Global Brain Activity Flashcards
Although CSF is similar to plasma, there are 2 key differences, where the concentrations are lower in CSF than in plasma. What are these 2 differences?
- CSF has higher K+ and amino acid concentration than plasma
- CSF has lower K+ and a higher amino acid concentration than plasma
- CSF has higher K+ and a lower amino acid concentration than plasma
- CSF has lower K+ and amino acid concentration than plasma
- CSF has lower K+ and amino acid concentration than plasma
- K+ (plasma = 4.7 and CSF = 2.9mEq)
- amino acids (plasma = 2.6 and CSF = 0.03mEq)
What is the glymphatic system?
- a waste clearance in the CNS, essentially a lymphatics system of the brain
- CSF flows into the paravascular space around cerebral arteries, combining with interstitial fluid and parenchymal solutes, and exiting down venous paravascular spaces
What are the 2 methods by which CSF is able to leave the brain?
- diffuse into veins and ventricles
- arachnoid granulation and diffusion into veins
- arachnoid granulation and glymphatic system
- glymphatic system and ventricles
- arachnoid granulation and glymphatic system
1 - arachnoid granulation (into venous sinus and out through internal carotid artery), likely superior sagittal sinus
2 - through glymphatic system (brains lymphatic system)
What does hypertonic (relative to extracellular fluid) mean?
- fluid outside of the cell has a high osmolarity
- solute concentration in the cell is lower than fluid surrounding it
- cations/anions leave the cell to dilute and water follows
- cell shrinks
What does hypotonic (relative to extracellular) mean?
- fluid outside of the cell has a low osmolarity
- solute concentration in the cell is higher than fluid surrounding it
- cations/anions enter the cell to dilute and water follows
- cell expands and can rupture
What does isotonic mean?
- solute concentration in the cell is equal to outside the cell
- cations/anions do not move
- cell remains stable
What is hypernatremia and hyponatremia?
- hypernatremia = high levels of Na+
- hyponatremia = low levels of Na+
Cells of the brain tend to operate at isotonic states. What will happen if there is a sudden decrease in Na+ concentration in the extracellular fluid in the brain?
- fluid will flow into the intracellular compartments of the brain to dilute Na+ concentration inside the cell
- cells in the brain will swell as water follows Na+
- causes cerebral oedema
Cells of the brain tend to operate at isotonic states. If there is a sudden decrease in Na+ concentration in the extracellular fluid the fluid will flow into the intracellular compartments of the brain and the cells in the brain will swell, which will causes cerebral oedema. If the brain swells what can happen to the blood vessels of the brain?
- they become compressed
- blood flow will be decreased
- causes cerebral compression
Cells of the brain tend to operate at isotonic states. If there is a sudden decrease in Na+ concentration in the extracellular fluid the fluid will flow into the intracellular compartments of the brain and the cells in the brain will swell, which will causes cerebral oedema. If the brain swells the can compress blood vessels in the brain, blood flow will be decreased and this will cause cerebral compression. There is a safety system in place in the brain that can help to remove excessive CSF if there is too much fluid in the brain, what is this safety system?
- plug release
- pressure stop valve
- pressure compressor
- pressure stop valve
- CSF is removed through arachnoid granulations
- CSF then enters the venous system and out through internal jugular vein
If there is too much fluid in the brain, the pressure stop valve is able to remove CSF through arachnoid granulation, into the venous sinus and then out of the brain via the internal jugular vein. In addition to this what 2 other charged molecules can cells secrete in an attempt to increase the hypo-osmotic concentrations in the extracellular fluid?
- Na+ and K+
- K+ and amino acids
- Ca2+ and amino acids
- K+ and Cl-
- K+ and amino acids
- amino acids (AA) (glutamine, glutamate, taurine)
- pumping out K+ and AA reduces osmolality inside the cell
- reduces the risk of fluid flowing into the cells causing cerebral oedema
- THIS is a slow process by the body to maintain homeostasis
Cerebral oedema is when there is too much fluid in the brain, and is generally due to hyponatraemia (low Na+) in the extracellular space. This can cause cause fluid to flow into cells, which is dangerous in the brain as the brain can swell causing nerve death. What are a few of the most common symptoms patients may present with if they are hyponatraemic?
- nausea
- vomiting
- anorexia
- headaches
- lethargy
- disorientation
- muscle cramps
Cerebral oedema is when there is too much fluid in the brain. What are the most common signs that clinicians can see in patients?
- seizures
- coma
- hyporeflexia
- Cheyne-Stokes respiration (gradual increase, decrease, apnea then stop)
- respiratory depression
- hypothermia
What does central pontine myelinolysis, also referred to as osmotic demyelineation syndrome) mean if we break down the name?
- pontine = refers to pons of the brain stem
- myelin = refers to myelin that covers axons
- sis = indicates destruction
- so destruction of myelineated axons in the pons due to osmotic changes
The following can occur in patients who are hyponatremic (low Na+):
- low extracellular Na+ = fluid flows into the cells to maintain osmosis (dilute intracellular concentration), causing oedema.
- cells of the brain try to mediate this by secreting K+ and other osmolites (amino acids and glucose) to lower intracellular concentrations. This will stop water entering cells and maintain osmosis, but can take up to 48 hours.
- clinician may attempt to correct the Na+ imbalance too quickly and give the patient high Na+ fluids. The cells do not have sufficient time to correct the osmotic balance as Na+ cannot easily enter the cell and it takes time for K+ and osmolites to re-enter the cell.
- patient becomes hypertonic = high Na+ extracellularly, meaning water leaves the cell to dilute extracellular Na+ and maintain osmosis and the cells shrink
This can damage the cells and even cause cell death. What is this called if this occurs in the pons of the brain?
- Central Pontine Myelinolysis
- myasthenia gravis
- multiple sclerosis
- neural infarct
- Central Pontine Myelinolysis, also called osmotic demyelination syndrome
Central Pontine Myelinolysis, also called osmotic demyelination syndrome is damage to the myelineated axons located centrally in the pons. This can be very serious, given how important the pons are in communication between the spinal cord and the cerebral cortex. What can this lead to for the patient?
- quadriplegia (paralysis from the neck down)
- pseudobulbar palsy (inability to control muscles)
- seizures
- coma
- death
Cells of the brain tend to operate at isotonic states. What will happen if there is a sudden increase in Na+ concentration in the extracellular fluid in the brain?
- fluid will flow out of the extracellular compartments of the brain to equalise Na+ concentrations
- fluid will leave cells to reduce hypertonic Na+ extracellularly
- cells in the brain will shrink
- causes haemorrhage from veins and arteries and reduced cerebral blood flow
Cells of the brain tend to operate at isotonic states. If there is a sudden increase in Na+ concentration in the extracellular fluid in the brain, water will flow out of the cell to maintain osmosis. Thus can cause the cells to shrink causing haemorrhage in veins and arteries. What do the cells of the brain try to do in an attempt to compensate for this?
- cell increase K+ and amino acid uptake to achieve equilibrium with outside of the cell, so water will not leave the cell, causing the cells to shrink
- aim is to maintain osmosis with outside of the cell
What is the relationship between arterial PCO2 and cerebral blood flow, keeping in mind that CO2 in the body is a powerful vasodilator.
- increase in arterial PCO2 = increase in cerebral blood flow
- decrease in arterial PCO2 = decrease in cerebral blood flow
Amyloid precursor protein (APP) is a transmembrane protein (half in and outside the cell) that is involved in neuronal cell growth and repair. Once its function is completed it is soluble and removed after it is broken down by alpha and gamma secretase. However, if gamma and beta secratase break down the APP, what can this lead to?
- part of the APP remains and is not soluble
- creates monomer beta-amyloid that then clump and stick together
What is a computerised tomography (CT), also referred to as a CAT scan?
- multiple X-rays applied using an arch like machine
- provides a cross sectional image of the patient
- based on density, more density = whiter
What plane is the section cut and what type of imaging has been used in the image below?
- axial/transverse slices
- CT because the skull is super bright (remember X-rays)
What is the benefit of having a CT scan on a computer when compared to an X-ray?
- X-ray has 5 basic densities (bone, metal, fat, air, fluid)
- CT can be changed on a scale making it easier to distinguish between tissues of similiar densities
- changing of the scale through windowing and levelling
What is default mode network which is measured through functional MRI?
- the brain when it is said to be at rest or not doing anything
- despite no instructions patterns in blood flow are common
The default mode network which is measured through functional MRI is the brain when it is said to be at rest or not doing anything. Despite no instructions patterns in blood flow are common. What are the 3 places it is common numbered 1-3 in the image?
1 - medial temporal cortex
2 - medial prefronal cortex
3 - medial parietal cortex
What does the posterior cortical hot zone, or just hot zone refer to in the brain?
- no instructions are given to patients when imaging the brain
- patterns in blood flow can be seen
- common posteriorly, medial temporal cortex, medial pre-fronal cortex and medial parietal cortex
