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Cells & control
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importance of mitosis
growth: needed for growth of multi-cellular organisms
repair: needed to repair/replace damaged tissue
asexual reproduction: used in all body cells (except egg/sperm)
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cancer
Genes control rate of cell division: change in gene can cause cell to divined uncontrollably
Can result in tumour: mass of abnormal cells
Cancer: if tumour invades/destroys surrounding tissue
Malignant tumour
Benign tumour
Grow quickly
Grow slowly within membrane – easily removed
Invade tissue
Don’t invade tissue
Metastasis
As tumour grows, cancer cells detach: spread through
blood stream to form secondary tumour elsewhere
Causes: Chemical carcinogens: chemicals that cause cancer / damage DNA
Tobacco/Alcohol
Asbestos when inhaled: building/insulation material
Ionising radiation: Ultraviolet/X-rays
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importance of cell differentiation in development of specialised cells: Allows cells to work more efficiently
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Stem cells
Animals
embryonic stem cells: can differentiate into any type of cell in body
Form from zygote
Totipotent – cells from early stage embryo: can divide to produce any type of specialised cell
Once specialised: stem cells in those area are more limited in type of specialised cells they can produce
In medicine: can be rejected
Therapeutic cloning: embryo produced with same genes as patient – harvested to obtain embryonic stem cells
Not rejected: patient’s own genes
Isolated to produce cells patient needs
Adult stem cells:

multi/pluripotent: differentiation into limited cell types – used to replace damaged cells: blood/skin
only found in bone marrow
In medicine: less useful – make limited types of cells
Induced pluripotent stem cells: normal adult body cells reprogrammed to grow into stem cells
Less likely to be rejected: patients own cells
Limited numbers – more difficult to isolate
Plants: Meristems: only plant cells that divide by mitosis
Found at root/shoot tips
Can differentiate throughout plant’s whole life
Produce unspecialised cells: become any type of cell when cell reaches its final position (can re-differentiate if moved)
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Brain
Cerebellum:
Voluntary muscular activity – motion/balance/ability to learn
cerebral hemisphere: senses/imagination/thinking/memory
Occipital lobe: vision
Parietal lobe: consciousness
Frontal lobe: personality/speech
Temporal lobe: hearing
medulla oblongata / brain stem – spinal cord
Involuntary actions: digestion/breathing/heart beat
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limitations in treating damage/disease in brain/spinal injuries/brain tumours:
Enclosed in skull / complex / delicate/ easily damaged
Damaged nervous system: Cells can’t repair themselves
Brain tumour – Tumour expands: starts to squash parts of brain
Radiotherapy: high energy x-ray beams to kill tumour cells – can damage healthy cells & can only be done once
Chemotherapy: inject drugs that kill actively dividing cells
Harder to get drugs to brain cells – it has natural filter: blood/brain barrier
Spinal cord damage
Stops electrical impulses passing between brain/elsewhere
Paralysis
Damage in
lower body: legs paralysed
Upper body: neck/legs/arms paralysed – quadriplegin
Adult stem cells can’t differentiate into neurones
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reflex arc: sensory/relay/motor neurones
Automatic/rapid
Impulse reflects out of spinal cord – doesn’t involve brain
To protect body from damage – blink/cough/withdrawal

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eye defects
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