Physiology: Cerebrospinal Fluid and Production

Question 1

Cerebrospinal Fluid

Answer 1

Clear, colourless liquid composed mostly of water

Question 2

What produces CSF?

Answer 2

Secretory epithelium of the choroid plexus

Question 3

Where is CSF formed?

Answer 3

Formed in the ventricles and then circulates in the subarachnoid space then absorbed into venous circulation.

Question 4

CSF functions

Answer 4

mechanical protection
homeostatic function
circulation

Question 5

CSF mechanical protection

Answer 5

shock absorbing medium that protects brain tissue

Question 6

CSF homeostatic function

Answer 6

pH of CSF affects pulmonary ventilation and cerebral blood flow
Transports hormones

Question 7

CSF circulation function

Answer 7

Medium for minor exchange of nutrients and waste products between blood and brain tissue

Question 8

What does CSF supply and remove

Answer 8

Supplies water, amino acids and ions

Removes metabolites

Question 9

Normal CSF composition

Answer 9

Clear and colourless
Contains little protein (15-45mg/dl)
Little immunoglobulins
1-5 cells/ml

Question 10

Embryonic development of brain and ventricular system

Answer 10

At 3 weeks, the developing nervous system consists of a tube- neural canal

Cavity’s give rise to the adult brain ventricles and the spinal cords central canal

Choroid plexus develops from cells in the walls of the ventricles

Choroidal cells are specialised secreting cells that produce CSF

Question 11

Choroid Plexus

Answer 11

network of capillaries in walls of ventricles

Question 12

Choroid Plexus development

Answer 12

Developing arteries invaginate the roof of the ventricle to form the choroid fissure

Involuted ependymal cells along with the vessels enlarge into villi and form the choroid plexus, responsible for CSF production

Choroid plexus located in 3rd, 4th and lateral ventricles

Question 13

CSF Production

Answer 13

CSF secretion involves the transport of ions across the epithelium from the blood to CSF

Ions: Na+, Cl-, HCO3-

Secretion can occur because of the polarised distribution of specific ion transporters in the apical or basolateral membrane of epithelial cells

Question 14

CSF constituency

Answer 14

Secretion of fluid by the choroid plexus depends on the active Na+ transport across the cells into the CSF

Electrical gradient pulls along Cl- and both ions drag water by osmosis.

CSF has lower K+, glucose and protein than blood plasma
It has higher Na+ and Cl-

Question 15

CSF and arterial BP

Answer 15

Production of CSF. in choroid plexuses is an active secretory process and not directly dependent on arterial blood pressure.

Question 16

Ventricular System (4)

Answer 16

Ventricles are connected

Intraventricular foramina
- lateral ventricles to 3rd ventricle

Cerebral aqueduct
- 3rd ventricle to 4th

Median Aperture

• Foramen of. Magendie
• 4th ventricle to subarachnoid space

Lateral Aperture

• Foramen of Luschka
• 4th ventricle to subarachnoid space

Question 17

CSF Circulation

Answer 17

1. CSF formed in choroid plexuses of each lateral ventricle
2. Flows to 3rd ventricle through 2 narrow openings called inter ventricular foramina
3. More CSF added by choroid plexus in roof of 3rd ventricle
4. Flows through aqueduct of midbrain (cerebral aqueduct) and into 4th ventricle
5. Another choroid plexus in 4th ventricle adds more CSF
6. CSF then enters the subarachnoid space through 3 openings in roof of 4th ventricle (median and lateral apertures)
7. Then circulates in central canal of spinal cord

Question 18

Amount of CSF produced per day

Answer 18

500ml of CSF produced and absorbed every day

- pressure and volume remains constant

Question 19

CSF ventricular circulation and outflow

Answer 19

Directional flow through the ventricular system into the subarachnoid space (SAS) between Pia and dura mater.

CSF return to venous blood through arachnoid granulations into superior sagittal sinus (SSS)

Brain interstitial fluid makes up the final portion of CSF and drains to the CSF through perivascular spaces

Question 20

blood brain barrier site

Answer 20

Endothelial cells in brain capillaries

Question 21

What does the blood brain barrier consist of?

Answer 21

Capillary endothelium, basal membrane and perivascular. astrocytes

Tight junctions between brain endothelial cells prevent paracellular movement of molecules

Question 22

part of the brain without BBB

Answer 22

Circumventricular organs

Pineal gland

Question 23

BBB and CSF

Answer 23

BBB is determining factor for clinical CSF analysis

Question 24

pathologies of Ventricles, choroid plexus and CSF

Answer 24

Tumours
Ventricular haemorrhage
Hydrocephalus
Idiopathic intracranial hypertension

Question 25

Tumours

Answer 25

Colloid Cyst
- often found at inter ventricular foramen

Ependymomas
- arising from ependymal cells lining the ventricles

Choroid plexus tumours

Question 26

Ventricular Haemorrhage

Answer 26

Epidural Haematoma
- arterial bleed between skull and dura

Subdural haematoma
- venous bleed between dura and arachnoid

Subarachnoid haemorrhage

Question 27

Hydrocephalus

Answer 27

Accumulation of CSF in ventricular system or around brain

Subsequent enlargement of one or more ventricles and increase in CSF pressure

Question 28

idiopathic intracranial hypertension

Answer 28

Enigmatic condition

Symptoms include headache and visual disturbances due to papilloedema

Despite increase CSF pressure, no imaging features of hydrocephalus

Question 29

Papilloedema

Answer 29

Optic disc swelling due to increased intracranial pressure transmitted to subarachnoid space surrounding optic nerve

Question 30

Papilloedema Visual Symptoms

Answer 30

Enlarged blind spot
Blurring of vision
Visual obscurations
Loss of vision