Endocrine System

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-Ductless
-products are secreted directly into the blood
-mediate many actions such as metabolism, growth and reproduction

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ENDOCRINE GLANDS

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function as both an endocrine and exocrine gland

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PANCREAS

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the chemical that neurons secrete is sometimes called....

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NEUROHORMONE

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secreted as both a neurotransmitter and a hormone

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NOREPINEPHRINE

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derived from the amino acid tryosine and tryptophan. they include hormones secreted by the adrenal medulla, thyroid and pineal glands.
derived from y and w

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AMINES

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ADH
INSULIN
GROWTH HORMON

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POLYPEPTIDE AND PROTEINS

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consist of a protein bound to one or more carbohydrate groups.
examples are FHS and LH

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GLYCOPROTEINS

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these are lipids derived form cholesterol.
they include the hormones testosterone, estradiol, progesterone and coritsol

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STEROIDS

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are soluble in lipids
non polar
can gain entry into their target cells
include steroid hormones and thyroid hormones

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Lipophilic hormones

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are secreted only by the adrenal cortex and the gonads.

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steroids

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secretes sex steroids

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gonads

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secretes corticosteroids including cortisol and aldosterone

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adrenal cortex

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why cant glycoprotein and polypeptide hormones be taken orally

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because they would be digested into inactive fragments before being absorbed into the blood. thus, insulin dependent diabetics must inject themselves with this hormone

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include polypeptides, glycoproteins and the catecholamine hormones
-secreted by the adrenal medulla, epinephrine and norepinephrine
-derived from the amino acid tryosine

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Polar water soluble hormones or hydrophilic hormones

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preproinsulin--> proinsulin--->Insulin....
which one is active and which one is inactive

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insulin the only one active, prepro and pro are both inactive form

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do not travel in the blood as do hormones, instead they diffuse across a narrow synaptic cleft to the membrane of the post synaptic cleft

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neurotransmitters

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posterior pituitary
-water retention and vasoconstriction
-polypeptide

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ADH

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posterior pituitary
-uterine and mammary contraction
-polypeptide

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oxytocin

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beta cells in islets of langerhans
-cellular glucose uptake, lipogenesis(fat formation) and glycogenesis(formation of glycogen)
-polypeptide

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insulin

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-alpha cells in islets of langerhans
-polypeptide
-hydrolysis of stored glycogen and fat

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Glucagon

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anterior pituitary
-stimulation of adrenal cortex
polypeptide

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ACTH

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-parathyroid
increase in blood CA concentration
polypeptide

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parathyroid hormone

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Anterior pituitary
glycprotein
stimulation of growth, development and secretory activity of the target glands

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FSH, LH, TSH

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1. synergistic effect
2.permissive effects
3.antagonistic effectss

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Hormone interactions

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when two or more hormones work together to produce a particular result
-effects may be additive or complementary

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Synergistic

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the aciton of epinephrine and norepinephrine on teh heart, increasing cardiac rate

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additive

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the ability of the mammary glands to produce and secrete milk in lactation requires synergistic action of many hormones such as estrogen, cortisol, prolactin and oxytocin

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complimentary

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one hormone enhances responsiveness of target organ to the second hormone or increase activity of a second hormone

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Permissive

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example of permissive

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prior exposure to estrogen, for example induces the formation of receptor proteins for progesterone, which improves the response of the uterus when it is subsequently exposed to progesterone. estrogen thus has a permissive effect on the responsiveness of the uterus to progesterone.

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actions of one antagonizes effects of another

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antagonistic

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example of antagonistic effect

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lactation during pregnancy is inhibited because the high concentration of estrogen in the blood inhibits the secretion and action of prolactin

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what causes fat formation

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insulin

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what promotes fat breakdown

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glucagon

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definition of half-life

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time required for the plasma concentration of a given amount of the hormone to be reduced to half its reference level

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which hormone has a half life of several days?

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Thyroid hormone

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amounts of certain hormones or chemicals that the body produces . they are usually small.

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physiological concentrations

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amounts of a chemical or hormone
that we give patients by administering a drug and these are usually larger than what the body would produce naturally
ie they are larger doses

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pharmacological concentration

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what would small amounts of gonadotropin releasing hormone (gnHr) secreted by the hypothalmus do?

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increase the sensitivity of anterior pituitary cells to further GnRH stimulation

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what is priming effect?

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when hormones can effect responsiveness of target cells

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anabolic steroids

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synthetic androgens (male hormones) that promote protein synthesis in muscle and other organs.

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what inhinits the secretion of FSH and LH and what does it cause

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High levels of exogenous androgens from the pituitary and cause atrophy of the tested and erectile dysfunction

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high concentrations of polypeptide hormones causes a decrease in the number of receptor proteins in their target cells

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downregulation

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how is desensitization prevented?

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many polypeptide and glycoprotein hormones are secreted in spurts rather than continuously....called pulsatile secretion

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what hormones are needed during the pulsatile secretion

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GnRH and LH is needed to prevent desensitization
- when these hormones are presented in a continuous fashion they produce a decrease in gonadal function

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what are lipophilic hormones

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steroids and thyroxine

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the receptor proteins for lipophilic hormones are located where

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within the cytoplasm and nucleus

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what are the water soluble hormones

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catecholamines, polypeptides and glycoproteins

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lipophilic hormone receptors

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function within the nucleus,
activate gene transcription

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list the 3 domains of the nuclear hormone receptor structure

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1.ligand binding domain- binds hormone
2. transactivation domain
-activated transcription
3. dna binding domain--
-binds dna on hormone response elements

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what must occur before binding to DNA

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nuclear hormone receptor must first be activated by binding to their hormone ligands

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the nuclear receptors are said to constitute a superfamily compose of what two major families

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1. steroid family
2. thyroid family
- includes vitamin D and A receptor

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the receptors for unknown hormone ligands are called

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orphan receptors

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steroid hormone action

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steroid hormones evert their effects by entering their target cells and binding to nuclear receptor proteins, stimulation genetic transcription....called genomic action

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what is the process of two receptor units coming together at the two half sites

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dimerization
occurs in steroid hormones

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what is homodimer and where does it occur

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when both receptor units of the pair on the half site are the same..
occur with the steroid receptor

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what happens when a steroid hormone ligand binds to its nuclear receptor protein and changes the receptor protein structure

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1. removal of a group of proteins called heat stroke proteins that prevent the receptor from binding to the DNA
2. Recruitment of co-activator proteins while co-repressor proteins are prevented from binding to a receptor

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Inhiibts genetic transcription

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Co-repressor

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activates genetic transcription

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Co-activator

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true or false?

only the free thyroxine and T3 can enter the target cells

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true

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where are the thyroid receptors located

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the thyroid receptor proteins are located i the nucleus bound to DNA

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why is the thyroid receptor a heterodimer (having two different receptors)

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because the thyroid receptor for T3 binds to only one of the half sites, the other DNA half site binds to the receptor for a vitamin A derivative called 9-cis retinoic acid receptor

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what happens in the absence of T3

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thyroid receptors recruit corepressor proteins that inhibit genetic transcription

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what happens when T3 is present

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corepressor proteins are removed and degraded by proteosomes while coactivator proteins are recruited to activate genetic transcription

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what hormones use second messengers?

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catecholamines(epinephrine and norepinephrine), polypeptides and glycoproteins because they cannot pass through the lipid barrier fo the target cells plasma membrane

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we can distinguish second messenger systems because of the activation of?

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1. adenylate cyclase
2.phospholipace C
3. Tyrosine Kinase

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what is the mechanism of thyroid hormone action

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1. thyroxine is carried to the target cell bound to its plasma carrier protein, dissociates from its carrier and passes through the plasma membrane of its target cell
2. in the cytoplasm t4 is converted to t3 which uses binding proteins to enter the nucleus.
3. the hormone receptor complex binds to DNA
5. stimulating the synthesis of new mRNA
6. the newly formed mRNA codes for synthesis of new proteins which produce the hormonal effects in the target cell

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What hormones cant pass through the lipid barrier of the target cells plasma membrane and require second messengers?

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catecholamines, ploypeptides, and glycoproteins

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the activation of adenylate cyclase, phospholipase C and tyrosine kinase describes what

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Second messenger system

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sequence of events involving cAMP as a second messenger system

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1. the hormone binds to its receptor on the outer surface of the targets cells plasma membrane
2. hormone-receptor interaction acts by means of G-proteins to stimulate the activity of adenylate cyclase onthe cytoplasmic side of the membrane.
3. activated adenylate cyclase catalyzes the conversion of ATP to cyclic AMP (cAMP) within the cytoplasm.
4. cAMP activates protein kinase enzymes that were already present in the cytoplasm in an inactive state.
5.activated cAMP dependent protein kinase transfers phosphate groups to phosphorylate other enzymes in the cytoplasm
6. the activity of specific enzymes is either increased or inhibited by phosphorylation
7. Altered enzyme activity mediates the target cells response to the hormone

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the adenylate cyclase-cyclic AMP second messenger system

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1. the hormone binds to its receptor in the plasma membrane of the target cell.
2 this causes the dissociation of G-proteins allowing the free alpha subunit to activate adenlate cyclase
3. this enzyme catalyzes the production of cAMP which removes the inhibitory subunit from protein kinase
4. active protein kinase phosphorylates other enzyme proteins activating or inactivating specific enzymes and thereby producing the hormonal effects on the target cell

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The phospholipase C-Ca second messenger system

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1. the hormone binds to its receptor in the plasma membrane of its target cell causing the dissociation of G-proteins
2l a G-protein subunit travels through the plasma membrane and activates phopholipace c, which catalyzes the breakdown of a particular membrane phospholipid into diacylglycerol and IP3.
IP3 enters the cytoplasm and binds to its receptor in the endoplasmic reticulum, causing the release of stored ca. the ca then diffuses into the cytoplasm, where it acts as a second messenger to promote the hormonal effects in the target cells.

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tyrosine kinase

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located in plasma membrane and specifically adds phosphate groups to the amino acid tyrosine within the proteins

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what does the pituitary gland (hypophysis) include

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anterior pituitary and posterior pituitary

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adenohypophysis

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anterior lobe
consist of two parts in adults 1. the pars distalis and the pars tuberalis.
- endocrine tissue
-produces its own hormones

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Neurohypophysis

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posterior lobe
-neural part of pituitary gland
-consist of pars nervosa also called posterior pituitary
-nerve fibers extend through the infundibulum along with small neuroglia-like cells called pituicytes
-stores and releases hormones that are produced by the hypothalmus

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pars intermedia

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-fetal structure
-regresses in adults

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the hormones secreted by the anterior pituitary are called what

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trophic hormones. term is used because of high concentrations of the anterior pituitary hormones cause their target organs to hypertrophy while low levels cause their target organs to atrophy

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Growth hormone

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aka somaatotropin
promotes the movement of amino acids into cells and the imcorporation of these amino acids into proteins promoting tissue growth
-

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amino acids

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make proteins which is needed for growth

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growth hormone hyposecretion in childhood

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pituitary dwarfism

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hypersecretion in childhood

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gigantism

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hyposecretion in adulthood

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pituitary cachexi
-premature aging due to tissue atrophy

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hypersecretion in adulthood

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acromegaly
-soft tissue and bone thickening

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Thyroid stimulating hormone

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stimulates thyroid gland growth
stimulates thyroid hormone production
-t4 and t3

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adrenocorticotrophic hormone (ACTH)

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stimulates release of adrenocortical hormones from adrenal cortex and glucocorticoids

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Follicle stimulating hormone

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stimulates the growth of ovarian follicles in females and the production of sperm cells in the testes of males
-gonadotropin acts on gonads

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Luteinizing hormone

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females: stimulates ovulation and corpus luteum (temporary endocrine hormone produces estrogen to maintain pregnancy until placenta takes over)
-Males- stimulates testosterone production

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what are the gonadotropic hormones

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FSH and LH

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ProLactin

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stimulates milk production from mammary glands
-increases sensitivity of testes to LH
- act on kidneys to help regulate water ad electrolyte balance

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posterior pituitary hormones

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ADH and Oxytocin

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ADH

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water retention by distal nephron regions

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Oxytocin

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-uterine contractions in females
-Mammary gland contraction in females
-rises during male ejaculation

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hypothalamo-hypophyseal portal system

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hypothalmic hormones transported to median eminence
-hormones enter caps travel via venule to second capillar network that surrounds anterior pituitary

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what hormones stimulate the adrenal cortex, thyroid and gonads to secrete their hormones

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ACTH
TSH
FSH
LH

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how is the anterior pituitary hormone secretion controlled

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by hormones secreted by the hypothalamus

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ACTH
anterior pituitary hormone

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TARGET TISSUE: ADRENAL CORTEX
ACTION: stimulate secretion of glucocorticoids
REGULATION OF SECRETION: stimulated by CRH and inhibited by glucocorticoids

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TSH
anterior pituitary hormone

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target tissue: thyroid gland
actions: stimulates secretion of thyroid hormones
regulation of secretion: stimulated by TRH, inhibited by thyroid hormones

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GH
anterior pituitary hormone

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target tissue: most tissue
actions: promotes protein synthesis and growth, lipolysis and increased blood glucose
regulation of secretion: inhibited by somatostatin, stimulated by growth hormone releasing hormone

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FSH
anterior pituitary hormone

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target tissue: gonads
actions: promotes gamete production and stimulates estrogen production in females
regulation of secretion: stimulated by GnRH and inhibited by sex steroids and inhibin

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PRL
anterior pituitary hormone

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target tissue:mammary glands and other sex accessory organs
actions: promotes milk production in lactating females
regulation of secretion: inhibited by PIH

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LH
anterior pituitary hormone

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Target tissue: Gonads
Principal actions: stimulate sex hormone secretion, ovulation and corpus luteum formation in females, stimulates testosterone secretion in males
regulation of secretion: stimulated by GnHR and inhibited by sex steroids

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Thyrotropin releasing hormone (TRH)
hypothalmic hormone

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stimulates the release of TSH

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Corticotropin releasing hormone (CRH)
hypothalmic hormone

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stimulates release of ACTH from anterior pituitary