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Endocrinology Exam 1 ReviewOverview- 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 streamo Primary endocrine glands Hypothalamus Pituitary Pineal Thyroid & parathyroid Thymus Adrenal Pancreas Gonadso Secondary endocrine glands Heart Kidneys GI tract Skin Adipose tissue- Endocrine system differs from the nervous system, although some neurotransmitters can acts as hormonesNervous Endocrinesecreted byneuron endocrine cellacts on neuron, muscle orglandmost cell typessignal neurotransmitter hormonetravels across synapse via bloodstreamonset of effectimmediate delayedduration of effectbrief longFeedback loops- 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 compensateo heart is working harder; increasesoxygen demando heart must meet this demand, heart rate increaseso heart develops more muscle mass,causing it to work harder, incr O2 demand and cycle continueso treated w/ β-blockers to make slower, more forceful beatso athletes get to rest because the stimulus ends; allows for angiogenesis (increased formationof vasculature to the heart)Classic hormone interactions1. antagonism: the effects of two hormones oppose each otherex: insulin & glucagon on blood glucose2. Additive: effects of hormones favor each other and sumex: growth hormone, thyroid hormone, testosterone3. Synergism: effects of hormone favor each other but net effect is greater than sumex: glucagon, cortisol, and epinephrine on blood glucose4. Permissiveness: one hormone is needed for another to exert its effects1ex: thyroid hormone is permissive for epi b/c it causes expression of adrenergic receptorsPrimary 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 cellsurface, 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 cellreceptors 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 menstruateReceptor Types- enzyme-linkedo tyrosine kinase is common- G-protein-coupledo Gs, Gq, Gi- Channel-linked/ligand gatedo Fast: receptor and channel are the same proteino Slow: receptor is coupled to the channel GPCRs- ligand binds, causing conformational change- alpha subunit dissociates and activates enzyme, channel, etc- causing amplification cascadeGs – Stimulatory – activates adenylyl cyclase, which increases [cAMP].Gq – activates phospholipase C, which cleavesPIP2 into IP3 and DAG.Gi – Inhibitory – inhibits adenylyl cyclase, and thus decreases [cAMP].Phosphodiesterase degrades cAMP, can cause signal to end. Second messengers- Calciumo Induces muscle contraction Changes electric potential Binds calmodulin to activate protein kinaseo Stored in mitochondria, smooth ER and boneo 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 receptorReceptor agonists bind to receptor and mimicnormal response.2Receptor 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 AxisHigher brain centers, aka the central nervoussystem 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 sugarHormone release may also be regulated by circadian rhythms (light/dark cycles), Established by the pineal gland, located just next to the optic chasm. 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, releasedin pulsatile fashion- contains groups of functionally distinct cells called nuclei - Oxytocin and ADH are synthesized as preprohormones, then transported to posterior pituitary and storedGnRH deficiency- Can be suppressed by stress, drugs, alcohol- 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. Hypothalamic Hormone GPCR Anterior PituitaryThyrotropin-releasing hormone (TRH)GqReleases thyrotropin (TSH) and prolactinCorticotropin-releasing hormone(CRH)GsReleases corticotropin (ACTH)Gonadotropin-releasing hormone (GnRH)GqReleases LH and FSH (gonadotropins)Growth Hormone releasing hormone (GHRH)GsReleases growth hormoneGrowth Hormone Inhibiting Hormone (GHIH, somatostatin)GiInhibits release of growth hormone, prolactin, TSHProlactin-stimulating hormone (PRF/PRH)not wellknownReleases prolactinProlactin-inhibiting hormone (PIH, dopamine)GiInhibits release of prolactin The posterior pituitary releases oxytocin andantidiuretic hormone (ADH). Both are nonapeptides (9 amino acids) with similar structures that differ only by two amino acids. Oxytocin - Synthesized as


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UMD BSCI 447 - Endocrinology Exam 1 Review

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