Chapter 16: Endocrine System Flashcards
Basic Endocrine System Stuff
control system of the body; initiates responses slowly; long duration responses; acts via hormones released into the blood; acts at diffuse locations (can be anywhere that blood can reach); hormones act of long distances
Exocrine Glands
have ducts; secretes substances (not hormones) to a epithelial surface
Endocrine Glands
ductless; release hormones into the extracellular fluid (interstitial fluid- fluid that surronds all cells and plasma- fluid within blood vessels)
Hormones
long distance chemical signals released by endocrine glands into ECF; travel through out body via blood and lymphatic vessels; intitate changes in target cells; effective in tiny amounts
What are the types of hormone classification?
amino acid based; steroid hormones; basically water soluble and lipid soluble
Amino Acid Based Hormones
most cells; all except thyroid are water soluble and cannot cross plasma membrane of target cell; receptors embedded in plasma membrane of target cell (bc they cannot pass bilayer); require help of second messengers to relay messages to target cells interior such as cyclic AMP
ADD CYCLLIC AMP STUFF
Benefit of Second Messenger
it amplifies the hormone signal
What does amino acid based hormones change in target cells?
open or close ion channels (alters membrane permeability); activate/deactive enzymes; induce secretory activity; stimulate mitosis
Steroid Hormones
sex hormones and adrenocortical hormones; estragen, testosterone, progesterone, cortisol, aldesterone; ALL are lipid soluble; pass through plasma membrane and bind to intracellular receptors of target cells ALL derived from cholesterol; direct gene activation mechanism; steroid and thyroid hormones alter gene expression by turning genes on or off in target cells
ADD DIRECT GENE AACTIVATION
ADD LIPID V. WATER SOLUBLE
What are the three types of endocrine gland stimuli?
humoral stimulus, neural stimulus, hormonal stimulus; the three types trigger hormone synthesis and release from endocrine glands
Humoral Stimulus
changing blood levels of ions or nutrients; ex) low ca2 in blood triggers parathyroid gland to release parathyroid hormone (PTH)
Neural Stimulus
nervous system stimulates endocrine gland directly; ex) sympathetic ner. sys. triggers adrenal medulla to relase epinephrine and norepinephrine (fight/flight response)
Hormona Stimulus
release of hormone is cause by another hormone; ex) releaseing and inhibiting hormones of hypothalamus stimulate anterior ppituitary galnd to release its hormones, some of which stimulate other endocrine glands to release their hormones
Tropic Hormones
hormones that stimulate the release of other hormones
Nervous sys. has the ability to…
override (modulate) endocrine sys to maintain homeostasis; ex) bodys response to long term stress
Target Cell Specificity
hormones circulate throughout body but ONLY affect cells that have receptors for them (target cells); cells cannot respond to a hormone if they lack receptors for that hormone
Factors influencing Target Cell Activation
blood levels of hormone; number of receptors on or in target cells; hormone recepter affinity (strength of binding)
What happens to receptors when there is persistently low hormone levels?
stimulate cells to increase the number of receptors; aka up-regulation
What happens to receptors when there is persistently high hormone levels?
stimulate cells to decrease the number of receptors; aka down regulation
How do high affinity receptors act?
they bind readily to their hormone therefore receptors are activated even if a small amount of hormone is present
How do low affinity receptors act?
will only become activated if there is a large amount of hormone present
Permissiveness
occurs when one hormone requires another hormone to exert its full effect; thyroid hormone has a permissive effect on reproductive system development
Synergism
occurs when 2 hormones that have the same effect on a target cell combine to amplify the response; when glucagon and epinephrine act tgether live releases 150% more glucose into the blood
Antagonism
occurs when one hormone opposes the action of another hormone; insulin lowers blood glucose level while glucagon increases blood glucose levels
Hypothalamus
made of nervous tissue but still a endocrine organ; region of the brain that links the nervous and endocrine systems
Functions of the hypothalamus
chief integration center of the autonomic nervous system (ANS); regulates body temp, hunger, thirst, and sleep/wake cycles ; synthesizes (makes) two hormones (oxytocin and ADH) which is released by the posterior pituitary gland; synthesizes releasing and inhibiting hormones which regulate anterior pituitary hormone release
What are the releasing/inhibiting hormones synthesized by the hypothalamus?
growth hormone releasing hormone (GHRH); growth hormone inhibiting hormone (GHIH or somatostatin); thyrotropic releasing hormone (TRH); corticotropin releasing hormone (CRH); gonadotropin releasing hormone (GnRH); prolactin releasing hormone (PRH)
Pituitary Gland
sits in sella turcica of sphenoid
Posterior Pituitary
aka neurohypophysis; composed of neural tissue; communicates with hypothalamus via hypothalamis-hypophyseal tract; stores and releases oxytocin and ADH
Oxytocin
stimulated by impulses from hypothalamic neurons in response to stretching of the uterine cervix or suckling of infant at breast; inhibited by lack of appropriate neural stimuli; target organ/effect- uterus: stimulates uterine contractions; initiates labor; breast: initiates milk ejection; effects of hyper/hypo secretion- unknown
Antidiuretic Hormone
stimulated by hypothalamic response to increased blood solute concentration or decreased blood volume; inhibited by adequate hydratioon of the body and by alcohol; target organ/effect- kidneys: stimulate kidney tubule cells to reabsorb water from the forming urine back into the blood; hypersecretion= syndrom of inappropriate ADH secretion (SIADH); hyposecretion= diabetes insipidus
ADD SIADH AND DIABETES INSIPIDUS
Anterior Pituitary
aka adenohypophysis; composed of glandular tissue; communicates with hypo thalamus via hypophyseal portal sys (portal vein with capillary beds at each end); produces 6 hormones in response to hypothalamis releasing and inhibiting hormones
TSH, ACTH, FSH and LH are…
tropic hormones
What hormones are produced by the anterior pituitary?
growth hormone (GH); thyroid stimulating hormone (TSH); adrenocorticotropic hormone (ACTH); follicle stimulating hormone (FSH); luteininzing hormone (LH); prolactin (PRL)
Growth Hormone
GH; somatostatin; stimulated by GHRH release which is triggered by low blood levels of GH and other triggers ; inhibited by feedback inhibition exerted by GH and insulin like growth factors and other triggers by either increases GHIH or decreased GHRH release; target/effect: liver, muscle, bone, stimulates somatic growth, growth promoting effects mediated indiractly by IGFs; hyposecretion = pituitary dwarfism; hypersecretion = gigantism in children; acromegaly in adults
Thyroid Stimulating Hormone
TSH; stimulated by TRH and in infacnts indirectly by cold temp; inhibited by feedback inhibition exerted by thyroid hormones on anterior pituitary and hypothalamus and by GHIH; target/effect: thyroid gland- stimulates thyroid gland to release thyroid hormones; hyposecretion- hypothyroidism; may cause myxedema; hypersecretion- hyperthyroidism; effects similar to those of graves disease where antibodies mimis TSH
Adrenocorticotropic Hormone
stimulated by CRH; stimuli that increase CRH relesase include fever, hypoglycemia, and other stressors; inhibited by feedback inhibition exerted by glucocoriticoids; target/effect- adrenal cortex: promotes release of glucocorticoids and androgens
Follicle Stimulating Hormone
stimulated by GnRH; inhibited by feedback inhibition exerted by inhibin and estrogens in females and testosterone in males; target/effects: ovaries/testes: in females, stimulates ovarian follicle maturation and production of estrogen; in males stimulates sperm production; hyposecretion- failure of sexual maturation; hypersecretion- no important effects
Luteinizing Hormone
stimulated by GnRH; inhibited by feedback inhibition exerted by estrogens and progesterone in females and testosterone in males; target/effects- overies/testes- in females, triggers ovulation and stimulates ovarian production of estrogens and progesterone; in males, promotes testosterone production; hypersecretion- no important effect; hyposecretion- failure of sexual maturation
Prolactin
stimulated by decreased PIH; release enhanced estrogens, birth control pills, breast feeding, and dopamine blocking drugs; inhibited by PIH (dopamine); target/effects- breast secretory tissue- promotes lactation (makes milk); hyposecretion- poor milk production in nursing women; hypersecretion- inappropriate milk production
Thyroid Gland
largest purely endocrine gland in the body; only endocrine gland to stores its hormone (TH) extracellularly
Thyroid Hormone
TH; body main metabolic hormone; exists in two forms: thyroxine and triiodothyronine
Thyroxine
T4 ;main form secreted by follicular cells
Triiododthyronine
T3; 10 x more active than T4; most T4 converted to T3 at target cells
Regulation of TH Secretion
Rising TH blood levels and GHIH inhibit release of TRH and TSH; falling TH blood levels and exposure to cold (in infants) stimulate hypothalamus to release TRH
Effects of TH
targets most body cells; increased basal metabolic rate and body heat production (calorigenic effect); promotes glucose catabolism (production of ATP); regulates tissue growth and developement; promotes reprodutive ability; maintain BP
Hyposecretion of TH
results from defects in or surgical removal of thyroid galnd, inadequate TRH or TSH< GHIH or too little iodine in diet
Cretinism
in infants; hyposecretion of TH; macroglossia (enlarged tongue); umbilical hernia; mental retardation and stunted growth
Myxedema
in adults; hyposecretion of TH; low metabolic rate; chills and constipation; thick, dry skin, and puffy eyes; lethargy and mental sluggishness; goiter develops if hypothyroidism due to lack of dietary iodine
Hypersecretion of TH
graves disease- autoimmune condtion (abnormal antibodies mimic TSH); high metabolic rate; sweating; rapid, irregular heartbeat; weight loss; protruding eyeballs
Calcitonin
secretion stimulated by increased blood calcium; NO known physiological role in humans; at pharmacological levels used to treat Pagets disease and osteoporosis (inhibits osteoclast activit and stimulates ca2 uptake and incorporation into bone); pagets disease- excessive breakdown of bone with irregular bone reformation
Parathyroid Glands/Hormone
4-8 glands with variable location; PTH most important hormone regulating blood calcium levels; secretion stimualted by decrease blood ca2; primarily targets bone, kidneys and intestines
Hyposecretion of PTH
hypoparathyroidism; causes hypocalcemia; makes neurons more excitable (tingling sensations, tetany and convulsions); if untreated (respiratory paralysis and death)
Hypersecretion of PTH
hyperparathyroidism; causes hypercalcemia; depresses nervous system (abnormal reflexes); enhances formation of kidney stones
Adrenal Glands
superior to kidneys and consists of- capsule (fibrous); cortex (glandular); and medulla (nervous tissue)
What does the adrenal cortex consist of?
zona glomerulosa (mineralocorticoids); zona fasciculata (glucocorticoids); zona reticularis (gonadocorticoids)
Mineralocorticoids
in zona glomerulosa; primarily aldosterone; essential for life; target kidney tubules (regulates na, k, h20, in ECF); stimulate Na REABSORBTION from tubules; h2o follows na; cause secretion of k into tubules
Regulators of Aldosterone Release
renin-angiontensin-aldosterone mechanism; K in plasma; ACTH; atrial natriuetic peptide (ANP)
Hyposecretion of Aldosterone
causes Addisons disease; weight loss; decreased na and increased k in blood; severe dehydration and hypotension; bronzing of skin (early sign of addisons)
Hypersecretion of Aldosterone
causes aldosteronism; edema and hypertension (excess na retention); excessive excretion of k
Glucocorticoids
in zona fasciculata; primarily cortisol; target most cells; at normal levels, helps keep blood glucose levels constant; at higher levels, helps deal with chronic stress; mobilize (breaks down) stored lipids and proteins (increase blood levels of fatty acids and amino acids); increased blood glucose via glycogen breakdow and gluconeogenesis; prolonged exposrure to glucocorticoids suppress inflammatory and immune responses
Hyposecretion of Cortisol
causes addisons disease
Hypersecretion of Cortisol
causes cushings syndrome; increase blood glucose (steroid diabetes); loss of muscle and bone protein; na and h20 retention (which leads to hypertension and edema); cushnoid signs- swollen moon face, redistricution of to abdomen and back of neck and increase in infections
Gonadocorticoids
low levels of androgens; androgens converted in tissues to testosterone or estrogen; developemnt of axillary and pubic hair in females at puberty; contributes to female sex drive; source of estrogen (and testosterone) after menopause; in zona reticularis
Hyposecretion of Androgens
no known effects
Hypersecretion of Androgens
causes adrenogenital syndrome (masculinization of females); if conginetal, enlarged clitoris; recocious puberty; failure to menstruate or abnormal periods; excessive facial hair
Adrenal Medulla
produces epinephrine (80%) and norepinephrine (20%); reinforces sympathetic NS responses to short-term stres (fight or flight response)
Hyposecretion from Adrenal Medulla
not a problemH
Hypersecretion from Adrenal Medulla
prolonged fight or flight response
Pineal Gland
produces melatonin; peak production at night; induces drowsiness; influences circadian rhythm
Pancreas
has exocrine and endocrine functions; pancreatic islets produce hormones tha tregulate blood glucose levels (endocrine); acinar cells prduce digestive enzymes (exocrine)
Glucagon
produced by alpha cells of islets; release stimulated by decreased blood glucose; raises blood glucose; targets liver cells– breaks down glycogen to glucose (released into blood), promotes gluconeogenesis
Insulin
produced by beta cells of islets; release stimulated by increase blood glucose; lowers blood glucose; targets most body cells; stimualtes all cells except live, kidney, and brain to take up glucose removing it from blood; inhibits gluconeogenesis
Diabetes Mellitus
caused by hyposecretion (type 1) or hypoactivity (type 2) of insulin; blood glucose remains high after a meal; 3 cardinal signs- polyuria (increase urine output), polydipsia (increase water intake), polyphagia (increase appetite)
Ovaries
porduce female sex hormone s
Estrogens
maturation of female reproductive organs; appearance of secondary sex characteristis at puberty
Progesterone (+ estrogens)
breast development at puberty; monthly changes in uterine mucosa
Testes
produces male sex hormones
Testosterone
maturation of male reproductive oragns; appearance of secondary sex characteristic at puberty; production of sperm; responsible for male sex drinve
Placenta
temporary endocrine organ of pregnacy; secretes human chorionic gonadotropin (hCG) and high levels of estrogen and progeserone brginning in 2nd month; maintain health of placenta
Human Chorionic Gonadotropin
hCG; prompts ovary to continue production of estrogen and testosterone until placenta takers over; presence of hCG in mothers blood indicates pregnancy
Adipose Tissue
secretes leptin which supresses appetite
Atria of Heart
secretes atrial natriuretic peptide (ANP) which inhibits Na reabsorption and secretion of aldosterone to lower BP
Kidney
secretes erythropoietin which stimulates red bone marrow to produce more RBCs
Thymus
secretes thymosins which are involved in normal development of immune cells and immune response[p
