Cerebrospinal Fluid and Cerebral Circulation

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Questions and Answers

What is the primary site of cerebrospinal fluid formation?

  • Subarachnoid space
  • Choroid plexus of the ventricles (correct)
  • Cerebral cortex
  • Spinal dorsal root ganglia

Approximately how much cerebrospinal fluid is normally present within the cerebral cavity?

  • 150 milliliters (correct)
  • 1700 milliliters
  • 30 milliliters
  • 850 milliliters

Which structure primarily aids in the protection of the brain and spinal cord by regulating substances in cerebrospinal fluid?

  • Cerebral arteries
  • Blood-brain barrier
  • Choroid plexus (correct)
  • Ependymal cells

What is the average rate of cerebrospinal fluid formation in adults?

<p>20-25 ml/hour (D)</p> Signup and view all the answers

Where does the internal carotid artery branch off to supply oxygenated blood predominantly to the cerebrum?

<p>Circle of Willis (A)</p> Signup and view all the answers

Which of the following statements about cerebrospinal fluid is incorrect?

<p>CSF is formed exclusively in the lateral ventricle. (D)</p> Signup and view all the answers

How much cerebrospinal fluid is produced by an adult in one day?

<p>550 ml (C)</p> Signup and view all the answers

What is the approximate total capacity of the cerebral cavity that contains cerebrospinal fluid?

<p>1600 to 1700 milliliters (D)</p> Signup and view all the answers

What is the osmotic pressure of cerebrospinal fluid (CSF) compared to plasma?

<p>Approximately equal to that of plasma (D)</p> Signup and view all the answers

Which ion concentration in CSF is approximately 15% greater than that in plasma?

<p>Potassium ion (D)</p> Signup and view all the answers

What is the primary structure through which cerebrospinal fluid is absorbed into the venous sinuses?

<p>Arachnoid granulations (B)</p> Signup and view all the answers

Which of the following components has a concentration of approximately 20-40 mg/100 ml in CSF?

<p>Proteins (C)</p> Signup and view all the answers

What does the specific gravity of CSF range from?

<p>1.004-1.007 (D)</p> Signup and view all the answers

How is the circulation of cerebrospinal fluid mainly aided?

<p>Arterial pulsations of the choroid plexuses (C)</p> Signup and view all the answers

What is the average pressure range of cerebrospinal fluid in mm of H2O?

<p>60-150 mm of H2O (D)</p> Signup and view all the answers

What is the characteristic color of healthy cerebrospinal fluid?

<p>Clear and transparent (D)</p> Signup and view all the answers

What is the daily formation rate of cerebrospinal fluid (CSF)?

<p>550 milliliters (B)</p> Signup and view all the answers

Which part of the cerebrospinal fluid (CSF) has the largest volume?

<p>Subarachnoid space (A)</p> Signup and view all the answers

What primarily stimulates the secretion of fluid by the choroid plexus?

<p>Active transport of sodium ions (D)</p> Signup and view all the answers

Which ions are primarily involved in increasing the osmotically active substances in the CSF?

<p>Sodium and chloride (A)</p> Signup and view all the answers

What is the volume range of cerebrospinal fluid present within the ventricles?

<p>30-40 ml (B)</p> Signup and view all the answers

Where does a small quantity of cerebrospinal fluid originate from besides the choroid plexus?

<p>From the brain itself (C)</p> Signup and view all the answers

How does the transport of sodium ions affect the formation of cerebrospinal fluid?

<p>It leads to osmosis of water (A)</p> Signup and view all the answers

What is the approximate total quantity of cerebrospinal fluid in the body?

<p>150 milliliters (A)</p> Signup and view all the answers

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Study Notes

Cerebrospinal Fluid (CSF) Overview

  • CSF is a clear, colorless fluid found in cerebral ventricles, spinal canal, and subarachnoid spaces.
  • It plays a crucial role in protecting the brain and spinal cord.

Cerebral Circulation

  • The Circle of Willis is a vital arterial junction at the base of the brain.
  • Internal carotid arteries branch out here, supplying over 80% of the cerebrum with oxygenated blood.

CSF Formation

  • CSF is primarily produced by the choroid plexus in the lateral, third, and fourth ventricles.
  • About 30% of CSF originates from ependymal cells and brain capillaries.
  • The choroid plexus, a highly vascular structure covered by ependyma, actively secretes CSF.

Mechanism of CSF Formation

  • Formation process involves secretion and filtration through capillaries and ependymal cells.
  • A blood-CSF barrier regulates substance entry, protecting the central nervous system (CNS).
  • Total cerebral cavity capacity is approximately 1600 to 1700 ml, with CSF occupying about 150 ml.

CSF Statistics

  • CSF is produced at a rate of 20-25 ml/hour, or about 550 ml/day, turning over approximately 3.7 times daily.
  • Distribution: 30-40 ml in the ventricles, 110-120 ml in the subarachnoid space (75-80 ml spinal, 25-30 ml cranial).

Secretion by Choroid Plexus

  • Choroid plexus resembles a caulifower structure and secretes fluid via active sodium transport, attracting chloride and water.
  • CSF composition features an osmotic pressure similar to plasma, with variations in sodium, chloride, potassium, and glucose levels.

CSF Absorption

  • Arachnoidal villi allow CSF absorption into venous sinuses.
  • Villi consist of fingerlike projections that facilitate the passage of CSF, proteins, and larger particles into the bloodstream.

CSF Composition

  • Proteins: 20-40 mg/100 ml
  • Glucose: 50-65 mg/100 ml
  • Cholesterol: 0.2 mg/100 ml
  • Sodium: 147 meq/Kg H2O
  • Calcium: 2.3 meq/Kg H2O
  • Urea: 12.0 mg/100 ml
  • Creatinine: 1.5 mg/100 ml
  • Lactic Acid: 18.0 mg/100 ml

Characteristics of CSF

  • Appears clear and transparent, with a specific gravity of 1.004-1.007.
  • Reaction is alkaline, and it does not coagulate.
  • Average cell count: 0-3 cells/cmm.
  • Normal pressure range: 60-150 mm of H2O; various activities can increase pressure.

CSF Circulation Pathway

  • CSF is produced in the lateral ventricle, flows through the interventricular foramen (foramen of Monro) to the third ventricle.
  • It moves via the cerebral aqueduct to the fourth ventricle.
  • From the fourth ventricle, it enters the subarachnoid space surrounding the brain and spinal cord through the foramina of Magendie and Luschka.
  • Arterial pulsations assist in the circulation of CSF.

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