Psych Assignment
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Bill Rustom Cruz January 7, 2011
BSECE
5 SENSES OF THE HUMAN BODY
Sense of Smell –
Smell, one of the five special senses (see Sense Organs) by which odors are
perceived. The nose, equipped with olfactory nerves, is the special organ of smell. The olfactory
nerves also account for differing tastes of substances taken into the mouth, that is, most
sensations that appear introspectively as tastes are really smells.
Sensations of smell are difficult to describe and classify, but useful categorizations have
been made by noting the chemical elements of odorous substances. Research has pointed to the
existence of seven primary odors — camphorlike, musky, floral, peppermintlike, ethereal (dry-
cleaning fluid, for example), pungent (vinegarlike), and putrid — corresponding to the seven types
of smell receptors in the olfactory-cell hairs. Olfactory research also indicates that substances
with similar odors have molecules of similar shape. Recent studies suggest that the shape of anodor-causing chemical molecule determines the nature of the odor of that molecule or substance.
These molecules are believed to combine with specific cells in the nose or with chemicals within
those cells. This process is the first step in a series that continues with the transmission of
impulses by the olfactory nerve and ends with the perception of odor by the brain.
Sense of Hearing - Hearing (sense), one of the five main senses, by which sound waves are
perceived by the organ of hearing — the ear — in vertebrate animals. The process of sound
perception is called audition. The physical stimulus of auditory sensation is the vibration of some
material object. The vibration is transmitted from the object to the ear, under ordinary conditions,
by a wave movement of air particles.
Sense of Touch - one of the five senses (see Sense Organs) in humans and other animals, by
which the body perceives contact with substances. In humans, touch is accomplished by nerve
endings in the skin that convey sensations to the brain via nerve fibers. Nerves end in or between
the cells of the epidermis, the outer layer of the skin, in all parts of the body. In one complex
form of nerve ending, the terminals form tiny swellings, or end bulbs; characteristic of this form
are the Pacinian corpuscles found in the sensitive pad of each finger. Touch is the least
specialized of the senses, but acuteness can be sharpened by use; for example, people who are
blind exhibit a remarkable delicacy of the tactile sense in their ability to read the fine, raised
letters of the Braille system.
Sense of Taste - one of the five special senses (see Sense Organs), in humans and other animals,by which four gustatory qualities (sweetness, sourness, saltiness, and bitterness) of a substance
are distinguished. Taste is determined by receptors, called taste buds, the number and shape of
which may vary greatly between one person and another. In general, women have more taste
buds than men. A greater number of taste buds appears to endow a greater sensitivity to
sweetness, sourness, saltiness, and bitterness. In humans, the taste buds are located on the surface
and sides of the tongue, the roof of the mouth, and the entrance to the pharynx. The mucous
membrane lining these areas is invested with tiny projections of papillae, each of which in turn is
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invested with 200 to 300 taste buds. The papillae located at the back of the tongue, and called
circumvallate, are arranged to form a V with the angle pointing backward; they transmit the
sensation of bitterness. Those at the tip of the tongue transmit sweetness, whereas saltiness and
sourness are transmitted from the papillae on the sides of the tongue. Each flask-shaped taste bud
contains an opening at its base through which nerve fibers enter. These fibers transmit impulses
directly to the brain. In order for a substance to stimulate these impulses, however, it must be in
solution, moistened by the salivary glands. Sensations of taste have been determined to be
strongly interrelated with sensations of smell.
Sense of Sight - Vision, ability to see the features of objects we look at, such as color, shape,
size, details, depth, and contrast. Vision is achieved when the eyes and brain work together to
form pictures of the world around us. Vision begins with light rays bouncing off the surface of
objects. These reflected light rays enter the eye and are transformed into electrical signals.
Millions of signals per second leave the eye via the optic nerve and travel to the visual area of
the brain. Brain cells then decode the signals into images, providing us with sight.
Almost all animals respond to light. The one-celled amoeba responds to light by turning in its
direction. Bees have complicated eyes that contain many lenses for sensing colors and shapes of
flowers. However, it is the vertebrates (animals with backbones) that have eyes and a brain that
work together to process light into true images. Human vision is particularly unique in that the
human brain can process visual images and use them to create language and pictures and to store
information for future use.
The eyes of many vertebrates are specialized for certain situations. Bats see best at night. Birds
of prey, such as hawks and eagles, are able to see extremely small details, such as tiny rodents
viewed from high in the air.