2. Homeostasis Pt2 Flashcards
How did they used to map the brain?
- as the brain is protected by the skull
- early information on its functions only came from studying the effects of damage to different parts
How do they map the brain now?
- modern techniques like ‘magnetic resonance imaging’ (MRI) can show us scans of patients brains to see the effects of tumours, strokes etc.
- you can also remove parts of the skull and electrically stimulate areas of the brain to map the areas, often before surgery
What are the problems with MRI?
- MRI can only diagnose a problem not treat it
- it can only be used on patients that have no metal in there bodies due to prior surgeries
What are the problems with opening the skull for brain surgery?
It risks damaging the very delicate neurones and synapses, especially when we don’t fully understand what each area does.
It’s delicacy & complexity makes it hard to investigate
What are the problems with drugs to treat brain disorders?
- drugs can by used but many struggles to cross the membrane surrounding the brain so don’t reach it
- the range of chemicals released by synapses can be easily disrupted with serious side-effects
What does the sclera in the eye do?
White outer layer of the eye
Providing protection
What does the cornea in the eye do?
It’s the transparent front section of the sclera
It allows light into the eye and bends (refracts) the light to aid focus
What does the iris in the eye do?
- a ring of muscle which can contract or relax to change the amount of light passing through to the retina
- it constricts in bright light to protect the retina from damage or dilates in low light to allow more light to reach the light-sensitive cells
What does the retina in the eye do?
It’s a Layer of light-sensitive receptor cells
What does the optic nerve do?
Carries impulses from the retina to the brain to be processed and interpreted as a visual image
What’s our blind spot?
The point where the optic nerve leaves the eye so there’s no retina to detect light
Explain accommodation
-the process of changing the shape of the lens to focus on near or distant objects
Explain what happens to the eye when it tries to focus on something in the distance?
- the ciliary muscles relax, allowing the suspensory ligaments to pull the lens tight
- this pulls the lens flat and thin, and only slightly refracts light rays
Explain what happens to the eye when it tries to focus on something close up
- the ciliary muscles contract, loosening the suspensory ligaments
- the lens is then thicker and refracts light rays more strongly
What’s the scientific word for shortsightedness?
Myopia
Rays of light don’t focus on the retina
Explain how myopia/shortsightedness works?
- if your lens is too curved or your eyeball is too long the light is refracted too much and the light rays focus in front of the retina
- this causes the rays that reach the retina from distant objects to be out of focus and blurry
If your short sight you can’t see objects which are ………. ……….
Far away
How do contacts/glasses work for people with myopia/short-sightedness?
Glasses/contacts which are concave spread out the light before it reaches the eye so the lens can then focuses the rays correctly
Explain how hyperopia/longsightedness works?
- if your lens is too flat and thin, or your eyeball is too short your lens can’t refait the light rays enough so they focus behind the retina
- this causes objects to become blurry
- it often gets worse with age as the ciliary muscles get weaker
What’s the scientific word for longsightedness?
Hyperopia
What kind of glasses do you use for longsightedness and explain how they work?
- convex glasses/contact lenses
- they refract the light before it reaches the eye so the lens doesn’t have to
What are 3 new types of technology to improve eyesight? And how are they dangerous?
- laser eye surgery
- Lens replacement
- Permanent contact lenses
These surgeries are new and carry risks of damage to retina, infection or possible cataract formation in lens replacement
Explain how laser eye surgery works?
-once your eye has stopped growing, a laser can be used to change the shape of the cornea
Explain how laser eye surgery works to tread myopia
-the thickness of the cornea is decreased to reduce refraction
Explain how laser eye surgery works to treat hyperopia
The curvature of the cornea is changed to increase refraction
Explain how lens replacement works?
Surgery can replace a faulty lens with an artificial one that refracts the light the correct amount
Explain how a permanent contact lens works
A permanent contact lens can be implanted into the eye to aid the natural lens
How would you carry out an investigation to test if practise improved reaction speed?
- sit on a stool and rest your non-dominate arm on the desk
- your patterned hold one end of the ruler level with index finger and thumb then drops it
- catch the ruler as quickly as possible
- repeat 10 times and plot a graph
