Moderate

A reflex action does not involve the:

Correct answer: A. Brain

  • A. Brain
  • B. Motor neuron
  • C. Sensory neuron
  • D. Spinal cord

Explanation

This simple reflex circuit includes each of the four elements of a neural pathway. (1) The sensory neuron has pain-sensitive endings in the skin and a long fiber leading to the spinal cord. That neuron stimulates (2) an association neuron in the spinal cord, which in turn stimulates (3) a motor neuron, also in the cord. The axon of the motor neuron carries action potentials to (4) muscles, causing them to contract and withdraw the body part from the damaging stimulus. The sensory neuron also makes a synapse on association neurons not involved in the reflex that carry signals to the brain, informing it of the danger.

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About Coordination and Control

Coordination depends on receptors, neurons, synapses and nerve impulses, with reflex actions traced through the reflex arc and the roles of major brain regions. Chemical coordination covers endocrine glands and hormones, including how hormones regulate growth, metabolism, reproduction and internal balance, unlike rapid nervous control.

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