Receptors

• Receptors are specific. describe this ?


  They only detect one particular stimulus eg light
• Different types of receptors do what?


  Detect a different type of stimulus
• What can receptors be?


  cells

  proteins on cell surface membranes
• What does it mean if a Nervous system receptor is in its resting state?


  not being stimulated
• Describe what there is when a nervous system receptor is in its resting state?


  There is a difference in charge between the inside and the outside of the cell

  • this is generated by ion pumps & ion channels
  • this means there is a voltage across the membrane
• What is voltage aka?


  Potential difference
• What is a cell's resting potential?


  The potential difference when a cell is at rest is called its resting potential
• When is potential difference altered?


  When stimulus detected, cell membrane is excited and becomes more permeable , allowing more ions to move in and out of the cell - altering the potential difference
• What is the generator potential?


  The change in potential difference due to a stimulus
• When is a bigger generator potential produced?


  A bigger stimulus excites the MEMBRANE MORE, causing a bigger MOVEMENT OF IONS and a BIGGER CHANGE IN POTENTIAL DIFFERENCE

  • so a bigger generator potential produced
• What happens if the generator potential is big enough?


  It will trigger an ACTION POTENTIAL.
• What is an action potential?


  An electrical impulse along a neurone
• An action potential is only triggered if what?


  If the generator potential reaches a CERTAIN LEVEL (threshold level)
• Action potentials are all what?


  All ONE SIZE, so the strength of the stimulus is measured by the frequency of action potentials
• What is the strength of the stimulus measured by?


  The frequency of action potentials (the number of action potentials triggered during a certain time period)
• What happens if the stimulus is too weak?

  The generator potential will NOT REACH THE THRESHOLD, so there is NO ACTION POTENTIAL