Hypothalamus• Part of brain – Regulates ANS, emotions, feeding/satiety, thirst, body temperature, etc. – Hormones related to these functions • ―Releasing hormones‖ • Axonal transport to posterior lobe
Anterior Pituitary• ―Releasing‖ hormones regulate AP aka adeno hypo physis ―glands‖ ―under‖ ―growth‖• All proteins – TSH (thryoid stimulating hormone/thyrotropin) – ACTH (adrenocorticotropic hormone) – FSH (gonadotropin) – LH (gonadotropin) • Tropins/tropic hormones – GH (growth hormone) – Prolactin-releasing H Hypothalamic Pituitary Axis Animation : IP Web
Anterior P. Homeostatic ImbalancesGrowth hormone (GH or hGH) – Promotes mitosis, cell division – Elongation of long bones, etc. – Healing of wounds Lack of hGH retards growth – Hypersecretion in youth produces giantism – Hyposecretion in childhood produces pituitary dwarfism – Hypersecretion in adult produces acromegaly
Pituitary—Posterior lobe• Oxytocin – Stimulates smooth muscle contraction of uterus & mammary glands.• Antidiuretic H. – Stimulates water reabsorption in collecting ducts. – Stimulates vasoconstriction (vasopressin) – Lack diabetes insipidus
Posterior Pituitary Homeostatic ImbalancesADH – Hyposecretion produces diabetes insipidus ―tasteless‖ – Excessive thirst and urination • central or neurogenic DI • gestagenic or gestational DI • nephrogenic DI • dipsogenic DI Diabetes Insipidus Foundation, Inc.
Thyroid Gland• Location in neck – Inferior to larynx – Anterior & lateral to trachea• Composed of follicles – Follicle cells produce thyroglobulin • Thyroxin (T4) • Triiodothyronine (T3) – Both ―thyroid hormone‖, body’s major metabolic hormone• Parafollicular/ C cells • Calcitonin – Decreases blood Ca2+ by depositing it in bones
Homeostatic imbalances• Hypothyroidism results – Myxedema (in adults) – Goiter—low levels of iodine – Cretinism (in children)• Hyperthyroidism results – Graves disease
Parathyroid Glands• Four small glands embedded in posterior of thyroid – Parathyroid hormone (PTH) – Stimulates osteoclasts to free Ca2+ from bone – Stimulates Ca2+ uptake from intestine & kindey Hormonal Regulation of Calcium
Parathyroid Homeostatic Imbalances• Severe hyperparathyroidism causes massive bone destruction• If blood Ca2+ fall too low, neurons become overactive, resulting in tetany
Feedback Loop• Negative feedback in calcium homeostasis. A rise in blood Ca2+ causes release of calcitonin from the thyroid gland, promoting Ca2+ deposition in bone and reducing reabsorption in kidneys.• A drop in blood Ca2+ causes the parathyroid gland to produce parathyroid hormone (PTH), stimulating the release of Ca2+ from bone.• PTH also promotes reabsorption of Ca2+ in kidneys and uptake of Ca2+ in intestines.
Adrenal GlandsOne on top of each kidney• Cortex – Corticosteroid – glandular• Medulla – Catecholamines – neurohormonal • Epinephrine • Norepinephrine
Adrenal Cortex• Cortex – Activity stimulated by ACTH – Controls prolonged responses by secreting corticosteroids. – Mineralcorticoids • Aldosterone regulate salt and water balance – Glucocorticoids • Cortisol regulate glucose metabolism and the immune system. – Gonadocorticoids • Androgens • Estrogens
Adrenal Cortex Imbalances• Hypersecretion leads to Cushing’s disease – ACTH-releasing tumors or side effects of corticoid drugs.• Hyposecretion leads to Addison’s Disease – Deficits in glucocorticoids and mineralcorticoids
Adrenal Medulla• Medulla – The adrenal medulla mediates short–term responses by secreting catecholamine hormones. – Cells are modified neurons (lack axons) • Epinephrine (adrenaline) • Norepinephrine (noreadrenaline) – enable a rapid ( fight-or-flight ) responses to stress by increasing blood glucose and blood pressure and directing blood to the heart, brain, and skeletal muscles.
Pancreas• Consists of two major types of secretory tissues which reflects its dual function – Exocrine gland • secretes digestive juice • localized in the acinar cells – Endocrine gland • releases hormones • localized in the islet cells (islets of Langerhans)
Pancreatic Islets• ―About a million‖ embedded in pancreas• Control centers for blood glucose – Insulin from beta cells – Glucagon from alpha cells
Islets of Langerhans• Insulin stimulates glucose uptake, glycogenesis• Glucagon stimulates glycogenolysis, glucose release from liver (vs gluconeogenesis)
Feedback Loop•A rise in blood glucosecauses release of insulinfrom beta cells thepancreas, promotingglucose uptake in cellsand storage as glycogenin the liver.•A fall in blood glucosestimulates alpha cells inthe pancreas to secreteglucagon, which causesthe liver to break downglycogen and releaseglucose.
Gonads• Ovaries – Estrogens – Progesterone• Testes – Testosterone• Reproductive functions when we study reproductive system.
Pineal gland• Melatonin – ? Inhibits early puberty – ? Day/night cycles • Timing of sleep, body temperature, appetite• Secretes melatonin during darkness – Participates in setting the body’s clock• Melatonin is a potent antioxidant• Melatonin is high when young and is reduced as we age
Thymus• Thymus gland• Thymopoietins, thymic factor, thymosins – Influence development of T lymphocytes