genetics and nervous system Flashcards
Sclera
Tough outer protective layer of eyeball
purpose of lens
changes shape to focus light on retina
aqueous humour
transparent liquid which lets light enter pupil
purpose of iris
contains muscles which control amount of light entering eye
fovea
contains highest density of cones in retina
optic nerve
contains the axons of sensory neurones carrying signals to the brain
cornea
refracts light into the eye
purpose of pupil
hole in iris which allows light to enter back of eye
vitreous humour
transparent liquid (in the eyeball) providing structure and allowing light to reach retina
chorid
layer containing blood vessels and absorbs lihht
ciliary body
contains muscles which allow the lens to change shape
conjunctiva
transparent layer which lubricates the cornea
What is pupil reflex?
in high light, pupil constricts to reduce light entering eye.
in low light, pupil dilated to maximise light teaching the back of the eye.
Radial muscle
Contract in dim light, causing pupil to dilate
Circular muscles
Contract in bright light
Causes pupil to constrict
What happens to lens when looking at close objects
Ciliary muscles contract
Lens becomes short and fat
Light is refracted greatly
What happens to lens looking at far objects
Ciliary muscles relax
Lens is stretched and flat
Light is barely refracted
what are cataracts
Cloudy patches on lens
Stop light from entering eye
Causes of cataracts
Aging or eye injury
When the tissue of eye lens breaks down
How to fix cataracts
Surgically replacing the lens with an artificial one
What is myopia
short sightedness
Causes light to refract too much, focusing before it hits the retina
What is hyperopia
long sightedness
when light isn’t refracted enough, causing it to not focus when it hits the retina
how to fix myopia
wear concave lenses, causing light to refract kess
how to fix hyperopia
wear concave lenses, causing light to refract more
what is colour blindness caused by
cones in the retina not working properly
how to fix colour blindness
you can’t
cone cells can’t be replaced
Cerebrum
Largest part of brain
Different parts control movement, memory, language and vision
What are cerebral hemispheres
Halves of cerebrum
Left hemisphere controls right side of body
Cerebellum
At back of brain
Controls muscle coordination and balance
Medulla oblongata
At the base of the brain (top of spinal cord)
Controls unconscious activity
What does CT scan show
Shows structures of brain but not functions
However if a part of brain is damaged and we can see that a function is lost, we can work out which part of brain controls that function
How do CT scans work
Use x rays to produce an image of brain
What do PET scans show
Both structure and function of brain
Show which areas of the brain are active
How do PET scans work
Patient is injected with radioactive chemical called Tracer
Tracer builds up in active cells
PET scanner shows where tracer has built up
Why is it hard to treat CNS
Neurones don’t readily repair themselves and scientist can’t repair CNS tissue either
Parts of the CNS are also hard to reach
What is non coding DNA
DNA that doesnt code for amino acids
They control whether a gene is on or off
Transcription (protein synthesis)
-RNA bonds with DNA in nucleus, forming mRNA
-mRNA leaves nucleus and attaches to ribosomes via cytoplasm
What is tRNA
Transfer RNA which has an amino acid on them.
They bring the amino acids to the ribosomes to make protien
What is translation (protein synthesis)
(after transcription)
On the ribosome, tRNA attaches to mRNA’s complementary codon and transfers its amino acid.
The tRNA then leaves and finds another amino acid.
What mutations do changes in the base sequence of non-coding DNA cause
If the change is where RNA polymerase binds during transcription, no mRNA is produced
How can DNA mutations occur
-Mistakes can occur during cell division
-DNA can be damaged by environmental factors
What mutations do changes in the base sequence of coding DNA cause
A change in base sequence can change the sequence of amino acids, changing the shape of the final protein
