Alexis Rice Summary Chapter 13 Endocrine System Collection of specialized cells and tissues that secrete hormones Hormones have access to every cell Each hormone acts only on specific cells target cells Only specific cells have receptors for specific hormones Endocrine control is slower than nervous system Endocrine and nervous systems interact Endocrine Glands Ductless organs that secrete hormones into blood interstitial Hormones Chemical messengers secreted by endocrine glands fluid lymph Circulate in the bloodstream Act on specific cells in the body Steroid Hormones Structurally related to cholesterol Lipid soluble chemically derived from cholesterol Activate specific genes to produce specific proteins Slower acting than non steroid hormones minutes to hours Non steroid Hormones Structurally relates to proteins Lipid insoluble Water soluble Bind to receptors on target cell membranes Work through intermediate mechanisms to activate existing enzymes Faster action than steroid hormones seconds to minutes Negative Feedback Loops of Hormones Many hormones participate in internal homeostatic control mechanisms Negative feedback loop involving hormones includes the following Endocrine gland serves as the control center Hormone is the pathway between the control center and the effectors Target tissues or organ are effectors Hypothalamus Homeostatic control center of the brain Links nervous system and endocrine system Produces two hormones of its own Monitors and controls hormone secretions of the pituitary gland Pituitary Gland Master gland Secretes eight different hormones that regulate other endocrine organs Two lobes posterior and anterior Posterior Pituitary Connection to hypothalamus by neuroendocrine cells Hormones made in hypothalamus stored in posterior pituitary Hormones ADH and oxygen made in cell bodies in hypothalamus are transported down axons to axon endings in posterior pituitary Posterior pituitary hormones non steroidal Antidiuretic hormone ADH Conserves water in kidneys Regulates water balance in body Oxytocin neuroendocrine reflex Causes uterine contractions during labor and milk ejection through Releasing and inhibiting hormones from hypothalamus travel to pituitary through The release of each anterior pituitary hormone is controlled at least partially by Anterior Pituitary Controlled by hypothalamus pituitary portal system the hypothalamus Anterior Pituitary Hormones ACTH adrenocorticotropic hormone Stimulates adrenal cortex to release glucocorticoids cortisol TSH thyroid stimulating hormone Acts on thyroid gland promoting release of thyroid hormones FSH and LH gonadotropins Stimulate growth development and function of ovaries and testes Not produced until about age 10 13 puberty Increase in production initiates sexual maturation and development at puberty Stimulates development of mammary glands and milk production Prolactin Growth Hormone Has widespread effects on body Major effects on bone muscle Most of its growth promoting effects occur during childhood and adolescence Pituitary Disorders Hypersecretion and Hyposecretion Diabetes Insipidus Hyposecretion of ADH results in inability to conserve water appropriatley Causes excessive urination dehydration thirst Hypersecretion of growth hormone in childhood Excessive growth hormone over a long period in adults Gigantism Acrosmegaly Pituitary Dwarfism Hyposecretion of growth hormone over a long period in adults Pancreas Secretes Glucagon Insulin and Somatostatin Pancreas has both exocrine and endocrine functions Pancreatic hormones are involved in regulating blood glucose levels Endocrine cells in Islets of Langerhans within the pancreas secrete the following three hormones Alpha cells secrete glucagon Beta cells secrete insulin Delta cells secrete somatostatin Glucagon Raises blood sugar Insulin Lowers blood sugar Causes breakdown of glycogen to glucose in liver Promotes uptake of sugar by cells in liver muscle and adipose tissue Promotes conversion of glucose into glycogen proteins fat Inhabits secretion of glucagon and insulin regulates other hormones Somatostatin Adrenal Glands Adrenal Cortex outer layer Adrenal medulla inner layer Adrenal Cortex Glucocorticoids and Mineralocorticoids Glucocorticoids Cortisol is an example Secretion mediated through hypothalamus pituitary secretions Maintain blood glucose levels during prolonged fasting Suppress inflammatory responses Mineralocorticoids Aldosterone is an example Regulate sodium potassium water balance Act on kidneys promoting sodium reabsorption and potassium excretion Adrenal Medulla Epinephrine and Norepinephrine Adrenal Medulla Neuroendocrine organ Secretion stimulated by Sympathetic nervous system Hormones Nonsteroidal Epinephrine and norepinephrine Enhance function of sympathetic nervous system fight or flight response Thyroid and Parathyroid Glands Thyroid located just below larynx in neck Parathyroid glands embedded in back of thyroid Both thyroid and parathyroid involved in calcium balance Thyroid also involved in regulating metabolism Thyroid Gland Thyroxine Speeds Cellular Metabolism Secretion mediated through hypothalamus pituitary secretions Steroidal hormones Thyroxine T4 and Triiodothyronine T3 Both regulates production of ATP from glucose affect metabolic rate Calcitonin Lowers blood calcium levels Decreases rate of bone resorption by inhibiting osteoclasts Stimulates uptake of calcium by bones Parathyroid Hormone PTH Controls Blood Calcium Levels Response to lowered blood calcium levels Secretion Action Removes calcium and phosphate from bone Increases absorption of calcium by the digestive tract Causes kidneys to retain calcium and excrete phosphate Major regulator of blood calcium concentration in adults Testes Produce Testosterone Functions of testosterone and other androgens Before birth responsible for development of external male genitalia Regulates development and normal functioning of sperm male reproductive At onset of puberty organs and male sex drive Regulates development of male secondary sex charachteristics Small amounts of androgens produced by adrenal glands in both sexes Initiates development of secondary sex characteristics Ovaries Produce Estrogen and Progesterone Hormones steroidal Estrogen Regulates menstrual cycle Progesterone Regulates menstrual cycle Other Glands and Organs Also Secrete Hormones Thymus Thymosin and Thymopoietin Assist maturation of T lymphocytes Most active during early development and childhood Pineal