Intro, Brain organisation & Brain structure (MRI) Flashcards
Aristotle thought that the brain exists for what purpose?
Merely to cool the blood
Describe the coronal plane
Shoulder to shoulder, paralell to walls
Describe the sagittal plane
Nose to the back of the head. perpendicular to the coronal plane
Describe the transverse plane
Around the body, parallel to the floor
The top bumps on the cerebrum are called ___ and the dips between these are called ___
Top bumps = gyri (singular = gyrus)
Dips = Sulci (singular = sulcus)
The deepest sulci are called
Fissures
What do gyri do?
The increase the surface area of the brain, enabling many more cells to be packed tightly in any unit of volume
What does the frontal lobe of the cerebrum do?
Higher brain functions, planning and reasoning
What does the parietal lobe of the cerebrum do?
Attention and self-representation
What does the temporal lobe of the cerebrum do?
Sound processing, language and memory
What does the occipital lobe of the cerebrum do?
Visual processing
What is the limbic lobe composed of?
Structures from the frontal, parietal and temporal lobes
What does the limbic lobe do?
Bodily regulation, emotion and motivation
If you take a coronal (shoulder to shoulder) slice through the brain, where is grey and white matter found?
Grey matter forms a border along the outside of the cerebral cortex, white matter pads out the middle
What are the patches of grey matter on the inside of the brain called?
Grey matter nuclei
Describe grey matter nuclei
The have old evolutionary histories and specialised functions
What is the ‘Neurone Doctrine’?
Spanish neuroscientist Santiago Ramón y Cajal thought that brain tissue is composed of neurones
What is the Law of Dynamic Polarisation?
The idea that a neurone receives signals at its dendrites and cell body and transmits them as action potentials in one direction
Motor neurones are
Multipolar
Sensory neurones are
Unipolar
Describe a unipolar neurone
Long, cell body sticks out from axon
Describe a bipolar neurone
Short, cell body in middle of axon
Describe a multipolar neurone
Long, cell body at one end of axon
Describe an axonic neurone
Very short, no axon
Give one excitatory and one inhibitory neurotransmitter
Excitatory = Glutamate Inhibitory = GABA
Where do the four main neurotransitter systems originate from in the brain?
The grey matter nuclei in the brain stem
How do the ascending neurotransmitter systems operate through?
Volume transmission
Give two facts about the functions of glial cells
1) They bring nutrients to neurones and clear away waste
2) They produce myelin to insulate axons
Give four key types of glial cell
Ependymal cells
Astrocytes
Microglia
Oligodendrocytes
What is the function of ependymal cells?
They form protective boundaries around collections of cells
State the function of astrocytes
They communicate with the blood supply for nutrient exchange
State the function of microglial cells
They are immune specialists and provide the CNS’ first line of defence
State the function of oligodendrocytes
They provide myelination for axons
What is cytoarchitecture?
The study of the structural arrangement of neurons within the central nervous system
Why is it hard to image grey matter nuclei?
They sit deep in the brain so EEG or MRI struggles to pick them up
Where does blood enter the head and neck from?
The carotid artery
Describe neurovascular coupling
It is complex
When neurones fire, the local oxygen conusmption increases, this drops the local oxygen consumption. Therefore, the elasticity of the surrounding capillaries are adjusted.
The blood-brain barrier is formed by what type of cell?
Endothelial cells
What can using specialist stains/antibodies specific to biochemical components be useful for?
One can visualise different aspects of micro-morphology
What do histological techniques not allow people to study?
Development or neurodegeneration
Paul Lauterbur did what?
Published the first MRI image in 1973
What did Sir Peter Mansfield do?
Enabled MRI scans to be acquired in seconds rather than hours
How is the superconducting electromagnet in an MRI kept cool? Why does it need to be kept cool?
Liquid helium is used, so the longitudinal magnetic field (B0) remains stable over time
What are gradient coils? What do they enable?
Loops of wire around a cylindrical core. They enable the spatial encoding of the MR signal
How many sets of gradient coils does an MRI scanner have?
3, in the X, Y & Z directions
The water molecule consists of
1 oxygen and 2 hydrogen atoms
What charge is an electron?
Negative
How do the protons of hydrogen atoms spin?
Around in an axis with random orientation relative to each other
Describe the 4 steps to how an MRI scan works
- Place human in MRI scanner.
a. At the moment, the hydrogen protons are spinning randomly - Switch on the main magnetic field (B0)
a. This causes the protons to align their spin axis’ with the direction of the main magnetic field - B0 - Switch on the RF coils
a. This delivers an electromagnetic pulse at a 90d angle to the B0
b. The interaction of our small magnetic field (B1) and the main magnetic field (B0) causes the phase of the proton precession orbits
c. It also tips the axis of the proton procession plane 90d relative to the scanner magnetic field.
d. This occurs because we excite the protons by introducing energy into the system when applying the RF pulse - Switch off the RF coils
a. This will remove the B1 field and the system will want to return to its equilibrium
b. The protons will want to return to their alignment with the B0
c. Longitudinal relaxation (T1) and transverse relaxation (T2) will occur.
How do we know that MRI really works?
We can use post-mortem MRI to cross reference the images we get with histological treatments of the same tissue
Define longitudinal relaxation?
What time constant is this related to?
The tendency of hydrogen protons to realign from the B1 to the B0.
Related to T1
