intro to neuroscience Flashcards
CT
method of 2D/3D imaging measuring the X-ray attenuation through a tissue
Magnetic Resonance Imaging (MRI)
2D/3D imaging by detecting signals produced by protons in water and fat molecules
T2 MRI
signal intensity related to water content (signal intensity increases with increased water content)
T1 MRI
signal intensity related to the differences in white and grey matter (they have different cellular structure)
Diffusion-weighted MRI
microscopic diffusion of water molecules is measured (in a specific direction)
PET
2D imaging based on detecting gamma rays produced by injected radiopharmaceutical
Radiopharmaceutical
molecule (given either intravenously or orally) with a radioisotope attached
what makes humans dominant species in comparison to other primates?
greatly developed frontal lobe
describe the relationship between grey mass and number of neurons in the cerebral cortex for humans?
many more neurons per grey mass
what is the encephalocentric theory?
theory the brain is the centre of sensation and understanding
what is the cardiocentric theory?
theory that the heart is the centre of sensations and intelligence
what is the dura and what is its function?
bag surrounding the brain that contains the CSF and brain: acts as a conduit for clearing out toxins, provides nutrients to the brain, mechanically acts as a cushion
what cells make up the grey matter?
- glia
- astrocytes
- neurons
what structures are involved in a typical brain cell?
- cell body
- axons
- dendrites
what is the function of dendrites?
receives signals from other neurons
what is the function of the axon?
axons transmit the processed signal in the cell body
brain structure of functional localisation
primary somatosensory cortex
phineas gage (significant frontal lobe damage)
- personality changes
- fitful
- irreverent
- impatient
monsieur loborgne (lesion in broca’s area)
- only able to utter syllable: Tan Tan
- broca’s area identified to be responsible for speech
glioblastoma
highly infiltrative brain tumour
how does a CT scan work?
- x-ray tube rotates around the patient
- x-rays beamed through the patient
- detectors detect the x-rays on the other side
- measure the attenuation of the x-rays to lots of different tissues
how can MRI be used to measure anatomical changes?
- grey and white matter proportions
- degenerative change
- developmental abnormalities
- disease-specific changes
what is the difference between white and grey matter?
grey matter: inter and intra-cellular compartments have free motion
white matter: 50% of tissue volume is myelin structures
difference in T1 of white matter and grey matter?
T1 of WM>GM
How does T2 weighted MRI work?
- H+ atoms in HO have one proton
- the nucleus is positively charged (spins and acts as a magnet)
- this spin generates a signal because the radio frequency interacts with protons
- signal picked up by radiofrequency coils, computer processing produces an image
- therefore more water= stronger signal and structural changes in the tissue are picked up
what is white matter?
wiring between the grey matter
what is the purpose of the myelin sheath?
enables electrical signals to progress from one part to the other
what happens in MS?
myelination is lost
what does a bright signal mean?
brighter the signal, more anisotropy (shows where the white matter tracts are)
what does a diffusion tensor MRI show?
coloured lines show the direction and connectivity of the corticospinal tract coming up to the core of the brain- powerful tool for understanding degenerative disease
explain the difference between signal intensity in arterial and venous blood in the brain?
- arterial blood has a uniform magnetic field
- increased glucose and oxygen extraction leads to increased blood flow
- Oxy-Hb moves from arterial to venous, due to inc blood flow
- Oxygen is released in the brain and so left with deoxy-Hb in the venous circulation which is paramagnetic
- presence of paramagnetic deoxy-Hb causes a non-uniform magnetic field
- therefore there is a reduction in signal intensity
- veins have a lower signal intensity than the arteries
how does a BOLD fMRI work?
blood-oxygen-level-dependent imaging: based on differing signal intensities in venous and arterial
gross structural and pathological change
CT, MRI
anatomical and developmental change
MRI
metabolite levels
MRS
blood flow
CT, PET, MRI
metabolism
PET
connectivity
MRI
functionality
MRI, PET
receptors
PET
