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System

Nervous system

Not medically reviewed · Content last updated · 1 min read ·

This is the date the draft was written, not a medical review date.

The nervous system receives sensory information, integrates it and generates motor and autonomic responses. It is divided into the central nervous system (brain and spinal cord) and the peripheral nervous system (cranial and spinal nerves, ganglia and plexuses).

Terminologia Anatomica (Latin): Systema nervosum

Components

The brain comprises the cerebrum, diencephalon, brainstem and cerebellum, protected by the meninges and bathed in cerebrospinal fluid within the ventricular system. The peripheral system includes 12 pairs of cranial nerves, 31 pairs of spinal nerves and the autonomic (sympathetic and parasympathetic) divisions.

Function

Sensory pathways convey modalities such as touch, pain and special senses to the brain, while motor pathways control voluntary and reflex movement. The autonomic system regulates visceral function, and higher centres underlie cognition, language, memory and behaviour.

Clinical correlations

Stroke, epilepsy, neurodegenerative disease, demyelination, meningitis, traumatic injury and peripheral neuropathy are common neurological problems. Localising a lesion from the clinical examination (upper versus lower motor neuron, level, side) is the central diagnostic skill.

Common exam points

  • Divide the system into CNS and PNS, and the PNS into somatic and autonomic.
  • Name the 12 cranial nerves and classify each as sensory, motor or mixed.
  • Distinguish upper from lower motor neuron signs.
  • Sympathetic outflow is thoracolumbar; parasympathetic outflow is craniosacral.
  • Meningeal layers (dura, arachnoid, pia) and the circulation of cerebrospinal fluid.
  • Arterial supply of the brain: carotid and vertebrobasilar systems joined by the circle of Willis.

References

  1. Drake RL, Vogl AW, Mitchell AWM. Gray's Anatomy for Students. Elsevier — Tier 3 (textbook)
  2. Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. Wolters Kluwer, 8th edition (2018) — Tier 3 (textbook)
  3. Kandel ER, Koester JD, Mack SH, Siegelbaum SA. Principles of Neural Science. McGraw-Hill, 6th edition (2021) — Tier 3 (textbook)
  4. Haines DE, Mihailoff GA. Fundamental Neuroscience for Basic and Clinical Applications. Elsevier, 5th edition (2018) — Tier 3 (textbook)

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