Cerebrospinal fluid (CSF) is primarily produced by the choroid plexus of the lateral, third, and fourth ventricles. The normal rate of CSF production and total volume are approximately:
- A 0.1 mL/min; total volume 50 mL
- B 1.5 mL/min; total volume 300 mL
- C 0.35 mL/min; total volume 120–150 mL ✓
- D 0.05 mL/min; total volume 30 mL
Correct answer: C. 0.35 mL/min; total volume 120–150 mL
Explanation
CSF is produced at approximately 0.35 mL/min (500 mL/day) by active secretion at the choroid plexus (Na+/K+-ATPase and carbonic anhydrase driven). Total CSF volume is 120–150 mL, with approximately 25 mL in the ventricles and the remainder in the spinal and cranial subarachnoid spaces. It is absorbed at the arachnoid granulations (villi) into the dural venous sinuses, driven by a hydrostatic pressure gradient. The entire CSF volume turns over approximately 3–4 times per day.
Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.
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