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Lecture 1 BSCI447 Endocrinology Dr Tammatha O Brien Overview exocrine glands have ducts that lead to the external environment sweat gland mammary glands glands secreting digestive enzymes endocrine glands are ductless secrete into blood stream o Primary endocrine glands Hypothalamus Pituitary Pineal Thyroid parathyroid Thymus Adrenal Pancreas Gonads o Secondary endocrine glands Heart Kidneys GI tract Skin Adipose tissue Endocrine system differs from the nervous system although some neurotransmitters can acts as hormones Nervous neuron neuron muscle or gland neurotransmitter across synapse immediate secreted by acts on signal travels onset of effect Feedback loops duration of effect brief Endocrine endocrine cell most cell types hormone via bloodstream delayed long most hormones are regulated via negative feedback loops end product and or effect stop the stimulus example of positive feedback loop and pathology o heart attack causes portion of heart tissue to die which forces heart to compensate o heart is working harder increases oxygen demand o heart must meet this demand heart rate increases o heart develops more muscle mass causing it to work harder incr O2 demand and cycle continues o treated w blockers to make slower more forceful beats o athletes get to rest because the stimulus ends allows for angiogenesis increased formation of vasculature to the heart Classic hormone interactions 1 antagonism the effects of two hormones oppose eachother ex insulin glucagon on blood glucose 2 Additive effects of hormones favor each other and sum ex growth hormone thyroid hormone testosterone 3 Synergism effects of hormone favor each other but net effect is greater than sum ex glucagon cortisol and epinephrine on blood glucose 4 Permisseveness one hormone is needed for another to exert its effects ex thyroid hormone is permissive for epi b c it causes expression of adrenergic receptors Primary disorders are caused by an abnormality in the endocrine organ that secretes the hormone Secondary disorders are abnormality of the tropic hormone of anterior pituitary Tertiary disorders result from abnormality originating in hypothalamus very rare Hydrophilic hormones bind receptors on cell surface whereas lipophilic hormones steroid hormones diffuse plasma membrane and bind internal receptors Response depends on concentration of hormone of receptors and affinity down regulation occurs when excess hormone is present up regulation occurs when little hormone is present Androgen Insensitivity Syndrome genetic disorder causing defective cell receptors for androgens testosterone body does not respond to testosterone defaults to female appearance no menses although this can get confusing in highly trained female athletes who have low cholesterol and typically do not menstruate Receptor Types enzyme linked o tyrosine kinase is common G protein coupled o Gs Gq Gi Channel linked ligand gated o Fast receptor and channel are the same protein o Slow receptor is coupled to the channel GPCRs ligand binds causing conformational change alph subunit dissociates and activates enzyme channel etc causing amplification cascade Gs Stimulatory activates adenylyl cyclase which increases cAMP Gq activates phospholipase C which cleaves PIP2 into IP3 and DAG Gi Inhibitory inhibits adenylyl cyclase and thus decreases cAMP Phosphodiesterase degrades cAMP can cause signal to end Second messengers Calcium o Induces muscle contraction Changes electric potential Binds calmodulin to activate protein kinase o Stored in mitochondria smooth ER and bone o Supplements can lead to increased menstrual cramping or deregulated heart rate vitamin D needed for Ca uptake IP3 induces calcium release Second messengers allow amplification of signal from one hormone one receptor Receptor agonists bind to receptor and mimic normal response Receptor antagonists bind receptor but produce no response Ex Endorphins bind mu receptors to produce analgesia Morphine is agonist so it produces the same effect thus is used as a pain killer Nalaxone aka Narcan is a mu receptor antagonist Heroin is a derivative of Morphine thus narcan is used to treat heroin OD


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UMD BSCI 447 - Endocrinology

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