JSC ASTANA MEDICAL UNIVERSITY THE DEPARTMENT OF PHYSIOLOGY

JSC "ASTANA MEDICAL UNIVERSITY" THE DEPARTMENT OF PHYSIOLOGY The hypothalamus, hypophysis, adrenal gland system Done by: Laura Rais 226 -GM Astana 2012

HYPOTHALAMUS Ø Ø Ø The hypothalamus is located below the thalamus, just above the brain stem. It is responsible for a variety of the autonomic nervous system. One important function of the hypothalamus is linking the nervous system to the endocrine system, via the pituitary gland. The hypothalamus responds to many different signals, both internal and external to the body It responds to hormones carried in the blood, olfactory stimulation and steroid stimulation. External factors affecting the hypothalamus include stress that triggers a variety of responses, and light that controls functions such as sleep.

FUNCTIONS OF THE HYPOTHALAMUS The hypothalamus is vital for living as it plays a very important role. It controls certain metabolic processes and other activities of the Autonomic Nervous System. It synthesizes and secretes neurohormones, often called hypothalamicreleasing hormones. These hypothalamic releasing hormones control and regulate the secretion of pituitary hormones.

FUNCTIONS OF THE HYPOTHALAMUS CAN BE LISTED AS: controls the release of 8 major hormones by the pituitary gland controls body temperature control of food and water intake, hunger and thirst control of sexual behavior and reproduction control of daily cycles in physiological state and behaviour also known as circadian rhythm mediation of emotional responses

HYPOTHALAMIC RELEASING HORMONES Seven releasing hormones are made in the hypothalamus Thyrotropin-releasing hormone (TRH) Corticotropin-releasing hormone (CRH) Gonadotropin-releasing hormone (Gn. RH) Growth hormone-releasing hormone (GHRH) Growth hormone-release inhibiting hormone (GHIH) Prolactin-releasing factor (PRF) Prolactin-inhibiting hormone (PIH)

HYPOTHALAMIC RELEASING HORMONES: SECRETION Is influenced by emotions Can be influenced by the metabolic state of the individual Delivered to the anterior pituitary via the hypothalamic-hypophyseal portal system Usually initiates a three-hormone sequence

HYPOTHESIS OR PITUITARY GLAND The pituitary gland is located below the hypothalamus. Nine major hormones are produced here. These hormones act primarily to influence other endocrine glands. The posterior lobe of the pituitary regulates water conservation, milk letdown, and uterine contraction in women. The anterior lobe regulates the other endocrine glands.

THE ANTERIOR PITUITARY Is also called the Adenohypophysis Secretes tropic hormones in a pulsatile fashion Synthesizes various hormones in various specific cell populations

ANTERIOR PITUITARY HORMONES Each of anterior pituitary hormone is synthesized by a cell population. Corticotropes Lactotropes - ACTH - Prolactin Somatotropes - GH Thyrotropes - Thyrotropin Gonadotropes - FSH, LH

ANTERIOR PITUITARY HORMONES Growth Hormone (GH, Somatotropin): primary hormone responsible for regulating body growth, and is important in metabolism Thyroid-stimulating Hormone (TSH): stimulates secretion of thyroid hormone & growth of thyroid gland Adrenocorticotropic Hormone (ACTH): stimulates cortisol secretion by the adrenal cortex & promotes growth of adrenal cortex

ANTERIOR PITUITARY HORMONES Follicle-stimulating Hormone (FSH): Females: stimulates growth & development of ovarian follicles, promotes secretion of estrogen by ovaries. Males: required for sperm production Luteinizing Hormone (LH): Females: responsible for ovulation, formation of corpus luteum in the ovary, and regulation of ovarian secretion of female sex hormones. Males: stimulates cell in the testes to secrete testosterone Prolactin: Females: stimulates breast development and milk production. Males: involved in testicular function

HYPOTHALAMIC HORMONE EFFECTS ON THE ANTERIOR PITUITARY Thyrotropin-releasing hormone (TRH) Stimulates release of TSH (thyrotropin) and Prolactin Corticotropin-releasing hormone Stimulates release of ACTH (CRH) (corticotropin) Gonadrotropin-releasing hormone (Gn. RH) Stimulates release of FSH and LH (gonadotropins) Growth hormone-releasing hormone (GHRH) Growth hormone-inhibiting hormone (GHIH) Stimulates release of growth hormone Inhibits release of growth hormone {Prolactin-inhibiting hormone (PIH) Stimulates release of prolactin Prolactin-inhibiting hormone (PIH) Inhibits release of prolactin

GROWTH HORMONE ACTIVITY Increases plasma free fatty acids (FFA) - source of energy for muscle tissue Increases hepatic glucose output Decreases insulin sensitivity in muscle Is protein anabolic hormone Exerts its growth-promoting through interactions [mainly induction of Insulin-like Growth Factor I (IGFI)]. IGF-I synthesis is stimulated by GH Major source of IGF-I is the liver; IGF-I is also locally produced in other tissues

ENDOCRINE CONTROL: THREE LEVELS OF INTEGRATION Hypothalamic stimulation–from CNS Pituitary stimulation–from hypothalamic trophic Hs Endocrine gland stimulation– from pituitary trophic Hs

ENDOCRINE CONTROL: THREE LEVELS OF INTEGRATION

MULTIPLE STIMULI FOR HORMONE RELEASE: NERVOUS &ENDOCRINE Stimuli Multiple Stimuli for Hormone Release: Nervous & Endocrine. Stretch Glucose Insulin levels Reflex Lower blood glucose Reduces stimulus Reduces insulin release

MULTIPLE HORMONES CAN TARGET A CELL/TISSUE Growth Hormone Somatomedins Thyroxin All have receptors on many tissues Stimulate pathways for growth

POSTERIOR PITUITARY Comprised of the endings of axons from cell bodies in the hypothalamus (supraoptic and paraventricular) Axons pass from the hypothalamus to the posterior pituitary via the hypothalamohypophysial tract Posterior pituitary hormones are synthesized in the cell bodies of neurons in the supraoptic and paraventricular nuclei Hormones synthesized in the hypothalamus are transported down the axons to the endings in the posterior pituitary Hormones are stored in vesicles in the posterior pituitary until release into the circulation Principal Hormones: Vasopressin & Oxytocin

SECRETION OF POSTERIOR PITUITARY HORMONES

OXYTOCIN Is synthesized as the precursor hormone: preprooxyphysin Acts primarily on the mammary gland uterus Increases contraction of smooth muscle of the vas deferens Secretion May is increased during labor also act to facilitate sperm transport in uterus (non-pregnancy state)

POSTERIOR PITUITARY: REGULATION OF OSMOLALITY Plasma osmolality is monitored by osmoreceptors in the hypothalamus Increases in plasma osmolality stimulates secretion of vasopressin Small changes above the normal plasma osmotic pressure (285 mosm/kg) stimulate release of vasopressin

VASOPRESSIN (ADH) Is also known as antiduretic hormone (ADH) Participates in body water regulation (Water is lost from lungs, sweat, feces and urine on a daily basis) AVP and Water Balance • The maintenance of water balance in the body is extremely important for proper functioning of cells. • There are two main compartments of the body: intracellular and extracellular (includes interstitial space and plasma). • Water moves freely between compartments depending upon osmotic gradients.

THE ADRENALS Mammals Adrenal medulla is the inner core which produces adrenaline (epinephrine) and norepinephrine. Have an adrenal gland above each kidney. Adrenal cortex is the outer shell that produces the steroid hormones cortisol and aldosterone.

ADRENAL MEDULLA The adrenal medulla releases adrenalin (epinephrine) and norepinephrine in times of stress. Identical to the effects of the sympathetic nervous system, but longer lasting. Accelerated heartbeat, increased blood pressure, higher levels of blood sugar and increased blood flow to heart and lungs.

ADRENAL CORTEX The adrenal cortex produces the steroid hormone cortisol (hydrocortisone). Reduces inflammation. Synthetic derivatives such as prednisone are used as anti-inflammatory agents. Stimulates carbohydrate metabolism. The adrenal cortex also produces aldosterone. Aldosterone acts in the kidney to promote the uptake of sodium & other salts from the urine. These salts are important in nerve conduction. Aldosterone and PTH are the only two hormones essential for survival.

THE PANCREAS The pancreas is located behind the stomach and is connected to the small intestine by a small tube. It secretes digestive enzymes into the digestive tract (exocrine function). Endocrine function – production of insulin and glucagon.

GLUCOSE HOMEOSTASIS The islets of Langerhans in the pancreas secrete insulin and glucagon. Insulin removes glucose from the blood. Glucagon returns glucose to the blood.

DIABETES Diabetes mellitus, perhaps the best-known endocrine disorder, is caused by a deficiency of insulin or a decreased response to insulin in target tissues. Marked by elevated blood glucose levels. Type I diabetes mellitus (insulin-dependent diabetes) is an autoimmune disorder in which the immune system destroys the beta cells of the pancreas. Type II diabetes mellitus (non-insulin-dependent diabetes) is characterized either by a deficiency of insulin or, more commonly, by reduced responsiveness of target cells due to some change in insulin receptors.