Ch. 17 - Endocrine System Flashcards
Endocrine system
composed of ductless glands of epithelial tissue within a connective tissue framework that synthesize and secrete hormones to be transported to target cells.
target cells
have specific receptors for a hormone
How do hormones travel
Hormones are released into interstitial fluid and then into the blood where they are transported. They randomly leave the blood and enter into interstitial fluid where they bind to target cells’ receptors.
Nervous system vs. Endocrine
Both are the control systems of the body and release ligands that bind to receptors on particular target cells. Unlike nervous, endocrine is more widespread and transfers hormones everywhere, has longer reaction times and effects
Functions of the Endocrine system
regulating development, growth, and metabolism, maintaining homeostasis of blood comp. and volume, controlling digestive processes and reproductive activities
Regulating development, growth, and metabolism
regulate embryonic cell division and differentiation. Regulate metabolism (anabolism and catabolism.
ligands
chemical messangers
maintaining homeostasis of blood comp & volume
regulate blood solute concentrations, blood volume, cellular concentration, and platelet #
controlling digestive processes
hormones influence secretory processes and movement of materials in digestive tract
controlling reproductive activities
hormones affect development and function of reproductive systems and the expression of sexual behaviors.
Endocrine glands with solely endocrine function
pituitary, pineal, thyroid, parathyroid, adrenal
endocrine cells found in clusters in organs with other functions
hypothalamus, skin, thymus, heart, liver, stomach, pancreas, small in., adipose ct, kidneys, gonads
hormonal stimulation
a gland cell releases its hormone when some other hormone binds to it
humoral stimulation
a gland cell releases its hormone when there is a certain change in levels of a nutrient or ion in the blood.
nervous stimulation
a gland cell releases its hormone when a neuron stimulates it.
Steroids
lipid-soluble made from cholesterol
gonadal steroids (estrogen) adrenal steroids (cortisol)
calcitriol is more accurately a sterol
biogenic amines (monoamines)
modified amino acids, water soluble except for TH.
Includes catecholamines, thyroid hormone, melatonin
Thyroid hormone
a biogenic amine made from a pair of tyrosines. is nonpolar and lipid soluble.
Proteins
most hormones, water-soluble chain of amino acids
Local hormones
signaling molecules that don’t circulate in blood
Eicosanoids
type of local hormone formed from fatty acids within phospholipid bilayer of membrane. Synthesized through an enzymatic cascade; stimulate pain and inflammatory response. NSAIDS block prostaglandins (type of eicosanoid)
Eicosanoid formation
Phospholipase A2 removes arachidonic acid from phospholipid. Other enzymes then convert arachidonic acid to a type of eicosanoid
Water-soluble hormones
are polar and can’t diffuse so must use membrane receptors. Goes through a signal transduction pathway. This works in that the hormone (first messenger) binds to a receptor on cell membrane. this activates a g-protein which causes activation of a membrane enzyme (like adenylate cyclase). This activated enzyme makes the second messenger- the chemical that modifies cellular activity.
Action/Results of water-soluble hormones
with different signal transduction pathways comes different results. Enzymes can be activated/inhibited, muscles contract/relax, membrane permeability changes, cellular secretions released, growth stimulated.
Hormone interactions on target cell
different hormones bind simultaneously and can react as synergistic, permissive, or antagonistic
Synergistic interactions
One hormone reinforces activity of another hormone. ex: estrogen and progesterone.
Permissive interactions
One hormone requires activity of another hormone. ex: for oxytocin to stimulate milk ejection there has to be prolactin to make milk.
Antagonistic interactions
One hormone opposes activity of another hormone. ex: glucagon vs. insulin
Hypothalamus controls the…
pituitary gland.
Pituitary gland controls the…
thyroid, adrenal glands, liver, testes, ovaries
Pituitary gland
known as hypophysis. Lies inferior to hypothalamus in sell turcica of sphenoid. It is pea-sized and connected to hypothalamus via the infundibulum. portioned into anterior and posterior parts.
Posterior Pituitary
neurohypophysis. smaller part of pituitary that has hypothalamic neurons that project through infundibulum and release hormones in post. pit.
Somas in paraventricular nucleus and supraoptic nucleus
Axons in hypothalmo-hypophyseal tract of infundibulum
Synaptic knobs in pars nervosa.
Anterior Pituitary
hypothalmo-hypophyseal portal system of blood vessels connects hypothalamus to ant. pit.
Hypothalamo-hypophyseal portal system
has primary plexus (capillary network near hypothalamus), secondary plexus (capillaries near ant. pit. and hypophyseal portal veins that drain primary plexus to transport to secondary.
Interactions between hypothalamus and posterior pituitary
Posterior pit. stores and releases oxytocin (ot) and antidiuretic H (ADH). These hormones are made in hypothalamus’ neurosecretory cells, packed into vesicles, transported via fast axonal transport and released from synaptic knobs when neurons fire.
Antidiuretic hormone (vasopressin)
made in supraoptic nucleus. Functions to decrease urine production, stimulate thirst, and constrict blood vessels.
Oxytocin
made in paraventricular nucleus. Functions: uterine contraction, milk ejection, emotional bonding.
Interactions between hypothalamus and anterior pituitary
hypothalamus hormonally stimulates anterior pituitary to release hormones. Hypothalamus secretes regulatory hormones that travel via portal blood vessels to pituitary. This causes ant. pit. to secrete hormones into general circulation.
Hormones of the hypothalamus
releasing hormones, inhibiting hormones
Releasing hormones
Increases secretion of ant. pit. hormones. Includes thyrotropin-releasing hormone, prolactin-releasing hormone, gonadotropin RH, corticotropin RH and growth hormone RH.
Inhibiting hormones
decrease secretion of anterior pituitary hormones. Includes Prolactin-inhibiting hormone and growth-inhibiting hormone
Hormones of anterior pituitary
TSH, PRL, adrenocorticotropic hormone (ACTH), gonadotropins (FSH & LH), Growth hormone
Thyroid-stimulating hormone (TSH)
release is triggered by TRH from hypothalamus. Causes release of thyroid hormone from thyroid gland. (released by ant. pit.)
Prolactin (PRL)
release triggered by PRH, inhibited by PIH from hypothalamus. Causes milk production, mammary gland growth in females. (released by ant. pit.)
Adrenocorticotropic hormone (ACTH)
release is triggered by CRH (corticotropin releasing hormone). causes release of corticosteroids by adrenal cortex. (released by ant. pit.)
Gonadotropins
Follicle-stimulating hormone (FSH) and luteinizing hormone (LH). In females, these regulate ovarian development and secretion of estrogen and progesterone. In males these help with sperm development and secretion of testosterone. (released by ant. pit.)
Growth Hormone (GH, Somatotropin)
causes liver to secrete insulin-like growth factors 1 & 2. (IGFs). GH and IGFs function synergistically to stimulate cell growth and division. Regulation of release is controlled through hormonal stimulation (GHRH & GHIH) from hypothalamus… amount of GHRH released is determined by age, time, nutrient levels and exercise.
Effects of growth hormone (what it does)
stimulates IGFs (similar function to GH) from liver - all cells have receptors for IGF or GH. Stimulates increased protein synthesis, cell division, cell differentiation, release of nutrients from storage… Stimulates glycogenolysis, gluconeogenesis, lipolysis and inhibits glycogenesis and lipogenesis.
gluconeogenesis
conversion of nutrients (outside food) to glucose.
Anatomy of thyroid gland
inferior to thyroid cartilage of larynx, anterior to trachea. broken into two lobes, left and right connected at midline by an isthmus. Vascularization gives it a red color. Composed of follicles.
follicular cells
cuboidal epithelial cells surrounding a central lumen in the thyroid gland, synthesize thyroglobulin and TH
colloid
a viscous, protein-rich fluid that is housed in thyroid gland’s follicle lumen.
parafollicular cells
cells between follicles that make calcitonin
calcitonin
synthesized and released from parafollicular cell of thyroid. hormone that decreases blood calcium levels and can be stimulated by stress from exercise. Inhibits osteoclast activity; stimulates kidneys to increase calcium excretion
iodine
required to make thyroid hormone where it goes through a series of steps in the thyroid
T3
triiodothyronine (3 iodo made in thyroid) t3 and 4 are moved by carrier molecules. T3 is partially inactivated
T4
tetraiodothyronine (thyroxine) most target cells convert this to t3 (more active form), but thyroid gland produces more T4
Hypothalamic-pituitary-thyroid axis
refers to the set of steps and the link between the organs in order to get something done. For example: cold temp, hypoglycemia, high altitude etc. causes hypothalamus to release TRH. TRH causes ant. pit. to release TSH. TSH binds to follicular cell’s receptors which triggers release of TH. Release two forms of TH, T3 and T4.
Thyroid hormone
increases metabolic rate and protein synthesis in targets. stimulates synthesis of sodium-potassium pumps in neurons. Stimulates increased amino acid and glucose uptake and increases # of cellular respiration enzymes within mitochondria. Fosters ATP production.
calorigenic
something that generates heat and raises temperature. (TH is calorigenic)
hyperthyroidism
results from excess TH production. Increased metabolic rate, weight loss, hyperactivity, heat intolerance. Caused by t4 ingestion, excessive pituitary stimulation, or loss of feedback control in thyroid (graves disease). treated by removing the thyroid and giving hormonal supplements.
hypothyroidism
results from decreased production of TH. low metabolic rate, lethargy, cold intolerance, weight gain. caused by decreased iodine intake, loss of pituitary stimulation of thyroid, or destruction of thyroid (hashimotos thyroiditis) treated with thyroid hormone replacement.
goiter
enlargement of thyroid usually due to insufficient dietary iodine preventing thyroid from producing TH. Not common in US since iodine was added to table salt.
Anatomy of adrenal gland
on superior surface of each kidney. retroperitoneal; embedded in fat and fascia. contains two regions: medulla and cortex.
Adrenal medulla
forms inner core of each adrenal gland. Red-brown due to blood vessels. Releases epinephrine and norepinephrine with sympathetic stimulation.
Adrenal cortex
synthesizes over 25 corticosteroids. Yellow due to lipids. has 3 regions producing different steroid hormones: zona glomerulosa, fasciculata, and reticularis.
Hormones of the adrenal cortex
mineralocorticoids, glucocorticoids, gonadocorticoids, cortisol.
Mineralocorticoids
hormones that regulate electrolyte levels. Made in zona glomerulosa (thin outer layer)
Aldosterone
type of mineralocorticoid that fosters Na retention and K secretion
Glucocorticoids
hormones that regulate blood sugar; made in zona fasciculata (larger, middle adrenal cortical layer)
effects of cortisol
type of glucocorticoid that causes target cells to increase blood nutrient levels. Liver cells increase glycogenolysis and gluconeogenesis; decrease glycogenesis. Adipose cells increase lipolysis and decrease lipogenesis. Many body cells break down proteins to amino acids. Liver cells use amino acids for gluconeogenesis. Most cells decrease glucose uptake, raising bg.
Gonadocorticoid
sex hormones; made in zona reticularis (thin, inner layer)
Androgens
male sex hormones made by adrenals; converted to estrogen for females. Amnt. produced from adrenals is less than testes.
Theraputic doses of corticosterone
used to treat inflammation. Inhibits inflammatory agents and suppresses immune system. At high doses it increases risk of infections, cancer, retention of h20 and sodium, and inhibits ct repair.
Cushing syndrome
chronic exposure to excessive glucocorticoid hormones in people taking corticosteroids or adrenal gland produces too much. Symptoms include obesity, hypertension, excess hair growth, kidney stones, and menstrual irregularities.
Addison disease
adrenal insufficiency; chronic shortage of glucocorticoids and sometimes mineralocorticoids. May develop from lack of ACTH or lack of response to it. Symptoms include weight loss, fatigue, weakness, hypotension, skin darkening. Oral corticosteroids treat it.
adrenogenital syndrome (congenital adrenal hyperplasia)
inability to synthesize corticosteroids which leads to overproduction of ACTH. high ACTH increases size of adrenal gland and production of testosterone-like hormones. This masculinizes hormones
Stress Response
stressors elicit hypothalamus to initiate a neuroendocrine response. 3 stages
3 stress response stages
alarm reaction (initial response of epinephrine release and SNS activation), stage of resistance (occurs after depletion of glycogen stores, adrenal secretes cortisol to raise bg to help meet energy demands), and stage of exhaustion (after weeks or months in a stress response, depletion of fat stores results in protein breakdown for energy leading to weakening of the body and illness)
Anatomy of the pancreas
behind stomach, b/w duodenum and spleen.
Acinar cells
pancreatic cells that generate exocrine secretions for digestion. They make up the vast majority of the pancreas as saclike acini
Pancreatic islets (of Langerhans)
contain clusters of endocrine cells (alpha and beta cells)
alpha cells
pancreatic cells that secrete glucagon
beta cells
pancreatic cells that secrete insulin
delta cells
secrete somatostratin
f cells
secrete pancreatic polypeptide
normal bg
70-110
diabetes mellitus
inadequate uptake of glucose from blood. chronically elevated glucose, blood vessel damage. leading cause of retinal blindness, kidney failure, and nontraumatic amputations in US. associated w/ increased heart disease and stroke
type 1 diabetes
absent or diminished release of insulin by pancreas, occurs in younger individuals. autoimmune, requires daily injections
type 2 diabetes
decreased insulin resistance, obesity is a major cause in development. older individuals, treated with diet, exercise and meds.
gestational diabetes
if untreated, causes risk to fetus and increased delivery complications. increases chance of developing t2d.
hypoglycemia
glucose below 60. Caused by insulin overdose, exercise, alcohol use, liver or kidney disfunction, deficiency in glucocorticoids or GH, genetics. symptoms= hunger, dizziness, confusion, sweating, sleepiness. Glucagon given if unconscious.
pineal gland
small unpaired body in epithalamus of diencephalon. secretes melatonin to cause drowsiness and regulates circadian rhythm and can effect mood. Melatonin influences GnRH secretion
parathyroid gland
small structures on back of thyroid gland (between 2-6 of them, usually 4). Contains chief cells and oxyphil cells
Chief (principal) Cells
make PTH (parathyroid hormone). This increase blood calcium by taking it from bones, decreasing its loss in urine and activating calcitriol hormone
Thymus
epithelial cells secrete thymic hormones. The thymus is located anterior to top of heart and is only active during childhood. It is a maturation site for T-lymphocyte white blood cells.
Endocrine Heart Tissue
in heart atria; secretes atrial natriuretic peptide (ANP). This lowers bp by increasing urine output and dilating blood vessels.
Kidney Endocrine Cells
releases erythropoietin (EPO). Secretions occurs in response to low blood oxygen to increase red blood cell production.
Liver Endocrine Secretions
Insulin-like growth factors and the inactive hormone angiotensinogen. it is converted into angiotensin II by enzymes from the kidney and lung blood vessels. Angiotensin II helps raises bp by causing vessel constriction, decreases urine output and stimulates thirst.
Stomach Endocrine Secretions
Gastrin; increases secretion and motility in stomach for digestion.
Small intestine endocrine secretions
secretes secretin and cholecystokinin (CCK) into blood. Secretin stimulates secretion of bile and pancreatic juice. CCK stimulates release of bile from gall bladder.
Skin Endocrine Function
light converts modified cholesterol to vitamin D3 which is released into blood. Vit. D3 is converted to calcidiol by liver enzyme which is then converted to calcitriol by kidney enzyme. Calcitriol is the active hormone that raises blood calcium. Stimulates Ca from bone, decreases Ca loss in urine, and stimulates Ca absorption in intestine
Adipose Connective Tissue Endocrine secretions
leptin; controls appetite by binding to neurons in hypothalamus. Lower body fat is associated with less leptin and this stimulates appetite. Other adipose endocrine effects include increased risk in cancer and delayed puberty in males. Low adipose interferes with menstrual cycle.
glycogenolysis
breakdown of glycogen into glucose
glycogenesis
synthesis of glycogen
lipolysis
breakdown of triglycerides
lipogenesis
formation of triglycerides
Thyroid hormone and ATP production
hepatocytes (liver cells) are stimulated to increase blood glucose through glycogenolysis & gluconeogenesis. Adipose cells stimulated to increase blood glycerol and fatty acids. TH increases lipolysis. This saves glucose for the brain. TH also increases respiration rate to meet additional o2 demand (mitochondria), hr increase and force of contraction, more blood flow and causes heart to increase receptors for epinephrine and norepinephrine.
glucose-sparing effect
body cells use fats and other energy sources to save glucose for the brain to run.
Regulation of cortisol release
Cortisol and corticosterone increase nutrient level in blood. release regulated by hypothalamic-pituitary-adrenal axis. late stages of sleep, stress, or low level cortisol stimulates hypothalamus to release CRH. CRH stimulates ant. pit. to release ACTH. ACTH stimulates adrenal cortex to release cortisol. Cortisol then inhibits release of CRH and ACTH
Lowering high bg with insulin
beta cells detect high bg and release insulin. Insulin binds to target receptor cells and initiates 2nd messenger systems. Once blood glucose falls, glycogenesis and lipogenesis is stimulated. Most body cells increase nutrient uptake in response to insulin (amino acid for protein synthesis, glucose)
Cells that do not require insulin to take in glucose
neurons, kidney, hepatocytes, RBCs
Raising low bg with glucagon
Alpha cells release glucagon and 2nd messengers cause body cells to release stored nutrients into blood. hepatocytes release glucose, adipose cells release fatty aids and glycerol. lipolysis, glycogenolysis, and gluconeogenesis is stimulated.
