Endocrine System

Topics: Hypothalamus, Endocrine system, Hormone Pages: 12 (2219 words) Published: March 8, 2013

* Hypothalamus Although it is part of the brain, the hypothalamus secretes several hormones and is very closely related to the activity of the endocrine system.

* The hormones it secretes are:
* Releasing hormones – stimulate the secretion of specific anterior pituitary hormones * Release inhibiting hormones – inhibit the secretion of specific anterior pituitary hormones

* A small pea-sized gland also called the hypophysis.
* Located at the base of the brain
* Lies in the sella turcica (saddle-like depression of the sphenoid bone) * Attached to the hypothalamus by a short slender stalk called the infundibulum

Anterior pituitary
* Consists of two lobes
* Anterior pituitary – (Adenohypophysis)
* Composed of glandular tissue
* No direct neural connection between the anterior pituitary and the hypothalamus * However, there is a vascular connection between the hypothalamus and the anterior pituitary

* Hormones (releasing or inhibiting) that are secreted by the hypothalamus are carried in the blood via a capillary bed associated with the hypothalamus. * The vessels merge to form the hypophyseal portal veins

* These give rise to a capillary bed in the anterior pituitary * These releasing and inhibiting hormones regulate the hormone secretions of the anterior pituitary. * Secretes six major hormones

* Four of the six hormones are termed tropic
* Hormones which regulate the secretory action of other glands. * Because of this, the anterior pituitary is often called the master gland * These six hormones are:
* Growth hormone (GH)
* Prolactin (PRL)
* Thyroid stimulating hormone (TSH)
* AKA thyrotropin
* Adrenocorticotropic hormone (ACTH)
* Gonadotropic hormones
* Follicle stimulating hormone (FSH)
* Luteinizing hormone (LH)
* Growth Hormone (GH)
* Regulated by 2 antagonistic hypothalmic hormones
* GHRH – growth hormone releasing hormone
* GHIH – growth hormone inhibiting hormone
* GH exerts a profound effect on growth
* Target Organs: all cells and tissues.
* Also exerts powerful metabolic effects
* Synthesis of proteins from amino acids
* Breakdown of fats and carbohydrates for energy

* Prolactin or (PRL) – stimulates milk production in lactating women * PRH – prolactin releasing hormone
* PIH – prolactin inhibiting hormone
* Decrease in PRL = poor milk production in lactating women * Increase PRL = cessation of menses in women and impotence and infertility in men

* Thyroid stimulating hormone (TSH) –
* Stimulates normal development and secretory activity of the thyroid gland. * The secretion of TSH is stimulated by the production of thyrotropin-releasing hormone (TRH) * Rising levels of TSH feed back on the hypothalamus to decrease TRH which in turn decreases TSH

* Adrenocorticotropin (ACTH) –
* The hypothalamus secretes corticotropin-releasing hormone (CRH) which stimulates the anterior pituitary to secrete ACTH which * Stimulates the cortex or outer layer of the adrenal glands to secrete certain hormones called corticosteroids.

Gonadotropic Hormones
* The target glands are the gonads in both sexes.

* Follicle Stimulating hormone (FSH) Stimulates the development of * The ova or egg in the female
* Initial production of the sperm in males
* Later testosterone takes over this function

* Luteinizing Hormone:
* Works with FSH to cause maturation of the egg-containing ovarian follicle * Triggers ovulation in the female
* Stimulates the release of the ovarian hormones
* Estrogen
* progesteron
* In males, stimulates the...
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