Quiz 8 Flashcards
Endocrine vs. exocrine
endocrine- secrete hormones directly into ECF (pituitary, adrenal, etc)
exocrine- products discharged through ducts (salivary, sweat)
What are hormones?
chemical messengers; either proteins, pepties, amino acid derivatives, or steroids
paracrine vs. autocrine
paracrine- hormone acts on neighboring cell
autocrine- hormone acts on itself
Second messenger system
Hormone binds to receptor, activates G protein, which activates enzyme, which causes production of “second messenger”- causes reaction
Endocrine System characteristics
- slow, prolonged
- hormones broken down by liver, excreted in urine
- supplies all cells with receptor
- UNCONSCIOUS
Neuro System characteristics
- fast
- can “switch off”
- supplies ONLY muscles and glands
- hypothalamus controls ANS
- conscious brain can control
Negative feedback loop
stops production and secretion of hormone once specific response has occured
What are glands stimulated by?
- changing blood levels
- stimulating hormone
- nerve stimulus
- gene expression
Adrenal cortex and its hormones
glomerulosa- “salts” -aldosterone
fasciculata- “sugars” - glucocorticoids
reticularis- “sex” - androgens
Aldosterone
major role in ECF Na and K concentrations and total fluid balance
- 60% bound to plasma proteins
- 20 minute half life
What stimulates aldosterone release?
- HYPERKALEMIA
- angiotensin II
- hyponatremia
- ACTH
RAAS
1) renin released from kidney in response to hypovolemia, SNS stim, hypotension, hyponatremia
2) renin acts on angiotensinogen to form angiotensin I
3) angiotensin I -> angiotensin II by ACE in lungs
4) angiotensin II causes vasoconstriction and release of aldosterone
Where does aldosterone exert effects and what does it do?
DCT and principal cells of collecting ducts- reabsorption of Na, secretion of K (expands ECF and elevates BP)
What is the major glucocorticoid?
cortisol/hydrocortisone
How much cortisol produced daily?
15-30 mg/day, mostly in the morning
Cortisol characteristics
- highly protein bound
- free cortisol is active form
- stress/surgery increases production (100 mg/day)
- ACTH controls secretion
- metabolized by liver
Cortisol negative feedback loop
1) cortisol inhibits release of CRH from hypothalamus
2) cortisol decreases ACTH synthesis and release from anterior pituitary
Glucocorticoids effect on carb metabolism
- stimulates gluconeogenesis
- decrease glucose uptake and use by muscles
- overall increase blood glucose concentration
Glucocorticoids effect on protein metabolism
- decrease synthesis and increase catabolism in all body cells except liver
- effect on skeletal muscles- weak and atrophic
Glucocorticoids effect on fat metabolism
- FFA mobilized from adipose tissue
- enhanced oxidation of FFA
- enables use of FFA for energy when glucose limited
- distinct obesity- chest, abd, intrascapular, buffalo torso, moon face)
Glucocorticoids effect on inflammation and immunity
- diminishes inflammatory response
- suppresses proinflammatory cytokines
- decreases antibody production
- decreases eosinophils and lymphocytes
- stablizes lysosomal membranes
What is the primary androgen?
testosterone
Catecholamines of medulla
- 80% epi
- 20% NE
- both metabolized in liver and kidney by COMT
Where are catecholamines stored and how are they released?
chromafin granules; released by stimulation of sympathetic nerves
Anterior and posterior lobes of anterior pituitary
anterior- adenohypophysis
posterior- neurohypophysis
Hormones of anterior pituitary
FSH, LH, ACTH, TSH, prolactin, GH (FLAT PiG)
hormones of posterior pituitary
ADH, oxytocin
growth hormone
skeletal development and body growth, regulates protein and carb metabolism
Adrenocorticotropic hormone (ACTH)
regulates release of hormones from adrenal gland and growth of adrenal cortex
TSH
controls growth and metabolism of thyroid gland and secretion of thyroid hormones
FSH
stimulates ovarian follicle development in females and spermatogenesis in males
LH
induces ovulation in females, stimulates testes to produce testosterone in males
prolactin
promotes mammary gland development and milk production; inhibits synthesis and secretion of LH and FSH; increased in pregnancy
What inhibits ACTH?
increased cortisol levels and opioids
What stimulates ACTH?
corticotropin releasing hormone, hypoglycemia, stress, trauma, sepsis, alpha adrenergic stim, decreased cortisol, circadian rhythm
When is ACTH the highest?
2 hours before and just after awakening
Growth hormone characteristics
- aka somatotropin
- release stimulated by GHRH from hypothalamus
- inhibited by GHIF (somatostatin)
- secretion also stimulated by stress, deep sleep, exercise, hypoglycemia
Where are the posterior pituitary hormones synthesized?
hypothalamus- travel down via pituitary stalk
oxytocin
stimulates milk secretion and contraction of uterus
ADH/vasopressin
acts on collecting ducts to increase free water reabsorption through aquaporins (increases blood volume, urine osmo, decreases serum osmo)
What stimulates ADH?
1) increase in plasma osmo (osmoreceptors in hypothalamus)
2) decrease in blood volume by >10-20% (peripheral varoreceptors and atrial stretch receptors)- afferent signal through vagus/glossopharyngeal nerves)
Factors that influence ADH release
hypotension, stress, pain, PPV, hyperthermia, beta adrenergic stim, histaimes, volatile agents, smoking, nausea
Pancreas functions
- exocrine- acinar cells (synthesize digestive enzymes and bicarbonate for digestion)
- endocrine- islets of langerhans (4 types of cells)
Islet of Langerhans cells
Beta- secrete insulin and amylin
alpha- secrete glucagon
delta- secrete somatostatin
pancreatic polypeptide -inhibits exocrine pancreatic secretion
Glycolysis
breakdown of glucose to pyruvate or lactate
glycogenesis
storage of glucose as glycogen
gluconeogensis
formation of glucose from lactate, pyruvate, aa, and glycerol
lipogenesis
formation and storage of fat as triglycerides
lipolysis
breakdown of stored triglycerides to FFA and glycerol
Obligate vs. facultative tissues
- obligate- can only use glucose as energy (brain, medulla, RBCs)- ketones used during starvation
- facultative- use glucose for energy if available (can use amino acids or fats)- muscles and most other tissues
Insulin
- secreted in capillaries and portal circulation
- 50% removed by 1st pass
- daily secretion 60 units/delivery is 30 units
Metabolic effects of insulin
- liver and muscle- promotes storage of glycoge, inhibits gluconeogenesis
- stimulates uptake of amino acids- promotes protein synthesis and inhibits breakdown
- carbs are converted to FFA and glycerol- stored as triglycerides, inhibits breakdown, limits use of fats for fuel when glucose high
Insulin effect on ion transport
stimulates uptake of K, Mg, and phosphate into cells
Factors that stimulate insulin release
amino acids, GI hormones, PSNS stimulation, beta adrenergic stimulation, ACTH, vagal stimulation
Factors that inhibit insulin release
hypoglycemia, somatostatin, glucagon, cortisol, GH, alpha adrenergic stimulation, stress
Glucagon
- biological antagonist to insulin
- increases plasma glucose and enhances hepatic glucose output via gluconeogensis and breakdown of liver glycogen
- blood glucose <90 stimulates release
- works with GH, cortisol, and epi
Somatostatin
- inhibits insulin and glucagon secretion
- decreases motility of stomach, duodenum, and gall bladder contraction
- decreases GH release
- decreases secretion and absorption within GI tract
- extends time over which food and nutrients are digested and absorbed
Type 1 diabetes
- absolute insulin deficiency- dependent on exogenous insulin
- beta cell destruction (symptoms when >80% destroyed)
- prone to DKA
Type 2 diabetes
- impaired insulin secretion, peripheral insulin resistance, abnormal fat metabolism, excess hepatic glucose production
- obesity
- insidious onset
- prone to HHS
What connects 2 lobes of thyroid?
isthmus
Follicles of thyroid
- lined by epithelial cells
- produce and secrete T4 and T3
Thyroid hormone functions
- increase cellular activity
- required for normal growth
- growth and development of brain during fetal and postnatal
- augment HR and contraction
- enhance secretion of digestive juices and GI motility
- increased hormone secretion of most endocrine glands ( especially pancreas)
What is necessary for T4 and T3 production?
iodine
Regulation of thyroid hormone secretion
1) TRH released from hypothalamus
2) TRH causes ant. pituitary to produce and secrete TSH
3) TSH causes increased thyroid gland activity
4) if overactivity, excessive amounts of TH produced
Calcium regulation
- 99% in bone
- 1% in ECF
- changes in protein may affect Ca status
- alkalosis- increases protein binding, decrease serum iCal
3 forms of serum calcium
9%- nonionized, bound to anions
41% non ionized, bound to proteins
50%- ionized and diffusible, active
PTH
- secreted from chief cells of parathyroid in response to low serum iCal, high phosphate, low mag
- increases extracellular calcium concentration, decreases phosphate
Direct effects of PTH
bone resorption (osteoclasts), increased reabsorption from DCT, phosphate excretion in PCT
Indirect effects of PTH
promotes formation of vitamin D which enhances calcium and phosphate absorption from intestines
PTH feedback loop
small decrease in circulating iCal produces rapid increase in PTH secretion and vice versa
Difference b/w calcium chloride and gluconate
calcium chloride has higher concentration
Vitamin D
- absorbed from GI or produced enzymatically by UV light
- inactive form converted in liver and kidney to active
- active increases Ca, Mg, phosphate absorption
- inadequate- rikets, osteomalacia
Calcitonin
- secreted by thyroid in response to elevated iCal
- lowers serum calcium
- weak effect- inhibits osteoclasts (osteoblasts more prevalent)
Symptoms of hypocalcemia
hyperreflexia, muscle spasm, tetany, perioral paresthesias, laryngospasm, Chvostek (twitching of face), Trousseau’s (flexion of wrist and thumb)
