Cell signalling

• In multicellular organisms communication between cells is important. this happens through cell signalling
• What is cell signalling

  Where nearby cells or distant cells communicate with each other
• Most cell signals are chemicals in nature such as growth factors, hormones, neurotransmitters and extra cellular components
• What is endocrine signalling 


  Signalling over a long distance where the endocrine gland releases a hormone which enters the blood and travels to the target organ/tissue
• What is paracrine signalling 


  Occurs between two cells which are close to each other. it can occur directly between the cells if they are adjacent to each other or via the tissue fluid
• What is autochrome signalling 


  Where a cell releases a signalling molecule which will bind to a receptor in the plasma membrane of the cell to initiate a response
• nervous system

  1. Vesicles containing neurotransmitters move down to the synapse and fuse with the plasma membrane.
  2. causing the neurotransmitters to be released into the synapse
  3. as there isn’t many neurotransmitters at the receiving cell they diffuse across down the concentration gradient
  4. the neurotransmitters attach to the receptors on the receiving cell causing a nervous impulse
• Endocrine system

  1. a signalling molecule travels in extracellular fluid from a different cell in the body to the plasma membrane
  2. the signalling molecule binds to a complementary receptor molecule triggering a transduction pathway within the cell
  3. this pathway activates a cellular response