Download Reflex Arcs

Reflex Arcs
• Nerve impulse pathways that are responsible
for involuntary actions
• Look like the pathway you drew and labeled:
Receptor to
Sensory neuron to
(optional step) Interneurons in the CNS (a reflex
center) to
Motor neurons to
Effector
Reflexes
• Automatic subconscious responses to
changes within or outside the body:
– Maintain homoestasis: blood pressure, heart
rate, respirations, digestion, temperature
– Automatic actions: swallowing, coughing,
sneezing, vomiting
2 Examples of Types of Reflexes (?)
1. Knee-jerk reflex (patellar tendon reflex)
– Employs only 2 neurons: sensory neuron
communicating directly with a motor neuron
2. Withdrawal reflex:
– A response to painful stimuli
– Sensory neuron takes impulse to interneurons
in the spinal cord reflex center, where it is
transmitted to motor neurons.
– Other interneurons carry impulses to the brain
for processing of the experience and pain.
Knee-jerk Reflex (Fig. 9.16)
Withdrawal Reflex (Fig. 9.17)