Global Brain Activity Flashcards
Does plasma and CSF have similar ionic compositions?
No. CSF - less protein + K+.
Similar Na+, HCO3- and osmolarity.
Is the osmolarity of plasma and CSF the same?
Yes
Does K+ directly affect the brain?
No, usually affects heart first then a secondary affect on brain.
Which ion is fundamental for osmolarity?
Na+
Which ions can affect the brain?
Na+, Ca2+, Mg+, P
What is the normal range for Na+?
135-145mmol/L
What happens to a cell in hyponatraemia?
Too much water outside of the cell with Na+, so water moves in + swells cell
How does hyponatraemia affect the brain?
Cells in brain swell due to water moving into cell to (cerebral oedema), which causes decreased blood flow and cerebral compression.
How does the brain compensate in acute hyponatraemia?
Shifts out CSF into systemic circulation, then pushes K+ out to try and also draw water out of cell.
It also pushes other molecules out to shift water + stop cells continuing to expand.
What is beer potomania?
Drink large amounts of beer cause dilutional hyponatraemia, no time for compensation mechanisms
What common anti-epileptic medication causes hyponatraemia?
Carbamazepine
What does it mean when the brain herniates?
Tissue is displaced in the brain to where it shouldn’t be
What are some common symptoms of cerebral oedema?
Nausea
Vomiting
Anorexia
Headaches
Lethargy
Disorientation
Muscle cramps
What are some common signs of cerebral oedema?
Seizures
Coma
Hyporeflexia
Cheyenne-stoking
Respiratory depression
Hypothermia
What system in the brain stem affects our consciousness level?
Reticular activating system
When treating chronic hyponatraemia, what should you be careful of?
Raising Na+ too quickly, can cause Central Pontine Myelinolysis (Osmotic Demyelination Syndrome)
If you over correct hyponatraemia, instead of drawing water out and having a normal sized cell, what happens to the cell?
It shrivels + damages the cytoskeleton.
Can also get demyelination
What can Central Pontine Myelinolysis cause?
Quadriplegia
Pseudobulbar Palsy
Seizures
Coma
Death
What happens to a cell in hypernatraemia?
Too little water outside cell, water moves out of cell + cell shrinks
How does hypernatraemia affect the brain?
Cells shrink which can cause haemorrhage from tears in veins or arteries
How does the brain compensate in hypernatraemia?
Uptake K+ into cell
Uptake of osmolytes into cells (glutamine, glutamate + taurine) which are protective against cell damage
What can an overcorrection of hypernatraemia cause?
Cerebral oedema
What is the normal serum pH?
7.35-7.45
What respiratory mechanism helps correct a metabolic disorder?
Increase or decrease in ventilation
Can Co2 cross the BBB?
Yes
How does Co2 affect cerebral blood flow?
Co2 regulates cerebral blood flow.
More Co2 = more blood flow
Less Co2 = less blood flow
Would hyperventilation cause acidosis or alkalosis?
alkalosis
Would hypoventilation cause acidosis or alkalosis?
Acidosis
What are some symptoms as a result of hyperventilation?
Lightheadedness
Syncope
Seizures
Hypocalcaemia
What are some symptoms as a result of hypoventilation?
Morning headaches
Visual disturbances
Confusion
How is a pneumocephalogram done?
Inject air into spinal cord via lumbar puncture + then rotate patient.
What do you need to change when looking at CT images, in order to look at different components of the brain?
Grey scale
What are some benefits to CT scans?
Quick
Metal compatible
Cheap
What are some downsides to CT scans?
Low resolution especially in the posterior fossa
Radiation
Is an MRI high or low resolution?
High
What are some pro’s of MRI’s?
Detailed
Wide range of imaging possibilities
No ionising radiation
What are some cons of MRI’s?
Metal can be a problem e.g. PPM
Claustrophobia
Time consuming (prone to motion artefact)
Loud
Can heat up body
What is an fMRI?
Functional MRI
Brain requires glucose to be transported in, causing arterioles to dilate.
Measures characteristic difference of deoxy-Hb + oxy-Hb, indirectly measuring neuronal activity based on vascular response.
Poor spatial and temporal resolution.
What is meant by default mode network?
Activity of the brain when doing nothing. Consists of the medial prefrontal cortex, medial parietal cortex and medial temporal lobes.
Can be affected by ADHA, schizophrenia, autism + Alzheimers.
What does nuclear medicine involve?
Radioactive isotope attached to a drug that can bind to an area of interest.
Radioactive emissions are measured and imaged with a gamma camera.
PET (Positron Emission Tomography); Inject with radioactive substance emitting positrons. Positrons collide with tissue electrons, emitting gamma rays in opposite directions.
When might a PET scan be used?
Pre-surgical assessment of complex seizures where MR normal
Evaluate memory loss + differentiate types of dementia
What is a SPECT?
Single Photon Emission Computed Tomography
2D images from multiple angles, reconstructed into 3D. Can use isotopes with single gamma ray.
Worse spatial resolution + more radiation than PET (but cheaper)
What scan is most common to determine whether tremors are from Parkinsons?
DaTscan - Dopamine Transporter to ioflupane 123
