Untitled Flashcards Set

Sensory Perception
4-7
II. CHEMORECEPTION
A. OLFACTION
Olfaction (the sense of smell) is the detection of chemical particles carried in the air, often from objects
at a distance, and the “sorting out” of these sensations into a variety of categories. Molecules pass into the
nose in the region of the olfactory mucosa, in the upper part of the nasal cavity. Receptor sites are
contained in neurons whose axons extend to the brain as the olfactory nerve. Olfactory discrimination
varies with attentiveness, state of the mucosa (congested or clear), hunger (hungry individuals show more
sensitivity), sex (in general, women have keener sensitivity), and smoking (decreases sensitivity).
Knowledge of odors is aided by the stimulation of other receptors (especially sight and taste). In this way
we can describe odors as pungent, acrid, cool, or irritating. The exercises in this section will demonstrate
habituation, detection of odor intensity, and odor recognition.
PROCEDURE:
Olfactory Habituation – When you are exposed to an odor for a prolonged period of time, your ability
to detect it decreases. On your table find a small vial of cinnamon oil. Open the vial and, with one nostril
blocked, inhale the odor from the vial (hold the vial approximately 15cm from your nose). Continue to
hold the vial near the nose and breathe normally. At some point you will no longer be “aware” of this
odor.
1. How long does this take? __________ min.
2. Allow a minute or two for recuperation and repeat the test.
3. Answer the following questions.
a. Has the power to detect this odor returned?
b. For the second trial, did it require the same amount of time for the sense of smell to
become fatigued as it did the first time? If not, explain why.
Recognition and Identification of Odors - Note the set of numbered vials on your table. Each vial
contains a different sample. It is best to do only two or three at a time and give your nose a rest.
1. Take a quick sniff of each vial and record what you think the odor is in the column marked “Trial
1” in Table 4-1. If you cannot recognize the odor, leave the space blank.
2. Once you have completed this, obtain a copy of the “Odor Selection List” from your instructor.
Again, sniff the contents of each vial and use the list to help you identify the odors. Record your
responses in the column “Trial 2.” Once everyone is done, your instructor will review the answers.
You can put a check mark next to the responses you correctly identified.

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Table 4-1. Odor Recognition Test Results
Sample # Trial 1: Odor Identification Trial 2: Odor Identification
• How did having a list affect your ability to correctly identify the odors?
B. GUSTATION (TASTE)
The sense of taste in humans results from special chemoreceptors in the mouth and pharynx, called taste
buds; there are over 10,000 taste buds, most of which are on the tongue. Each taste bud is a barrel-shaped
structure composed of columnar epithelial cells. Some of the cells give support while others act as
chemical receptors. Besides sensing texture, temperature, and pain, taste buds respond to four basic taste
properties; sweet, salty, sour, and bitter. Each taste bud is most sensitive to one of these. The more
sensitive the receptor is to a particular taste, the more rapidly the nerve fires, sending this information to
the brain for processing. Taste buds are typically grouped to specific regions of the tongue and these can
be mapped. And, as you will see in this exercise, the senses of taste and smell are linked.
PROCEDURE: (this experiment will be done in the hallway)
1. Work with your lab partner. Both students will select one lollipop each. Don’t let your partner
see the lollipop.
2. Close your eyes and pinch your nose shut (breathe through your mouth). Your partner will hand
you the lollipop. Once you put the lollipop in your mouth you can open your eyes but keep your
nose pinched closed.
3. While keeping your nose closed, can you detect the sweetness from the sugar? _________ Can
you tell what flavor the lollipop is? ___________ If you are doing things correctly, you should
not be able to identify the flavor. Recall how when you have a cold or head congestion you cannot
taste things very well. Our reliance on the sense of smell is quite important when it comes to taste.
4. Un-pinch your nose. Can you identify the flavor now? ____________.
5. What other senses help you to determine the flavor of the lollipop?

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III. MECHANORECEPTION
A. EAR ANATOMY
Examine the structure of the human ear in Figure 4-5 as well as the models available in lab. The ear is
divided into three regions; the outer, middle, and inner ear. The outer ear consists of the pinna and the
external auditory canal (also called the external acoustic meatus), which ends at the eardrum. After
swimming, water in the external canal gives the sensation of “water in the ear.” A build up of earwax will
also interfere with the transmission of sound to the eardrum (tympanic membrane).
The middle ear consists of the region between the eardrum and the oval window of the cochlea. It is
comprised of three tiny ear bones called the malleus (hammer), incus (anvil), and stapes (stirrup). The
middle ear is connected to the pharynx by the Eustachian tube. It functions to equalize pressure on both
sides of the eardrum. Respiratory infections can sometimes travel from the throat to the middle ear, via
this tube, and result in painful inflammation and infection.
The inner ear consists of the cochlea and semicircular canals. The cochlea contains the organ of Corti,
which is the actual organ of hearing. Within the cochlea are three connected, fluid-filled canals; the
cochlear canal (adjacent to the organ of Corti), the vestibular canal (which connects to the oval window),
and the tympanic canal (which connects to the round window). The semicircular canals of the inner ear
are responsible for the sense of equilibrium, or maintenance of balance. Locate these structures in Figure
4-5 and on the ear model in lab.
Figure 4-5. Anatomy of the Human ear
Sound waves are channeled by the pinna into the external auditory canal. The waves then strike the
tympanic membrane (ear drum) and set up a series of vibrations, which are in turn transmitted to the ear
bones (hammer, anvil, and stirrup) and amplified over ten times. The stirrup rests over the oval window
of the cochlea where the vibrations are transmitted through the vestibular canal to the tympanic canal.
Along the way the receptors (tiny hair cells of the organ of Corti) are stimulated. The round window
moves outward to alleviate the pressure created by the movement of the oval window. The movement of
the hair cells stimulates nerve impulses, which are then transmitted to the auditory nerve, which carries
the signal to the brain for processing. Your TA will demonstrate this with the functional ear model. In
External auditory
canal

Sensory Perception
4-10
addition to the ear model, examine the block containing the individual ear bones. In the space that follows,
trace the pathway of sound conduction from the pinna to the auditory nerve.
Write the following terms in order:
tympanic membrane oval window incus external auditory canal
malleus auditory nerve pinna stapes cochlea
pinna → ___________________________________ → _____________________________ →
________________________ → _______________________ → ________________________ →
_________________________ → ______________________ → _________________________
Figure 4-6. Pathway of sound in the ear
B. HEARING
A sound wave is made up of a disturbance of air molecules; regions of compression in which air molecules
are close together and the pressure is high, and areas of rarefaction where molecules are farther apart and
the pressure is lower. Individual molecules travel only short distances, but disturbances passed from one
molecule to another can travel many miles. It is by these disturbances (i.e. sound waves) that sound energy
is transmitted. The sound “dies out” only when so much of the original energy has been dissipated that
one sound wave can no longer disturb the surrounding air molecules.
The waves associated with speech and most other common sounds are not simple and regularly spaced,
but are made up of many frequencies of vibration. The frequency of vibration of a sound source is
perceived as its pitch. The faster the vibration frequency, the higher the pitch; the units are hertz (Hz).

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The entire range of frequencies for humans extends from 20 to 20,000 cycles per second, or hertz (Hz).
However, the sounds most keenly heard by humans are those from sources vibrating at frequencies
between 1,000 Hz and 4000 Hz. The conversational voice of the average male is approximately 120 Hz
and that of the average female is 250 Hz.
The amplitude of a sound wave is perceived as loudness and is measured in units of decibels (dB). The
threshold is the lowest decibel setting that the subject can hear a selected frequency. Hearing is
considered “normal,” for a given frequency at thresholds up to 25 dB. Threshold readings in the range of
26 - 40 dB suggest mild hearing loss, while threshold readings in the range of 41 - 60 dB indicate serious
hearing loss. One of the most common causes of hearing loss is exposure to loud or continuous noise,
which causes wear and tear to the hairs and nerve cells in the cochlea.
Figure 4-7. Sound waves: frequency and amplitude
C. TOUCH PERCEPTION
While often overlooked, the skin is classified as an organ because it is composed of all four of the main
tissue types (epithelial, connective, muscular, nervous). Skin is part of the integumentary system, which
includes hair, nails, and two specialized glands; sweat and sebaceous. The most obvious function of the
skin is that of protection, however, the skin also aids in body temperature regulation, vitamin D synthesis,
and sensation to touch, pressure, pain, and temperature. Refer to Figure 4-8 for the basic anatomy.

Sensory Perception
4-12
The skin has two main regions, the epidermis and the dermis. Both of these layers rest upon a
subcutaneous layer, called the hypodermis, which joins these two layers to the underlying muscles and
bones. The hypodermis is composed of loose connective tissue, collagen and elastic fibers, adipose tissue,
and macrophages. About one-half of one’s body fat is found in this region. Specialized sensory
structures in the dermis enable us to sense light touch (Meissner’s corpuscles) and deep pressure
(Pacinian corpuscles). Free nerve endings provide sensory input for pain, heat, and cold. Today you will
investigate touch perception by performing a simple test