Lesson · A.3.1

The nervous system

How the brain, spinal cord, and nerves are organised and how a signal moves from one neuron to the next, the framework the HESI A2 anatomy and physiology subtest builds every nervous system question on.

ObjectiveA.3.1Read5 minExam weightRegulation and Control ≈ 16% of Anatomy & Physiology

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What you will be able to do

  • You can place a structure correctly into the central or peripheral nervous system, and into the somatic or autonomic subdivision.
  • You can describe the parts of a neuron and the order in which a nerve impulse travels through them.
  • You can name the four major regions of the brain and the one job each is tested on most often.

What the lesson concludes

  • The CNS is the brain and spinal cord. The PNS is every nerve outside them.
  • Sensory (afferent) neurons carry signals toward the CNS. Motor (efferent) neurons carry signals away from it.
  • The autonomic nervous system splits into sympathetic (fight or flight) and parasympathetic (rest and digest), and the two usually pull in opposite directions on the same organ.
  • A nerve impulse travels dendrite, then cell body, then axon, then crosses a synapse to the next cell.
  • The brainstem runs the functions you cannot live without: breathing and heart rate.