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 Commication and Signal Transduction

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Intercellular commication and signal transduction

Intercellular Commication and Signal Transduction

Chapter 4


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


Intercellular commication and signal transduction

Figure 4-21


Intercellular commication and signal transduction

Receptor-enzyme:

Tyrosine kinase pathway


Hormones

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


Intercellular commication and signal transduction

Mechanism of hydrophilic hormones via cyclic AMP second messenger pathway


Intercellular commication and signal transduction

Comparison of Nervous System and Endocrine System


Animation mechanism of action of a peptide hormone

Animation: Mechanism of action of a peptide hormone


Animation mechanism of action of a steroid hormone

Animation: Mechanism of action of a steroid hormone


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?


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