Module 1 - Cells

Cell signalling

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  • Created by: Nick
  • Created on: 08-05-10 17:45


Cells communicate via cell signalling. The three main ways in which animal cells can do this are by; Neurones, hormones and local hormones.


  • Neurones transmit information electrically over long distances.
  • At the end of each neurone is a swelling that contains vesicles of a chemical transmitter substance known as a neurotransmitter.
  • When a nerve impulse reaches the end of the neurone, these vesicles travel to the membrane and release molecules of neurotransmitter by exocytosis across the synapse.
  • On the next neurone, or on an effector (e.g. muscle cell or gland cell), there are receptor molecules that detect the neurotransmitter molecules.
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  • Endocrine cells secrete hormones into the bloodstream. Hormones have effects on their target cells, which are the only cells that detect the hormone and respond to it.
  • Receptor molecules on the cell surface or inside the cell combine with the hormone, triggering a series of events inside the cell leading to the cell's response.
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Local hormones

  • Some cells release molecules that travel short distances to adjoining cells. examples of these local hormones are histamine and cytokines.
  • During an immune response, some lymphocytes release cytokines that stimulate other lymphocytes to divide by mitosis and secrete antibodies.
  • Cytokines also stimulate phagocytes to become more active.
  • The hormones insulin and glucagon do not cross cell membranes to divide as they are large, water-soluble molecules. - So therefore, glycoprotein receptor molecules on the cell surface detect insulin.
  • Steroids e.g. testosterone are fat-soluble, so they can cross phospholipid bilayers and interact with receptors inside cells.
  • Many drugs are made to have a shape complementary to receptor molecules.
  • Agonists - mimic the effect of the signalling molecule.
  • Antagonists - block receptors to stop the signalling molecule having any effect.
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