0-1 Chapter 17 - Endocrine System Flashcards
four principal mechanisms of communication between cells
gap junctions
neurotransmitters
paracrine (local) hormones
Hormones
gap junctions
pores in cell membrane allow signaling molecules, nutrients, and electrolytes to move from cell to cell
neurotransmitters
released from neurons to travel across synaptic cleft to second cell
paracrine (local) hormones
secreted into tissue fluids to affect nearby cells
hormones
chemical messengers that travel in the bloodstream to other tissues and organs
endocrine system
glands, tissues, and cells that secrete hormones
endocrinology
the study of this system and the diagnosis and treatment of its disorders
endocrine glands
organs that are traditional sources of hormones
hormones
chemical messengers that are transported by the bloodstream and stimulate physiological responses in cells of another tissue or organ, often a considerable distance away
major organs of endocrine system
pineal gland hypothalamus pituitary gland thyroid gland thymus adrenal gland pancreas parathyroid gland gonads
exocrine glands
–have ducts carry secretion to an epithelial surface or the mucosa of the digestive tract –‘external secretions’
–extracellular effects (food digestion)
endocrine glands
–no ducts
–contain dense, fenestrated capillary networks which allows easy uptake of hormones into bloodstream
–‘internal secretions’
–intracellular effects such as altering target cell metabolism
liver cells defy rigid classification
releases hormones, releases bile into ducts, releases albumin and blood-clotting factors into blood (not hormones)
Comparison of Nervous and Endocrine Systems (Differences)
both serve for internal communication
–nervous -both electrical and chemical
–endocrine -only chemical
Comparison of Nervous and Endocrine Systems (Differences)
speed and persistence of response
–nervous -reacts quickly (1 -10 msec), stops quickly
–endocrine -reacts slowly (hormone release in seconds or days), effect may continue for weeks
Comparison of Nervous and Endocrine Systems (Differences)
adaptation to long-term stimuli
–nervous -response declines (adapts quickly)
–endocrine -response persists (adapts slowly)
Comparison of Nervous and Endocrine Systems (Differences)
area of effect
–nervous -targeted and specific (one organ)
–endocrine -general, widespread effects (many organs)
Nervous and Endocrine Systems (Similarities)
several chemicals function as both hormones and neurotransmitters
–norepinephrine, cholecystokinin, thyrotropin-releasing hormone, dopamine and antidiuretic hormone
Nervous and Endocrine Systems (Similarities)
some hormones secreted by neuroendocrine cells
(neurons) that release their secretion into the bloodstream
–oxytocin and catecholamines
Nervous and Endocrine Systems (Similarities)
both systems with overlapping effects on same target cells
–norepinephrine and glucagon cause glycogen hydrolysis in liver
Nervous and Endocrine Systems (Similarities)
systems regulate each other
–neurons trigger hormone secretion
–hormones stimulate or inhibit neurons
target organs or cells
those organs or cells that have receptorsfor a hormone and can respond to it.
Anatomy of Hypothalamus
- shaped like a flattened funnel
- forms floor and walls of third ventricle of the brain
- regulates primitive functions of the body from water balance and thermoregulation to sex drive and childbirth
- many of its functions carried out by pituitary gland
Pituitary Gland
(Hypophysis)
•suspended from hypothalamus by a stalk –infundibulum
•location and size
–housed in sella turcica of sphenoid bone
–size and shape of kidney bean
infundibulum
suspends pituitary gland from hypothalamus
Pituitary Gland composed of two structures
composed of two structures with independent origins and separate functions
–adenohypophysis (anterior pituitary)
–neurohypophysis(posterior pituitary)
adenohypophysis
(anterior pituitary)
constitutes anterior three-quarters of pituitary
–has two segments:
•anterior lobe (pars distalis)
•pars tuberalissmall mass of cells adhering to stalk
–linked to hypothalamus by hypophyseal portal system
hypophysealportal system
- hypothalamic releasing and inhibiting hormones travel in hypophyseal portal system from hypothalamus to anterior pituitary
- hormones secreted by anterior pituitary
neurohypophysis
constitutes the posterior one-quarter of the pituitary
–has 3 parts:
•median eminence, infundibulum, and the posterior lobe (pars nervosa)
neurohypophysis is
nerve tissue, not a true gland
•nerve cell bodies in hypothalamus pass down the stalk as hypothalamo-hypophysealtract and end in posterior lobe
•hypothalamic neurons secrete hormones that are stored in neurohypophysis until released into blood
eight hormones produced in hypothalamus
–six regulate the anterior pituitary
–two are released into capillaries in the posterior pituitary when hypothalamic neurons are stimulated (oxytocin and antidiuretic hormone)
six releasing and inhibiting hormones stimulate or inhibit the anterior pituitary
–TRH, CRH, GnRH, and GHRH are releasing hormones that affect anterior pituitary secretion of TSH, PRL, ACTH, FSH, LH, and GH
–PIH inhibits secretion of prolactin, and somatostatin inhibits secretion growth hormone & thyroid stimulating hormone by the anterior pituitary
Hypothalamic Hormones
two other hypothalamic hormones are
oxytocin (OT)and antidiuretic hormone (ADH)
–both stored and released by posterior pituitary
–right and left paraventricular nuclei produce oxytocin(OT)
–supraoptic nuclei produce antidiuretic hormone (ADH)
–posterior pituitary does not synthesize them
anterior lobe of the pituitary synthesizes and secretes six principal hormones
•two gonadotropin hormones that target gonads –FSH (follicle stimulating hormone) –LH (luteinizing hormone) •TSH (thyroid stimulating hormone) •ACTH (adrenocorticotropic hormone) •PRL (prolactin) •GH (growth hormone)
FSH
FSH (follicle stimulating hormone)
•stimulates secretion of ovarian sex hormones, development of ovarian follicles, and sperm production
LH
(luteinizing hormone)
•stimulates ovulation, stimulates corpus luteum to secrete progesterone, stimulates testes to secrete testosterone
TSH
(thyroid stimulating hormone)
–stimulates secretion of thyroid hormone
ACTH
(adrenocorticotropic hormone)
–stimulates adrenal cortex to secrete glucocorticoids
PRL
(prolactin)
–after birth stimulates mammary glands to synthesize milk, enhances secretion of testosterone by testes
GH
(growth hormone)
–stimulates mitosis and cellular differentiation
Posterior Pituitary Hormones
produced in hypothalamus
–transported by hypothalamo-hypophyseal tract to posterior lobe
–releases hormones when hypothalamic neurons are stimulated
•ADH(antidiuretic hormone)
•OT(oxytocin)
ADH
(antidiuretic hormone)
–increases water retention thus reducing urine volume and prevents dehydration
–also called vasopressin because it can cause vasoconstriction
OT
(oxytocin)
–surge of hormone released during sexual arousal and orgasm
•stimulate uterine contractions and propulsion of semen
–promotes feelings of sexual satisfaction and emotional bonding between partners
–stimulates labor contractions during childbirth
–stimulates flow of milk during lactation
–promotes emotional bonding between lactating mother and infant
Control of Pituitary Secretion
rates of secretion are not constant
–regulated by hypothalamus, other brain centers, and feedback from target organs
anterior lobe control
releasing hormones and inhibiting hormones from hypothalamus
•in cold weather, pituitary stimulated by hypothalamus to release TSH, leads to generation of body heat
posterior lobe control
neuroendocrine reflexes
neuroendocrine reflex
hormone release in response to nervous system signals
negative feedback
increased target organ hormone levels inhibits release of hormones
positive feedback
stretching of uterus increases OT release, causes contractions, causing more stretching of uterus, etc. until delivery
Growth Hormone
GH has widespread effects on the body tissues
–especially cartilage, bone, muscle, and fat
•induces liver to produce growth stimulants
insulin-like growth factors (IGF-I) or somatomedins(IGF-II)
- stimulate target cells in diverse tissues
- IGF-I prolongs the action of GH
- hormone half-life –the time required for 50% of the hormone to be cleared from the blood
insulin-like growth factors (IGF-I) or somatomedins(IGF-II)
causes
protein synthesis increases
lipid metabolism increased
carbohydrate metabolism
electrolyte balance
pineal gland
attached to roof of third ventricle beneath the posterior end of corpus callosum
•after age 7, it undergoes involution(shrinkage)
pineal gland
main function
may synchronize physiological function with 24-hour circadian rhythms of daylight and darkness
–synthesizes melatonin from serotonin during the night
seasonal affective disorder
(SAD) occurs in winter or northern climates
–symptoms -depression, sleepiness, irritability and carbohydrate craving
–2 to 3 hours of exposure to bright light each day reduces the melatonin levels and the symptoms (phototherapy)
Thymus
•thymus plays a role in three systems: endocrine, lymphatic, and immune
•bilobed gland in the mediastinum superior to the heart
–goes through involution after puberty
•site of maturation of T cells important in immune defense
Thymus secretes
secretes hormones (thymopoietin, thymosin, and thymulin) that stimulate development of other lymphatic organs and activity of T-lymphocytes
Thyroid Gland Anatomy
largest endocrine gland
–composed of two lobes and an isthmus below the larynx
–dark reddish brown color due to rich blood supply
thyroid follicles
sacs that compose most of thyroid
–contain protein rich colloid
–follicular cells –simple cuboidal epithelium that lines follicles
thyroid follicles secrete
secretes thyroxine (T4 because of 4 iodine atoms) and triiodothyronine (T3) –T4 which is converted to T3 –increases metabolic rate, O2consumption, heat production (calorigenic effect), appetite, growth hormone secretion, alertness and quicker reflexes
parafollicular (C or clear) cellssecrete
calcitonin with rising blood calcium
–stimulates osteoblast activity and bone formation
thyroid follicles are filled with
colloid and lined with simple cuboidal epithelial cells (follicular cells).
Parathyroid Glands
usually four glands partially embedded in posterior surface of thyroid gland
–can be found from as high as hyoid bone to as low as aortic arch
Parathyroid Glands secrete
secrete parathyroid hormone (PTH) –increases blood Ca2+ levels •promotes synthesis of calcitriol •increases absorption of Ca2+ •decreases urinary excretion •increases bone resorption
Adrenal Gland
small gland that sits on top of each kidney
•they are retroperitoneal like the kidney
•adrenal cortex and medulla formed by merger of two fetal glands with different origins and functions
adrenal medulla
inner core, 10% to 20% of gland
•has dual nature acting as an endocrine gland and sympathetic ganglion of sympathetic nervous system
adrenal medulla innervated by
innervated by sympathetic preganglionic fibers
when stimulated release
catecholamines(epinephrineand norepinephrine) and a trace of dopamine directly into the bloodstream
catecholamines
effect is longer lasting than neurotransmitters
–increases alertness and prepares body for physical activity –
•mobilize high energy fuels, lactate, fatty acids, and glucose
•glycogenolysisand gluconeogenesisboost glucose levels
•glucose-sparing effect because inhibits insulin secretion
–muscles use fatty acids saving glucose for brain
–increasesblood pressure, heart rate, blood flow to muscles, pulmonary air flow and metabolic rate
–decreasesdigestion and urine production
Adrenal Cortex
surrounds adrenal medulla and produces more than 25 steroid hormones called corticosteroidsor corticoids
Adrenal Cortex
three layers of glandular tissue
zona glomerulosa
zona fasciculate
zona reticularis
zona glomerulosa
(thin, outer layer)
•cells are arranged in rounded clusters
•secretes mineralocorticoid–regulate the body’s electrolyte balance
zona fasciculata
(thick, middle layer)
•cells arranged in fascicles separated by capillaries
•secretes glucocorticoids
zona reticularis
(narrow, inner layer)
•cells in branching network
•secretes sex steroids
mineralocorticoids
zona glomerulosa
–regulate electrolyte balance
–aldosterone stimulates Na+retention and K+excretion, water is retained with sodium by osmosis, so blood volume and blood pressure are maintained
glucocorticoids
–regulate metabolism of glucose and other fuels
–especially cortisol, stimulates fat and protein catabolism, gluconeogenesis(glucose from amino acids and fatty acids) and release of fatty acids and glucose into blood
–helps body adapt to stress and repair tissues
–anti-inflammatory effect becomes immune suppression with long-term use
sex steroids
zona reticularis
–androgens –sets libido throughout life; large role in prenatal male development (includes DHEA which other tissues convert to testosterone)
–estradiol–small quantity, but important after menopause for sustaining adult bone mass; fat converts androgens into estrogen
Adrenal Gland Interactions
medulla and cortex of adrenal gland are not functionally independent
•medulla atrophies without the stimulation of cortisol
•some chromaffin cells of medullary origin extend into the cortex
–they stimulate the cortex to secrete corticosteroids when stress activates the sympathetic nervous system
Pancreas
exocrine digestive gland and endocrine cell clusters (pancreatic islets) found retroperitoneal, inferior and posterior to stomach
pancreatic islets
1-2 million pancreatic islets (Islets of Langerhans) produce hormones
–other 98% of pancreas cells produces digestive enzymes
insulin secreted by
B or beta () cells
–secreted during and after meal when glucose and amino acid blood levels are rising
–stimulates cells to absorb these nutrients and store or metabolize them lowering blood glucose levels
diabetes mellitus
insufficiency or inaction is cause of diabetes mellitus
Pancreatic Hormones
glucagon
somatostatin
pancreatic polypeptide
gastrin
glucagon
secreted by A or alpha () cells
–released between meals when blood glucose concentration is falling
–in liver, stimulates gluconeogenesis, glycogenolysis, and the release of glucose into the circulation raising blood glucose level
–in adipose tissue, stimulates fat catabolism and release of free fatty acids
–glucagon also released to rising amino acid levels in blood, promotes amino acid absorption, and provides cells with raw material for gluconeogenesis
somatostatin
secreted by D or delta () cells
–partially suppresses secretion of glucagon and insulin
–inhibits nutrient digestion and absorption
pancreatic polypeptide
secreted by PP cells or F cells)
–inhibits gallbladder contraction and secretion pancreatic digestive enzymes
gastrin
secreted by G cells
–stimulates stomach acid secretion, motility and emptying
hyperglycemic hormones
raise blood glucose concentration
–glucagon, growth hormone, epinephrine, norepinephrine, cortisol, and corticosterone
hypoglycemic hormones
blood glucose
–insulin
The Gonads
ovaries and testes are both endocrine and exocrine
exocrine product
whole cells -eggs and sperm (cytogenic glands)
endocrine product
gonadal hormones –mostly steroids
ovarian hormones
–estradiol, progesterone, and inhibin
testicular hormones
testosterone, weaker androgens, estrogen and inhibin
functions of estradiol and progesterone
–development of female reproductive system and physique including adolescent bone growth
–regulate menstrual cycle, sustain pregnancy
–prepare mammary glands for lactation
inhibin suppresses
inhibin suppresses FSH secretion from anterior pituitary
testicular hormones
testosterone and other steroids from interstitial cells (cells of Leydig) nestled between the tubules
–inhibinfrom
testosterone
testosterone and other steroids from interstitial cells (cells of Leydig) nestled between the tubules
•stimulates development of male reproductive system in fetus and adolescent, and sex drive
•sustains sperm production
inhibin
inhibin from sustentacular (Sertoli) cells
•limits FSH secretion in order to regulate sperm production
skin
keratinocytes convert a cholesterol-like steroid into cholecalciferol using UV from sun –Vitamin D is a steroid hormone
liver
involved in the production of at least five hormones
–converts cholecalciferol into calcidiol
–secretes angiotensinogen(a prohormone)
•precursor of angiotensin II (a regulator of blood pressure)
–secretes 15% oferythropoietin (stimulates bone marrow)
–hepcidin –promotes intestinal absorption of iron
–source of IGF-I that controls action of growth hormone
kidneys
plays role in production of three hormones
–converts calcidiol to calcitriol, the active form of vitamin D
•increases Ca2+ absorption by intestine and inhibits loss in the urine
–secrete renin that converts angiotensinogen to angiotensin I
•angiotensin II created by converting enzyme in lungs
–constricts blood vessels and raises blood pressure
–produces 85% of erythropoietin–
•stimulates bone marrow to produce RBCs
heart
–cardiac muscle secretes atrial and brain natriuretic peptides (ANP and BNP) in response to an increase in blood pressure
stomach and small intestine
secrete at least ten enteric hormones secreted by enteroendocrine cells
adipose tissue
secretes leptin
–slows appetite
osseous tissue
osteocalcinsecreted by osteoblasts
–increases number of pancreatic beta cells, pancreatic output of insulin, and insulin sensitivity of other body tissues
–inhibits weight gain and onset of type II diabetes mellitus
placenta
secretes estrogen, progesterone and others
Hormone Chemistry
three chemical classes –steroids -peptides and glycoproteins –monoamines (biogenic amines) •all hormones are made from either cholesterol or amino acids with carbohydrate added to make glycoproteins
steroids
- derived from cholesterol
- secreted by gonads and adrenal glands
- estrogens, progesterone, testosterone, cortisol, corticosterone, aldosterone, DHEA, and calcitriol (vitamin D)
peptides and glycoproteins
- created from chains of amino acids
- secreted by pituitary and hypothalamus
- oxytocin, antidiuretic hormone, releasing and inhibiting hormones, and anterior pituitary hormones
–monoamines (biogenic amines)
- derived from amino acids
- secreted by adrenal, pineal, and thyroid glands
- epinephrine, norepinephrine, melatonin, and thyroid hormone
Hormone Synthesis: Steroid Hormones
synthesized from cholesterol –differs in functional groups attached to 4-ringed steroid backbone
Peptides
- synthesized in same way as any protein
- at first is an inactive preprohormone
- first several amino acids is a signal peptide that guides it into cisterna of rough endoplasmic reticulum
- signal peptide removed to form prohormone
- Golgi does final transformation to hormonepackaged for secretion
Hormone Synthesis: Insulin
begins as preproinsulin, then becomes proinsulin
•when connecting peptideis removed, two polypeptide chains are formed that make up insulin
Monoamines
melatonin is synthesized from amino acid tryptophan, and other monoamines from amino acid tyrosine
–thyroid hormone is composed of 2 tyrosines
T3 and T4 Synthesis
follicular cells
TSH
follicular cells
–absorb iodide(I-)ions from blood and store in lumen as a reactive form of iodine
–synthesize thyroglobulin and store in lumen
•forms colloid
•contains lots of tyrosine
–tyrosine and iodine combine to form thyroxine (T4) bound to thyroglobulin
–stored in follicle
TSH
–stimulates follicular cells to remove T4from thyroglobulin for release into plasma
–most T3is produced in liver or by target cells removing an iodine from circulating T4
–95% T4and 5% T3
Chemistry of Thyroid Hormone
MIT contains one iodine atom, DIT has twoT3-combination of MIT plus DITT4 -combination of two DITs
Hormone Transport
monoamines and peptides
most monoamines and peptides are hydrophilic
–mix easily with blood plasma
Hormone Transport
steroids and thyroid hormone
steroids and thyroid hormone are hydrophobic
–bind to transport proteins (albumins and globulins synthesized by the liver)
–bound hormones have longer half-life
•protected from liver enzymes and kidney filtration
–only unbound hormone leaves capillaries to reach target cell
Hormone Transport
thyroid hormone
thyroid hormone binds to three transport proteins in the plasma
–albumin, thyretin and TBG (thyroxine-binding globulin)
–more than 99% of circulating TH is protein bound
Hormone Transport
steroid hormones
bind to globulins
–transcortin –the transport protein for cortisol
Hormone Transport
aldosterone
short half-life; 85% unbound, 15% binds weakly to albumin and others
Hormone Receptors
hormones stimulate only those cells that have receptors for them
Hormone Receptors
receptors are protein or glycoprotein molecules:
–on plasma membrane, in the cytoplasm, or in the nucleus
•receptors act like switches turning on metabolic pathways when hormone binds to them
•usually each target cell has a few thousand receptors for a given hormone
receptor-hormone interactions exhibit
specificity and saturation
specificity
specific receptor for each hormone
saturation
saturated when all receptor molecules are occupied by hormone molecules
Hormone Mode of Action
hydrophobic hormones
–penetrate plasma membrane and enter nucleus
–act directly on the genes changing target cell physiology
–estrogen, progesterone, thyroid hormone act on nuclear receptors
–take several hours to days to show effect due to lag for protein synthesis
Hormone Mode of Action
hydrophilic hormones
–cannot penetrate into target cell
–must stimulate physiology indirectly
Thyroid Hormone
thyroid hormone enters target cell by diffusion –mostly as T4with little metabolic effect
•within target cell, T4is converted to more potent T3
•T3enters target cells and binds to receptors in chromatin
•activates genes
Peptides and Catecholamines: Hydrophilic
hormone binds to cell-surface receptor •receptor linked to second messenger system on other side of the membrane •activates G protein which •activates adenylate cyclase •produces cAMP •activates or inhibits enzymes •metabolic reactions: –synthesis –secretion –change membrane potentials
Other Second Messengers
- diacylglycerol (diglyceride) second-messenger system
- inositol triphosphate second-messenger system
- act on cell metabolism in a variety of ways
Enzyme Amplification
- hormones are extraordinarily potent chemicals
- one hormone molecule can trigger the synthesis of many enzyme molecules.
- very small stimulus can produce very large effect
- circulating concentrations very low
Modulation of Target Cell Sensitivity
target cell sensitivity adjusted by changing the number of receptors
up-regulation
regulation means number of receptors is increased
–sensitivity is increased
down-regulation
regulation reduces number of receptors –cell less sensitive to hormone –happens with long-term exposure to high hormone concentrations •bind to other receptors •converted to different hormone
Hormone Interactions
most cells sensitive to more than one hormone and exhibit interactive effects
synergistic effects
–multiple hormones act together for greater effect
•synergism between FSH and testosterone on sperm production
permissive effects
–one hormone enhances the target organ’s response to a second later hormone
•estrogen prepares uterus for action of progesterone
antagonistic effects
–one hormone opposes the action of another
•insulin lowers blood glucose and glucagon raises it
Hormone Clearance
•hormone signals must be turned off when they have served their purpose
•most hormones are taken up and degraded by liver and kidney
–excreted in bile or urine
metabolic clearance rate
(MCR)
–rate of hormone removal from the blood
–half-life-time required to clear 50% of hormone from the blood
–faster the MCF, the shorter is the half-life
stress
caused by any situation that upsets homeostasis and threatens one’s physical or emotional well-being
•injury, surgery, infection, intense exercise, pain, grief, depression, anger, etc
general adaptation syndrome
(GAS)
–the consistent way body reacts to stress –typically involves elevated levels of epinephrine and glucocorticoids (especially cortisol)
general adaptation syndrome
occurs in three stages:
- alarm reaction
- stage of resistance
- stage of exhaustion
Alarm Reaction
•initial response
•mediated by norepinephrine from the sympathetic nervous system and epinephrine from the adrenal medulla
–prepare body to fight or flight
–stored glycogen is consumed
–increase in aldosterone and angiotensin levels
•angiotensin helps raise blood pressure
•aldosterone promotes sodium and water conservation
Stage of Resistance
after a few hours, glycogen reserves gone, but brain still needs glucose
•provide alternate fuels for metabolism
•stage dominated by cortisol
•hypothalamus secretes corticotropin-releasing hormone
•pituitary secretes an increase in ACTH
pituitary secretes an increase in ACTH
–stimulates the adrenal cortex to secrete cortisol and other glucocorticoids
–promotes the breakdown of fat and protein into glycerol, fatty acids, and amino acids –for gluconeogenesis
glucose-sparing effect
cortisol has glucose-sparing effect –inhibits protein synthesis leaving free amino acids for gluconeogenesis
–adverse effects of excessive cortisol
–depresses immune function
–Increases susceptibility to infection and ulcers
–lymphoid tissues atrophy, antibody levels drop, and wounds heal poorly
Stage of Exhaustion
•when stress continues several months, and fat reserves are gone, homeostasis is overwhelmed
–marked by rapid decline and death
•protein breakdown and muscle wasting
•loss of glucose homeostasis because adrenal cortex stops producing glucocorticoids
•aldosterone promotes water retention and hypertension
–conserves sodium and hastens elimination of K+and H+
–hypokalemia and alkalosis leads to death
•death results from heart and kidney failure or overwhelming infection
paracrines
chemical messengers that diffuse short distances and stimulate nearby cells
–unlike neurotransmitters not produced in neurons
–unlike hormones not transported in blood
•a single chemical can act as
a hormone, paracrine, or even neurotransmitter in different locations
–histamine
- from mast cells in connective tissue
* causes relaxation of blood vessel smooth muscle
nitric oxide
•from endothelium of blood vessels, causes vasodilation
somatostatin
•from gamma cells, inhibits secretion of alpha and beta cells
catecholamines
•diffuse from adrenal medulla to cortex
Eicosanoids
important family of paracrines
–derived from fatty acid called arachidonic acid
lipoxygenase
converts arachidonic acid into leukotrienes
leukotrienes
mediates allergic and inflammatory reactions
cyclooxygenase
converts arachidonic acid to three other types of eicosanoids
prostacyclin
•inhibits blood clotting and vasoconstriction
thromboxanes
- produced by blood platelets after injury
- overrides prostacyclin
- stimulates vasoconstriction and clotting
prostaglandinsincludes
- PGE: relaxes smooth muscle in bladder, intestines, bronchioles, uterus and stimulates contraction of blood vessels
- PGF: opposite effects
Anti-inflammatory Drugs
- cortisol and corticosterone
* aspirin, ibuprofen, & celecoxib (Celebrex)
•cortisol and corticosterone
–steroidal anti-inflammatory drugs (SAIDs)
–inhibit inflammation by blocking release of arachidonic acid from plasma membrane and inhibit synthesis of eicosanoids
•disadvantage –produce symptoms of Cushing syndrome
aspirin, ibuprofen, & celecoxib (Celebrex)
–nonsteroidal anti-inflammatory drugs (NSAIDs)
•COX inhibitors since block cyclooxygenase (COX)
•do not affect lipoxygenase function or leukotriene production
•useful in treatment of fever and thrombosis
–inhibit prostaglandin and thromboxane synthesis
Endocrine Disorders
variations in hormone concentration and target cell sensitivity have noticeable effects on body
hyposecretion
inadequate hormone release
–tumor or lesion destroys gland or interferes with its ability to receive signals from another gland
hypersecretion
excessive hormone release
–tumors or autoimmune disorder
pheochromocytoma
tumor of adrenal medulla secretes excessive epinephrine and norepinephrine
toxic goiter
(graves disease) –autoantibodies mimic effect of TSH on the thyroid causing thyroid hypersecretion
Pituitary Disorders
hypersecretion of growth hormone (GH)
acromegaly
thickening of bones and soft tissues in adults
•especially hands, feet and face
–problems in childhood or adolescence
gigantism
gigantism if hypersecretion
dwarfism
pituitary dwarfism if hyposecretion –rare since growth hormone is now made by genetically engineered bacteria
Thyroid Gland Disorders
congenital hypothyroidism
myxedema
goiter
congenital hypothyroidism
(decreased TH)
–hyposecretion present a birth (formerly cretinism)
–treat with oral thyroid hormone
myxedema
(decreased TH)
–adult hypothyroidism
–treat with oral thyroid hormone
goiter
any pathological enlargement of the thyroid gland
endemic goiter
•dietary iodine deficiency, no TH, no feedback, increased TSH stimulates hypertrophy
toxic goiter
(Graves disease)
•autoantibodies mimic the effect of TSH on the thyroid causing hypersecretion
•overgrown thyroid produces functional TH
Parathyroid Disorders
hypoparathyroidism
hypoparathyroidism
- surgical excision during thyroid surgery
* fatal tetany in 3 -4 days due to rapid decline in blood calcium level
hyperparathyroidism
excess PTH secretion
•parathyroid tumor
•bones become soft, fragile, and deformed
•Ca2+ and phosphate blood levels increase
•promotes renal calculi formation
Adrenal Disorders
Cushing syndrome adrenogenital syndrome (AGS)
Cushing syndrome
excess cortisol secretion
–hyperglycemia, hypertension, weakness, edema
–rapid muscle and bone loss due to protein catabolism
–abnormal fat deposition
•moon face and buffalo hump
Diabetes Mellitus
most prevalent metabolic disease in world
–disruption of metabolism due to hyposecretion or inaction of insulin
Diabetes Mellitus
symptoms
- polyuria(excess urine output), polydipsia(intense thirst) and polyphagia(hunger)
- revealed by elevated blood glucose, glucose in urine and ketones in the urine
polyuria
excess urine output
polydipsia
intense thirst
polyphagia
hunger
transport maximum
limit to how fast the glucose transporters can work to reabsorb
–excess glucose enters urine and water follows it
•causes polyuria, dehydration, and thirst
Types of Diabetes Mellitus
Type 1
Type 2
Type 1
(IDDM) –5 to 10% of cases in US
–insulin is always used to treat Type 1
•insulin injections, insulin pump, or dry insulin inhaler
•monitoring blood glucose levels and controlled diet
–hereditary susceptibility if infected with certain viruses (rubella, cytomegalovirus)
–autoantibodies attack and destroy pancreatic beta cells
Type 2
(NIDDM) –90 to 95% of diabetics
–problem is insulin resistance
•failure of target cells to respond to insulin
–risk factors are heredity, age (40+),obesity, and ethnicity –Native American, Hispanic, and Asian
–treated with weight loss program and exercise since:
•loss of muscle mass causes difficulty with regulation of glycemia
•adipose signals interfere with glucose uptake into most cells
–oral medications improve insulin secretion or target cell sensitivity
pathogenesis
cells cannot absorb glucose, must rely on fat and proteins for energy needs -weight loss and weakness
–fat catabolism increases free fatty acids and ketones in blood
ketonuria
ketonuria promotes osmotic diuresis, loss of Na+ and K+, irregular heartbeat, and neurological issues
ketoacidosis
ketoacidosis occurs as ketones decrease blood pH
–deep, gasping breathing and diabetic coma are terminal result
chronic pathology (chronic hyperglycemia)
leads to neuropathy and cardiovascular damage from atherosclerosis and microvascular disease
•arterial damage in retina and kidneys (common in type I), atherosclerosis leads to heart failure (common in type II)
diabetic neuropathy
nerve damage from impoverished blood flow can lead to erectile dysfunction, incontinence, poor wound healing, and loss of sensation from area
