How much does the brain weigh without cerebrospinal fluid?

How much does the brain weigh without cerebrospinal fluid?

• A. 25 grams
• B. 125 grams
• C. 500 grams
• D. 1 kilogram

Answer: (A)

Estimating brain mass after removing cerebrospinal fluid hinges on knowing typical brain weight and how much CSF is in the skull. An adult brain with CSF present weighs about 1.3 to 1.4 kilograms. Cerebrospinal fluid volume is roughly 150 milliliters, and since CSF has a density close to water, that adds about 150 grams. Subtracting that fluid from the total leaves around 1.15 to 1.25 kilograms of brain tissue. Among common options, this is best approximated by about 1 kilogram. The smaller values (25 g, 125 g, 500 g) are far too light for an adult brain, while 1 kilogram is the closest best estimate after removing CSF.

Estimating brain mass after removing cerebrospinal fluid hinges on knowing typical brain weight and how much CSF is in the skull. An adult brain with CSF present weighs about 1.3 to 1.4 kilograms. Cerebrospinal fluid volume is roughly 150 milliliters, and since CSF has a density close to water, that adds about 150 grams. Subtracting that fluid from the total leaves around 1.15 to 1.25 kilograms of brain tissue. Among common options, this is best approximated by about 1 kilogram. The smaller values (25 g, 125 g, 500 g) are far too light for an adult brain, while 1 kilogram is the closest best estimate after removing CSF.