state. For example, during an emergency the body's
heart and respiration rate increases. After the
emergency, the parasympathetic system will decrease
heart and respiration rate to normal. The sympathetic
and parasympathetic systems counterbalance each
other to preserve a harmonious balance of body
functions and activities.
THE ENDOCRINE SYSTEM
I d e n t i f y
endocrine glands and the hormone(s) they
produce, and determine the effect each
hormone has on the body.
Homeostasis, the self-balancing of the bodys
internal environment, is achieved and maintained by
the endocrine system and the nervous systems. These
systems work alone and together to perform similar
functions in the body: communication, integration,
and control. Their communication capabilities provide
the means for controlling and integrating the many
different functions performed by organs, tissues, and
cells. The endocrine system, however, performs these
functions by different mechanisms than the nervous
The endocrine system sends messages by way of
chemical messengers called hormones. Minute
amounts of these hormones are secreted from
endocrine gland cells into the blood and distributed by
the circulatory system. Endocrine glands secrete
hormones directly into the blood, because they have no
duct system. The glands of this system are often called
ductless glands. Cells that are affected by the hormone
are referred to as target organ cells.
Today, many hormones can be extracted from the
glands of animals or produced synthetically. Medical
officers may prescribe these naturally derived or
synthetic hormones for patients who are deficient in
them or who might otherwise benefit from their use.
For example, oxytocin (the hormone which stimulates
uterine contractions during pregnancy) has been
synthesized and is used during the delivery process for
women who are deficient in this hormone.
The hormone-producing glands include the
hypothalamus, pituitary, thyroid, parathyroids,
adrenals, pancreas, and gonads (the testes and ovaries)
The hypothalamus, a structure in the brain,
synthesizes chemicals that are secreted to the pituitary
Sense of smell.
Eye movement, size of pupil, and eye focus.
Sensations of head and face and chewing movements.
Abduction of eye (muscles that turn eye outward).
Facial expressions, secretion of saliva, and sense of taste.
Sense of hearing and balance or equilibrium sense.
Taste and other sensations of the tongue, swallowing movements, secretion of
Sensations of movement (e.g., decrease in heart rate, increase in peristalsis, and
contracting of muscles for voice production).
Shoulder movements, turning movements of the head, and voice production.
Table 1-3.Cranial Nerves