Endocrinology Exam 1 Review Feedback loops 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 Endocrine endocrine cell most cell types hormone via bloodstream delayed brief long secreted by acts on signal travels onset of effect duration of effect most hormones are regulated via negative feedback loops short loop pituitary feeds back to hypothalamus Long loop target gland gives feedback to pituitary or hypothalamus 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 each other 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 Permissiveness one hormone is needed for another to exert its effects 1 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 change ligand binds causing conformational alpha 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 2 Receptor antagonists bind receptor but produce no response Ex Endorphins bind mu receptors to produce analgesia Morphine is agonist Narcan is a mu receptor antagonist treats heroin OD The Hypothalamic Pituitary Axis Higher brain centers aka the central nervous system stimulate the hypothalamus where set points are stored The Hypothalamus secretes tropic hormones to communicate with pituitary which then secretes hormones to individual endocrine glands Tropic hormones cause release of another hormone Humoral control also affects hormone release Something in the blood that is not a tropic hormone causes hormone secretion parathyroid hormone calcitonin release by low high calcium insulin glucagon release by high low blood sugar Hormone release may also be regulated by circadian rhythms light dark cycles Established by the pineal gland located just next to the optic chasm Hypothalamic Hormone Thyrotropin releasing hormone TRH Corticotropin releasing hormone CRH GPCR Gq Gs Gonadotropin releasing hormone GnRH Growth Hormone releasing hormone GHRH Growth Hormone Inhibiting Hormone GHIH somatostatin Gq Gs Gi Prolactin stimulating hormone PRF PRH not well known A stress is considered as any change from homeostasis The pituitary gland hangs from the hypothalamus and has two functional lobes The posterior pituitary is nervous tissue and secretes oxytocin and AHD The anterior pituitary is glandular tissue and secretes TSH ACTH FSH LH GH Prolactin and Endorphins Hypothalamus synthesizes neurohormones released in pulsatile fashion contains groups of functionally distinct cells called nuclei Oxytocin and ADH are synthesized as preprohormones then transported to posterior pituitary and stored GnRH deficiency alcohol Can be suppressed by stress drugs Early in life leads to delayed onset of puberty Later in life leads to infertility more pronounced in women Amenorrhea anovulation can lead to ovarian failure due to insufficient estrogen Releases corticotropin ACTH Releases LH and FSH gonadotropins The posterior pituitary releases oxytocin and antidiuretic hormone ADH Both are nonapeptides 9 amino acids with similar structures that differ only by two amino acids Releases growth hormone Inhibits release of growth hormone Oxytocin prolactin TSH Synthesized as preprooxyphysin Stimulates Releases prolactin o Uterine contractions in labor 3 Prolactin inhibiting hormone Anterior Pituitary PIH dopamine Releases thyrotropin TSH and prolactin Gi Inhibits release of prolactin o Milk ejection into breast ducts o Smooth muscle contraction of vas Aquaporin 2 is produced and inserted into the