3.6

• Response

  Action brought due to a stimulus
• Effector

  the cell, tissue, organ or system that carries out the response
• Coordinator

  the link between receptor and effector; acts as the ‘switchboard’ connecting information from each receptor to the appropriate effector
• Receptor

  Organ/cells that transfer energy from stimulus to a form that can be processed by the body.
• Stimulus

  Detectable change in environment

  • Internal/External
• Advantages of responding

  Increases chance of survival - Away from harmful stimuli

  Away from harmful stimuli

  Towards a food source

  Those that are more fit pass on their alleles = selection pressure
• Receptors are specific


  Only responds to the stimulus it is designed to
• Receptors are transducers


  Changes stimuli information into nerve impulses

  • Generator potential into action potential.
• Stretch mediated sodium ion channels


  A special type of sodium ion channel that changes its permeability sodium ions when it changes shape is stretched due to mechanical pressure.
• Information is sent through nerve impulses.
• Neurotransmitters transmit an action potential from one neurons to another.