Central Nervous System

What is the Central Nervous System (CNS)?

The central nervous system (CNS) consists of the brain and spinal cord. It processes sensory information, coordinates movement and bodily functions, and supports thought, emotion, and memory. The peripheral nervous system (PNS) carries signals between the CNS and the rest of the body.

Components of the Central Nervous System

• Brain

  The brain includes the cerebrum, cerebellum, and brainstem. These regions have different structures and functions, but work through connected neural circuits.

• Spinal Cord

  The spinal cord is a long, cylindrical bundle of nervous tissue that extends from the brainstem to approximately the first or second lumbar vertebral level in adults. It carries signals between the brain and body and contains circuits for certain reflexes.

Functions of the Central Nervous System

• Integration and Processing

  The CNS integrates and processes sensory information received from various parts of the body, allowing it to form a coherent perception of the external environment and internal bodily states. It also processes motor commands, directing the body to perform specific actions in response to changing circumstances.

• Coordination and Control

  The CNS coordinates and controls the body's various functions, including movement, balance, and the activities of internal organs. Neural pathways and feedback loops help maintain homeostasis, the regulation of the body’s internal conditions, while responding to changes outside it.

• Cognition and Emotion

  The CNS plays a central role in higher cognitive functions such as learning, memory, language, reasoning, and problem-solving. It also regulates emotions, allowing for the expression and modulation of feelings in response to both internal and external stimuli.

Protection and Support of the Central Nervous System

• Meninges

  The meninges are a series of three protective membranes (dura mater, arachnoid mater, and pia mater) that surround and support the brain and spinal cord. They provide a physical barrier against infection, injury, and inflammation.

• Cerebrospinal Fluid

  Cerebrospinal fluid (CSF) is a clear, colorless liquid that circulates within and around the CNS, providing both mechanical support and nutrient delivery. CSF helps cushion the brain and spinal cord, reducing the risk of injury from sudden movements or impacts.

• Blood-Brain Barrier

  The blood-brain barrier (BBB) is a selective barrier formed by specialized endothelial cells that line the blood vessels in the brain. The BBB regulates movement between blood and brain tissue, limiting many substances while supporting controlled transport. It does not exclude every harmful substance.

Sources and evidence

• OpenStax: Anatomy and Physiology 2e: The Central Nervous System. Explains the brain, spinal cord, and their major structures.
• Richard Daneman and Alexandre Prat: The Blood-Brain Barrier.