10th Class Biology Chapter 18 Notes | Get Now

10th Class Biology Chapter 18 Notes cover Pharmacology, an important and highly practical chapter in the 10th class biology syllabus. This chapter explains what drugs are, where they come from, how they’re classified, and how they affect the human body. Since pharmacology directly connects to health and medicine, it’s a chapter students find genuinely useful in daily life, not just for exams.

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Let’s go through the key concepts covered in these 10th Class Biology Chapter 18 Notes.

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What Is Pharmacology?

Pharmacology is defined as the study of drug composition, properties, medical applications, and sources of drugs. It is important to note that pharmacology is not the same as pharmacy, which refers to a profession, even though the two terms are often confused.

History of Pharmacology

Clinical pharmacology existed even in the Middle Ages, when early pharmacologists focused mainly on natural substances like plant extracts. Until 1890, the subject of pharmacology was known as Materia Medica. Pharmacology developed into a proper biomedical science in the 19th century.

What Is a Drug?

A drug is any substance that, when absorbed into the body of a living organism, alters normal body functions. A more specific term, pharmaceutical or medicinal drug, refers to any chemical substance used in the diagnosis, cure, treatment, or prevention of a disease.

Sources of Medicinal Drugs

This is one of the most important sections in the 10th Class Biology Chapter 18 Notes, as it frequently appears in long-answer exam questions.

Drugs are obtained from six major sources:

1. Synthetic Drugs

These do not occur naturally but are synthesized in laboratories by pharmaceutical companies. Aspirin is a common example.

2. Drugs from Plants

Many important drugs like antibiotics, cardiotonics, and certain analgesics come from plants:

• Digitalis – a cardiotonic used to stimulate the heart, made from the leaves of foxglove
• Morphine – a pain reliever obtained from opium, which comes from the juice of the poppy plant
• Marijuana – an addictive illegal drug also sourced from plants

3. Drugs from Fungi

Some medicines come from fungi, the most famous example being the antibiotic penicillin, obtained from the fungus Penicillium notatum.

4. Drugs from Animals

Drugs from animals are usually their glandular products, including:

• Fish liver oil
• Musk
• Bee’s wax
• Certain hormones
• Antitoxins

5. Drugs from Minerals

Several common drugs come from minerals:

• Iodine – used in making tincture of iodine, which helps prevent infection when applied to cuts and bruises
• Silver nitrate – applied in powder form on wounds to stop bleeding and prevent infection

6. Drugs from Bacteria

Many antibiotics, such as streptomycin, are obtained from bacteria.

Classification of Medicinal Drugs

Drugs are classified on the basis of their chemical properties and modes of action. This section of the 10th Class Biology Chapter 18 Notes covers the principal categories of medicinal drugs.

Main Categories of Drugs

1. Analgesics – pain killers that reduce pain (e.g., aspirin, paracetamol)
2. Antibiotics – inhibit or kill bacteria within or on the body (e.g., tetracycline, cephalosporins)
3. Sedatives – induce sedation by reducing irritability or excitement (e.g., diazepam)
4. Vaccines – develop immunity against viral and bacterial infections (e.g., smallpox, whooping cough, hepatitis B)
5. Antiseptics – reduce the possibility of infections on skin (e.g., tincture of iodine)
6. Disinfectants – destroy microorganisms found on non-living objects

Prescription vs. Non-Prescription Drugs

• Prescription drugs are sold only with a physician’s prescription, such as barbiturates, tranquilizers, and antibiotics.
• Non-prescription drugs can be sold over the counter because they’re considered safe enough, such as aspirin and some cough medicines.

Antibiotics and Antibiotic Resistance

Antibiotics are a major focus area in these 10th Class Biology Chapter 18 Notes because of their widespread medical use and growing resistance issues.

What Are Antibiotics?

An antibiotic is a drug that kills or retards the growth of bacteria. They are chemicals produced by or derived from microorganisms like bacteria and fungi.

Types of Antibiotics

• Bactericidal antibiotics – kill bacteria directly
• Bacteriostatic antibiotics – work by stopping bacterial growth

Major Groups of Antibiotics

1. Cephalosporins – interfere with bacterial cell wall synthesis; used to treat pneumonia, sore throat, tonsillitis, and bronchitis
2. Tetracyclines – broad-spectrum bacteriostatic antibiotics that inhibit bacterial protein synthesis; used for respiratory, urinary, and intestinal infections (not recommended for children under 8)
3. Sulfonamides (Sulpha drugs) – synthetic, broad-spectrum bacteriostatic antibiotics that inhibit folic acid synthesis in bacteria; used to treat pneumonia and urinary tract infections

Antibiotic Resistance

Antibiotic resistance occurs when bacteria are no longer affected by commonly used antibiotics. This happens because:

• Bacteria repeatedly exposed to the same antibiotic can change over time.
• Bacteria can transfer resistance genes to other bacteria.
• Unethical usage, such as using antibiotics against viral infections, worsens the problem.

This growing issue makes some infections much harder to treat, even with newer antibiotics.

Vaccines and How They Work

Vaccines are another key topic in the 10th Class Biology Chapter 18 Notes, especially the historical background and mechanism of action.

Definition and History

A vaccine is a material containing weakened or killed pathogens, used to produce immunity by stimulating antibody production. In 1796, British physician Edward Jenner demonstrated that intentional infection with cowpox protected people from smallpox, leading to the term “vaccination.”

Mode of Action of Vaccines

1. Pathogens contain special proteins called antigens.
2. When a vaccine enters the bloodstream, white blood cells are stimulated.
3. B-lymphocytes recognize the weakened or dead pathogens and begin producing antibodies.
4. Memory cells are produced, providing protection against future infections with the same pathogen.
5. If real pathogens later enter the blood, existing antibodies quickly destroy them.

Most vaccines are administered by injection, though some are given orally or via nasal spray. Some vaccines, like tetanus vaccines, require booster shots since they don’t provide lifetime immunity.

Addictive Drugs

This section of the 10th Class Biology Chapter 18 Notes covers drugs that create dependency, an important topic for understanding drug abuse and its social effects.

What Are Addictive Drugs?

Addictive drugs make a person dependent on them. With continued use, the person’s body becomes familiar with the drug, and they struggle to function without it.

Categories of Addictive Drugs

1. Sedatives

These interact with the central nervous system to depress its activities, causing dizziness, lethargy, and slowed brain function. Long-term use can lead to serious psychological effects.

2. Narcotics

Narcotics are strong pain killers, often prescribed alongside milder pain relievers like paracetamol or aspirin. Examples include:

• Morphine – derived from opium; acts on the central nervous system to relieve pain
• Codeine – also derived from opium
• Heroin – the most commonly abused narcotic; a semi-synthetic drug from morphine

3. Hallucinogens

These cause changes in perception, thought, emotion, and consciousness. Examples include:

• Mescaline – derived from cactus
• Psilocin – derived from mushrooms
• Marijuana – obtained from the flowers, stems, and leaves of the marijuana plant

Problems With Drug Addiction

Drug addiction creates several serious problems, including:

• Withdrawal from social contact
• Increased crime rates
• Legal consequences, since possession of narcotics is a violation of law
• Psychological issues, including violent behavior in some cases

Precautions for Using Medicines

The final part of this chapter offers practical safety guidance, useful beyond exams.

Important precautions include:

1. Always follow the prescribed dosage.
2. Check the expiry date before use.
3. Never take medicine prescribed for someone else.
4. Complete the full duration of treatment, especially with antibiotics.
5. Consult a doctor before stopping or changing treatment.
6. Use special dosages for children when required.
7. Avoid taking medicine in the dark.
8. Carry prescription medicines when necessary for health reasons.
9. Keep medicines out of children’s reach.
10. Never use tampered medicines — report them to a pharmacist.

FAQs

Q1: What is covered in 10th Class Biology Chapter 18 Notes?
These notes cover pharmacology basics, sources and classification of drugs, antibiotics, antibiotic resistance, vaccines, addictive drugs, and precautions for using medicines safely.

Q2: What is the difference between antibiotics and antiseptics?
Antibiotics inhibit or kill bacteria within or on the body and are used to treat infections. Antiseptics reduce the possibility of infection on the skin, such as tincture of iodine applied to cuts and wounds.

Q3: What are the main sources of medicinal drugs?
Medicinal drugs come from six main sources: synthetic laboratory production, plants, fungi, animals, minerals, and bacteria. Each source provides different types of drugs, such as antibiotics, analgesics, and hormones.

Q4: How do vaccines protect the body from disease?
Vaccines contain weakened or killed pathogens that stimulate the immune system to produce antibodies and memory cells. These memory cells provide long-term protection against future infections by the same pathogen.

Q5: What is the difference between narcotics and hallucinogens?
Narcotics are strong pain killers like morphine and codeine, often used medically for severe pain. Hallucinogens, like mescaline and marijuana, cause changes in perception, thought, and consciousness rather than relieving pain.

Q6: Why are 10th Class Biology Chapter 18 Notes important for exams?
These notes simplify complex pharmacology concepts like drug classification, antibiotic resistance, and vaccine mechanisms into clear, exam-focused points, helping students revise efficiently before their board exams.