Intro

Question 1

Is there a link b/w size of body and size of one’s brain?

Answer 1

Yes. If you have a larger body, then there’s more input and motor control nerves that have to be mapped to the brain. = there is a relationship b/w the two

Question 2

Every neuron is connected to…

Answer 2

up to 10,000 other neurons.

Question 3

Human cortical structure

Answer 3

-Around 4mm thick
-Comprised of 6 layers
Creates a network of neurons that are involved in our processing.

Question 4

What is the significance of the convolutions on the surface of the brain?

Answer 4

It means that the layer of cortex is very much bigger, than if it was simply a layer that was wrapped around the white matter.

Question 5

What is the white matter?

Answer 5

The axonal structures that connect the different parts of the cortex together, connects the cortical grey matter to the deep grey matter.

Question 6

What is the Encephalocentric theory?

Answer 6

The brain is the seat of sensation and understanding. Alcmaeon came up with it.

Question 7

What is the Cardiocentric theory?

Answer 7

Aristotle stated that the brain was nothing more than a cooling agent of body heats. He believed that the seat of the soul and understanding was in the heart.

Question 8

What did Galen state about the brain?

Answer 8

He reached the conclusion that the nerves and spinal cord were composed of the same substance of the brain.

Question 9

What is the cellular structure of the brain?

Answer 9

(skull)
Dura
SAS
Arachnoid
Pia
Glia limitans
Astrocyte
Virchow-Robin space
Neuron
Microgliali cell

Question 10

Brain network is susceptible to a variety of diseases. E.g.?

Answer 10

E.g. Diseases of the vascular system = blockage of arteries, can be related to diet, alcohol and nicotine use = blockage of blood flow to particular parts of the brain = stroke

Question 11

Brain network is susceptible to a variety of diseases. Examples?

Answer 11

E.g. ‘s
Diseases of the vascular system = blockage of arteries, can be related to diet, alcohol and nicotine use = blockage of blood flow to particular parts of the brain = stroke
Diseases of the cells themselves. e.g. astrocytes become cancerous = proliferations of the cells = brain tumour
Diseases of the axon. These are myelinated structures , so in multiple sclerosis you get demyelination of these = damages the transmission of these cellular signals.

Question 12

What is paredolia?

Answer 12

It’s when you misinterpret sensory input.

Question 13

X-ray absorption explained

Answer 13

Some absorption is from the tissue in the hand and very heavy absorption is from the bones.

Question 14

Planar X-ray

Answer 14

Possible. E.g. The brain. Because the brain is surrounded by the skull (bony structure = strongly absorbs the X-rays), it’s not possible to see in any great detail any anatomical structure of the soft tissue of the brain.

Planar skull x-rays are still relevant and useful for traumatic brain injuries. However, for determining soft tissue structure, straightforward planar X-rays are not useful.

Question 15

X-ray Computer Tomography (CT)

Answer 15

Method of 2D and 3D imaging be measuring X-ray attenuation through tissue

Developed to view the brain: Brain tumours, Traumatic brain injury, Strokes

Sign X-rays through the body, the same way as the planar film.

Beam of X-rays that are picked up by an array of detectors on the other hand of the body.

This beam and detector array is rotated all around the body and you take signal intensities @ different angles round the whole body.

Then with math. processing, can turn into cross-sectional image that separates high intensity absorption of bone from the soft tissue within.

Question 16

What does X-ray CT not offer?

Answer 16

It does not give very good delineation of the grey and white matter structures within the brain. It only provides a single contrast image.

Question 17

Where are the magnets in our body?

Answer 17

Our brain is 75% H2O = proton (+tively charged and spins around on its own axis) = magnetic moment –> millions of these bar magnets within every cubic millimetre of tissue.

Question 18

Magnetic Resonance Imaging (MRI)

Answer 18

2D and 3D imaging by detecting the signal from the protons in water and fat molecules. A wide variety of imaging methods are possible including T1, T2, diffusion, perfusion, and functional.

We use magnets in the body to generate a signal that emanates from within the body tissue, that is picked up with an MR imaging system to create pictures.

Question 19

Nuclear Magnetic Resonance (NMR)

Answer 19

Strong magnetic field and chemical sampling solution, that sits within that magnetic field.

Put a radio frequency pulse in and that interacts with the protons in chemical sample you want. Set 2nd coil, where we pick up a radio freq output = detected + amplified and turned into an NMR spectrum.

Question 20

What doe the peaks on the NMR spectrum show?

Answer 20

These peaks relate to different chemicals. They relate to signals coming from the sample at different freq’s.

Question 21

Current MRI scanner

Answer 21

A strong magnetic field = magnetisation all the tissue.

magnetisation from protons of H in H20 and fat in the
tissue.

Magnetisation direction can be manipulated by radiofreq. pulses to produce an MRI signal to create an image.

Intensity of image depends on H20 content, tissue structure, blood flow, perfusion, diffusion, parametrics etc.

Question 22

What T1 and T2?

Answer 22

Properties of the tissue. They depend very much on tissue structure and are diff b/w diff tissue types and pathologies.

T2-weighted MRI. An MRI method which produces images with the signal intensity related to the tissue T2 relaxation time. T2 increases with increased water content

T1-weighted MRI. An MRI method which produces images with the signal intensity related to the tissue T1 relaxation time. T1 is different between grey and white due to their different cellular structure.

T2 is a measure of how long the NMR signal lasts. Put a radio freq pulse in, stimulate a signal, that you can pick up. If it lasts a very long time, it has a long T2 and so it shows up bright. CSF shows up very bright and light.

T1 is related to the time it takes for the magnetisation, to re-align w/ a magnetic field. Put radio freq’s in, that interact w/ the magnetisation, this knocking out the magnetisation out of alignment. When you’re in a strong magnetic field, this magnetisation aligns w/ the magnetic field. The radio freq pulses knock it out of alignment. Then the magnetisation comes back into alignment w/the magnetic field. CSF shows up very dark because it takes a long time to align.

Question 23

Why do grey and white matter have very different T1 relaxation times?

Answer 23

This is due to the H20 that’s generating the signal, is in a very different structural environment b/w these 2 tissue types.

Grey matter: cell body, dendrites and H2O (intra + extra-cellular)

White matter: Have long axonal pathways, surrounded by myelin sheath (consist of CH3 and Ch2 in terms of their structure)
The protons within the water, that move up and down the axonal pathway themselves, they can exchange with the myelinated protons. = myelinated protons w/ very short T1, reduce the average T1 of the average T1 of the water in the white matter.

Question 24

How much cortical development does one get?

Answer 24

This is dependent on: genetics (early key factor), environment, education, emotional, nutrients, toxins, alcohol, or drug abuse, synaptic pruning and myelination changes: sensory & motor systems complete 1st (pre and early school), higher order functions still developing up to early adulthood.

Question 25

Diffusion MRI overview

Answer 25

An MRI method that allows the microscopic diffusion of water molecules to be measured in a specific direction.

Generating an MR signal from water. This water is diffusing in all directions within the cellular structures in the from, from which you get MR signals.

Question 26

Diffusion MRI in detail

Answer 26

1) A neurofibril containing water
2) The water can diffuse easily along the length of the axonal pathway- cannot move much, due to the myelinated structures side to side
3) High diffusion along the axonal pathway in one direction but restricted diffusion across it.

Techniques used by MRI: measure how freely water can diffuse and this can measured in different directions, which then helps decide which direction offers the max and min diffusion = that helps work out the orientation of the axon within the brain.

Question 27

What’s an anisotropy map?

Answer 27

Shows that if diffusion is measured in different direction, is very high in one direction and very low in other directions.

Grey matter has no myelinated structures = shows up dark (no anisotropy diffusion, its all the same in all directions)
White matter has very high diffusion orientation and restricted diffusion orientation = maps out the white matter

Question 28

Positron Emission Tomography PET

Answer 28

2D imaging by detecting the gamma rays produced from an injected radiopharmaceutical

Question 29

Radiopharmaceutical

Answer 29

A molecule that can be given intravenously or orally that has a radioisotope attached and that has diagnostic or therapeutic use. The molecule may have properties that allow it to target specific cell receptors, organs, or undergo specific metabolic processes in the body.