CSF Flashcards
Body fluid breakdown
Give an example of a transcellular fluid
Saliva (modified in some way)
BBB is under direct control by _____ ______
Glial cells - they control what can and cannot gain access to IS fluid of brain
Explain vesicular transfer
Exocytosis - release of substance
Endocytosis - captured
Transcytosis - the whole process
What do the glial cells form
Very tight junctions => BBB
Ensures endothelial cells of vasculature of the BVs delivering blood to brain are wedged
What is the rate of passage of lipid soluble substances proportional to
Directly proportional to lipid solubility and inversely proportional to size
What structure creates the tight junctions
Endfeet of astrocytes induce tight junctions
Name the 2 places where CSF is produced
- Within ventricles - choroid plexi capillary network
- Around SA of everywhere in the brain, by astrocytes
What cells share a function with astrocytes
Ependymal cells
What are the choroid plexi
Network of capillaries found within ventricles (2 lateral and a 3rd and a 4th - reservoirs of CSF)
Define CSF
A ‘sink’ of EC fluid filtered from blood that supplies and drains the interstitium
How much CSF is in our body
Where is it found and in what proportion
140-150ml
Ventricles - 25ml
Spinal cord central canal - 30ml
Sub-arachnoid space - majority of volume
How does the movement of CSF occur
Through systolic pulsations of arterial system - compression of ventricles and subarachnoid space
Diagram of brain
Rate of production of CSF
550 ml/day (0.35ml/min)
=> turns over 3.7 times/day
50-70% of CSF is produced by ______ ______
Choroid plexi
What is the 2nd way in which CSF is produced
Blood vessel to IS transfer - regulated by astrocytes
How is CSF reabsorbed
Through arachnoid villi into veins via venous sinuses
The CSF production by BV to IS transfer facilitates what
Rapid delivery of O2 and nutrients to a local area
How much does the brain weigh in air
1400g
What is the effective weight of brain floating in CSF
50g
Components of meninges
Dura, arachnoid and pia mater
CSF fills subarachnoid space
What does the buoyancy of CSF permit
Attachments to support brain
- BVs
- Nerve roots
- Fine fibrous arachnoid trabeculae
What is a less invasive way of measuring ICP
CSF pressure is often a guide of ICP
What is the normal range of CSF pressure
How can it be taken
65-195 mmCSF or 5-15 mmHg
Lumbar puncture procedure (between L3-L4)
How can ICP be raised
Through obstruction of venous system, intracranial mass, brain oedema
CSF composition overview
what ion has a profound effect on electrically excitable tissues
Ca2+
Analysis of CSF
What is the composition of EC fluid in CNS highly regulated by
BBB (hence glial cells)
What parts of the brain receive blood in an unfiltered form
What are these sites
Circumventricular organs
- Neurohypophysis (senses hormones - need to know real practical picture)
- Area postrema
- Hypothalami nuclei e.g. OVLT, supraoptic and paraventricular nuclei
- Subfornical organ
* Sites of physiological and endocrine feedback systems within the brain
What allows the maintenance of the integrity of the BBB, despite these circumventricular organs
Rapid venous drainage from these sites
