Lesson 3 - Endocrine Pt 1 Flashcards
(130 cards)
1
Q
gap junctions
A
pores in cells membranes that allow signaling molecules, nutrients, and electrolytes to move from cell to cell
2
Q
neurotransmitters
A
released from neurons to travel across the synaptic cleft to a second cell
3
Q
paracines
A
secreted into tissue fluids to affect nearby cells
4
Q
hormones
A
chemical messengers that travel in the bloodstream to stimulate physiological responses in other tissues and organs
5
Q
endocrine system
A
glands, tissues, and cells that secrete hormones
6
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endocrinology
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the study of the endocrine system and the diagnosis and treatment of its disorders
7
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endocrine glands
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organs that are sources of hormones
8
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exocrine glands
A
have ducts that carry secretion to an epithelial surface or the mucosa of the digestive tract: “external secretions”
9
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examples of exocrine glands
A
sweat glands
10
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endocrine glands
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no ducts; contain dense, fenestrated capillary networks which allow easy uptake of hormones into the bloodstream: “internal secretions”
11
Q
what kind of effects do endocrine glands produce?
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intracellular effects such as altering target cell metabolism
12
Q
speed and persistence of response: nervous
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reacts quickly (msec timescale) and stops quickly
13
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speed and persistence of response: endocrine
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reactly slowly (seconds or days), effects may continue for days or longer
14
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adaptation to long-term stimuli: nervous
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response declines, adapts quickly
15
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adaptation to long-term stimuli: endorcine
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responses persist, adapts slowly
16
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area of effect: nervous
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targets and specific (one organ)
17
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area of effect: endocrine
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general, widespread effects (many organs)
18
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True or False: Chemicals can only act as hormones or neurotransmitters, not both
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false, several function as BOTH hormones and neurotransmitters
19
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examples of chemicals that are both hormones and neurotransmitters (3)
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norepinephrine, dopamine, and antidiuretic hormone
20
Q
both the nervous and endocrine system can have similar effects on target cells (example)
A
both norepinephrine and glucagon cause glycogen hydrolysis in the liver
21
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an example of how the nervous system and endocrine system can regulate each other
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neurotransmitters can affect glands and hormones can affect neurons
22
Q
cells that share characteristics with both the nervous and endocrine system are called
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neuroendrocine cells; neuron-like cells that secrete oxytocin into the blood
23
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target organs/cells
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those organs or cells that hve receptors for a hormone and can respond to it
24
Q
what do some target cells posses?
A
enzymes that convert a circulating hormone to its more active forms
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three chemical classes of hormones
steroid, monoamines, and peptides
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lipid-derived hormones
derived from fats like sex steroids from gonads and corticosteroids from adrenal glands
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monoamines (biogenic amines)
made from amino acids, like tyrosine used to produce the catecholamines and thyroid hormone
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catecholamines (3)
dopamine, epinephrine, and norepinephrine
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peptide hormones
created from chains of amino acids
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examples of peptide hormones (4)
thyroid-stimulating hormone, luteinizing hormone, follicle-stimulating hormone, insulin
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prohormones
inactive molecules that are converted to the active hormones before or after they are secreted; many peptide hormones are synthesized as these
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steroids
derived from cholesterols
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leukotrienes
have secondary roles as hormones causing inflammation during allergic reactions
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prostaglandins
involved in coordinating local cellular activities and can be converted to thromboxanes (vasoconstrictor) or prostacyclins (vasodilator)
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eicosanoids
derived from arachidonic acid (a 20-carbon fatty acid)
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steroids released by reproductive organs: testes
androgens
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steroids released by reproductive organs: ovaries (2)
estrogens and progestins
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steroids released by reproductive organs: cortex of adrenal glands
corticosteroids
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steroids released by reproductive organs: kidneys
calcitriol
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proinsulin
a prohormone, has a middle portion called a connecting peptide that is removed to form the active form of insulin (two peptide chains connected by disulfide bridges)
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melatonin is synthesized from
amino acid tryptophanh
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what are some monoamines synthesized from?
tyrosine
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don't forget slide 19, you don't understand it
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hormone secretion fluctuates on...(5)
- the circadian rhythm
- a woman's monthly cycle
- under the influence of neural, hormonal, or humoral stimuli
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stimuli for hormone secretion: neural stimulation
nerve fibers supply some endocrine glands and elicit the release of their hormone
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examples of neural stimuli for hormone secretion (2)
- the sympathetic nervous system stimulates the adrenal medulla to secrete epinephrine and norepinephrine in situations of stress
- in childbirth, the positive feedback loop of oxytocin
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stimuli for hormone secretion: hormonal stimuli
hormones from the hypothalamus regulate secretion by the anterior pituitary gland
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examples of hormonal stimuli for hormone secretion
pituitary hormones stimulate other endocrine glands to release thyroid hormone, sex hormones, and cortisol
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stimuli for hormone secretion: humoral stimuli
refers to blood-borne stimuli; rising blood glucose concentration stimulates the release of insulin
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rising blood glucose concentration stimulates the release of _____
insulin
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low blood osmolarity stimulates the secretion of _____
aldosterone
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low blood calcium level stimulates the secretion of _____
parathyroid hormone
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hormones may or may not be stored prior to secretion: peptide hormones and catecholamines
stored in secretory vesicles of the endocrine cell until needed and released by exocytosis when the cell receives a stimulus to do so
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hormones may or may not be stored prior to secretion: steroid hormones
these are not stored, but are released as fast as they are synthesized by diffusion through the cell surface
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hormones may or may not be stored prior to secretion: thyroid hormone
diffuses freely through plasma membranes, but does accumulate in the gland awaiting stimulus for secretion (TSH); stored in the extracellular spaces enclosed by the thyroid follicles
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stimuli such as _____ and _____ can increase the synthesis and release of a steroid hormone by several-fold within hours
FSH, ACTH
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most monoamines and peptides are _____, and mix easily with blood plasma
hydrophilic
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steroids and thyroid hormones are _____, and have protein carriers
hydrophobic
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transport proteins
albumins and globulins synthesized by the liver that help hormones last longer in blood
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bound hormones
hormones that have bound to a transport protein
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only _____ hormone leaves capillaries to reach the target cells
unbound (free)t
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thyroid hormone binds to _____, _____, and _____
albumin, thyretain, and thyroxine-binding globulin (TBG)
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steroid hormones bind to _____
globulin
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hormone receptors
protein or glycoprotein molecules on plasma membranes, in the cytoplasm, or in the nucleus
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hormone receptors act like
switches, turning on metabolic pathways when the hormone binds to them
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hormone specificity
receptor for one hormone will not bind another hormone
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hormone saturation
when all receptor molecules are occupied by hormone molecules
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peptides and catecholamines are
hydrophilic, cannot penetrate target cell membrane; they bind to surface receptors and activate intracellular processes, metabolic pathways through second messenger systems
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three major second-messengers
1. cyclic adenosine monophosphate (cAMP)
2. diacylglycerol (DAG)
3. inositol triphosphate (IP3)
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reasons unbound hormones only last about one hour in blood (3)
- diffuse out of the bloodstream and bind onto receptors on target cells
- are broken down and absorbed by cells of the liver or kidneys
- broken down by enzymes in the blood plasma of interstitial fluid
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cAMP as a second messenger (example) (6)
1. hormone-receptor binding activated a G protein
2. G protein activates adenylate cyclase
3. adenylate cyclase produces cAMP
4. cAMP activates protein kinase
5. protein kinases phosphorylate enzymes, activating some and deactivating others
6. activated enzymes catalyze metabolic reactions with a wide range of possible effects on the cell
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where do steroid/thyroid hormone bind in the cell? (2)
receptors in the cytosol or nucleus
- if receptors in the cytosol, the hormone:receptor is transported into the nucleus
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hormone-receptor complex
a hormone bound to its specific receptor
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signal amplification (cascade effect)
seen in hormones that trigger second messengers; one hormone molecule triggers the synthesis of a large number of enzyme molecules
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how potent are hormones?
very small stimulus can produce very large effects; it allows the circulating hormone concentrations to remain relatively low
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up-regulation
number of receptors is increased; sensitivity is increased
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down-regulation
number of receptors is reduced; call less sensitive to hormone and also happens with long-term exposure to high hormone concentrations
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hypothalamus
shaped like a flattened funnel, forms the floor and walls of the third ventricle of the brain
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functions of the hypothalamus (4)
regulating primitive functions from water balance and thermoregulation to sex drive and childbirth
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pituitary gland (hypophysis)
suspended from the hypothalamus by a stalk (infundibulum)
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two parts of the pituitary gland
anterior and posterior pituitary
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anterior pituitary
adenohypophysis
constitutes anterior three-quarters of the pituitary
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how is the anterior pituitary linked to the hypothalamus?
via blood vessels of the hypophyseal portal system
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_____ _____ in the hypothalamus connected to _____ _____ in the anterior pituitary by _____ _____
primary capillaries, secondary capillaries, portal venules
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hypothalamic hormones _____ anterior pituitary cell secretions
regulate
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posterior pituitary
neurohypophysis
constitutes the posterior quarter of the pituitary; composed of nerve tissue but isnt a real gland
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nerve cell bodies in the hypothalamus pass down the stalk as the _____-_____ _____ and end in the posterior lobe
hypothalamo-hypophyseal tract
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hypothalamic neurons secrete hormones that were stored where?
in the neurohypophysis (posterior pituitary) until released into the blood
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six hypothalamic hormones regulate the anterior pituitary
1. gonadotropin-releasing hormone (GnRH)
2. thyrotropin-releasing hormone (TRH)
3. corticotropin-releasing hormone (CRH)
4. prolactin-inhibiting hormone (PIH)
5. growth hormone-releasing hormone (GHRH)
6. somatostatin
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gonadotropin-releasing hormone (GnRH)
stimulates release of gonadotropins (FSH, LH) from the anterior pituitary
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thyrotropin-releasing hormone (TRH)
stimulates the release of thyroid-stimulating hormone (TSH, thyrotropin) from the anterior pituitary
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corticotropin-releasing hormone (CRH)
stimulates release of adrenocorticotropic hormone (ACTH, corticotropin) from the anterior pituitary
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prolactin-inhibiting hormone (PIH)
inhibits the release of prolactin from the anterior pituitary
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growth hormone-releasing hormone (GHRH)
stimulates release of growth hormone (GH) from the anterior pituitary
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somatostatin
inhibits the release of GH and TSH from anterior pituitary
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two hypothalamic hormones are store in the posterior pituitary and released on demand, what are they?
oxytocin (OT) and antidiuretic hormone (ADH)
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oxytocin (OT)
stimulates labor concentrations (uterus) and milk release (mammary glands), also released during sexual arousal and orgasm for satisfaction emotional bonding
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where is oxytocin produced?
in the paraventricular nuclei of the hypothalamus
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antidiuretic hormone (ADH)
aka vasopressin, it stimulates water retention by the kidneys thus reducing urine volume and preventing dehydration
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where is antidiuretic hormone produced?
by the supraoptic nuclei of the hypothalamus
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the anterior lobe of the pituitary synthesizes and secretes these six major hormones
1. follicle-stimulating hormone (FSH)
2. luteinizing hormone (LH)
3. thyroid-stimulating hormone (TSH)
4. adrenocorticotropic hormone (ACTH)
5. prolactin (PRL)
6. growth hormone
102
follicle-stimulating hormone (FSH)
aka follitropin
stimulates the secretion of ovarian sex hormones, development of ovarian follicles, and sperm production
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luteinizing hormone (LH)
aka lutropin
stimulates ovulation, corpus luteum secretion of progesterone, and testosterone secretion by testes
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gonadotropins
FSH and LH, they target the ovaries and testes
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thyroid-stimulating hormone (TSH)
aka thyrotropin
stimulates secretion of thyroid hormone (TH) from the thyroid gland
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adrenocorticotropic hormone (ACTH)
aka corticotropin
stimulates adrenal cortex to secrete glucocorticoids
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prolactin (PRL)
after birth, stimulates mammary glands to synthesize milk
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growth hormone (GH)
aka somatotropin
stimulates mitosis and cellular differentiation
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arginine vasopressin (AVP)
another name for antidiuretic hormone because it can cause vasoconstriction (but only at unnaturally high concentrations)
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how are hormonal rates of secretion regulated? (3)
they are regulated by the hypothalamus, other brain areas, and feedback from target organs
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hypothalamic and cerebral control of hormone secretion
brain monitors conditions and influences anterior pituitary accordingly
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in time of stress, the hypothalamus triggers the release of _____
ACTH - adrenocorticotropic hormone
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during pregnancy, the hypothalamus triggers _____ secretion
prolactin
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the posterior pituitary is controlled by _____ reflexes
neuroendocrine
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what triggers the release of ADH when they detect a rise in blood osmolarity?
hypothalamic osmoreceptors
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infant suclking triggers hypothalamuc response to release _____
oxytocin
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negative feedback inhibition
increased target organ hormone levels inhibits release of hypothalamic and/or pituitary hormones
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example of negative feedback inhibition
thyroid hormone inhibits release of TRH by the hypothalamus and of TSH by the anterior pituitary
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growth hormone (GH) has widespread effects including:
- inducing the liver to produce growth stimulants
- stimulate target cells in diverse tissues
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somatomedins
insulin-like growth factors IGF-1 and IGF-II
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growth hormone half-life
6-20 minutes
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IGF-1 half-life
about 20 hours
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mechanisms of GH-IGF action: protein synthesis
boosts transcription and translation; also increases amino acid uptake into the cells
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mechanisms of GH-IGF action: lipid metabolism
stimulates adipocytes to catabolize fats, release fatty acids for body cells to use as fuel instead of proteins; aka the protein-sparing effect
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mechanisms of GH-IGF action: carbohydrate metabolism
mobilizing fatty acids reduces dependence of most cells on glucose, freeing more for the brain aka the glucose-sparing effect; stimulates glucose secretion by the liver
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mechanisms of GH-IGF action: electrolyte balance
promotes Na+, K+, and Cl- retention by the kidneys, enhances Ca2+ absorption in the intestine; makes electrolytes available to growing tissues
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mechanisms of GH-IGF action: growth
stimulates bone, cartilage, and muscle growth especially during childhood and adolescence
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GH secretion fluctuates with....
- time of day
- activity level
- age
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where can GH secretions be high? (3)
- high secretion during the first two hours of sleep
- can peak in response to vigorous exercise
- activated by ghrelin
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ghrelin
a hormone released by the stomach that activates GH
