8. Reflex Action and the Reflex Arc

• Simple reflexes: inborn, unlearned. Cranial reflexes involve 2 neurons (sensory + motor), e.g. blinking. Spinal reflexes involve 3 neurons (sensory, relay, motor), e.g. withdrawing the hand from a hot object.
• Conditioned reflexes: learned through repeated experience and coordinated by the brain, e.g. salivating at the sight of food (Pavlov’s dogs).

Reflex arc pathway: Stimulus → Receptor → Sensory neuron → (Relay neuron, in spinal reflexes) → Motor neuron → Effector → Response.

Components of a reflex arc

• Importance: enables automatic, involuntary adjustment to changes (e.g. balance), and helps maintain homeostasis (breathing rate, blood pressure).