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Biology Revision - The Human Reactive
System and Drugs (Unit 2)
The Human Reactive System
1. The Nervous System
The nervous system consists of the brain, spinal cord, and a complex network of neurons.
This system is responsible for sending, receiving, and interpreting information from all parts
of the body.…

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The motor neurone goes from the Co-ordinator to the effector, in the CNS. The direction of
the impulse goes towards the motor end plates on the muscle fibres at approximately
100m/s. This is due to the myelin sheath - the fat insulates the electricity, allowing the
impulse to speed up…

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When pain is detected by a sensory receptor in your finger, it sends an impulse along a
sensory neurone to a relay neurone in your spinal cord. The relay neurone sends an impulse in
an arc via a motor neurone to an effector, a muscle, which contracts, pulling your hand…

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Addiction is a physical or psychological need for a habit-forming substance, such as a drug or
an alcohol. In physical addiction, the body adapts to the substance being used and gradually
requires increased amounts to reproduce the effects originally produced by smaller doses.
You cannot manage without the drug when…

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o Damage or failure of the kidneys, resulting in the need for transplant and/or dialysis
o Damage or failure of the liver, requiring transplant and/or interferon treatment
o It causes alterations of circuitry in the brain that may create permanent impairment)
o The reproductive system (especially prenatal effects in pregnant…

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Definition: Any of a class of drugs that lower the levels of low-density lipoproteins (LDL)
cholesterol in the blood by inhibiting the activity of an enzyme involved in the production of
cholesterol in the liver.
What are their uses?
Statins are medicines, so they are good for you. They are…

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3. Smoking
Smoking kills. In Britain alone, nearly 100,000 people die each year from diseases caused by
smoking. This is twelve times the number killed in road accidents.
Tobacco smoke contains about 1000 chemicals, many of which are extremely harmful to the
body. Here are some of the poisonous ones:…

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structures outside the lungs. Pain lung action can be a common symptom of lung cancer
because it is a bi-product of the restricted airflow in the lungs.
Other diseases include peripheral vascular disease, which can lead to limb loss, ischaemic
heart disease, strokes, bladder cancer, memory loss, exacerbation of asthma,…

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If a woman smokes tobacco whilst pregnant, miscarriage or stillbirth is likely. If the baby is
born, it is likely to be a premature birth and the baby is likely to be underweight or to have
various types of birth defects.
A lot of smoker's babies die for unknown reasons.…

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It can also lead to an increased risk of a variety of cancers, particularly breast cancer and
cancer of the gullet. It is also frequently associated with mental health problems, such as
depression and anxiety.
Alcohol poisoning symptoms
· Confusion
· Loss of coordination
· Vomiting
· Seizures
· Irregular…




This is an all you need to know set of notes with diagrams on the nervous system and drugs. The notes are detailed and explain the key points of the topics well. They would be suitable for any candidate needing to know about the nervous system.

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