Introduction To Clinical Neuroscience Flashcards
What lobe is the most developed in humans?
→ The frontal lobe
What is the dura and what does it contain?
→ the ‘bag’ that surrounds the brain
→ contains CSF that surrounds the brain
What is the function of the dura?
→ Cushions the brain from impact
How much energy does the brain use?
→ 20-30% of the energy
What makes up grey matter?
astrocytes
→ Neurons
→ glia
What are the connections between grey matter?
→ white matter
What do dendrites do?
→ They receive signals from other neurons and get processed by the cell body and the signal is transmitted to other cells
What happens when the frontal lobe is damaged and give an example?
→ Phineas Gage
→ Personality changes
→ irreverent, impatient
What is Alzheimers?
→ Deposition of proteins that damage the brain
What do products of blood breakdown show up as on an X-Ray?
→ Bright marks
What creates MRI images?
→ magnets within us
How does NMR work?
→ Hydrogen atoms have protons
→ Nucleus spins and acts like a small magnet
→ A radiofrequency pulse is given out which interacts with all the protons
→ Protons spin and generate a signal
What is isotropic diffusion?
→ the same diffusion in all directions
What is anisotropic diffusion?
→ Strong lateral diffusion but perpendicularly weak
How can water move in white matter tracts?
→ it can diffuse easily
→ restricted from moving side to side
What is anisotropy a marker of?
How much damage is done
Describe the principle that is used when measuring brain activity
→ Deoxy Hb is paramagnetic
→ it causes a reduction in the MRI signal intensity
→ when doing something (talking) more O2 and glucose are needed
→ Deoxy Hb is washed out
→ The signal should increase
How do PET scans work?
→ Injected radionuclides
→ they decay by emitting a positron
→ It doesn’t travel very far before bumping into an electron
→ the two join together and annihilate and emit a gamma ray
→ The gamma rays are emitted in equal and opposite directions to conserve momentum
Give an example of how Parkinsons is detected using a PET scan?
→F18 nucleus is attached to dopamine
→ this is picked up by dopamine receptors
→ in normal controls there is a lot of dopamine receptors in the caudate and putamen
→ in patients with parkinsons they are reduced so the signal is less bright
How thick is the cortical cortex?
→4mm thick comprised of 6 layers
What is one way the gut is connected to the brain?
→vagus nerve
What type of cells in the brain network can turn cancerous?
astrocytes
What is pareidolia?
the tendency to perceive a specific, often meaningful image in a random or ambiguous visual pattern
What is cortical homunculus?
→the brain’s physical representation of the human body;
→The surface area of cortex dedicated to a body part
What does the cortical homunculus tells us?
→that humans are very vocal, sensation of hands
What is facial agnosia?
→can’t recognise face.
What is glioblastoma?
– highly infiltrative, result of cancerous cells.
→They are diffusive
What is hippocampal sclerosis?
→Reduced hippocampus structure
→can cause seizures, found in Alzheimers and other dementias
What are planar x-rays useful for?
→for traumatic brain injuries and structures in them
How do x-ray CT work?
→X-ray through the body and picked up by detectors which rotate it round whole of body.
→With mathematical processing can be turned into image
What is a limitation of x-ray CT?
→There is no delineation of grey and white matter within brain- just a single contrasts
What does MRI depend on?
→different places in the body contain different amounts of water
What does the intensity of an image depend on?
→water content, →tissue structure, →blood flow, →perfusion, →diffusion, paramagnetic
Describe the differences between T1 and T2 images.
→T1-weighted images are produced by using short TE and TR times
→proton energy within fatty tissues of the body
→T2 images fattyANDwater-based tissues of the body
What does increased tissue water and loss of cellular structure lead to?
→Increased T2
What does T1w images give?
→grey/white matter contrast
Compare water molecules in grey and white matter
→In grey matter water in both the intra- and extracellular compartments has relatively free motion.
→In white matter approximately 50% of the tissue volume is accounted for by myelin structures which has low T1 relaxation time
→Hence the average T1 of WM < GM
When does cortical folding occur?
→before baby is born. Changes still occur right up to early adulthood
What is MR spectroscopy?
compares the chemical composition of normal brain tissue with abnormal tumor tissue
→ informs on metabolic processes in different diseases
What happens to glutamate that is picked up by postsynaptic neuron?
→picked up by astrocytes and converted back to glutamine back to presynaptic neuron
Where is cerebral blood flow higher?
→higher in grey matter compared to white
→The oxygen extraction factor can be measured in PET
What is penumbral tissue?
→the part of an acute ischemic stroke that is at risk of progressing to infarction but is still salvageable if perfused.
Why does WM show up bright on fMRI and have a low T1 relaxation time?
→Protons interact with CH3 in the myelin which reduces the T1 relaxation times of the white matter
→Myelinated have low T1 relaxation time
