L1.1.5.1: Reflex Arc

• REFLEX ARC

  ● Neural pathways where reflexes occur

  ● Involve both CNS and PNS structures
• REFLEX ARC

  ● 2 types of reflex arcs: two-neuron reflex arcs and three-neuron reflex arcs
• TWO-NEURON REFLEX ARCS

  • Simplest type
  • Ex: patellar (knee-jerk) reflex
• THREE-NEURON REFLEX ARCS

  • Consists of 5 elements
  • Ex: flexor (withdrawal) reflex
• 5 ELEMENTS OF 3-NEURON REFLEX ARC

  • Sensory Receptor
  • Sensory Neuron
  • Integration Center (CNS)
  • Motor Neuron
  • Effector Organ
• Sensory Receptor

  • Reacts to stimulus
• Sensory Neuron

  • Carries messages to the integration center
• Integration Center (CNS)

  • Process information and directs motor output
• Motor Neuron

  • Carries message to an effector
• Effector Organ

  • Muscle or gland to be stimulated