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Transcript
Endocrine System: How Hormones Control Bodily Functions Objectives of Chapter Describe the general function of various hormones What do they do? What inhibits or stimulates their release? Name the glands the hormones are released from Explain how hormones exert their effects on target cells Review diseases associated with excessive or deficient hormone secretion Endocrine System Endocrine system - cells, tissues, organs (glands) secrete “hormones” into body fluids (ie blood stream) Exocrine glands - into ducts Functions 1. regulate metabolic processes; 2. aid in transporting substances through cell membranes; 3. regulate water balance 4. reproduction, development & growth Hormone Action & Type Hormones work on “target cells” Steroid hormones; lipid based, derived from cholesterol Amine/peptides/protein; Glycoproteins Action of Steroid Hormones (fig. 13.5; p. 473) Action of Non-Steroid Hormones Control of Hormonal Secretions Hypothalamus; tropic hormones; neural control pituitary (“master”) gland Changes in internal environment ie – hydration states are detected and series of events cause water retention Nervous system Negative feedback system Hormones of Anterior Pituitary Gland (table 13.6; p. 485) Growth hormone (GH) Stimulates in size & rate of reproduction of body cells movement of A.A. into cells; protein synthesis; fat utilization, decreases glucose use; Promotes growth of long bones Stimulated by: sleep, protein deficiency, low blood glucose, high intensity exercise Abnormal secretion: dwarfism vs acromegaly, bovine growth hormone (milk) Follicle-stimulating hormone (FSH) develop. egg-containing follicles in ovaries; stimulates secretion of “estrogen”; males, stim. production of sperm cells Luteinizing hormone (LH) promotes secretion of sex hormones; estrogen, testosterone; releases egg cell in females Levels of both at puberty **together are called “gonadotropins” Prolactin (PRL) promotes secretion of milk from mammary glands Thyroid Stimulating Hormone Adrenocorticotropic Hormone (ACTH) Posterior Pituitary Hormones Oxytocin contracts muscles in uterine wall & milk-secreting glands; controlled by stretch in uterine & vaginal walls, & stimulation of breasts Antidiuretic hormone (ADH) causes kidneys to water excretion; can blood pressure ; controlled by plasma concentration & blood volume osmorecptors in hypothalmus, stretch receptors in blood vessels Hormones of Thyroid Gland (table 13.7; p. 487) Thyroxine (T4) metabolism of carbs, fats, & protein; protein synthesis; accelerates growth; stimulates nervous system Triiodothyronine (T3) o same as above; more potent; **both have affects on metabolism Calcitonin blood calcium levels by inhibiting release from bone; deposition in bone controlled by blood calcium levels Parathyroid Glands Secretes Parathyroid Hormone (PTH); Opposite effects of calcitonin Ca++ levels in blood; Releases Ca++ from bone; Conserves Ca++ at kidneys; Influences vitamin D to help small intestine absorb Ca++ Adrenal Glands (table 13.11 & 13.10) Adrenal cortex aldosterone; cortisol; Sex hormones – “adrenal androgens” Adrenal Medulla epinephrine; *norepinephrine Adrenal Cortex (figure 13.31) Aldosterone; causes kidney to conserve Na+ & excrete K+; retains water responds to ’s in composition of blood; stimulated by ACTH Adrenal Cortex (figure 13.33) Cortisol maintain glucose levels; inhibits protein synthesis; promotes fat breakdown; stimulates liver to make glucose from A.A. & glycerol (gluconeogenesis) *control inflammation Factors causing secretion: prolonged exercise, low blood sugar levels, excessive stress Adrenal Medulla 2 Hormones Epinephrine (adrenalin); *Norepinephrine; *together know as catecholamines; Effects resemble result of sympathetic nerve fibers “fight or flight” Epinephrine primary hormone Release stimulus comes from nerve fibers from hypothalamus in response to “stress” Adrenal Medulla (table 13.10) o Metabolic rate Increases Pancreas (table 13.12) Glucagon – helps to blood glucose stimulated by blood glucose glycogenolysis (liver); lipolysis (adipose cell); gluconeogensis in liver Insulin – helps to blood glucose stimulated by blood glucose allows glucose, fats, & amino acids to move into all cells muscle & liver - glycogen, triglyceride, protein adipose cell - triglyceride (promotes storage of fat) inhibits gluconeogensis Other Endocrine Glands Pineal gland – (brain) melatonin – inhibited by light & stimulated by darkness involved in “circadian rhythms”; female reproductive cycle; ? (seasonal affective disorders) Thymus gland secretes thymosin; production of white blood cells (immunity) Reproductive glands ovaries – estrogen & progesterone testes - testosterone Conditions Associated with Abnormal Secretions of These Hormones What Happens When the Body Does Not Produce and Release these Hormones Properly?? Special Topics involving the Endocrine System Diabetes mellitus (hormone relationship “insulin”); difficulty maintaining blood glucose levels Type 1 (insulin-dependent); 15% of diabetics, usually before 20 yrs autoimmune response destroying pancreatic cells which produce insulin (beta cells); require insulin injections Type 2 (non-insulin-dependent) 85% of diabetics, usually after age of 40 (not any more though), associated with obesity Receptors on cells are damaged & don’t respond to insulin Treatment - monitor carbohydrate intake, exercise, weight loss, possibly medication Growth Hormone Excessive Release; may caused by tumor on anterior pituitary gigantism vs acromegaly Too little Release; initially used to treat medical conditions (dwarfism) Human Growth Hormone (hGH) many times used in combo. with steroids to enhance muscle size; connective tissue (strength gains don’t parallel muscle size gains) is illegal w/o prescription!! hGH Aging effect reversed by exogenous GH supplementation?? (negative side effects) Abnormal Thyroid Hormone Levels Hyperthyroidism metabolic rate sensitive to heat, hyperactivity, weight loss Graves Disease – auto-antibodies over-stimulate thyroid gland goiter Hypothyroidism metabolic rate sensitive to cold, sluggish, weight gain In children (Cretinism) stunted growth, mental retardation Hashimoto’s disease Disorders of Parathyroid Glands (table 13.8) Hyperparathyroidism depresses nervous system bone weakening fatigue, depression o *why would it do the above???? usually caused by tumor Hypoparathyroidism excites nervous system muscle cramps & seizures, diminishes blood calcium ion concentration usually caused by inadvertent surgical removal; injury Special Topics Involving the Endocrine System Addison’s disease adrenal cortex doesn't secrete sufficient hormones (autoimmune disease) low blood glucose levels (hypoglycemia), Na+, K+, dehydration, fatigue, low blood pressure Cushing’s disease over secretion of ATCH & cortisol due to corticosteroid drugs for many years, tumor on adrenal gland characterized by muscle wasting, blood glucose levels & blood pressure moon face (adipose tissue deposition), masculinized females due to sex hormone release Special Topics in Endocrine System Diabetes Insipidus impaired ADH function either receptors or hypothalamus prevents proper water regulation (constantly excrete water)