Hypothalamus
The hypothalamus, a section of the posterior
forebrain, is located above the pituitary gland and is intimately associated with it via a
portal system that carries blood directly from the hypothalamus to the pituitary. In most parts of
the circulatory system, blood flows directly back to the heart from capillaries, but in a portal
system blood flows from capillaries in one organ to capillaries in another.
When the hypothalamus is stimulated (by feedback from endocrine glands
or by neurons innervating it), it releases hormonelike substances called
releasing factors into the anterior-pituitary-hypothalamic portal circulatory
system. These hormones are carried directly to the pituitary by the portal
system. In their turn, these releasing factors stimulate cells of the anterior pituitary to
secrete the hormone indicated by the releasing factor.
This animation (Audio - Important) describes the interaction of the
hypothalamus and the pituitary.
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