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The brain

The brain. Techniques used to picture the brain. There are three different techniques used to create a picture of the brain: MRI (Magnetic resonance imaging) scan – Measures brain activity using magnets and radio waves.

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The brain

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  1. The brain

  2. Techniques used to picture the brain • There are three different techniques used to create a picture of the brain: • MRI (Magnetic resonance imaging) scan – • Measures brain activity using magnets and radio waves. • It detects the changes in blood oxygenation and flow that occur in response to neural activity. • When the brain is more active it uses more oxygen. • MRI’s can be used to produce activation maps that show which parts of the brain are involved in particular processes.

  3. CT (Computed tomography) scan – • Builds up a picture of the brain based on how much each part absorbs X-rays. • During a CT scan the person lies on a table that moves in and out of an x-ray which rides on a ring around the inside of a tube. • The x-ray is aimed at the patients head. • After passing through the head, the X-rays are sampled by one of the many detectors that line the machine’s circumference. • Images made using x-rays depend on the absorption of the beam by the tissue it passes through. • CT scans reveal the features of the brain but do not resolve its structure well. • PET (Positron Emission Tomography)scan uses the same techniques as a CT scan.

  4. Advantages of an MRI scan • An MRI scan can produce very detailed images of the brain and spinal cord. This makes MRI ideal for helping to diagnose conditions that affect the brain and nervous system. • For example: • Brain tumours. • Dementia.  • Alzheimer’s disease. • Stroke. • Parkinson’s disease. • Multiple sclerosis.  • Motor neurone disease. • Brain infections, such as meningitis and encephalitis. • Injuries to the brain or spinal cord. • MRI systems do not use ionizing radiation so have a very low incidence of side effects.

  5. Disadvantages of an MRI scan • People with pacemakers cannot have MRIs. • Some people who are morbidly obese cannot fit in into an MRI system. • Claustrophobic patients cannot usually make it through a MRI. • The machine makes a lot of noise during a scan.

  6. Advantages of a CT scan • CT scan is a painless non invasive procedure with good sensitivity to detect pathology of the head • CT scan is far superior to an MRI when evaluating skull fractures • CT scan can provide detailed images of the brain nervous tissue • CT scan is much cheaper than an MRI an equally as fast

  7. Disadvantages of a CT scan • CT scan is associated with a radiation • CT scan should never be done in a pregnant female because of the exposure of radiation risk to the foetus. • CT is not very good at identifying pathology of the soft tissues. • CT is not good at identifying areas of inflammation or infection of the brain compared to MRI

  8. Why are neurons unable to regenerate? • In the central nervous system there are two types of glial cells. • These cells inhibit axon regeneration. • These are; oligodendrocytes and astrocytes. • Both play key roles in the central nervous system; support and metabolism. • This growth-inhibiting action helps enormously in stabilizing the complex CNS. • These cells stop neurones from regenerating so that neurones stay in their intended place, rather than spreading out. • This is done as the CNS is very complex. • The inhibitors lock the connections into place. • Without these proteins, the CNS may not be able to organize itself and work properly. • The disadvantage of this is that the CNS has no ability to regenerate itself in the event of injury.

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