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106 terms

Chapter 17: Endocrine System

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Hormone
chemical messenger secreted into bloodstream, stimulates response in another tissue or organ
Target Cells
have receptors for specific hormone
Endocrine Glands
produce hormones
Endocrine System
includes hormone producing cells in organs such as brain, heart and small intestine
Endocrine Glands
no ducts release hormones into tissue fluids, have dense capillary networks to distribute hormones
Intracellular Effects
alter target cell metabolism
Exocrine Glands
ducts carry secretion to body surface or other organ cavity, extracellular effects (e.g. digestive enzymes-food)
Electrical Impulses and Neurotransmitter, adapts
quickly to continual stimulation
Hormones in Blood adapt
slowly (days to weeks)
Speed and Persistence of Response of nervous system
reacts quickly (1-10 msec), stops quickly
Speed and Persistence of Response of endocrine system
reacts slowly (seconds to days), may continue long after stimulus stops
local
specific effects on target organs
general
widespread effects on many organs
Neuroendocrine Cells
neurons that secrete hormones into ECF
Several Chemicals Function as both as
neurotransmitters and hormones (norepinephrine)
Endocrine and Nervous system have
overlapping effects on same target cells
Systems regulate each other
neurons trigger hormone secretion, hormones stimulate or inhibit meurons
Hypothalamus
shaped like a flattened funne, forms floor and walls of third ventricle, regulates primitive functions from water balance (thirst and sweat) to sex drive (rage), works with (attached to) pituitary gland
Pituitary Gland (hypophysis)
suspended from hypothalamus by stalk (infundibulum), housed in bone (sella turcica) of the skull
Pituitary Lobes
anterior, posterior and middle
Pituitary Development
the anterio lobe (adenoshypopysis) derives from embryonic oral tissue (glandular-adeno, teh pars tuberalis (middle lobe) also derives from oral glandular tissue (pars intermedius in fetus), the posterior lobe (neurohypophysis) derives from neural (brain) tissue
Anterior Lobe
"tropic" hormones (meaning they target other endocrine glands) are released from the hypothalamus and carried to the pituitary by a portal (means venule to cap. to ven. or arteriole to cap. to art. ) capillary system, gonadotropins target gonads (testes and ovaries), FSH (follicle stimulating hormone) and LH (luteinizing hormone), TSH (thyroid stimulating hormone), ACTH ( adrenocorticotropic hormone
Non-tropic hormones
PRL (prolactin) and GH (growth hormone)
Posterior Lobe of pituitary gland
stores and releases OT (oxytocin) and ADH (antidiuretic hormone)
OT and ADH are produced
in the hypothalamus and transported down to the posterior lobe by hypothalamo-hypophyseal tract (axons- cell bodies in hypothal.)
Hypothalamo-hypophyseal portal system - anterior lobe control
releasing hormones and inhibiting hormones of hypothalamus, gonadotropin- releasing hormone (GNRH), thyrotropin- releasing hormone (TRH), corticotropin- releasing hormone (CRH), prolactin - releasing factor (PRF), Prolactin- inhibiting factor (PIF), GH- releasing hormone (GHRH), GH- inhibiting hormone (GHIH) - aka somatostatin
Hypothalamo-hypophyseal portal system - posterior lobe control
neuroendocrine reflexes, hormone release in response to nervous system signals-suckling infant stimulates nerve endings -> hypothalamus -> posterior lobe -> oxytocin milk ejection, hormone release in response to higher brain center- milk ejection reflex can be triggered by a baby's cry
Negative Feedback
increase target organ hormone levels inhibits release of tropic hormones (short and long "loop")
Positive Feedback
stretching of uterus increase OT release, causes stretch of uterus, increase OT release, etc... until delivery
FSH (follicle stimulating hormone)
ovaries, stimulates development of eggs and follicles, testes, stimulates production of sperm
LH (luteinizing hormone)
females, stimulates ovulation and corpus luteum to secrete progesterone, males, stimulates interstitial cells of testes to secrete testosterone
ACTH (adrenocorticopropic hormone)
regulates response to stress, effect on adrenal cortex and secretion of glucorticoids
PRL (prolactin)
female, milk synthesis, male, increase LH sensitivity, thus increase testosterone secretion
ADH (antidiuretic hormone)
targets kidneys to increase water retention, reduce urine (vasopressin- constricts blood vessels), also functions as neurotransmitter
OT (oxytocin)
labor contractions, lactation (letdown), possible role sperm transport, emotional bonding
GH ( growth hormone)
targets liver to produce somatomedins- increase mitosis + cellular differentiation for tissue growth,
Protein Synthesis
mRNA translated, increase DNA transciption for increase mRNA production, enhances amino acid transport into cells, decrease catobolism
Lipid Metabolism
stimulates FFA and glycerol release, protein sparing
Carbohydrate Metabolism
glucose sparing effect- glucose stored as glycogen
Electrolyte Balance
promotes NA+, K+, Cl- retention, Ca2+ absorption
GH levels - childhood
bone, cartilage and muscle growth
GH levels - adulthood
declines with age
Pituitary disorders
hypopituitarism, panhypopituitarism, diabetes insipidus and hyperpituitarism
Hypopituitarism
pituitary dwarfism, childhood decrease GH
Panhypopituitarism
complete cessation of pituitary secretion, causes broad range of disorders
Diabetes Insipidus
decrease ADH, 10x normal urine output
Hyperpituitarism
Childhood- gigantism, adult - acromegaly (thickening of bones, soft tissues of hands, feet and face)
Pineal Gland
peak secretion 1-5 yr. olds, by puberty 75% lower, produces serotonin by day, converts it to melatonin at night
Thymus
location: mediastinum, superior to heart, shrinks (involution) after puberty, secretes hormones that regulate development and later activation of T-lymphocytes (immune cells)
Thyroid Gland
largest endocrine gland, anterior and lateral sides of trachea, 2 large lobes connected by isthmus, filled with colloid and lined with simple cuboidal epith. (follicular cells) that secretes 2 hormones, T3 + T4- T4 (tetraiodothyronine-thyroxine)- T3 (triiodothyronine- more powerful, but less abundant
TH Effects
body's metabolic rate and O2 consumption, calorigenic effecct- increase heat production, heart rate and contraction strength, respiratory rate
Parafollicular Cells
produce calcitonin that blood Ca2+, promotes Ca2+ deposition and bone formation especially in children
Thyroid Gland Disorders
congenital hypothyroidism, myxedema, endemic goiter, toxic goiter
Congenital Hypothyroidism (decrease TH)
infant suffers
Myxedema
adult hypothyroidism, decrease TH
Endemic Goiter
goiter- enlarged thyroid gland
Toxic Goiter
(graves disease)- antibodies mimic TSH, increase TH, exophthalmos (bulgiing of the eyeballs)
Parathyroid Glands
secrete PTH (parathyroid hormone)- blood Ca2+, decrease Ca2+ absorption, decrease Ca2+ urinary excretion and incrase bone resorption (destruction); hypoparathyroid vs. hyperparathyroid
Adrenal Glands
Adrenal Medulla, Adrenal Cortex
Adrenal Medulla
sympathetic ganglion innervated by sympathetic preganglionic fibers- stimulation causes release of (nore-) epinephrine
Adrenal Cortex
3 layers: (outer) zona glomerulosa, (middle) zona fasciculata, (inner) zona reticularis; secrete corticosteriods
Mineralocorticoids (zona glomerulosa) control
electrolyte balance, aldosterone promotes Na+ retention and K+ excretion
Corticosteroids
glucocorticoids (zona fasciculata- response to ACTH), especially cortisol, stimulates fat + protein catabolism, glucaneogenesis (from a.a's + FA's and release of fatty acids and glucose into blood to repair damaged tissues
Sex Steroids
(zona reticularis)- androgens (male hormones), including DHEA (other tissues convert to testosterone) and estrogen (important after menopause)
Adrenal Gland Disorders
Pheochromocytoma, cushing syndrome, adrenogenital syndrome, addison disease
Pheochromocytoma
tumor of adrenal medulla, with hypersecretion of (nor-) epinephrine, causes increase BP, increase metabolic rate, hyperglycemia, glycosuria, nervosuness, indigestion, sweating
Cushing Syndrome (adrenal tumor, excess ACTH)
causes hyperglycemia, hypertension, weakness, edema, muscle, bone loss with fat deposition shoulders + face
Adrenogenital Syndrome (AGS)
androgen hypersecretion cuases enlargement of penis or clitoris and prematrue onset of puberty, prenatal AGS in girls can result in masculinized genitals (photo), AGS in women can result in deep voice, beard, body hair
Addison Disease
hyposecretion of glucocorticoids and mineralocorticoids by adrenal cortex, hypoglycemia, Na+ and K+ imbalances, dehydration, hypotension, weight loss, weakness, causes increase pituitary ACTH secretion, stimulates melanin synthesis and bronzing of skin
Pancrease
retroperitoneal, inferior and dorsal to stomach
Mostly exocrine gland with pancreatic islets of endocrine cells that produce:
insulin, glucogan, somatostatin
Insulin (from B cells)
secreted after a meal with carbohydrates raises glucose blood levels, stimulates glucose and amino acid uptake, nutrient strage effect (stimulates glycogen/ stored glucose, fat and protein synthesis), antagonizes glucagon
Glucagon (from a cells)
secreted in very low carbohydrate and high protein diet or fasting, stimulates glycogenolysis (breakddown of glycogen into glucose), fat catabolism (release of FFA's) and promotes absorption of amino acids for gluconegensis (forming gluc, from fat and/ or protein)
Somatostatin
(growth hormone- inhibiting hormone, from delta () cells), secreted with rise in blood glucose and smino acids after a meal, paracrine secretion- modulates secretion of a + b cells
Diabetes Mellitus: signs and symptoms
poyuria (excess urine output), polydipsia (excess thirst), polyphagia (excess hunger), hyperglycemia, glycosuria, ketonuria (ketones are a product of fat catab.)
Osmotic Diuresis
blood glucose levels rise above transport maximum of kidney tubules, glucose remains (spills") in urine, osmolarity of blood increase and draws water in, this also increase urine osmol., drawing water into urine
Type I
(insulin- dependent diabetes mellitus- IDDM)- 10% of cases ("juvenile" onset), some cases have autoimmune destruction of b cells, diagnosed about age 12, treated with diet, excercise, monitoring of blood glucose and periodic injections of insulin or insulin pump
Typ II
(non-insulin- dep, diab. mell. - NIDDM) - 90% of cases ("adult onset), insulin resistance: failure of target cells to respond to insulin, 3 major risk factors are heredity, age (40+) and obesity, reated with weight loss program of diet and exercise, oral medication improve insulin secretion or target cell sensitivity
Acute Pathology
cells cannon absorb glucose, rely on fat proteins (weight loss + weakness)
Fat Catabolism
increase FFA's in blood and ketone bodies
Ketonuria
(ketones in urine) promotes osmotic diuresis, loss of Na+ and K+
Ketoacidosis
occurs as ketones decrease blood pH: if continued causes dyspnea (hyperventilating to try and get rid of acid) and eventually diabetic coma
Chronic Pathology
chronic hyperglycemia leads to neuropathy and cardiovascular damage, damage to retina and kidneys (common in type I), atherosclerosis leading to heart failure (common in type II), and gangrene
Hyperinsulinism
from excess insulin injection or pancreatic islet tumor, causes hypoglycemia, weakness and hunger, triggers secretion of epinephrine, GH and glucagon, side effects: anxiety, sweating and increase HR
Insulin Shock
uncorrected hyperinsulinism with disorientation, convulsions or unconsciousness
Granulosa Cells
wall of ovarian follicle- produces estradial, increases during first half of menstrual cycle
Corpus Luteum
follicle remnant after ovulation produces progesterone for at 12 days after ovulation or several weeks with pregnancy (eventually disintegrates)
Functions of estrogens and progesterone
development of female reproductive system and physique, regulate menstrual cycle, sustain pregnancy, prepare mammary glands for lactation
Both granulosa cells and corpus secrete and suppresses
inhibin and FSH secretion (neg. feedback)
Interstitial (leydig) cells (between seminiferous tubules)
produce testosterone
Functions (of testosterone)
developement of male reproductive system and physique, sustains sperm production and sex drive
Sustentacular (sertoli) Cells
secrete inhibin: suppresses FSH secretion, stabilizes sperm production rates
Heart
atrial natruicetic peptide (ANP)- decrease blood volume + decrease (blood pressure) BP, from increase Na+ and H2O loss by kidneys
Calcitriol
Ca2+ and phosphate: increase absorption, decrease loss for bone deposition (formation)
Erythropoietin
stimulates bone marrow to produce (red blood cells) RBC's
Stomach and Small intestines
enteric hormones (cordinate digestive motility (movement) and secretion)
Liver
angiotensinogen (a prohormone-precursor of angiotenisn II, a vasoconstrictor), erythropoietin (15%), and somatomedins- mediate action of GH
Placenta
secretes estrogen, progesterone and others (to regulate pregnancy and stimulate development of fetus and mammary galnds)
Steroids
derived from cholesterol (sex steroids, corticosteroids, etc...)
Peptides and glycoproteins
OT, ADH; all releasing and inhibiting hormones of hypothalamus; most of anterior pituitary hormones
Monoamines (biogenic amines)
derived from the amino acid tyrosine (catecholamines (morepinephrine, epinephrine, dopamine) and thyroid hormones)
Eicosonoids
important family of paracrine (not produced in neurons or transported in blood-travel short distance) secretions, derived from arachidonic
Lipoxygenase
converts arachidonic acid to leukotrienes that mediate allergic and inflammatory reactions
Cyclooxygenase
converts arachidonic aciid to prostacyclin
Prostacyclin
produced by blood vessel walls, inhibits blood clotting and vasoconstriction
Thromboxones
produced by blood platelets after injury, they override prostacyclin and stimulate vasoconstriction and clotting