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UCONN - PNB 2264 - Class Notes - Week 13

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UCONN - PNB 2264 - Class Notes - Week 13

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background image Endocrine 1: Mechanisms of Hormone Control  endocrine glands (without ducts) secrete into blood stream unlike exocrine 
glands (with ducts)
o allows systemic effects   The Nervous system vs Endocrine System  o Nervous One to one (or several) cells Localized signals  Short duration, rapid recovery  Action potential faster o Endocrine One cell to many cells Global effects Long duration, long recovery  No action potential  Slower o Exception: adrenal medulla  Neurohormone  Neurons function like endocrine cells  Secreted directly from neurons into the blood stream  Hormonal diversity o Origin 
o Function
o Structure
Peptide (protein) Water soluble – dissolve in plasma membrane  o Easy to excrete – short half life Genes code for it  made in inactive chain form- Preprohormones processed (cut into shorter chains) to become 
cleaved (proteolytic enzyme) to become Hormones  Ex. insulin, glucagon  Steroid Possess cholesterol backbone Differentiate based on side chains  Sex steroids  o Estrogen
o Progesterone 
o Testosterone 
Cortical steroids  
background image o Cortisol
o Aldosterone 
Lipid soluble  o Requires transport proteins 
o Slower to excrete – long half life 
Amine  Derived from single amino acids  Made from Tyrosine or Tryptophan  Tyrosine  o Thyroid hormones - Lipid soluble  Needs to be activated  o Catecholamines – water soluble  Epinephrine  Norepinephrine  Dopamine Tryptophan  o Melatonin  Hormone Mechanisms o Receptor Upregulation Increase sensitivity  o Receptor downregulation Decreases sensitivity  Lipid soluble hormone (can pass through plasma membrane) Steroid and Thyroid  (intracellular) Receptors are inside cell on nuclear envelope  Activate gene transcription (global/systemic effect) Amplification effect  Ex. estrogen  Estrogen receptor activates many downstream targets  Receptor status will dictate course of treatment  Water soluble (cannot pass through membrane) Peptides and Catecholamines Receptor on plasma membrane (extracellular receptors) Intracellular signaling enzymes (second messenger system) Amplify  Neurotransmitters that activate adrenergic and 
muscarinic receptors also use second messengers 
G Protein Coupled Receptors  o Water soluble hormones utilize 
o Three subunits
Alpha Gai Gas Gaq Beta
background image Gamma o When hormone or neurotransmitter binds to receptor from outside the  G-alpha is separated from complex o The cAMP Pathway (Gs) Stimulates adenyl cyclase (AC Enzyme that turns ATP into cyclic AMP  Effects Ion channel activity via CNGs (cyclic nucleotide gated ion 
Gene transcription via CREs (cAMP response element)  Phosphorylation via activation of Protein Kinase A  o Kinase adds a phosphate to protein- changes  structure and function  o On and off switch 
o May dictate protein shape, activity, stability, 
binding partners, or localization  o Occurs on Specific Amino Acid Residues (Serine,  Threonine, Tyrosine)  o Effect dependent on target tissue  Ex. Beta Adrenergic Receptor  Receptor binds to epinephrine  Gs coupled pathway  In fight or flight makes heart beat faster  o The Phosphodiesterase Pathway (Gi) Inhibit Adenyl Cyclase (AC) Stop cAMP production  Promote phosphodiesterase’s activity  Breaks down cAMP Ex. Alpha-2 Adrenergic Receptor  Activated by epinephrine  Receptor is using Gi During fight or flight causes blood vessels to contract in 
smooth muscle (gut)
The Lipid/Calcium Pathways (Gq) Gq activates Phospholipase C Cleaves PiP2 into IP3 and DAG in plasma membrane DAG activates Protein Kinase C  Adds phosphate  IP3 binds to receptors on Endoplasmic Reticulum to initiate 
Ca2+ release 
Muscle contraction  Ex. Alpha-1 adrenergic receptor 

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School: University of Connecticut
Department: Physiology
Course: Human Physiology and Anatomy
Professor: Kristen Kimball
Term: Fall 2018
Name: PNB 2264 Week 13
Description: These notes cover the entirety of the endocrine system.
Uploaded: 12/02/2018
8 Pages 76 Views 60 Unlocks
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