The Reflex Arc: Sensory, Relay and Motor Neurons

• What cells are responsible for quick reactions to pain?

  Neurons
• What structure do neurons form to facilitate quick reactions?

  A reflex arc
• What are the components of a reflex arc?

  • Sensory neuron
  • Relay neuron (in the spine)
  • Motor neuron
• What does the cell body of a neuron contain?

  The nucleus of the cell
• What are the two main structures on the length of a neuron?

  Axon and dendrites
• What are axon terminals responsible for?

  Converting electrical signals to chemical signals
• What is the function of the myelin sheath?

  Protects the cell and increases transmission speed
• What cells make up the myelin sheath?

  Schwann cells
• What is the process of a reflex action?

  1. Sensation detected by sensory receptors
  2. Electrical signal travels along dendrite to axon
  3. Signal converts to chemical at axon terminal
  4. Chemical crosses synaptic cleft to relay neuron
  5. Relay neuron sends signal to motor neuron
  6. Motor neuron activates effector (muscle)
• What is the effector in a reflex arc?

  The muscle activated by the motor neuron
• What happens to the information sent to the brain during a reflex action?

  It arrives after the body has moved
• What is the speed of the fastest neuron in the body?

  119 meters per second
• What is the name of the fastest neuron?

  Alpha motor neuron
• What is proprioception?

  Awareness of body position in space
• How fast does the alpha motor neuron transmit information?

  266 miles per hour
• What is the speed of type C neurons?

  One mile per hour
• Why are type C neurons slow?

  They are smaller and unmyelinated