Reflex Arcs

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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

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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

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2 Examples of Types of Reflexes (?)

• Knee-jerk reflex (patellar tendon reflex)
• Employs only 2 neurons sensory neuron
  communicating directly with a motor neuron
• 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.

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Knee-jerk Reflex (Fig. 9.16)
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Withdrawal Reflex (Fig. 9.17)