Pharmacology: Class 10 Biology

Key points

Pharmacology is the study of drugs and their effects on the body. A drug is any chemical substance that changes the working of the body or mind. Drugs that are used to prevent, cure or relieve a disease are called medicines. A medicine is useful only when it is taken in the right amount, for the right time and for the right illness.

Drugs come from several sources:

• Plants: quinine from cinchona bark for malaria, morphine from the opium poppy, and aspirin first obtained from willow bark.
• Microorganisms: penicillin from the mould Penicillium and other antibiotics.
• Animals: insulin from the pancreas of animals in the past, and some vaccines.
• Minerals and chemicals: antacids, iodine and many synthetic drugs made in laboratories.

Drugs are grouped by their action. Analgesics relieve pain. Antipyretics reduce fever. Antacids lower stomach acid. Antibiotics kill or stop the growth of bacteria. Antiseptics and disinfectants kill germs on the body and on objects. Sedatives calm the nervous system, and stimulants increase its activity. Vaccines build immunity.

Antibiotics are drugs that act on bacteria. Alexander Fleming discovered penicillin in 1928 when he saw that a mould stopped bacteria growing on a dish. Antibiotics do not work against viruses, so they are not useful for the common cold or influenza. Misuse, such as stopping the course early, lets resistant bacteria survive and spread, which is called antibiotic resistance.

Analgesics are of two types. Non narcotic analgesics, such as paracetamol and aspirin, relieve mild pain and reduce fever. Narcotic analgesics, such as morphine, relieve severe pain, but they cause addiction. Aspirin can irritate the stomach and should be avoided by children with viral fever. Medicines must be taken only on advice of a doctor.

A vaccine contains weakened or killed germs, or parts of them, which cause the body to make antibodies and memory cells without causing disease. Then a later infection is fought off quickly. Vaccines protect against polio, measles, tetanus, diphtheria, whooping cough, tuberculosis and hepatitis B. Immunisation programmes are important in Pakistan to prevent children's diseases.

Drug abuse is the use of a drug for non medical purposes, or in excess, without the advice of a doctor. Drug addiction (dependence) is the state in which the body and mind become so used to a drug that stopping it causes withdrawal symptoms and strong craving. A person may also develop tolerance, so that larger amounts are needed to get the same effect.

Common harmful substances and their effects:

• Alcohol: a depressant. It slows reactions, affects judgement, damages the liver (cirrhosis), stomach and brain, and leads to accidents. Alcohol is forbidden in Islam.
• Tobacco and cigarettes: contain nicotine, which is addictive, tar, which causes cancer, and carbon monoxide, which reduces oxygen carried by blood. They cause lung cancer, bronchitis, emphysema and heart disease. Smoke also harms people nearby.
• Narcotics (heroin, opium, morphine): depress the nervous system, are highly addictive and give severe withdrawal symptoms.
• Stimulants such as cocaine and caffeine in excess: speed up the heart and nervous system and may cause anxiety and heart problems.
• Cannabis (hashish) and other hallucinogens: change perception and mood and damage memory and mental health.

Drug abuse harms the individual by damaging the health and mind, and it harms the family and society through crime, loss of work, poverty and accidents. Injecting drugs with shared needles can spread hepatitis and HIV. Young people may start by peer pressure, curiosity, stress or easy availability.

Prevention of drug abuse needs several steps. These include education in schools and homes, avoiding bad company, healthy activities like sports, strong family support, strict laws against drug sale, and rehabilitation centres to treat addicts. Treatment is done gradually with medical care and counselling, because sudden stopping can be dangerous.

Safe use of medicines means reading the label, taking the right dose at the right time, completing the course of antibiotics, checking the expiry date, storing medicines away from children and heat, and never sharing prescribed medicines. Self medication and use of out of date medicines can be dangerous.

Study tip: Make a table of drug type, example, source and use, because most questions come from it. In answers on drug abuse give the effects on the individual, the family and society, and always add some preventive measures.

Definitions and flashcards

Say the meaning first, then open the card to check.

Short questions with model answers

These are the kind of questions asked for 2, 3 and 5 marks. Try each one before opening the answer.

Common mistakes

• Saying that antibiotics cure viral diseases.
• Stopping an antibiotic course when symptoms disappear.
• Confusing a drug with a medicine. All medicines are drugs, but not all drugs are medicines.
• Calling alcohol a stimulant. It is a depressant of the nervous system.
• Mixing the harmful agents in tobacco, for example giving carbon monoxide as the addictive substance instead of nicotine.

Practise this chapter

Practice questions and timed test Printable worksheet