation of retinal Image
 Refraction of light rays
 Accommodation of lens
 Constriction of pupil
 Convergence of eyes

22. Role of Photopigments
 Rods- photopigment in rods is rhodopsin; highly light
sensitive; breaks down into opsin and retinal; separation
of opsin and retinal in the presence of light causes an
action potential in rod cells; energy is needed to reform
rhodopsin retina
 Cones- three types of cones are present in the retina,
with each having a different photopigment; cone
pigments are less light sensitive than rhodophsin and
need brighter light to breakdown

23. Questions
 Deer can’t see color so wearing bright orange vests don’t
scare them off. It keeps other hunters from shooting
people with those vests instead of mistaking their
movements as an animal.
 Nearsighted means you cant see very good far and
farsighted means you cant see very well near.