PHYS Flashcards
Give the total volume of CSF present in the CNS at any given time (½)
150ml
Give the volume of the total daily production of CSF (½)
500ml /day
List four functions of cerebrospinal fluid (4)
- Constant external environment for neurons and glia
- Specific drainage route of CSF assists removal of harmful metabolites
- Mechanical cushioning
- Provides buoyancy – reduces effective weight
- Adjusts to changes in intracranial pressure due to alterations in cerebral blood flow
- All the functions performed by lymph
Describe 3 main functions of cerebrospinal fluid (3)
- Provides bouyancy – brain weighs less in CSF
- Provides a cushioning effect against impact
- Helps maintain a stable external microenvironment around the brain (i.e. homeostasis)
- Acts as a lymphatic system for removal of waste products draining into the venous system
Explain how the CSF compartment prevents intracranial pressure changes when blood flow to the brain is increased (4)
- Increased amounts of CSF are squeezed from the ventricles (1)
- Displaced CSF flows into the subarachnoid space around spinal cord (1)
- Dura mater lining spinal column is more elastic (1) Dura stretches to compensate for the increased volume (1)
The constituents of normal cerebrospinal fluid (CSF) are comparable to extracellular fluid (ECF).
- With reference to ECF, indicate whether the concentrations of glucose and of protein are higher or lower compared with CSF (1)
[Glucose] < & [Protein]
Is [Cl-] in normal CSF the same as in plasma? Explain your answer (1½)
Cl- is higher (½) to maintain electrical neutrality because the protein is very much lower (1)
3 y/o female’s day-care mother noticed one morning that she was not her active playful self but quite pale and felt feverish. Patient also complained of a headache. Gave her some paracetamol syrup and put her down for a nap. A few hours later patient’s condition had deteriorated. She was drowsy and weak, felt cold and clammy and had a purple spotty rash on her arms and chest. Dr did a blood culture and lumbar puncture. He suspected meningitis as there had been an outbreak in the area recently.
Explain…
Why she was drowsy and weak (2)
Why she felt cold and clammy (2)
Impaired neural function as a result of bacterial infection – cytokines, raised temperature, depleted energy supply (ATP)
Activation of sympathetic nervous system, vasoconstriction, sweating
2 y/o male’s caregiver at the crèche notices he is irritable and feverish. Gives him some paracetamol syrup. An hour later he is drowsy and not responding to his mom’s voice. Purplish spotty rash on his face and neck. Dr assesses him & immediately suspects meningococcal meningitis. Sends specimens to the lab and gives him a stat dose of an antibiotic. Superintendent immediately notifies the crèche and the authorities of the case before the diagnosis was confirmed by lab findings. Within the same week, 6 other patients from the area were admitted to hospital with meningococcal meningitis.
A lumbar puncture is usually performed in cases of suspected meningitis. Give two (2) examples of CSF analysis & indicate how this can assist with the diagnosis of the patient’s condition (2x2 = 4)
Cell counts: Distinguish between WBCs and RBCs (indicative of sub-arachnoid bleeding)
CSF chemistry: [Protein] > 100mg/10ml will cause CSF to be pale yellow in colour
High WBC count (100’s) will cause CSF to look cloudy
Bacteriological identification – using various cell staining techniques
CSF pressure measurements (normal: usually < 200mm H2O): Meningitis patients have markedly elevated CSF pressure – if persistent neurological deterioration may occur and indicate treatment (osmotic dehydrating agents, steroids)
