Anatomy and Physiology by Rod R Seeley 6th edition chapter 17 power-point

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Anatomy and Physiology, Sixth Edition
Rod R. SeeleyIdaho State University Trent D.
StephensIdaho State University Philip
TatePhoenix College
Chapter 17 Lecture Outline
See PowerPoint Image Slides for all figures and
tables pre-inserted into PowerPoint without notes.
Copyright The McGraw-Hill Companies, Inc.
Permission required for reproduction or display.
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Chapter 17

• Functional Organization of
• Endocrine System

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Endocrine System Characteristics

• Produce hormones
• In minute amounts secreted into interstitial
  spaces
• Enters circulatory system
• Acts on target tissues at another site
• Regulate activities of body structures
• Amplitude modulated signals
• Frequency-modulated signals
• Response slower and longer duration than nervous
  system

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Chemical Signals

• Intercellular Allow one cell to communicate with
  other cells as hormones
• Autocrine
• Released by cells and have a local effect on same
  cell type from which chemical signals released as
  prostaglandin
• Paracrine
• Released by cells and affect other cell types
  locally without being transported in blood as
  somatostatin
• Pheromones
• Secreted into environment that modify behavior
  and physiology as sex pheromones

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Chemical Structure of Hormones
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Control of Secretion Rate

• Most hormones are not secreted at constant rate
• Patterns of regulation
• Involves action of substance other than hormone
  on an endocrine gland
• Involves neural control of endocrine gland
• Involves control of secretory activity of one
  endocrine gland by hormone or neurohormone
  secreted by another endocrine gland

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Nervous System Regulation
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Hormonal Regulation
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Positive and Negative Feedback
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Control of Secretion Rate

• Negative-feedback
• Mechanisms that function to maintain homeostasis
  control most of hormone secretion
• Mechanisms of hormone secretion from endocrine
  tissue
• Nonhormone substance
• Stimulation by nervous system
• Hormone from another endocrine tissue

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Transport and Distribution

• Hormones dissolve in blood plasma and are
  transported in free form or bound to plasma
  proteins
• As concentration of free hormone molecules
  increase, more hormones molecules diffuse from
  capillaries into interstitial spaces to bind to
  target cells

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Transport and Distribution

• A large decrease in plasma protein concentration
  can result in loss of a hormone from the blood
  because free hormones are rapidly eliminated from
  circulation through kidney or liver
• Hormones are distributed quickly because they
  circulate in the blood

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Metabolism and Excretion

• Half-life The length of time it takes for half a
  dose of substance to be eliminated from
  circulatory system
• Long half-life
• Regulate activities that remain at a constant
  rate through time
• Short half-life
• Water-soluble hormones as proteins, epinephrine,
  norepinephrine
• These hormones have a rapid onset and short
  duration
• Hormones also eliminated by blood by excretion by
• Kidneys and liver
• Enzymatic degradation
• Conjugation
• Active transport

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Hormone Interaction with Target Tissues

• Hormones
• Ligands or chemical signals
• Binding site
• Receptor site
• Specificity

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Target Cell Response to Hormones

• Target tissues have receptor molecules specific
  for particular hormone

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Down and Up-Regulation

• Down-regulation
• Number of receptors decreases within target cells
• Up-regulation
• Some stimulus causes number of receptors for a
  hormone to increase within target cell

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Classes of Hormone Receptors

• Membrane-bound receptors bind to water-soluble or
  large-molecular-weight hormones
• Intracellular receptors bind to lipid-soluble
  hormones

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Membrane-Bound Hormone Receptors

• Proteins or glycoproteins that have polypeptide
  chains folded to cross cell several times
• Results of ligand binding
• Changes permeability of plasma membrane
• Alters activity of G proteins
• Alters activity of intracellular enzymes

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Activation of G Proteins
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G Proteins and Ca2 Channels
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G Proteins and Synthesis of cAMP
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Membrane-Bound Receptors
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Cascade Effect
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Intracellular Receptors

• Are proteins in cytoplasm or nucleus
• Hormones bind with intracellular receptor and
  receptor-hormone complex activates genes, DNA
  activated to produce mRNA, mRNA initiates
  production of certain proteins (enzymes) that
  produce response of target cell to hormone
• Slow-acting because time is required to produce
  mRNA and protein
• Processes limited by breakdown of
  receptor-hormone complex

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Intracellular Receptor Model