The Endocrine System.
Hypothalamus.
The hypothalamus is a
part of the brain located
inferior to the thalamus.
It serves
many different functions in the nervous system, and is
also responsible for the direct control of the endocrine system through the
pituitary gland.
The
hypothalamus contains special cells called neurosecretory cells that
secrete hormones:
- Thyrotropin-releasing
hormone (TRH)
- Growth
hormone-releasing hormone (GHRH)
- Growth
hormone-inhibiting hormone (GHIH)
- Gonadotropin-releasing
hormone (GnRH)
- Corticotropin-releasing
hormone (CRH)
- Oxytocin
- Antidiuretic hormone (ADH)
All of
the releasing and inhibiting hormones affect the function of the anterior
pituitary gland.
1.TRH
stimulates the anterior pituitary gland to release thyroid-stimulating hormone.
2. and
GHIH work to regulate the release of growth hormone—GHRH stimulates growth
hormone release, GHIH inhibits its release.
3.GnRH
stimulates the release of follicle stimulating hormone and luteinizing hormone .
4. CRH stimulates the release of adrenocorticotropic hormone.
The last
two hormones—oxytocin and antidiuretic hormone—are produced by the hypothalamus
and transported to the posterior pituitary, where they are stored and later released.
Pituitary Gland
The pituitary gland, also known as the hypophysis, is a small pea-sized lump of tissue connected to the inferior portion of the hypothalamus of the brain.
The pituitary gland is actually made of 2
completely separate structures: the posterior and anterior pituitary glands.
1.Anterior Pituitary:
The
anterior pituitary gland is the true glandular part of the pituitary gland.
The function of the anterior pituitary gland
is controlled by the releasing and inhibiting hormones of the hypothalamus.
The
anterior pituitary produces 6 important hormones:
o Thyroid
stimulating hormone (TSH), as its name suggests, is a tropic hormone
responsible for the stimulation of the thyroid gland.
o Adrenocorticotropic
hormone (ACTH) stimulates the adrenal cortex, the outer part of the adrenal gland, to
produce its hormones.
o Follicle
stimulating hormone (FSH) stimulates the follicle cells of the gonads to
produce gametes—ova in females and sperm in males.
o Luteinizing
hormone (LH) stimulates
the gonads to produce the sex hormones—estrogens in females and testosterone in
males.
o Human
growth hormone (HGH) affects many target cells throughout the body by
stimulating their growth, repair, and reproduction.
Prolactin (PRL) has many effects on the body,
chief of which is that it stimulates the mammary glands of the
breast to produce milk.
2.Posterior Pituitary: The posterior pituitary gland is actually not glandular tissue at all, but nervous tissue instead.
These neurosecretory cells secret 2 hormones in the
hypothalamus that are stored and released by the posterior pituitary:
1. Oxytocin
2.Antidiuretic hormone (ADH)
