Biology Reference
In-Depth Information
Pineal
gland
Hypothalamus
Pituitary gland
Parathyroid
glands
Thyroid gland
Thymus gland
Brain
Adrenal gland
Hypothalamus
Pancreas
Ovary
or
Testis
Posterior
Pituitary
Anterior
Pituitary
FIGURE 9-3.
Relationship between the hypothalamus (a region
of the brain) and the pituitary gland. The anterior
and posterior lobes of the pituitary have different
functions, as noted in the text.
FIGURE 9-2.
Human endocrine glands. The parathyroid glands are located behind the thyroid gland, and the
adrenal glands are located just above the kidneys.
chemical. The secreted regulator enters the intercellular fluid and then
binds the receptors, resulting in the regulation of the function of the same
cell. Paracrine regulation involves release of a molecular signal that
diffuses through the intercellular fluid and interacts with specific
receptors on other nearby cells. Neuroendocrine regulation occurs when
a neuroendocrine cell releases neurohormones into the bloodstream and
these bind to target cell receptors.
Hormones are classified on the basis of their structure. Peptide or protein
hormones (such as insulin, LH, or GH) are produced, like other
proteins, on ribosomes. They are stored within the cells in secretory
vesicles and are released by exocytosis in response to an appropriate
stimulatory signal. They act by binding to specific receptors on the
surface of target cells. In contrast, steroid hormones (such as
