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B3 Topic 1 Control Systems
Biological rhythms

Biological rhythms that happen across one day are circadian rhythms.
For example, in human brains there is a timing mechanism called a biological clock which regulates the things
that occur in our body over a 24 hour period and can be influenced by…

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Potatoes are often attacked by a fungus-like organism called potato blight that destroys their leaves,
thereby killing the plant. Some varieties of potato produce chemicals that kill it.
Plants are a key source of food for people. If pathogens destroy a crop our food supply is at risk. An example…

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Some of these lymphocytes become memory lymphocytes. The way the body responds to infection is called
the immune response. Making someone immune to a disease is called immunisation.

Are vaccines safe?

All young children in the UK are offered vaccinations to dangerous childhood diseases such as measles and
whooping cough.…

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Monoclonal antibodies

Monoclonal antibodies: many identical antibodies.
These were invented for making large quantities of antibodies for identifying particular substances.
A lymphocyte can divide over and again to make identical clones of itself. However, once it starts making
antibodies it becomes a B-lymphocyte and it can't divide anymore.
To get…

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These are often used in medicine. An example is pregnancy testing. Antibodies are placed on a strip that bind
with the hormone "human chorionic gonadotrophin" (hCG). This is found in the urine of women in the early
stages of pregnancy.
The strip is dipped into some urine and if there…

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The patient will need life-long medication to prevent the kidney being rejected. This suppresses the immune
system so the patient may catch colds more easily.

How kidneys work

Each kidney contains thousands of tiny, microscopic tubes called nephrons.


Blood flows in a network of capillaries called a Glomerulus which…

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ADH: not enough water

Step 1: The brain senses there is not enough water in the blood.
Step 2: The pituitary gland secrets more ADH.
Step 3: The ADH causes the kidneys to reabsorb more water.
Step 4: A small volume of concentrated urine is produced.

ADH: too much water…

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Progesterone: This maintains the lining of the uterus. It inhibits the production of FSH and LH. When
progesterone levels fall, and there is a low oestrogen level, the uterus lining breaks down. A low
progesterone level allows FSH to increase and the whole cycle starts again.
If the egg is…

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The main functions of the egg is carry the female DNA and nourish the developing embryo:
o 1) The egg contains nutrients in the cytoplasm to feed the embryo.
o 2) As soon as the egg is fertilised with a sperm, the egg's membrane quickly changes its structure to

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Sex-linked inheritance

Most of our chromosomes come in matching pairs. The two chromosomes in a pair have the same genes in
the same places but may have different alleles.
However, the X chromosome is much larger than the Y chromosome. As well as this, there are more genes on




very, very useful. tried to rate as 5 stars but unfortunately clicked on 1 star.



An exceptionally detailed and complete set of notes for Edexcel B3 topic containing information on immunology, the kidney, fertility and control systems as some of the topics included. These might be useful to students studying other specifications as well. Try using these alongside the related flashcards or a quiz to test your knowledge.



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Extremely useful, accidentally clicked 2 star when i went for 5



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