intercellular commication and signal transduction
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Intercellular Commication and Signal Transduction

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Intercellular Commication and Signal Transduction. Chapter 4. Intercellular Communication. Cells of body must communicate with one another Coordinates organ systems Takes place directly: Physical contact between cells Gap junctions Direct linkage of surface markers Or indirectly

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intercellular communication
Intercellular Communication
  • Cells of body must communicate with one another
  • Coordinates organ systems
  • Takes place directly:
    • Physical contact between cells
      • Gap junctions
      • Direct linkage of surface markers
  • Or indirectly
    • Extracellular chemical messengers or signal molecules
    • Specific to target cell receptors
chemical messengers
Chemical Messengers
  • Four types of chemical messengers
    • Paracrines
      • Local chemical messengers
      • Exert effect only on neighboring cells in immediate environment of secretion site
    • Neurotransmitters
      • Short-range chemical messengers
      • Diffuse across narrow space to act locally on adjoining target cell (another neuron, a muscle, or a gland)
chemical messengers1
Chemical Messengers
  • 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
  • Neurohormones
    • Hormones released into blood by neurosecretory neurons
    • Distributed through blood to distant target cells
chemical messengers2
Chemical Messengers
  • Cell responses brought about primarily by signal transduction
    • Incoming signals conveyed to target cell’s interior
  • Binding of extracellular messenger (first messenger) to receptor brings about intracellular response by either
    • Opening or closing channels
      • Chemically gated receptor channel
    • Activating second-messenger systems
      • Activated by first messenger
        • Receptor-enzyme
      • Relays message to intracellular proteins that carry out dictated response
        • G-protein coupled receptor


Tyrosine kinase pathway

  • Endocrinology
    • Study of homeostatic activities accomplished by hormones
  • Two distinct groups of hormones based on their solubility properties
    • Hydrophilic hormones
      • Highly water soluble
      • Low lipid solubility
    • Lipophilic hormones
      • High lipid solubility
      • Poorly soluble in water
class questions
Class Questions
  • There are 3 ways cells communicate. The 2 direct means of communication is through ___________ and _______________. Cells indirectly communicate through _______________.
  • Name and describe the 4 types of chemical messengers. Include which fluid medium they travel through: blood, extracellular fluid, intracellular fluid.
  • Why is a neurotransmitter different than paracrine signalling?
  • What is a syncytium?
  • What is a ligand? What is a receptor?
  • How does a chemical messenger “know” which organ to affect?
  • Name 3 ways that an extracellular chemical messenger can bring about an intracellular response.
  • Is the response between a chemical messenger and a particular receptor always the same?
  • How can a chemical receptor elicit a different response inside a cell?
  • In a second messenger system, where does the first messenger bind? Where is the second messenger?
class questions1
Class Questions
  • There are 2 major 2nd messengers: cyclic AMP and Ca2+ . Describe the action of a hydrophilic hormone via activation of the cyclic AMP 2nd messenger pathway. If you draw pictures, you must label everything and explain what is happening.
  • How does using an 2nd messenger system amplify the response inside the cell?
  • How do some chemical messengers affect gene activity (hence, protein synthesis) within a cell?
  • Which type of hormone can affect gene activity, hydrophilic or lipophilic? Why?