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Chapter 18 The Endocrine System communication between cells mechanisms direct cell-to-cell gap junctions cell-to-cell (short distance) paracrine local chemicals cell-cell neurotransmitters cell-to-cell (long distance) endocrine chemicals via bloodstream Table 18-1 Endocrine system cells (tissues, organs) that produce chemical messengers (hormones) that travel via the bloodstream to have distant effects Endocrine system classes of hormones: peptide: •amino acid derivatives •polypeptides lipid: •eicosaniods (from arachidonic acid) •steroids (from cholesterol) fig. 18-2 Endocrine system receptors and mechanism of action peptide hormones receptors on cell surface activate G proteins use second messengers (cAMP) activates enzymes alter cellular activity Endocrine system receptors and mechanism of action steroid hormones diffuse across membrane receptors in cytoplasm activate specific genes alter cellular activity 100 keys (pg. 599) “Hormones coordinate cell, tissue, and organ activities on a sustained basis. They circulate in the extracellular fluid and bind to specific receptors on or in target cells. They then modify cellular activities by altering membrane permeability, activating or inactivating key enzymes, or changing genetic activity.” Endocrine reflexes triggered by: humoral stimuli body fluid changes hormonal stimuli neural stimuli Endocrine reflexes many are controlled by negative feedback simple - complex - a single hormone two or more several steps many are controlled by the hypothalamus the “master gland” of the endocrine system: fig 18-6 posterior anterior pituitary gland pituitary gland produces 9 “peptide” hormones anterior TSH ACTH FSH LH prolactin GH MSH *posterior ocytocin ADH pituitary gland controlled by hypothalamus produces RH releasing hormones IH inhibiting hormones pituitary gland controlled by hypothalamus produces RH IH fig 18-7 pituitary gland anterior TSH ACTH FSH LH prolactin GH MSH thyroid gland adrenal gland gamete development reproduction milk production growth pigment cells pituitary gland an example 1 2 TSH thyroid gland 3 5 4 pituitary gland controlled by hypothalamus produces RH IH ADH OT fig 18-7 pituitary gland fig 18-9 the “master gland” 100 keys (pg. 604) “The hypothalamus produces regulatory factors that adjust the activities of the anterior lobe of the pituitary gland, which produces 7 hormones. Most of the hormones control other endocrine organs, including the thyroid gland, adrenal gland, and gonads. The anterior lobe also produces growth hormone, which stimulates cell growth and protein synthesis.” 100 keys (pg. 604) “The posterior lobe of the pituitary gland releases two hormones produced in the hypothalamus; ADH restricts water loss and promotes thirst, and oxytocin stimulates smooth muscle contractions in the mammary lands and uterus (in females) and the prostate gland (in males).” other endocrine organs thyroid glands C-cells of thyroid gland parathyroid glands adrenal glands cortex medulla pineal gland pancreas intestines, gonads, kidneys, adipose other endocrine organs thyroid glands produce thyroxine (T3, T4) affect all cells O2 use ATP production HR, bp erythropoiesis other endocrine organs thyroid glands C-cells of thyroid gland calcitonin blood [Ca2+ ] parathyroid glands PTH blood [Ca2+ ] 100 keys (pg. 612) “The thyroid gland produces (1) hormones that adjust tissue metabolic rates and (2) a hormone that usually plays a minor role in calcium ion homeostasis by opposing the action of parathyroid hormone.” to here 4/18 lec #39 other endocrine organs adrenal glands cortex mineralocorticoids aldosterone retain Na+ lose K+ glucocorticoids hydrocortisone anti-inflammatory medulla NE, E (Sympathetic ANS) 100 keys (pg. 616) “The adrenal glands produce hormones that adjust metabolic activities at specific sites, affecting either the pattern of nutrient utilization, mineral ion balance, or the rate of energy consumption by active tissues.” other endocrine organs pineal gland produce melatonin timing of sexual maturation protect from free radicals set circadian rhythms other endocrine organs pancreas produces digestive enzymes contains islets produce (4) hormones insulin glucagon pancreas insulin released when blood [glucose] is greater than ~110 mg/dl most cells in the body have insulin receptor insulin dependent pancreas insulin most cells in the body have insulin receptor insulin dependent insulin causes these cells to glucose absorption glucose utilization 4 blood [glucose] pancreas glucagon released when blood [glucose] is less than ~70 mg/dl stimulates: breakdown of glycogen breakdown of triglycerides production of glucose 4 blood [glucose] 100 keys (pg. 620) “The pancreatic islets release insulin and glucagon. Insulin is released when blood glucose levels rise, and it stimulates glucose transport into, and utilization by, peripheral tissues. Glucagon is released when blood glucose levels decline, and it stimulates glycogen breakdown, glucose synthesis and fatty acid release.” the “other” diabetes diabetes insipidus diabetes mellitus flow-through sweet What would make the urine sweet? Why would glucose be in the urine? diabetes mellitus causes •genetic mutations leading to low insulin production abnormal insulin defective receptors •pathological conditions •injury •immune disorder •hormonal abnormality diabetes mellitus types •type 1 insulin dependent (juvenile onset) controlled by insulin injections •type 2 insulin independent (adult onset) controlled by diet/lifestyle diabetes mellitus abnormally high blood [glucose] (hyperglycemia) so much glucose in the glomerular filtrate, that PCT can’t reabsorb it all… (transport proteins are saturated) … so some ends up in the urine glycosuria polyuria diabetes mellitus health problems much of the body thinks it is “starving” diabetic retinopathy diabetic neuropathy risk of MI (3x-5x) other vascular problems other endocrine organs intestines gonads kidneys digestive hormones reproductive hormones EPO, renin adipose, thymus, heart