Ch. 18 - Endocrine System Flashcards
What are autocrine hormones?
local hormones that are secreted by, and bind to, the same cell
What are paracrine hormones?
local hormones that are secreted into interstitial fluid and act on nearby cells
What are some characteristics of lipid-soluble hormones?
hydrophobic, nonpolar/uncharged; often bound to transport proteins
What are some characteristics of water-soluble hormones?
hydrophilic, polar/charged; circulate freely in the plasma
What are some examples of lipid-soluble hormones?
steroids, thyroid hormone, NO
What are some examples of water-soluble hormones?
- amine (NE, dopamine, serotonin)
- peptide/protein hormones (ADH, OT, GH)
- eicosanoid (prostaglandin)
What are 3 types of stimuli that trigger hormonal secretion?
- humoral stimuli
- neural stimuli
- hormonal stimuli
What is humoral stimuli?
changing levels of certain chemicals in blood or body fluids
What is receptor downregulation?
cell response to excess hormone by decreasing number of receptors
What is receptor upregulation?
cell response to decreased hormone by increasing number of receptors
How does the hypothalamus secrete releasing/inhibiting hormones?
via hypophyseal portal system to control secretion of ant pituitary hormones
neurosecretory cells –> capillaries of hypothalamus –> hypophyseal portal veins –> capillaries of ant pituitary
What are hormones produced by the anterior pituitary?
GH, TSH, FSH, LH, PRL, adrenocorticotropic hormone (ACTH), melanocyte-stimulating hormone (MSH)
What controls the release of GH from the somatotrophs of the anterior pituitary? Where do these hormones come from?
growth hormone-releasing hormone (GHRH) and growth-hormone-inhibiting hormone (GHIH) from hypothalamus
What is the primary function of GH?
produce insulin-like growth factors (IGFs) from liver, sk muscles, cartilage, bones
What are some effects of IGFs?
- increase cell growth and division by increasing a.a. uptake and prot synthesis & inhibiting prot breakdown
- stimulate glycogen breakdown to increase blood glucose level & stimulating lypolysis so FA can be used for ATP prod
How can gH lead to diabetes?
excess GH causes hyperglycemia
- pancreas releases insulin continually –> beta-cell burnout (no more insulin) –> leads to diabetes mellitus
What stimulates GH secretion?
low blood glucose, low blood FA acids, high blood a.a.
What stimulates GHRH secretion?
low blood glucose, low blood FA acids, high blood a.a.
What stimulates GHIH secretion?
high blood glucose, high blood FA acids, low blood a.a.
What does thyrotropin-releasing hormone trigger?
release of thyroid-stimulating hormone (TSH) from thyrotrophs of ant pituitary
What does TSH stimulate?
synthesis and secretion of T3 and T4 hormones from thyroid gland
Describe the negative feedback of TRH secretion
high levels of T3/T4 inhibit TRH secretion
What does gonadotropin-releasing hormone trigger?
release of FSH and LH from gonadotrophs of the anterior pituitary
What does FSH function in?
oocyte maturation, estrogen production, sperm production
What does LH function in?
ovulation, testosteron e production
What do prolactin-releasing hormone (PRH) and prolactin-inhibiting hormone (PIH) release?
prolactin from lactotrophs of ant pituitary
What is the function of PRL?
initiates and maintains milk production and secretion by mammary glands; released during pregnancy
What is the function of the corticotropin-releasing hormone (CRH) ?
stimulates release of ACTH and MSH from corticotrophs of ant pituitary
What is the function of ACTH?
stimulates cells of adrenal cortex to produce glucocorticoids
What do negative feedback loops control?
secretions of thyrotrophs, gonadotrophs, corticotrophs
What do inhibiting hormones (from hypothalamus) control?
secretions of somatotrophs, lactotrophs
What is the function of OT?
targets smooth muscle in uterus and breasts
What does OT do during delivery?
muscle contraction of uterus (+ feedback)
What does OT do after delivery?
contractions for expulsion of placenta; stimulates ejection of milk from breasts
What does the amount of ADH secreted depend on?
blood osmotic pressure and blood volume
What is the function of ADH?
decreases urine output, causes vasoconstriction
How do changes in blood volume affect ADH secretion?
increase in blood vol –> decrease in ADH secretion
decrease in blood vol –> increase in ADH secretion
What causes diabetes insipidus?
hyposecretion of ADH
- leads to dehydration, excretion of large amounts of dilute urine
What hormones does the thyroid gland produce?
T3, T4, calcitonin
What part of the thyroid gland produce T3 and T4?
thyroglobulin used by follicular cells (that surround the gland)
What part of the thyroid gland produce calcitonin?
parafollicular cells (between the thyroid follicles)
What is the function of calcitonin?
lower Ca2+ levels in blood
What are functions of thyroid hormones?
- increase basal metabolic rate (stimulate prot synthesis, increase cell resp, make and use more ATP)
- upregulate b-adrenergic receptors for E/NE
- work with GH/IGF to accelerate body growth
What does hypothyroidism in adults produce?
sensitivity to cold, low body temp, weight gain, mental/physical lethargy
What is Grave’s disease?
cause of hyperthyroidism; autoimmune disease that causes production of antibodies thatmimic TSH
What is Grave’s disease?
cause of hyperthyroidism; autoimmune disease that causes production of antibodies that mimic TSH
What happens when T3/T4 levels drop?
- hypothalamus secretes TRH
- anterior pituitary secretes TSH
- thyroid follicular cells produce T3/T4
- elevated T3 levels inhibit TRH and TSH release
What is the function of parathyroid hormone (PTH) ?
regulator of Ca2+, Mg2+, PO4 in blood; increases [electrolytes] in blood
Describe mechanism of PTH functions
- increase osteoclast activity; bone resorption release Ca2+ and PO4 into blood
- increases reabsorption of Ca2+ & Mg2+ by kidneys
- promotes formation of calcitriol by kidneys that enhances Ca2+ & Mg2+ absorption by intestinal cells
What does PTH oppose?
calcitonin (inhibits osteoclast activity!)
What can hypoparathyroidism lead to?
low levels of electrolytes
- muscle twitches, spasms, tetany
What can hyperparathyroidism lead to?
high levels of electrolytes
- promotes formation of kidney stones, excessive bone resorption (easily fractured)
What can hyperparathyroidism lead to?
high levels of electrolytes
- promotes formation of kidney stones, excessive bone resorption (easily fractured)
What parts of the adrenal glands produce steroids? NE/E?
outer cortex - steroid hormones
inner medulla - E/NE
How is the adrenal cortex divided?
3 zones
- glucocorticoids (glucose homeostasis, stress response)
- mineralocorticoids (mineral homeostasis)
- androgens
What are the effects of glucocorticoids?
resistance to stress
anti-inflammatory/immune suppression
Describe resistance to stress effects of glucocorticoids
- promote protein and fat breakdown to make ATP
- gluconeogenesis - convert a.a./FA to glucose to make atp
- enhance vasoconstriction (increase BP)
Describe anti-inflammatory effects of glucocorticoids
- decrease capillary permeability, WBC numbers, WBC activity
- delay tissue repair/wound healing
- also used in organ transplants to treat certain autoimmune diseases
What is Cushing’s syndrome? What does it lead to?
- high levels of circulating cortisol due to hypersecretion or exogenous hormone (use of immunosuppressive drugs)
- lead to hyperglycemia, poor wound healing, susceptibility to infections, fat redistribution
How are glucocorticoids regulated?
- hypothalamus releases corticotropin-releasing hormone (CRH)
- ant ptituitary releases ACTH
- adrenal cortex releases glucocorticoids
What is the function of aldosterone?
helps regulate blood pH; acts mainly on distal tubes/collecting ducts of the nephrons in the kidney
What are the effects of mineralocorticoids?
- regulates Na+/K+ homeostasis (Na+ reabsorption, K+ excretion)
- promote water reabsorption to regulate BP/BV
- promotes H+ excretion in urine to prevent acidosis
What would lead to aldosterone secretion?
dehydration, low Na+, low BP
What are the effects of androgens?
- promotes growth in boys/girls before puberty
- after puberty in M, insignificant bc testosterone from testes predominates
- after puberty in F, promotes libido; sole source of estrogens after menopause
What are the 3 stages of the stress response?
- fight-or-flight response
- resistance reaction (involves CRH, GHRH, TRH)
- exhaustion (suppression of immune system, muscle wasting, ulcers)
What does the stress response lead to an increase in?
- increase resources (FA, glucose in blood; breakdown of protein into a.a. for repair)
- increase metabolism (increase circulation/BP, respiration)
In the RAA pathway, what stimulates the release of renin?
- dehydration, Na+ deficiency, hemorrhage
- decreases BP/BV
- triggers increased renin from juxtaglomerular cells in kidneys
In the RAA pathway, what stimulates the release of angiotensin II?
- increased renin from kidneys + angiotensinogen from liver
- both cause increased angiotensin I
- circulates to lungs; then convert angiotensin I –> angiotensin II via angiotensin converting enzyme (ACE)
In the RAA pathway, what stimulates the release of aldosterone?
- increased angiotensin II stimulates adrenal cortex
2. increased K+ in ECF
What is the end result of the RAA pathway?
- increased BV and vasoconstriction of arterioles lead to increased in BP
In the RAA pathway, what stimulates increased levels of angiotensin I?
- increased renin converts angiotensin from liver
What is DHEA?
dehydroepiandrosterone; weak androgens produced by the adrenal cortex
What do pancreatic alpha cells produce?
glucagon –> raise blood glucose level
What do pancreatic beta cells produce?
insulin –> lowers blood glucose level
What is type I diabetes mellitus caused by?
absolute deficiency of insulin; often due to autoimmune attack of beta cells
What is type II diabetes mellitus caused by?
decreased sensitivity to insulin
e.g. downregulation of insulin receptor on target cells
What is diabetes mellitus characterized by?
- excessive urine production
- excessive thirst/eating
- FA broken down for energy
- excess glucose damages BV, leading to tissue ischemia, eye and kidney pathologies
How does diabetes mellitus lead to excessive urine production and excessive thirst?
high blood glucose causes glucose in urine, triggering osmotic diuresis (water pulled out of blood into urine along conc gradient)
How does diabetes mellitus lead to excessive eating?
due to lack of glucose available for cells (lack of receptors)
How does diabetes mellitus lead to FA being broken down for energy?
ketone bodies in blood make blood acidic
What hormones do the ovaries secrete?
2 estrogens (estradiol & estrone), progesterone, inhibin, relaxin
What is the function of estrogens and progesterone?
regulate repro cycle, maintain pregnancy, prepare mammary glands for lactation, maintain F secondary sex characteristics
What is the function of inhibin?
inhibits FSH secretion
What is the function of relaxin?
helps dilate uterine cervix during labour and delivery; increase flexibility of pubic symphysis
What hormones are secreted by the testes?
testosterone and inhibin
What is the function of testosterone?
regulate descent of testes, sperm production, maintenance of M secondary sex characteristics
What hormones does the thymus secrete?
secretes hormones involved in T lymphocyte maturation and activation and in various immune responses
What hormone does the heart release?
atrial natriuretic peptide (ANP) in response to high BP
- increases sodium and water secretion; opposite of aldosterone
What hormones do the kidneys release?
erythropoietin (in response to hypoxia), renin, calcitriol
