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Intercellular Commication and Signal Transduction

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 Commication and Signal Transduction

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  1. Intercellular Commication and Signal Transduction Chapter 4

  2. 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

  3. 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)

  4. 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

  5. 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

  6. Figure 4-21

  7. Receptor-enzyme: Tyrosine kinase pathway

  8. Hormones • 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

  9. Mechanism of hydrophilic hormones via cyclic AMP second messenger pathway

  10. Comparison of Nervous System and Endocrine System

  11. Animation: Mechanism of action of a peptide hormone

  12. Animation: Mechanism of action of a steroid hormone

  13. 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?

  14. 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?

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