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BIOLOGY ASSESSMENT - 3/12/20, HOMEOSTASIS + RESPONSE, STEM CELLS - Coggle…
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HOMEOSTASIS + RESPONSE
HOMEOSTASIS is the regulation of the body's internal conditions like body temperature, blood sugar levels, water content and oxygen and carbon dioxide levels.
Body Temperature - this is controlled to maintain the temperature at which the body's enzymes work best at.
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NEGATIVE FEEDBACK
Homeostatic control is achieved using negative feedback mechanisms: if the level of something rises, control systems reduce it again and it the level of something falls, control systems raise it again.
BLOOD SUGAR LEVELS
Blood sugar level - this is controlled to provide the cells with a constant supply of glucose for respiration. It is controlled by the release and storage of gluclose, which is in turn controlled by insulin.
WATER CONTENT
Water content - this is controlled to protect cells by stopping too much water from entering or leaving them. Water content is controlled by water loss from: the lungs, the skin, the body ( the urine produced by the kidneys).
STEM CELLS
STEM CELLS are cells that have not undergone differentation. A cell which which has not yet become specialised is called undifferentiated.
STEM CELLS IN HUMANS
Am embryo develops from a fertilised egg. All the cells in an embryo start off identical and undifferentiated. These are called embryonic stem cells and can be specialised to form any type of cell. They do this by switching genes on and off. E.G. if one of the embryonic stem cells formed a muscle cell and switch off genes that would cause it to become a different type of cell.
The embryonic stem cells recieve signals from other cells so that they turn the correct genes off and on. Most cells in a human embryo has eight cells. This is very early on in the development of the embryo.
A whole new organism with skin, eyes, heart, liver and all of the organs it needs, will develop from the embryonic stem cells. This allows the organism to have all the tissues it needs with the correct functions to be able to survive.
Some stem cells remain in the bodies of adult. Adults stem cells are found in limited numbers at certain locations in body, including the:
- brain
- eyes
- blood
- heart
- liver
- bone marrow
- skin
- muscle
Adult stem cells are unspecialised but can become specialised much later than embryonic stem cells. They can differentiate into related cell types only. For instance, adult stem cells in the bone marrow can differentiate into blood cells and ells of the immune system, but not brain cells.
STEM CELLS IN PLANTS
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Cells of the meristem divide by mitosis and produce unspecialised cells. These cells can differentiate to produce all types of plant cells at any time during the life of the plant. The main meristems are close to the tip of the shoot, and the tip of the root. In a growing, new cells are being produced continuously near the tip. As the cells become older, further away from the tip, they become differentiated - they enlarge and form vacuoles.