Endocrine System PDF

Friday, September 20, 2024 Endocrine System Travel through the general circulation to their target cells that are distant from their source ENDOCRINE GLAND - consists of ductless glands that secrete HORMONES into interstitial fluids, the horm...

Friday, September 20, 2024 Endocrine System Travel through the general circulation to their target cells that are distant from their source ENDOCRINE GLAND - consists of ductless glands that secrete HORMONES into interstitial fluids, the hormones then enter the blood - Rich in blood supply and some glands of the endocrine system perform - Goes to their target sites called target tissues, or effectors Insulin goes to skeletal organs for the glucose to be used for energy STIMULATION OF HORMONES 1. HUMORAL STIMULI - “blood”, sensitive to the blood levels of a particular substance; anytime there is something low in the blood, PTH is released 2. NEURAL STIMULI - associated with release of hormones via neural stimulation; sympathetic NS stimulates norepinephrine to stimulate releasing cortisol when a person is stressed out 3. HORMONAL STIMULI - another hormone can stimulate releasing other endocrine glands to release hormone INHIBITION OF HORMONES Humoral inhibition - every time a hormone is released, another hormone is released to inhibit that hormone gland origin - When a hormone’s release is sensitive to the presence of a humoral stimulus, there exits a companion hormone whose release is inhibited by the humoral stimulus Blood pressure control - aldosterone and atrial natriutic peptide, aldosterone to get the blood pressure rise and in any case aldosterone is overstimulated, atrial natriuretic will also be released to accompany aldosterone and balance its effect Neural Inhibition - neurotransmitters are released to inhibit hormones; neurotransmitters stop releasing hormones Hormonal inhibition - hormones inhibit other hormones to stop it from secreting 1   NEGATIVE FEEDBACK - hormone’s secretion is inhibited by the hormone itself, once blood levels have reached a certain point; hormones is regulated at a certain level POSITIVE FEEDBACK - self-propagating system whereby the stimulation of hormone secretion increases over time FUNCTIONS OF ENDOCRINE SYSTEM: 1. Regulate metabolism: thyroid hormone, cortisol 2. Control our food intake and digestion (Insulin, GI hormones): regulates the level of satiation 3. Modulation of tissue development (growth hormone, thyroid) 4. Regulation of ion levels (aldosterone, ANP, PTH, calcitonin): 5. Control of water balance (ADH, aldosterone, ANP): controls the solute concentration of blood 6. Changes in heart rate and blood pressure (TH, cortisol, aldosterone): 7. Control of blood glucose and other nutrients (insulin, glucagon) 8. Control reproductive functions (androgens, estrogen, testosterone) 9. Stimulation of uterine contractions and milk release (oxytocin, prolactin) 10. Modulation of immune system function (thymosin, cortisol): help produce the immune cells PITUITARY GLAND: - 1cm in diameter, weighing 0.5 - 1.0 g - Connected to the base of the brain, inferior to the hypothalamus’connected to the hypothalamus by the stalk called infundibulum - Divided into two lobes: anterior pituitary gland (adenohypophysis) 7 hormones; darker color, posterior (neurohypophysis) 2 hormones; the one connected to the brain; same tissue configuration of the hypothalamus - Another name is hypophysis - Pea-sized gland located in sella turcica in sphenoid bone of skull - Synthesized 9 hormones that control the function of other glands under the control hypothalamus, before it can secrete hormones, hypothalamus influence pituitary gland secretion - Sagittal cut to see the pituitary gland - Hypothalamic-pituitary portal system, hypothalamic-hypoficial portal system, blood vessels that will bring hormones from the hypothalamus to act on the anterior pituitary gland dependent on hypothalamus for hormone secretion - Releasing hormones - a hormone produced by the hypothalamus to stimulate the pituitary gland to release hormones 2   - Inhibiting hormones - once released by the hypothalamus to influence the pituitary gland to stop releasing hormones 5 RELEASING HORMONES OF THE HYPOTHALAMUS: MASTER GLAND OF THE BODY 1. GROWTH HORMONE RELEASING HORMONE - comes from the HYPOTHALAMUS to stimulate the anterior pituitary to release growth hormone 2. COTRISOL RELEASING HORMONE - released from the hypothalamus to stimulate the anterior pituitary to stimulate the pituitary to release another hormone to stimulate adrenal gland to release cortisol 3. THYROTROPIN RELEASING HORMONE - stimulate anterior to release TSH to stimulate 4. PROLACTIN RELEASING HORMONE - released to sitm ulate the anterior pituitary to release T to secrete prolaction \\ 5. GONADOTROPIN RELEASING HORMONE - released from hypothalamus to stimulate the anterior pituitary to release Luteinizing hormone and follicle stimulating - both hormones important in sexual development INHIBITING HORMONES GROWTH HORMONE INHIBITING HORMONE PROLACTIN INHIBITING HORMONE SOMATOSTATIN - neural cells; inhibit 2 hormones, inhibit growth hormone, thyroid stim ulating hormone from pituitary gland DOPAMINE - an inhibit prolactin, “feel good” hormone; will influence addiction to what makes you feel good ANTERIOR PITUITARY IS DEPENDENT ON HYPOTHALAMUS TO RELEASE HORMONES Stimuli within the nervous system regulate the secretion of releasing hormones ANTERIOR PITUITARY GLAND HORMONES 1. GROWTH HORMONE - target tissue (most tissue, bones, muscles, organs); increase gene expression, breakdown of lipids, and release of fatty acids from cells, increased blood glucose levels; GIANTISM - exaggerated bone growth before the closure of epiphyseal plate; ACROMEGALY - growth in bone diameter only after closure of epiphyseal plate; PITUITARY DWARFISM - abnormally stunted growth 2. THYROID STIMULATING HORMONE (TSH) -binds to membrane bound receptors on cells of the thyroid gland and stimulates the secretion of thyroid Hormone: INCREASED - 3   size of the thyroid gland and TH secretion; DECREASED - size of the thyroid gland and decrease of TH secretion 3. ACTH ADRENOCORTICOTROPIC HORMONE - CORTISOL RELEASING HORMONE - target gland is adrenal gland and release cortisol (stress hormone; hydrocortisone) whenever stressed out; 4. PROLACTIN - prolactin releasing hormone reach to anterior pituitary gland to release prolactin to stimulate breast for milk production 5. MELANOCYTE-STIMULATING HORMONE (MSH) - binds to membrane bound receptors on melanocytes and caused them to synthesize melanin: does not need stimulation from the hypothalamus; target organ is the skin 6. LUTEINIZING HORMONE - hypothalamus needs to release gonadotrophic releasing hormone ; target organ is ovary and testes to produce the hormones estrogen and testosterone 7. FOLLICLE STIMULATING HORMONE - GONADOTROPINS same as luteinizing hormone to stimulate ovum and sperm cells POSTERIOR PITUITARY GLAND HORMONES - doesn’t need a releasing hormone - produces its own hormone - Hypothalamus makes the two hormones and sends to posterior pituitary gland and will directly set it out - 1. ADH ANTIDIURETIC HORMONE “VASOPRESSIN” - target tissue is the kidney; a water- conservation hormone; prevents the output of large amounts of urine; INCREASED: SYNDROME OF INAPPROPRIATE ADH (SIADH) - water reabsorption in kidneys, less volume, inc blood volume: DECREASED - DIABETES INSIPIDUS - water reabsorption, more urine output, dec blood volume 2. OXYTOCIN - target tissue is the mammary gland; increase uterine contractions, increases milk letdown from the mammary glands; PROLACTIN makes the milk, OXYTOCIN release the milk THYROID GLAND - located beneath the larynx and located on each side of the trachea - Composed of two lobes connected by a narrow tissue called isthmus - Weighs about 20 g - Highly vascular THYROID FOLLICLE CELLS - produce the thyroid hormones: filled with colloid, produces thyroglobulin where TH are synthesized and stored 4   PARAFOLLICULAR CELLS OR C CELLS - secretes calcitonin IODINE - needed for hormone synthesis 2 TYPES OF THYROID HORMONE 1. THYROID HORMONE - target tissue are most cells of the body TRIODOTHYRONINE or T3 - three iodine attached to it, stronger one of the two TETRAIODOTHYRONINE or 3T4 - four iodine attached to it, most abundant CALCITONIN: FOR CALCIUM - secreted by the parafollicular or C CELLS, target tissue is the bone, causes blood calcium back to normal, deactivates osteoclasts but won’t affect osteoblasts DISEASES OF THE THYROID HYPERTHYROIDISM - have excess hormone, feels hot all the time, eat a lot but don’t gain weight, have bulging eyes, thin, tremors of the fingers, metabolism is overacting Graves disease - autoimmune disease wherein the immune system produces abnormal proteins that mimic TSH, which overstimulates the thyroid gland, exophthalmia HYPOTHYROIDISM - feel cold, don’t have any heat due to lack of hormone, easily get tired, feel fatigues, reducing hair, overweight and fat, lack hormones to break down Cretinism in infants - mental retardation, short 3 Pretibial myxedema - accumulation of fluid and other molecules in the subcutaneous tissue Iodine deficiency PARATHYROID GLAND -4 glands embedded in the posterior part of the thyroid gland - hypocalcemia: stimulates osteoclasts to dissolve bone and deposit calcium in blood, kidneys CELL TYPES: CHIEF CELLS - produce parathyroid hormone ( parathormone) - important in regulating 5   HYPERPARATHYROIDISM - bone resorption resulting in increase3 calcium levels; osteoclasts are more active to dissolve more bones; resolve into excess calcium and will cause kidney stones, emotionally unstable, memory loss HYPOPARATHYROIDISM - bone resorption and the formation of vitamin D , blood calcium levels decrease, nerves and muscles become excitable and produce spontaneous actin potentials, patients will have twitching due to low calcium and then muscles cannot move and actin potentials aren’t enough to contract ADRENAL GLAND - also called suprarenal gland - Two small glands located superior to each kidney - ADRENAL MEDULLA - inner part, marrow or middle: has one layer just called by its name - ADRENAL CORTEX - outer part, bark or outer: 3 layers (zona glomerulosa, zona fasciculata thickest layer, zona reticularis) - RIGHT ADRENAL - pyramidal in shape - LEFT ADRENAL GLAND - crescent in shape - The adrenal medulla and he adrenal cortex ADRENAL MEDULLA - arises from neural crest cells - Sympathetic division of the ANS secrete “fight or flight response” - Epinephrine/ adrenaline - Norepinephrine ADRENAL CORTEX - zona glomerulosa: aldosterone - mineralocorticoid; secretes secreted under low BP conditions; increases sodium reabsorption and then the water by the kidneys therefore increasing blood volume; increases potassium ion excretion in the kidneys, increase in the rate of hydrogen ion excretion in the urine - Na = IN, K and H2O = OUT Abnormality of aldosterone: may result to reduced blood levels of potassium ions, alkalosis (elevated pH of body fluids), increase absorption of sodium and H2O, then increase Potassium retention of Potassium and Hydrogen thus the blood will be too basic DECREASED - decrease sodium and H2O retention, increase Addison’s disease - low in cortisol and aldosterone; increased pigmentation, low blood pressure, 6   Don’t have the hormone to absorb the Na and H2O and excrete the K and H ZONA FASCICULATA - GLUCOCORTICOID Cortisol - stress hormone - increase lipid catabolism, Gluconeogenesis, Protein degradation, use of lipids and proteins to provide energy of cells, blood glucose and glycogen deposits in cells - Required for maturation of tissues - Decreases the intensity of the inflammatory and immune responses - Decreases glucose and amino acid uptake in skeletal muscle - Stimulated by the CRH from the hypothalamus and will be released by the pituitary gland to stimulate adrenal gland to release cortisol - Target organs: liver, fat, skeletal muscle, immune INCREASED CORTISOL: Cushing’s syndrome - moon-shaped faced, truncal obesity, abnormal hairiness (hirsutism), and hypertension, increased blood pressure Bone will become too brittle, easily gets fractures DECREASED CORTISOL: Addison’s disease ZONA RETICULARIS - ANDROGENS/ SEX HORMONES Androstenedione - weak androgen, for both males and females Generic term for steroid hormones that cause the development of male secondary sex characteristic Converted by peripheral tissues to the more potent androgen testosterone Stimulate pubic and axillary hair growth Increases sex drive in females Negligible in comparison with testosterone secreted by the testis ADRENAL MEDULLA Sympathetic nervous system through neural stimulation to stimulate the release of these hormones Fight or flight response 7   Release of stored energy sources to support increased physical activity Increased heart rate, which raises blood pressure Increased smooth muscle contraction in internal organ and skin blood vessels (vasoconstriction) which also raises blood pressure Increase blood flow to skeletal muscles Increase metabolism of tissues because we need to overcome the situation of the fight or flight 1. Epinephrine - higher in amount 2. Norepinephrine - has a better effect Increases cardiac output. Blood flow to skeletal muscles and heart; release of glucose and fatty acids into blood, generally prepares body for physical activity PHEOCHROMOCYTOMA - increased in both hormones; hypertension, headache, heavy sweating, increase in heart rate PANCREAS - located in the abdominal cavity, on the left upper quadrant - Both exocrine and endocrine gland - Head, neck, uncinate process, body, tail - Closely related with vascular structures in the abdomen - 60 - 100 mg of glucose INSULIN: produced by beta cells - islet of langerhans, target organs: liver, skeletal muscles, adipose tissues, appetite center for hypothalamus for satiety; increases uptake and use of glucose and amino acids going to the skeletal muscles and the liver Hypoglycemic effect: it’s supposed to lower glucose levels when it’s too high for blood glucose homeostasis Release when blood glucose levels are high Will make blood glucose decrease because glucose will go into skeletal muscles GLUCAGON: produced by the alpha cells; target organ: liver, increased breakdown of glycogen, release of glucose into the circulatory system - stimulus is hyperglycemic - Released when glucose levels are too low - Will make the blood glucose increase SOMATOSTATIN: produced by the delta cells, target: alpha and beta cells, inhibition of insulin and glucagon 8   CLINICAL CORRELATION: DIABETES MELLITUS: body’s inability to regulate blood glucose levels within the normal range TYPE 1: too little insulin production Glucose will be floating in the blood TYPE 2: either too few insulin receptors on target cells or defective receptors on target cells; insulin resistance; every time glucose is increased in the blood, pancreas release insulin, but the target organs does not let it absorb POLYURIA, POLYDIPSIA, POLYPHAGIA: Polyuria - always urinating Polyphagia - always hungry, Polydipsia - always thirsty because it will draw the water out of tissues Predisposed for blindness, kidney failure, lose a limb by blocking arteries and no blood supply Gestational diabetes - pregnant women can be diabetic, but will go away after labor, 35% of pregnant mother will develop a full blown diabetes TESTES AND OVARIES FEMALE REPRODUCTIVE HORMONES - produced primarily in ovaries, placenta (during pregnancy) n=and pituitary gland (FSH - stimulates production of follicles in ovary and LH - stimulates ovulation and production of estrogen and progesterone) ESTROGEN - aid in uterine and mammary gland development, maturation of genitalia, secondary sex characteristics, sexual behavior, and menstrual cycle PROGESTERONE - pregnancy hormone due to it increasing when a woman is pregnant which is still beneficial MALE REPRODUCTIVE HORMONE Secreted primarily testes and pituitary gland (FSH - stimulate to produce sperm cells, LH to produce testosterone) 9   TESTOSTERONE - produce by interstitial cells of the testes - aids in spermatogenesis, development of genitalia, maintenance of functional reproductive organs, secondary sex characteristics, sexual behavior, muscle enlargement, growth of body hair, voice changes, male sexual drive THYMUS - located on the upper part of the thoracic cavity in mediastinum - Start after birth, but stop functioning during puberty - Maturation of immune system for maturation of T-cells which is important to fight diseases - Will undergo involution as the person ages - Atrophies during puberty THYMOSIN hormone: target tissue: immune tissues PINEAL GLAND - posterior and superior to the Talamus - Located at the right and the left brain - Inhibits secretion of gonadotrophin-releasing hormone, thereby inhibiting reproduction MELATONIN: regulate sleep-wake cycle; inhibit reproductive function “photo period” - needs light to be produced and will be converted to SEROTONIN Other hormones 1. Gastrointestinal hormones - cells in the lining of the stomach and small intestines; digestive juices 2. Prostaglandins - almost all cells of the body can produce, for pain 3. Atrial natriutic peptide - secreted by the right atrium of the heart in response to elevated blood pressure DUE TO STRETCHING OF THE HEART MUSCLES - inhibits sodium reabsorption in the kidneys which results to more urine output 4. ERYTHROPOIETIN - secreted by the kidneys in response to reduced oxygen levels, acts on the bone marrow to increase the production of red blood cells; anemic if no erythropoietin 5. Human chorionic gonadotropin - hormone that maintain pregnancy produced by the placenta, is the one detected when taking pregnancy tests EFFECTS OF AGING ON THE ENDOCRINE SYSTEM 1. Decrease in the secretory activity 2. Decreased GH secretion 10   3. Thyroid hormones decreases - Blood calcium decreases, loss of bone matrix as parathyroid hormone incrreases to maintain blood levels of calcoum 11