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B2 Revision:Brain and Eye (Brain: (Parts of Brain: (Cerebrum (Divided into…
B2 Revision:Brain and Eye
Brain:
Part of CNS
Made of many interconnected nerurones
Parts of Brain:
Cerebrum
Divided into 2 cerebral hemispheres
Left hemisphere controls muscles on the right side of the body
Right hemisphere controls muscles on the left side of the body
Controls
M
ovement,
L
anguage,
M
emory,
I
ntelligence,
V
ision (My lunch munches in vimto)
Cerrebellum
Back of brain
Controls muscle coordination and balance
Medulla Oblongata
Base of brain, at the top of the spinal cord
Controls unconscious activities(e.g.breathing, heart rate)
Investigating:
PET scanners
Injected with a tracer
More active cells take up more tracer than less active cells
The person lies in the PET scanner and an image is produced showing where the tracer has built up.
Image shows which parts of the brain are active when the person is in the scanner
Used for both structure and function of brain at that time
Shows if brain is usually inactive or active so are useful for studying disorders that change the brain's activity
CT scanners
Uses an X-ray to produce an image of the main structures in the brain but doesn't show the functions
If the scanner shows a damaged brain structure and they have lost some function, the function of that part of the brain can be worked out
Treating problems in the CNS:
Hard to repair damage to the nervous system as neurones don't repair quickly
Some parts of the brain aren't easily accessible
Could damage spinal cord further, leading to permanent paralysis because signals from the brain are unable to reach muscles
May permanently damage surrounding parts of the brain if e.g. having a difficulty removing a brain tumour
Eye:
Structure:
Pupil
The hole in the centre of the eye where light enters
Iris
Contains muscles that allow it to control the diameter of the pupil, how much light enters the eye
Lens
Refracts light, focusing it on the retina
Retina
Layer at the back of the eye that contains 2 types of receptor cells
Rod cells
Sensitive to light intensity
Cone cells
Sensitive to colour
Cornea
Transparent outer layer found at the front of the eye that refracts light into the eye
Ciliary muscles and suspensory ligaments
Controls the shape of the lens
Optic Nerve
Information from light is converted into electrical impulses by the rods and cones on the retina
Carries these impulses from these receptors to the brain (a sensory neurons)
Accommodation:
The eye focuses light on the retina by changing the shape of the elastic lens
Looking at near objects:
Ciliary muscles contract, slackening suspensory ligaments
Lens becomes a more rounded shape increasing the amount light that's refracted
Looking at distant objects:
Ciliary muscles relax, allowing suspensory ligaments to pull tight
Pulls the lens into a less rounded shape which refracts the light by a smaller amount
Bright light causes reflex for circular muscles in the iris to contract making iris smaller
Dim light causes reflex for radial muscles in the iris to contract making iris wider
Short-sightedness
Can't focus on distant objects
Lens is the wrong shape and refracts the light too much or the eyeball is too long
Use glasses or contact lenses with a concave lens so the light rays focus on the retina
Long-sightedness
Can't focus on near ojects.
Lens is the wrong shape and refracts the light too little or the eyeball is too short
Use glasses or contact lenses with a convex lens so the light rays focus on the retina
Vision Problems:
Colour blindness
Can't tell the difference between certain colours
Red-green colour blindness(red or green cones in the retina aren't working properly so can't tell the difference)
No cure at the moment as cone cells can't be corrected
Cataracts:
Cloudy patch on lens which stops light entering eye normally
Blurred vision and colours looking less vivid and having difficulty seeing in bright light
Can be treated by replacing the faulty lens with an artificial one