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Endocrine System Chapter 36 Nervous vs Endocrine Nervous immediate acts thru electrical impulses and neurotransmitters effect is localized and short duration Endocrine acts thru chemicals – hormones effect is generalized and long term duration Impacts, Issues Video Hormones in the Balance Endocrine System Main Sources pituitary gland adrenal glands thyroid gland parathyroid glands pineal gland thymus gland hypothalamus (part of the brain) pituitary gland, anterior lobe pituitary gland, posterior lobe pineal gland thyroid gland parathyroid glands (four) thymus gland adrenal gland (one pair) medulla pancreatic islets ovaries (one pair of female gonads) testes (one pair of male gonads) Endocrine System Mechanism of a steroid hormone Hormones Classified as protein or protein derivative bind to receptor on cell membrane steroid receptors are located within the cytoplasm of the cell react with receptor site on selected cells secreted by endocrine glands, endocrine cells, and certain neurons travel through the bloodstream to nonadjacent target cells chemical signal communication between cells, body parts Hormones prostaglandins local hormone not carried by blood affects neighboring cells promotes pain and inflammation growth hormones local hormone promotes cell division Hormones pheromones affect metabolism influence the behavior of another individual active between animals not humans Feedback Mechanisms negative feedback helps to maintain homeostasis positive feedback enhances an already existing response Stimulus Blood level of thyroid hormone falls below a set point. Response + Hypothalamus – TRH – Anterior Pituitary TSH Thyroid Gland Thyroid hormone is secreted Rise in the blood level of thyroid hormone inhibits secretion of TRH and TSH. Hormone Action activation of receptor transduction of signal functional response Action of Hormones wide range of effects induce target cells 2 ways hormones can influence cell metabolism 1.) peptide hormone peptides, proteins, glycoproteins, modified amino acids Glucagon, ADH, oxytocin, TRH, insulin, somatotropin, prolactin, FSH, LH, TSH Action of Hormones ex.) muscle cells epinephrine binds to a receptor in the plasma membrane leads to the breakdown of glycogen to glucose never enters the cell 1st messenger hormone 2nd messenger sets metabolic machinery into motion * activates protein kinase as well as other enzymes * cascade effect which allows for many molecules of glycogen to be broken down which in turn enters the blood stream Protein Hormone Mechanism of a peptide hormone Protein Hormone hormone binds to a receptor at cell surface binding triggers a change in activity of enzymes inside the cell glucagon glucagon receptor cyclic AMP + Pi ATP cAMP activates protein kinase A Protein kinase A converts phosphorylase kinase to active form and inhibits an enzyme required for glucagon synthesis. Action of Hormones 2.) steroid hormone act more slowly action lasts longer limited to adrenal cortex, ovaries and testis Estrogens, progestins, androgens, cortisol, aldosterone derived from cholesterol enters the cell because they are lipids binds with DNA activates transcription inhibits transcription Steroid Hormones Mechanism of a steroid hormone The Hypothalamus region in the forebrain regulates internal environment contains hormone-secreting cells produces and releases ADH, Oxytocin interacts with pituitary contains releasing hormones hypothalamus pituitary gland Pituitary Gland pea-sized gland at base of hypothalamus two lobes posterior lobe stores and secretes hormones synthesized in the hypothalamus antidiuretic hormone (ADH) released in response to blood being concentrated goes to kidney * causes water to be reabsorbed negative feedback Pituitary Gland Oxytocin uterine contractions milk letdown positive feedback Pituitary Gland Posterior pituitary function Pituitary Gland anterior pituitary affecting other glands thyroid stimulating hormone (TSH) Triiodothyronine / tyroxine * both regulate metabolism and growth rate increases Pituitary Gland adrenocorticotropic hormone (ACTH) adrenal cortex release of cortisol raises blood sugar levels counteracts inflammation gonadotropic hormone follicle stimulating (FSH) luteinizing hormone (LH) stimulates ovaries and testis to produce gametes Pituitary Gland not affecting other glands meloncyte stimulating hormone (MSH) skin color changes prolactin (PRL) milk production carbohydrate / fat metabolism growth hormone skeletal and muscular growth increases the rate of amino acids entering cells to produce proteins Pituitary Gland Anterior pituitary function Pituitary Gland Hypothalamus and pituitary Thyroid Gland epiglottis thyroid cartilage (Adam’s apple) pharynx thyroid gland trachea (windpipe) anterior parathyroid gland posterior Thyroid/Parathyroid located in the neck largest gland stimulates all cells to metabolize faster more glucose broken down, more energy used contains triiodthyronine (T3) / thyroxine (T4) regulates metabolism and growth rate Thyroid/Parathyroid lack of iodine can result in a simple goiter hypothyrodism minimal production cretinism failure of thyroid to develop properly results in stunted growth myxedema adults lethargy, weight gain, loss of hair, slower pulse rate, lowered body temperature Thyroid/Parathyroid hyperthyroidism overproduction exophthalmic goiter eyes protrude due to swelling of the muscles that moves the eyes Parathyroid Gland Parathyroid hormone action Calcium Regulation calcium levels high calcitonin regulates calcium levels in the blood secreted by thyroid gland in response to high levels causes calcium to be deposited in the bone tissue osteoblasts reduces the activity and number of osteoclasts cell that causes the erosion of bone Calcium Regulation parathyroid glands calcium levels too low PTH released in response to low calcium levels promotes the activity of osteoclasts promotes the reabsorption of calcium by the kidneys activates vitamin D stimulates the absorption of Ca from the intestine Calcium Regulation hyperparathyrodism Ca levels too high results in tetany body shakes from continuous muscle contractions brought about by increased excitability of nerves hypoparathyrodism Ca levels too low bones become soft and fragile Adrenal Glands sit atop the kidneys consists of adrenal medulla inner portion produces epinephrine and norepinephrin brings about bodily changes emergency responsible for fight-flight response to stress and excitement effects are short term Adrenal Glands adrenal cortex outer portion secretes cortisol maintains glucose levels in the absence of food inhibits blood glucose uptake by muscle and other tissues causes breakdown of proteins to amino acids and conversion to glucose causes degradation of adipose tissue to fatty acids for use as energy source Adrenal Glands feedback control of cortisol secretion hypothalamus senses rise in glucose and secretes less releasing hormone (CRH) anterior pituitary responds by secreting less ACTH corticotropin-releasing hormone adrenocorticotropic hormone adrenal cortex slows its secretion of cortisol Adrenal Cortex Control of cortisol secretion Adrenal Glands mineralocorticoids regulate salt and water balance leads to an increase in blood volume and blood pressure Control of Glucose Metabolism Hormones and glucose metabolism Pancreatic Hormones lies between the kidney and near the duodenum secretes insulin high blood glucose (sugar) stimulates uptake of glucose by liver cells adipose cells muscle cells stored as glycogen lowers blood sugar Pancreatic Hormones glucagon low blood glucose major target are the liver and adipose tissue stimulates liver to break down glycogen uses fat and protein in preference to glucose as energy adipose tissue cells break down fat to glycerol and fatty acids liver then takes these up and uses them as substrates for glucose formation Diabetes Mellitus Excess glucose accumulates Type 2 Type 1 autoimmune disease usually appears in childhood insulin injections target cells don’t respond usually appears in adults diet, drugs