Nervous system and reflex arc

• Nerve cell

  Also called a neuron
• Neuron

  • Long
  • Thin
  • Lots of branch connections to either end
  • Adapted to carry electrical impulses from one point to another
• Synapse


  Connection between nerve cells where electrical impulses are converted to chemical signals to pass between cells
• Nerve cell communication

  1. Electrical impulse hits end of nerve

  2. Causes release of chemicals

  3. Chemicals diffuse across gap to next nerve cell

  4. Triggers another electrical impulse

  5. Electrical impulse continues along new neuron
• Central nervous system

  • Made up of brain and spinal cord
  • Where 'thinking' takes place
  • Takes in sensory information, decides what to do, sends out orders to the body
• Sensory neurons


  Carry information from receptors all over the body to the central nervous system
• Motor neurons


  Carry impulses from the central nervous system to effectors (muscles or glands)
• Reflex arc


  Nerve pathway that underlies unconscious reflexes
• Reflex arc


  1. Stimulus detected by receptor cells

  2. Sensory neuron carries impulse to spinal cord

  3. Relay neuron transfers impulse to motor neuron

  4. Motor neuron carries impulse to effector (e.g. muscle) to cause movement
• Reflexes are rapid and automatic, helping us avoid getting hurt