neurons

• neuron

  The basic building blocks of the nervous system. Process & transmit messages through electrical & chemical signals.
• sensory neuron

  -carry nerve impulses from the PNS to the CNS

  -in sense organs e.g., the eyes

  -when the impulses reach the brain they translate into sensations e.g., vision

  -stop at the spinal chord to allow for quick reflexes

  -long dendrites & short axons

  
• relay neuron

  -allow sensory & motor neurons to communicate

  -in brain & spinal chord (CNS)

  -short dendrites & short axons
• motor neuron

  -in the CNS

  -control muscle movement

  -release neurotransmitters that bind to the receptor muscles & triggers a response. Leads to movement.

  -short dendrites & long axons

  
• reflex arc

  -stimulus detected by sense organs in the PNS, sends message along sensory neuron

  -message reaches the CNS, connects with relay neuron

  -transfers to motor neuron

  -carries message to the effector e.g., muscle

  
  

  Example: touching a hot object

  -message only goes to the spinal chord which enables a quick reaction, message is sent to the brain after the hand has been removed