Exam 3 Endocrine: Endocrine Glands/Hormones and Mechanisms of Action

endocrine system relies of ____ to secrete hormones directly into the bloodstream

ductless glands

hormones travel to _______ equipped with receptor proteins

specific target cells

neurohormones come from ____ and regulate ____

hypothalamus, bodily functions

hormones cause ions to move ______ gradients to change _____

electrochemical, membrane potential

some chemicals act as both

hormones and neurotransmitters

(epinephrine)

to function in a physiological regulation, a chemical MUST

have target cells with specific receptors, combo of regulatory and receptor causes change in target, mechanism to turn off action of regulator

what are amines derived from

tyrosine and tryptophan

examples of amines

hormones from adrenal medulla, thyroid, pineal glands

polypeptides and proteins

longer chains of amino acids

insulin, glucagon, oxytocin, growth hormone

glycoproteins

polypeptides bound to a carbohydrate

FSH, LH

steroids are

lipids derived from cholesterol

examples of steroids (lipid based molecules)

testosterone, estradiol, progesterone, cortisol

steroid hormones are secreted by _____ and ____

adrenal cortex and gonads

what serves as the starting point for different steroid pathways

cholesterol--> pregnenolone

progesterone pathway to the adrenal cortex to produce

cortisol

progesterone leads to androstenedione in the gonads which produces ____

testosterone or even estradiol

polar hormones

water soluble, cannot pass through plasma membrane

need cell surface receptors

non polar hormones

insoluble in water (lipophilic), directly enter target cell to influence gene expression

thyroid and steroid hormones

pro hormones

inactive forms that must be cut and spliced before functioning

insulin

pre hormones

inactive after secretion and must be modified within target cell

T4-->T3, testosterone --> DHT

synergistic effects

two or more hormones work together to achieve outcome

additive synergistic effects

produce the same effect

epinephrine and norepinephrine increase heart rate

complementary synergistic effects

each hormone contributes a different piece of an overall process

milk production: estrogen, cortisol, prolactin, oxytocin

permissive effects

one hormone enhances cell response to another-- second hormone has no effect unless first has occurred

PTH increases sensitivity to vitamin D3, boosting calcium absorption

antagonistic effects

hormones work in opposite direction to maintain balance in the body

insulin lowers glucose while glucagon increases glucose

hormone half life

time required for plasma concentration of a given amount of hormone to be reduced by half

removed by liver and converted to less active products

elevated hormone levels (higher pharmacological concentrations)

bind to receptors of related hormones, unintended interactions

priming effects/upregulation

target cells respond to hormones by increasing number of receptors for hormone, more sensitive to to subsequent hormone release and have a greater response

desensitization and down regulation

prolonged exposure to high concentrations of hormones leads to decreased receptors

adipose tissue in response to insulin

pulsatile secretion

hormones released in spurts to avoid desensitization

hormone binding on target cells

highly specific, high affinity, low capacity to saturate receptor with hormones

lipophilic hormone receptors (NONPOLAR) are

in the cytoplasm or nucleus

steroids/thyroid hormones

water soluble hormone (POLAR) receptors are

on the outer surface of the plasma membrane

peptides

lipophilic hormones (steroids, thyroid hormone) are bound to ____ in the bloodstream

plasma carrier proteins

when lipophilic hormones reach target cell they ____ from the carrier and

dissociate, diffuse across the plasma membrane

lipophilic hormones once inside the cell bind to

nuclear hormone receptors in the nucleus

hormone receptors act as

transcription factors, activated by binding of hormone and affect gene expression

mechanism of steroid hormone genomic action

diffuse across membrane, bind to specific receptor in cytoplasm/nucleus, undergoes conformational change and activate receptor, binds to hormone response element on the DNA, mRNA translated into proteins, enzymes, etc

nuclear hormone receptors have two key domains:

ligand binding domain that binds hormone and DNA binding domain that interacts with DNA sequence

what happens when hormone binds to nuclear hormone receptor

activates receptor, attach to hormone response element on DNA

Two families of nuclear hormone receptors

steroid family, thyroid family

orphan receptors

receptors with unknown hormone

nongenomic (steroid) action

binds to plasma membrane receptor and activate G protein system

steroids form what kind of dimer on the hormone response element, where is this element?

homodimer, promoter region

coactivators and corepressors

needed in addition to steroid hormones, bind to nuclear receptor protein, change effect of hormone activate/suppress transcription factors

genomic action

classical mechanism of steroid hormone activity, directly influences gene transcription, takes longer but lasts longer

when a ligand binds, it triggers structural change and removes _____ which prevents the receptor from binding to DNA

heat shock protein

what happens when heat shock protein is removed

coactivator proteins can be recruited to form a complex that promotes DNA transcription of mRNA

postmenopausal women with ERpostive breast cancer are treated with

aromatase inhibitors

aromatase inhibitors

postmenopausal women, blocks conversion of testosterone to estradiol

premenopausal women with breast cancer are treated with

tamoxifen, a SERM

tamoxifen

given to premenopausal women with breast cancer, block estrogen in breast tissue but promotes estrogen effects in bones and endometrium

Her2 positive breast cancer is treated with

herptecin- monoclonal antibody that targets and blocks Her2 receptor

Action of Thyroid hormone

T4 transported into cell bound to carrier protein (thyroxine binding globulin, TBG), free form enters cell and converted to T3 (more active), receptor protein in nucleus where they bind to DNA and regulate expression

T3 is not ____ to a carrier and known as

bound, free iodide

hormone response element on DNA for thyroid has ____ half sites for ____ and _____

two, T3 receptor and derivative of vitamin A

Binding of T3 to the HRE leads to

removal of corepressors and recruitment of coactivators

Thyroid hormone action forms a ____ with the HRE

heterodimer

peptides and catecholamine hormones (nongenomic, POLAR) use ___ to trigger activation

second messengers

adenylate cyclase (cAMP) system

hormone binds to beta adrenergic receptor, alpha unit dissociates and activates adenylate cyclase which converts ATP to cAMP

increase in cAMP activates protein kinase A which leads to activation/deactivation of enzymes

____ degrades cAMP into AMP

phosphodiesterase

Phospholipase C system

epinephrine binds to alpha adrenonergic receptor, G protein dissociates and activates phospholipase C which breaks down PIP2 into IP3 and DAG

IP3 triggers release of Ca from the smooth ER into the cytoplasm which activates calmodulin to activate protein kinases

what receptors are used for epinephrine in the cAMP pathway

beta adrenergic

what receptors are used for epinephrine in the phospholipase C pathway

alpha adrenergic

important steps of cAMP

ATP, adenylate cyclase, cAMP, active protein kinases

important steps of phospholipase C

PIP2, IP3, increase Ca, calmodulin, active protein kinases

tyrosine kinase system is used by

insulin and growth factors

tyrosine kinase system

insulin binds to receptor and activates via phosphorylation

receptor phosphorylates insulin receptor substrates which triggers cascade of enzymatic activities in the cell

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