Composition and functions of cerebrospinal fluid 5 mark Question mbbs 1st theory exam physiology
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Cerebrospinal Fluid: Composition and Functions
Cerebrospinal fluid (CSF) is a clear, colourless fluid present in the ventricles of the brain and the subarachnoid space around the brain and spinal cord. It is formed mainly by the choroid plexus.
Composition
CSF is an ultrafiltrate of plasma, but its composition is actively regulated by the choroid plexus.
| Constituent | Concentration in CSF compared with blood |
|---|---|
| Water | About 99% |
| Sodium (Na⁺), chloride (Cl⁻), bicarbonate (HCO₃⁻) | Approximately equal |
| Potassium (K⁺), calcium (Ca²⁺) | Lower |
| Glucose | Lower, about two-thirds of blood glucose |
| Protein | Very low or negligible |
| Cholesterol | Negligible |
| Magnesium (Mg²⁺), creatinine | Higher |
| Cells | Normally absent or very few lymphocytes |
Normal CSF is sterile, has low protein, and contains no red blood cells.
Functions
- Mechanical protection: CSF acts as a shock absorber and protects the brain and spinal cord from injury.
- Buoyancy: It supports the brain, reducing its effective weight and preventing compression of nervous tissue.
- Maintains stable environment: It maintains a constant ionic composition and pH needed for normal neuronal activity.
- Nutrition: It supplies nutrients to nervous tissue.
- Removal of waste: It helps remove metabolic waste products and harmful substances from the CNS.
- Maintains intracranial pressure: Its formation, circulation, and absorption help maintain normal intracranial pressure.
Reference: Costanzo Physiology, Table 3.6, composition of CSF.
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Cerebrospinal Fluid: Composition and Functions
Cerebrospinal fluid (CSF) is a clear, colourless fluid found in the ventricles and subarachnoid space around the brain and spinal cord. It is formed mainly by the choroid plexus.
Composition
- It is about 99% water and is similar to plasma, but contains very little protein and no cells.
- Na⁺, Cl⁻ and HCO₃⁻: nearly equal to plasma.
- K⁺, Ca²⁺, glucose, amino acids and pH: lower than plasma.
- Mg²⁺ and creatinine: relatively higher than plasma.
- Proteins and cholesterol: negligible.
Functions
- Acts as a shock absorber and protects the brain and spinal cord from trauma.
- Provides buoyancy, reducing the effective weight of the brain.
- Maintains a stable ionic and chemical environment for neuronal function.
- Supplies nutrients and helps in removal of metabolic waste products.
- Helps maintain normal intracranial pressure.
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