PSL201Y1 Lecture Notes - Supraoptic Nucleus, Growth Hormone–Releasing Hormone, Paraventricular Nucleus Of Hypothalamus

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Published on 29 Nov 2011
School
UTSG
Department
Physiology
Course
PSL201Y1
Lecture 15 – ADH, Oxytocin and Growth Hormone
The hypothalamus and the pituitary gland are located at the base of
the brain. The two are connected by a tissue bridge called the infundibulum.
The pituitary gland is divided into posterior and anterior lobes. The anterior
pituitary is referred to as the adenohypophysis and the posterior pituitary as
the neurohypophysis.
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The hypothalamus contains two clusters of endocrine cells that send
their injections down into the posterior pituitary where the hormones they
synthesized are released. These two clusters include the supraoptic nucleus
and the paraventricular nucleus. Endocrine cells of the supraoptic nucleus
synthesize and secrete the hormone oxytocin. Endocrine cells of the
paraventricular nucleus synthesize and secrete ADH (anti diuretic hormone)
or vasopressin. Because these endocrine cells are located in the brain, they
are referred to as neurosecretory cells (endocrine cells). The projection of
both endocrine cell clusters terminate in the posterior pituitary, adjacent to a
rich blood supply, there is a capillary bed. When secreted by their endocrine
cells, oxytocin and ADH can drain directly into the vein in the posterior
pituitary. From there it enters the bloodstream, traveling towards their
target cells. Therefore, the posterior pituitary is simply a release point for
hormones.
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Functions of ADH
An anti diuretic inhibits the formation of urine. Urine is water with
added solutes. ADH regulates our total body water levels by its ability to
stimulate the reabsorption of water from the urine in the kidneys. It
regulates how much water is conserved in the blood versus the amount lost
in the urine. ADH also conserves blood volume. Blood is mostly water, with
proteins and a cellular component. ADH has the ability to stimulate water
reabsorption which also conserves the blood volume. The conservation of
blood volume also has the effect of conserving our blood pressure.
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