Endocrine System

The mammalian endocrine system consists of the endocrine hormones and the glands that produce them The major endocrine glands and organs are:The hypothalamus–pituitary complex

The hypothalamus is a part of the brain that contains clusters of specialized nerve cells called neurosecretory cells

Neurosecretory cells synthesize peptide hormones, store them, and release them when stimulated

The pituitary gland is pea-sized gland connected to the hypothalamus by a stalkThe pituitary consists of two distinct parts:

The anterior pituitary, which is a true endocrine gland, composed of several types of hormone-secreting cells enmeshed in a network of capillaries

The posterior pituitary, consisting mainly of a capillary bed and the endings of neurosecretory cells whose cell bodies are in the hypothalamusThe hypothalamus controls the release of hormones from both parts of the pituitaryHypothalamic hormones control hormone release in the anterior pituitary

Neurosecretory cells of the hypothalamus produce at least seven hormones that regulate the release of hormones from the anterior pituitaryThese hypothalamic hormones are called releasing hormones or inhibiting hormones, depending on whether they stimulate or inhibit the release of a particular pituitary hormone

Hypothalamic hormones control hormone release in the anterior pituitaryReleasing and inhibiting hormones are secreted into a capillary bed in the stalk connecting the hypothalamus to the pituitary, and travel through blood vessels to a second capillary bed that surrounds the endocrine cells of the anterior pituitaryThere, they diffuse out of the capillaries and bind to receptors on the surfaces of the pituitary endocrine cells.Some of these hypothalamic hormones, such as growth hormone-releasing hormone, stimulate the release of pituitary hormones, while others inhibit the release of pituitary hormonesThe anterior pituitary produces and releases several hormonesFour of these regulate hormone production in other endocrine glands:Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) stimulate the production of sperm and testosterone in males and the production of eggs, estrogen, and progesterone in females

Thyroid-stimulating hormone (TSH) stimulates the thyroid gland to release its hormones 

Adrenocorticotropic hormone (ACTH) causes the release of the hormone cortisol from the adrenal cortexThe remaining hormones of the anterior pituitary do not act on other endocrine glandsProlactin, in conjunction with other hormones, stimulates the development of milk-producing mammary glands in the breasts during pregnancy

Growth hormone acts on nearly all the body’s cells by increasing protein synthesis, promoting the use of fats for energy, and regulating carbohydrate metabolismDuring childhood, growth hormone stimulates bone growth, which influences human height; too little growth hormone results in dwarfism, and too much results in gigantism When the Anterior Pituitary MalfunctionsThe posterior pituitary releases hormones synthesized by cells in the hypothalamusThe hypothalamus contains two types of neurosecretory cells that send axons into the posterior pituitaryThese axons end in a capillary bed into which they release hormones that are then carried by the bloodstream to the rest of the bodyThese neurosecretory cells synthesize and release either antidiuretic hormone (ADH) or oxytocin.The posterior pituitary releases hormones synthesized by cells in the hypothalamus

Antidiuretic hormone (ADH) helps prevent dehydration by causing more water to be reabsorbed from the urine and returned to the bloodstream by the kidneys

Alcohol inhibits the release of ADH and increases urination, resulting in the loss of more water than is consumed 

Name of the gland	Location	Hormone secreted	Response of body to hormone
Pituitary	Floor of brain	1. Somatotrophin 2. Thyrotrophm 3. Gonadotrophin 4.Adrenocortico trophic hormone 5.Lutemising hormone	Growth of bones Activity of thyroid gland Activity of ovary and testis Stimulates secretion from adrenal cortex In males - secretion of testosterone. In female - Ovulation, development of corpus luteum and secretion of progesterone.
Thyroid	Neck	6.Folliclestimulating hormone	In male - spermatogenesis In female - growth of grafian follicles, estrogen secretion, milk production and secretion.
Ovary	Lower abdomen	Thyroxine Estrogen	General growth rate and metabolic activity Growth of the uterus and skeleton of the pelvis Control of the 28 days menstrual cycle in females.
Testis	Scrotal sac	Testosterone	Growth of hair on face, muscular development, deepening of voice, normal sexual behavior and development of male sex organs.
Adrenal	Attached to kidneys	Adrenalin	Increase in heart-beat rate. Rise in blood sugar. Dilation of the coronary artery. Dilation of the pupil of the eye.