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How does cerebrospinal fluid circulate through the brain and spinal cord?

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Diagram comparing action potential conduction in myelinated and unmyelinated axons, showing a neuron with labeled cell body, myelin sheath, nodes of Ranvier, and the flow of electrical signals along each type of axon. — nervous system In a myelinated axon, the myelin sheath prevents the local current (small black arrows) from flowing across the membrane. This forces the current to travel down the nerve fibre to the unmyelinated nodes of Ranvier, which have a high concentration of ion channels. Upon stimulation, these ion channels propagate the action potential (large green arrows) to the next node. Thus, the action potential jumps along the fibre as it is regenerated at each node, a process called saltatory conduction. In an unmyelinated axon, the action potential is propagated along the entire membrane, fading as it diffuses back through the membrane to the original depolarized region.

Cerebrospinal fluid (CSF) is primarily produced by the choroid plexus, a network of blood vessels located within the ventricles of the brain.12

The circulation follows a specific pathway:
* Production: Most CSF is secreted in the lateral ventricles.2
* Flow: The fluid drains through the interventricular foramina into the third ventricle, passes through the cerebral aqueduct in the midbrain, and enters the fourth ventricle in the hindbrain.2
* Distribution: Openings in the fourth ventricle allow the fluid to exit into the subarachnoid spaces, which surround both the brain and the spinal cord.23

Movement is driven by factors including the secretion and absorption process, blood pulsations, respiration, gravity, and physical movement. Ultimately, the fluid is absorbed into the venous system, primarily through arachnoid villi that project into the dural sinuses. This continuous circulation helps cushion the central nervous system, maintain intracranial pressure, and transport metabolic waste away from neural tissue.134