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Quiz yourself on Nervous SystemGet your flashcardsBuild my revision planTrack my progressHigher Brain Scanning and Vision Defects
Brain scanning techniques
Scientists use several scanning methods to study the brain:
- CT scans — use X-rays to build up a detailed image of brain structure. Useful for detecting tumours or bleeding.
- PET scans — detect radioactive tracers to show which brain areas are most active. Useful for mapping brain function.
- MRI scans — use strong magnetic fields to produce detailed images of soft tissue. No radiation involved.
These techniques have improved our understanding, but there are limitations: we still do not fully understand how complex behaviours, emotions, and memory work. Treating brain damage remains very difficult because neurones rarely regenerate.
Vision defects
| Defect | Cause | Effect | Correction |
|---|---|---|---|
| Myopia (short-sightedness) | Eyeball too long or lens too curved | Image focuses in front of retina — distant objects blurry | Concave (diverging) lens |
| Hyperopia (long-sightedness) | Eyeball too short or lens too flat | Image focuses behind retina — close objects blurry | Convex (converging) lens |
Both can also be treated with laser eye surgery (reshapes the cornea) or replacement lenses.
Figure 3: How myopia and hyperopia cause incorrect focusing of light on the retina
Figure 4: Corrective lenses redirect light to focus exactly on the retina
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