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197 Cards in this Set

  • Front
  • Back
what are the four mechanisms of intercellular communication?
1. direct communication
2. paracrine communication
3. endocrine communication
4.synaptic communication
what is direct communication?
-transmission through gap junctions
-usually limited to adjacent cells of the same type that are interconnected by connexons
-involves ions, small solutes, and lipid-soluble materials
what is paracrine communication?
transmission through extracellular fluid
-mediated by paracrine factors
-limited to local area where paracrine concentrations are high
-target cells must have appropriate receptors
what is synaptic communication?
-transmission across the synaptic clefts
-mediated by neurotransmitters
-limited to specific area
-target cells must have appropriate receptors
what is endocrine communication?
-transmission through bloodstream
-mediated by hormones
-target cells are in other tissues and organs which must have appropriate receptors
what three groups are hormones and paracrine factors divided into?
1. amino acid derivatives
2. peptide hormones
3. lipid derivatives
what are the three amino acid derivatives?
1. thyroid hormones
2. catecholamines (E, NE, dopamine)
3. melatonin
what are the catecholamines?
E, NE, and dopamine
what are peptide hormones?
-synthesized as prohormones
-includes all hormones secreted by hypothalamus, heart, thymus, digestive tract, and pancreas, and most of the pituitary gland
what are prohormones?
inactive molecules that are converted to active hormones
what are glycoproteins?
polypeptides that have carbonhydrate side chains
what are lipid derivatives? 2 types?
hormones that consist of carbon rings and side chains built from 1. fatty acids (eicosanoids) or 2. cholesterol (steroid hormones)
what are eicosanoids?
important paracrine factors that coordinate cellular activities and affect enzymatic processes (ex/ blood clotting)
-some have secondary roles as hormones
what are prostaglandions
second group of eicosandoids
-involved in coordinated local cellular activities
what are steroid hormones released by?
1. released by reproductive organs
-androgens by the testes
-estrogen and progestin by ovaries
2. cortex of adrenal glands (corticosteroids)
3. by the kidneys (calcitriol)
why do steroid hormones remain in circulation longer than peptide hormones?
because they are bound to specific transport proteins in the plasma
what does the hypothalamus secrete hormones involved with?
fluid balance, smooth muscle contraction, and the control of hormone secretion by ant. pituitary gland
what does the pituitary gland secrete?
hormones that regulate the adrenal cortex, thyroid gland, and reproductive organs, and a hormone that stimulates melanin production
what does the thyroid gland secrete?
hormones that affect metabolic rate and calcium levels in body fluids
what do the adrenal glands secrete?
-hormones involved with mineral balance, metabolic control, and resistance to stress
what does the adrenal medullae release?
E and NE during sympathetic activation
what do the pancreatic islets secrete?
hormones that regulate the rate of glucose uptake and utilization by body tissues
what does the pineal gland secrete?
melatonin, which affects reproductive function and helps establish circadian day/night rhythms
what do the parathyroid glands secrete?
hormone that is important to the regulation of calcium ion concentrations in body fluids
what are the five organs involved with endocrine functions?
1. heart
2. thymus
3. digestive tract
4. kidneys
5. gonads
what does the heart secrete?
hormones that regulate blood volume
what does the thymus secrete?
hormones involved in the stimulation and coordination of the immune system
what does the digestive tract secrete?
hormones involved in the coordination of system functions, glucose metabolism, and appetite
what do the kidneys secrete?
hormones that regulate blood cell production and the rates of calcium and phosphate absorption by the intestinal tract
what do gonads secrete?
-hormones affecting growth, metabolism, and sexual characteristics
-hormones coordinating activities of organs in reproductive system
how are hormones effects exerted in the cytoplasm?
the first messenger (hormone) uses a second messenger wich acts as an enzyme activator, inhibitor, or cofactor
once activated, how do most G proteins effect the levels of cAMP?
they change the concentration of cyclic-AMP (which is the 2nd messenger in cell)
if G proteins increase levels of cAMP what happens?
enzymes may be activated or ion channels may be opened= accelerates the metabolic activity of the cell
if G proteins decrease levels of cAMP what happens?
an inhibitory effect on the cell
once activated, what two things do G proteins have an effect on?
cAMP levels and Ca2+ levels``
once activated, what effect do G proteins have on Ca2+ levels?
Ca2+ is second messenger
-calcium ions themselves serve as messengers generally in combo with *calmodulin*
how do steroid hormones travel to its receptor cell?
by diffusing across the phospholipid bilayer to the receptors in the cytoplasm or nucleus
where are the receptor cells of the steroid hormones?
the cytoplasm or nucleus
what do steroid hormones alter?
the rate of DNA transcritption in the nucleus, changing the pattern of protein synthesis
what are the rsulting changes of alteration of DNA transcription by the steroid hormones?
directly affects the target cell's metabolic activity and structure
how are thyroid hormones transported across the membrane?
by carrier-mediated processes
once thyroid hormones enter the cells, what do they bind to?
mitochondria which increase mitochondrial rates of ATP production
what do the hormone-receptor complexes of the thyroid hormone do to the specific genes in the nucleus?
activate specific grans/change the rate of transcription= decreases or increases concentration of specific enzymes
what happens with antagonistic effects?
result depends on the balance
-effects are weaker than those produced by either hormone acting unopposed
what happens with additive effects?
-result is greater than the effect that each would produce acting alone
-some cases, net result is greater than the sum of the hormones individual effects
what is a synergistic effect?
when the net result of two hormones is greater than the sum of the hormones' individual effects
what happens with permissive effects?
first hormone is needed for the second to produce its effect
what happens with integrative effects?
-hormones produce difference, but complementary effects in tissues and organs
-important in coordinated the activities of diverse physiological systems
what two systems does the hypothalamus integrate?
endocrine and nervous
what two hormones do hypothalamic neurons synthesize?
antidiuretic hormone (ADH) and oxytocin (OXT)
what type of hormones does the hypothalamus secrete and their function?
regulatory hormones that control endocrine cells in the adrenal medullae of the pituitary gland
what happens when sympathetic division is activated?
adrenal medullae are stimulated directly and secrete epinephrine and norepinephrine
what do hormones secreted by the anterior lobe of the pituitary gland control?
activities of endocrine cells in the thyroid, adrenal cortex, and reproductive organs
what two hormones does the posterior lobe of the pituaity gland release?
ADH and oxytocin
what is the endocrine system?
includes all cell and body tissues that produce and/or secrete hormones or paracrine factors such as glands, organs and tissues
what are endocrine cells?
glandular secretory cells that release their secretions into extracellular fluid; ductless
what is the median eminence?
swelling near the attachment of the infundibulum; where neurons release regulatory factors into interstitial fluid
what are fenestrated capillaries?
allow relatively large molecules to enter or leave the bloodstream
where are fenestrated capillaries located?
the median eminence which is why secreteions enter the blood easily and makes it unusually permeable
what neurons manufactore ADH and OXT?
supraoptic and paraventricular nuclei
what constitiues the portal system?
capillary networks and interconnecting vessels
what is the function of the hypophyseal portal system?
-provides chemical communication by insuring all hypothalamic hormones entering the portal vessels will reach their target cells in the anterior lobe before mixing with the general circulation
-blood supply to adenohypophysis (anterior pit.)
-one way communication
what are portal vessels?
blood vessels that link two capillary networks
what are the two types of regulatory hormones of the anterior pit. gland?
1. releasing hormone (RH)
2. inhibiting hormone (IH)
what are releasing hormones?
they stimulate the synthesis and secretion of hormones at the ant. pit. gland
what are inhibiting hormones?
prevent the synthesis and secretion of hormones at the ant. pit. gland
what is the hypophysis?
pituitary gland; small, oval gland within the sella turcica
how many peptide hormones are released by the pituitary gland and how many for each lobe?
nine in total: 7 by the anterior and 2 by the posterior
what are the hormones of the anterior lobe?
1. TSH
2. ACTH
3. Gonadotropins- FSH and LH
4. GH
5. PRL
6. MSH
what is TSH?
-thyroid-stimulating hormone
-triggers the release of TRH (thyroid releasing hormone)
how does TSH show negative feedback?
when levels of T3 and T4 rise, rates of TRH and TSH production decline
what is ACTH?
-adrenocorticotropic hormone (corticotropin)
-controls the production and secretion of cortisol by the suprarenal cortex- glucose metabolism
what does ACTH target?
cells that produce hormones that affect glucose metabolism
what is the release of ACTH triggered by?
CRH (corticotropin-releasing hormone)
what does ACTH get its negative feedback from?
increasing levels of CRH and ACTH
what is the anterior pituitary called? posterior?
ant- adenohypophysis
post- neurohypophysis
what is FSH?
-triggered by?
-follicle-stimulating hormone
-promotes ovarial follicle development and estrogen secretion (2nd hormone); sperm production in males
what does FSH get its negative feedback from?
increasing levels of estorgens and testosterone
FSH triggered by?
GnRH
what are gonadotropins?
regulate activities of gonads and occurs under stimulation of the GnRH
what is GnRH?
gonadotropin-releasing hormone
what is FSH inihibited by?
inhibin, a peptide hormone released by testes and ovaries
what is LH?
luteinizing hormone
-triggered by GnRH
-initiates ovulation; when present with FSH, stimulates estrogen & testosterone secretion
what does it get its negative feedback from?
estrogens, progestines, androgens
what is prolactin? when is it inactive?
-PRL; initiales lactation
-released on a monthy cycle and is made anytime where are increases in estrogen levels
-inactive in prescence of estrogen and progestion
when is prolactin released and how?
during pregnancy by PRF
what does prolactin do?
-stimulstes mammary gland development and milk secretion
what does prolactin cause in males?
not well studied
-androgen production regulation
what does hypersecretion of prolactin cause in males? females?
males: erectile dysfunction
females: leads to galactorrhea (overproduction of milk) and amenorrhea (cessation of menstrual cycle
how does prolactin get its negative feedback?
by PIH which increases with increase in other hormones
what is MSH?
melanocyte stimulating hormone
- exact role in adults is unknown
-excessive levels of CRH can stimulate its release
-dopamine inhibits release
what is MSH released from?
pars intermedia in development, children, and pregnant woman
what does GH (growth hormone) stimulate?
cell growth and reproduction by accelerating rate of protein synthesis
what are somatomedins?
peptide hormones that increase the rate of amino acids and their incorporation into new proteins
what is the glucose-sparing effect?
when tissues stop the breakdown of glucose and use fatty acids to generate ATP
what is the main function os GH?
-promote synthesis and secretion of insulin-like growth factors (IGFs)
-peptide hormon similar to insulin and formerly called somatomedins
what are IGFs?
insulin-like growth factors that cause cells to grow and multiply by increasing their uptake of amino acids
where is IGF found?
in all tissues except liver
what stimulates GH release?
GHRH
-GH receptors in the liver- IGF production and secretion
-IGFs act locally as autocrines
what are the childhood/adolecenct growth effects of IGF?
increase growth rate of skeleton and skeletal muscles
what are the adulthood growth effects of IGF?
muscle and bone mass maintenance
what causes growth effects by IGF in general?
proliferation and differentiation of chondrocytes and myoblasts
-breakdown is equal to production so its maintained
what are the four metabolic effects of IGF?
1. enhance lipolysis in adipose tissue (make energy from fat)
2. decrease glucose uptake by most body cells (glucose sparing)
3. stimulates liver cells to release glucose
4. decrease ATP production from aa's
what are the two excess GH symptoms?
1. diabetagenic- symptoms of diabetes (diabetes mellitus type 2)
2. ketosis- decrease in blood pH and very dangerous
what does the neurohypophysis do?
-does not synthesize its hormones
-stores and releases hormones made in the hypothalamus whose axons form the hypothalamohypophyseal tract
what is OXT triggered by?
mechanical stimulation of mammary glands; birthing process
what are OXT target tissues?
uterus and breats
what does OXT do in males and non-pregnant women?
concentrations increase during secual arousal and orgasm; muscle contractions of the ductus deferens, prostate, uterus and vagaina
what is ADH triggered by?
variations in blood volume and osmotic pressure
what does OTX do?
stimulates smooth muscle contration in the uterus promoting labor and devlivery
why is oxytocin release a neuroendocrine reflex?
because its triggered by sensory input
what causes variations in blood volume and osmotic pressure?
-decreased urine production
-decreases water loss via sweating
-increases blood pressure by arteriole constriction
explain the negative feedback of ADH
low osmotic pressure of blood (or increased blood volume) inhibits osmoreceptors
what stimulates secretion of ADH? inhibits it?
stimulted by pain, stress, trauma, anxiety, acetycholine, nicotine, morphine
-inhibited by alcohol
what is autocrine signaling?
secreted as local mediators; affect secreting cell
why is endocrine signaling just as important as neuronal?
because its the only response from the cells that recioeve the message
-slow compared to neuronal signaling
how many amino acids are in polypeptides and protein hormones? where are the synthesized?
3-200 aa's; synthesized on RER of endocrine cells
where are biologicalled active hormones stored?
in vesicles within cytoplasm
what two things happen during exocytosis?
1. plasma membrane depolarization and increased cytosolic Ca2+
2. endocrine cell surface receptor and protein kinase activation
what are the two types of hormones involved in hormone synthesis?
1. steroid hormones
2. amine hormones
what are steriod hormones?
-synthesized from cholesterol thats stored in vaccules
-little storage
-diffuse across cell membrane
what are amine hormones derived from? formed by?
-derived from tyrosin
-formed by enzymatic action in cytoplasmic compartments of grandular cells
where are amine hormones stored?
in the cells (follicles or vesicles)
where does diffusion occur? exocytosis?
-diffusion in the thyroid for lipid soluble
-exocytosis in catecholamine for water soluble
how much hormone do most metabolic and endocrine function require?
very small amounts
what is negative feedback control?
controlled variable is degree of activity of the target issue, not how much hormone is secreted
what is negative feedback control?
controlled variable is degree of activity of the target issue, not how much hormone is secreted
what does the follicle cavity of the thyroid gland hold?
viscous colloid
what is a viscous colloid?
fluid containing large amounts of dissolved proteins
what is thyroglobin?
a globular protein that follicle cells synthesize and secrete into the colloid; contains tyrosine
what is tyrosine?
the building block of thyroid hormones
what is a thyroid follicle?
sac that stores hormones; made up of follicular cells
why dont T1 and T2 ever enter the blood?
because further breakdown occurs to recycle iodine
what are the functions of the thyroid hormone (TH)?
1. increase basal metabolic rate
2. stimulate synthesis of Na+/K+ ATPase
3. stimulate protein synthesis; increase use of glucose and fatty acids for ATP production; increase lipolysis; enhance cholesterol excretion
4. enhance actions of catecholamines
5. accelerate body growth (nervous/skeletal)
6. essential for development of fetal and neonatal brain
what is basal metabolic rate?
amount of energy needed to run all functions of the body
what are catecholamines?
NE and E
what happens when theres too much TH?
high BMR, hyperactive (ANS), irritable, heat intolerant, CV/heart problems, weight loss
what happens when there not enough TH?
development/CNS (Cretinism), low BMR, listless/slow, cold intolerant, obesity
what are the two cell populations the parathyroid glands atleast have?
1. parathyroid cells
2. oxyphils
what are oxyphils?
possibly depleted chief cells no longer making parathyroid hormone
what does the PTH (parathyroid hormone) monitor?
-blood calcium levels; when too low, PTH is secreted to increase concentration
what is the PTHs specific action?
increase number and activity of osteoclasts
what does PTH increase?
rate of calcium and magnesium absorption from GI tract into blood
what are C cells (parafollicular cells) and what hormone do they produce?
-they are inbetween follicle cells
-produce calcitonin (CT)
what does calcitonin do?
aids the regulation of calcium ion concentration in body fluids
what is calcitonins effect?
decrease in blood calcium concentration
what does calcitonin inhibit?
osteoclasts
what does calcitonin do to the uptake of calcium and phosphates?
accelerates the uptake into bone extracellular matrix
what does calcitonin stimulate?
calcium and phosphate excretion by the kidneys
when is calcitonin important in development?
during childhood, pregnancy, and starvation
if too little or too much, whats the effect of a normal healthy adult?
no symptoms
what is calcitonin a valuable therapy for?
paget disease which is a disorder in bone remodeling
what is calcitonin a valuable aid in?
the management of post-menopausal osteoprosis
what are the effects on the kidneys of the PTH?
-slows rate of calcium loss
-increases excretion of HPO42-
-promotes formation of calcitriol
what is calcitriol?
an active form of vitamin D
what does PTH increase?
the rate of calcium and magnesium absorption from the GI tract into the blood
what is hypoparathyroidism?
-blood calcium deficiency
what is the result of hypoparathyroidism?
spontaneous depolarization and tetany
what is hyperthyroidism?
excessive resorption of bone matrix: causes soft bones that are easily fractured, kidney stones, fatigue, personality changes, lethargy, and hardening of arteries by calcium deposit
when homeostasis is disturbed and calcium levels in the blood rise, what happens?
thyroid gland produces calcitonin->increased excretion by kidneys and calcium deposition in bone
when homeostasis is disturbed and calcium levels in the blood fall, what happens?
parathyroid gland secrete PTH-> increase reabsorption by kidneys, calcium release from bones, and increases calcitriol production
what is the steroid hormone that the adrenal cortex produces called?
theyre called adrenocortical steroids or simply corticosteroids
how do corticosteroids exert their effects?
by determnining which genes in the nuclei of their target cells are transcribed, and at what rate; affect cellular metabolism
what are the three zones of the adrenal cortex?
1. zona glomerulosa (outer region)
2. zona fasciculata (central)
3. zona reticularis (bordering eaching medulla)
what hormones are in the zona glomerulosa?
mineralocorticoids (MCs), primarily aldosterone
what are the hormonal effects in the zona glomerulosa?
-aldosterone increases renal reabsorption of Na+ and water
-also accelerates urinary loss of K+
what hormones are in the zona fasciculata?
glucocorticoids (GCs)
what are glucocorticoids (GCs)?
steroid hormones that affect glucose metabolism
what are the primary hormones of GCs?
1. cortisol
2. corticosterone
what does the liver convert some of the circulating cortisol to?
cortisone, a metabolically active glucocorticoid
what are the hormonal effects in the zona fasciciculata?
-glucose homeostasis
-resistance to stress
what hormones are in the zona reticularis?
androgens that may be converted to estrogens
what are the hormonal effects in the zona reticularis?
-development of pubic hair
-androgen synthesis
what four factors play a role in regulating aldosterone?
1. increased K+ in extracellular fluid= increased aldosterone release
2. increase in angiotensin II in extracellular fluid= increased aldosterone release
3. increased Na+ in extracellular fluid= decrease in aldosterone release
4. ACTH is necessary for secretion but not control rate
what cortex are mineralocorticoids in? what is the main one?
zona glomerulosa; aldosterone
what does aldosterone do?
-homeostasis of sodium and potassium ions
-adjusts blood pressure and blood volume
-promotes excretion of H+
what is the secretion of aldosterone controlled by?
RAA pathway
what disease is caused by hyposecretion of aldosterone?
Addison's disease
what is Addison's disease symptoms?
mental lethargy, anorexia, nausea, vomiting, weight loss, hypoglycemia, muscular weakness, bronzed skin, and CV symptoms
what zone are glucocorticoids in? what are the three different ones?
fasciculata
1. cortisol
2. corticosterone
3. cortisone
what are the functions of glucocorticoids?
-protein breakdown
-glucose formation (gluconeogenesis)-breakdown for energy
-lipolysis
-resistance to stress
-increased blood vessel sensitivity to vasoconstricting hormones
-anti-inflammatory effects
-depression of immune response
-turns on your appetite center
what anti-inflammatory effects do glucocorticoids have?
slow the regeneration of tissue, production of WBCs
-saves energy for other things causing
what happens when theres too much cortisol?
-overeating- obesity
-loss of muscle and connective tissue
-poor immune response
-reduced response to infections
-increased likelihood of diabetes mellitus
-cushing syndrome
what happens when theres too little cortisol?
nothing works
what is the exocrine pancreas?
99% of organs volume; clusters glands of cells and their attached ducts
what is the endocrine pancreas?
small groups of cells known as pancreatic islets or islets of langerhands
what are pancreatic islets?
endocrine clusters that constitute 1% of all cells in the panceas; vital to survival
what are the 4 cell types in the pancrease along with the hormone they produce?
1. alpha-glucagon
2. beta-insulin
3. delta- somatostatin (GHIH)
4. F cells- pancreatic polypeptide
what does glucagon do?
raises blood sugar by increasing rates of glycogen breakdown & glucose release
what does insulin to?
lowers blood sugar by increasing rate of glucose uptake and glycogen synthesis
what does somatostatin (GHIH) do?
suppresses the release of hormones of both alpha and beta cells (glucagon and insulin)
what do pancreatic polypeptide (PP) do?
suppresses actions of delta cells; help control rate of nutrient absorption
what does glucagon target?
-hepatocytes- glycogenolysis
-muscles- initiales glucose breakdown for the muscle use
what is type 1 diabetes and when is it usually diagnosed?
when insulin is not produced
-in children and young adults
-IDDM; previously known as juvenile diabetes
what is type 2 diabetes?
-adult-onset or noninsulin-dependent
-either body doesnt produce enough insulin or the cells ignore the insulin
what are the symptoms of type 1 diabetes?
- increased thirst and frequent urination
- extreme hunger
- weight loss
- fatigue
- blurred vision
what are the symptoms of type 2 diabetes?
all of the symptoms of type 1 diabetes plus:
-slow-healing sores or frequent infections
-areas of darkened skin