L19_NPB_101 - Lecture 19 •  SmartSite: – ...

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Unformatted text preview: Lecture 19 •  SmartSite: –  Lecture 19 Notes –  Midterm 1 (Wed 10/20): •  •  •  •  •  Reading (Recommended): •  Announcements: –  Relevant por?ons Chapter 4 & 18 30 MC ques?ons Covers lectures through Yesterday Star?ng Today, lectures on Midterm 2 Requires students to bring and use SCANTRON 2000 (blue) •  Review •  Endocrinology –  Introduc?on –  Smooth Muscle –  Exam Room (based on Last Name) –  CAF Office Hrs (197 Briggs) •  T 9 ­10 and 5 ­6 (Regular) •  M 5 ­7 •  Tu/Th 1 ­3 (Regular) •  A ­D in 1322 Storer •  E ­Z in 123 Sci Lec Hall (regular room) –  EL Office Hrs (2041A SLB) 1 REV: Smooth Muscle •  Spindle ­shaped cells with single nucleus •  Thick myosin & thin ac?n filaments, organized without sarcomeres (hence smooth without stria?ons) •  Chemical ac?va?on of Cross ­bridge •  Ca2+ source is from ECF (no organized SR) •  Two major types: –  Mul? ­unit •  neurogenic control; few gap junc?ons  ­ separate cell contrac?on –  Single ­unit •  several sources of excita?on; most cells connected via gap junc?ons  ­ cells act as a func?onal syncy?um 2 REV: Muscle •  All 3 Muscle Types: –  Similari?es: •  thin ac?n filaments which slide rela?ve to sta?onary thick myosin filaments •  Contrac?le elements respond to intracelluar Ca2+ signaling •  Use ATP as energy source for cross ­bridge forma?on & power stroke •  Cell structure, morphology and organiza?on of filaments •  Mechanisms of excita?on and coupling of excita?on ­ contrac?on •  Differences in contrac?le response speed and dura?on •  Source of Ca2+ 3 –  Differences: Endocrine System 4 Chemical Messengers •  Extracellular chemical messengers bring about cell responses primarily by signal transduc?on •  Binding of extracellular messenger (first messenger) to matching receptor brings about desired intracellular response by either –  Opening or closing channels –  Ac?va?ng second ­messenger systems •  Ac?vated by first messenger •  Relays message to intracellular proteins that carry out dictated response 5 –  Process by which incoming signals are conveyed to target cell’s interior Types of Intercellular Communica?on •  Paracrines –  Local chemical messengers –  Exert effect only on neighboring cells in immediate environment of secre?on site –  Short ­range chemical messengers –  Diffuse across narrow space to act locally on adjoining target cell (another neuron, a muscle, or a gland) 6 •  Neurotransmihers Fig. 4 ­20cd, pg. 114 Types of Intercellular Communica?on •  Hormones –  Long ­range messengers –  Secreted into blood by endocrine glands in response to appropriate signal –  Exert effect on target cells some distance away from release site –  Hormones released into blood by neurosecretory neurons –  Distributed through blood to distant target cells 7 •  Neurohormones Fig. 4 ­20ef, pg. 114 Hormones •  Endocrinology –  Study of homeosta?c ac?vi?es accomplished by hormones •  Hormones are secreted from individual cells within organs or cells organized into a dis?nct gland •  Two dis?nct groups of hormones based on their solubility proper?es –  Hydrophilic hormones •  Highly water soluble •  Low lipid solubility –  Lipophilic hormones •  High lipid solubility •  Poorly soluble in water 8 Endocrine System •  Overall func?ons –  Regulate organic metabolism and H2O and electrolyte balance –  Induce adap?ve changes to help body cope with stressful situa?ons –  Promote smooth, sequen?al growth and development –  Control reproduc?on –  Regulate red blood cell produc?on –  Along with ANS, control and integrate both circula?on and the diges?on & absorp?on of food 9 Fig. 18 ­1, pg. 662 Comparison of Nervous & Endocrine Systems Table 4 ­5, pg. 128 10 Nervous & Endocrine System Interac?ons •  Neurons secrete hormones (Neurohormones) •  Secre?on of hormones by some cells controlled by nervous system •  Hormones can affect –  –  –  –  –  –  –  Birth of new neurons Death of neurons Synapse forma?on Dendri?c branching Membrane poten?al Myelina?on of neurons Glial cell number/func?on •  Some chemical messengers can act as neurotransmihers OR hormones 11 Endocrine System •  Consists of ductless endocrine glands scahered throughout body •  Glands secrete hormones which travel through blood to target cells –  Target cells have receptors for binding with specific hormone –  Regulates or directs par?cular func?on –  Hydrophilic –  Lipophilic •  Two hormone categories based on solubility •  Amino Acid deriva?ves (Amines; i.e., Catecholamines) •  Pep?de hormones (most hormones) •  Steroid hormones (derived from cholesterol) •  Thyroid hormone (special case of Amino Acid deriva?ve) 12 Tropic Hormones •  Regulates hormone secre?on by another endocrine gland •  S?mulates and maintains their endocrine target ?ssues •  Example –  Thyroid ­s?mula?ng hormone (TSH) secreted from anterior pituitary s?mulates thyroid hormone secre?on by thyroid gland •  Also maintains structural integrity of thyroid gland 13 Effects of Hormone Proper?es •  Chemical proper?es of a hormone impacts storage, transport, metabolism, excre?on, and mode of ac?on at target cells •  The plasma concentra?on of free, biologically ac?ve hormone, which can interact with its target cells to produce a physiological response, depends on: –  The hormone’s rate of secre?on by the endocrine gland (the major factor for all hormones) –  Its rate of metabolic ac?va?on (for a few hormones) –  Its extent of binding to plasma proteins (for lipophilic hormones) –  Its rate of metabolic inac?va?on and excre?on (for all hormones) 14 Effects of Hormone Proper?es •  1. Secre?on vs. storage: –  Hydrophilic hormones can be stored in secre?on vesicles aker synthesis, secre?on can be regulated separately from synthesis –  Lipophilic hormones diffuse out of cells as soon as synthesized –  Secre?on rate can be pulsa?le and/or follow a circadian rhythm •  circa ~ “about”; dies ~ “day” 15 Effects of Hormone Proper?es •  2. Transport –  Hydrophilic hormones soluble in plasma –  Lipophilic hormones bound to both general and specific proteins in plasma 16 Effects of Hormone Proper?es •  3. Metabolism –  a. Inac?va?on •  Pep?des ­ cleaved by circula?ng proteases •  Steroid, thyroid hormones ­ modified to be more water soluble and more easily lost in urine •  Pep?des: cleaved by specific proteoly?c enzymes •  Steroid hormones, thyroid hormones: enzymes in target cells modify structure to produce more ac?ve hormone 17 –  b. Ac?va?on Effects of Hormone Proper?es •  4. Hormone ac?on on target cells –  A given receptor is specific for given hormone –  But, one hormone can have different effects in different ?ssues via dis?nct receptors –  Receptors are expressed in target ?ssues and upon hormone binding ini?ate biochemical chain of events that alters cell func?on –  Hydrophilic hormones act via receptors in target cell membrane –  Lipophilic hormones act via intracellular receptors that act in the cell nucleus •  i.e.nuclear receptors •  i.e. membrane receptors 18 Chemical Classifica?on of Hormones Table 4 ­4, pg. 118 19 A Common Membrane Receptor Ac?vated Pathway •  Mechanism of ac?on of hydrophilic hormones via ac?va?on of the cyclic AMP second ­ messenger pathway •  Protein kinase A targets –  Ion channels –  Other transporters –  Enzymes –  Transcrip?on factors •  alter gene transcrip?on Fig. 4 ­24, pg. 121 20 ...
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