CBSE Class 12 Biology Notes Chapter 8 Human Health and Diseases

Health is an important factor in enabling an individual to lead an effective and productive life. However, if an individual is suffering from any disease, it can hinder the body's normal functioning.

• Human health and diseases are significant factors in determining an individual's lifestyle. 
• According to WHO, health refers to the state of mental, social and physical well-being of an individual.
• A healthy lifestyle will help increase your immunity, strengthen bones, and lower the risk of heart disease.
• Malaria, dengue, chikungunya, and filariasis are parasites causing human disease.
• An individual inherits diseases from their parents at the time of birth.
• The ability to protect the body from any disease is called immunity.
• A balanced diet and regular physical activities will help an individual stay healthy.

According to the CBSE Syllabus 2023-24, the chapter on Human Health and Diseases comes under Biology and Human Welfare. Human Health and Diseases Notes are given in the article below for preparation for the CBSE Class 12 Biology Examination.

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Class 12 Biology Chapter 8 Notes – Human Health and Diseases

Factors Affecting Human Health

Human health is influenced by a number of factors which are as follows:

• Unhealthy diet
• Stress and Anxiety
• Lack of Exercise 
• Genetic Problem
• Pathogens

Types of Diseases

Various types of diseases are as follows:

Infectious Diseases

Infectious diseases, also known as communicable diseases, are caused by pathogens like bacteria or fungi and can be transmitted from one unhealthy person to another.

Non-Infectious Diseases

Non-infectious diseases, also known as non-communicable diseases, are chronic diseases that last a longer duration. They are caused by an unbalanced diet and unhealthy lifestyle.

Pathogens

• Pathogens refer to infectious microorganisms that can transmit infection from one person to another.
• They can easily enter the body of an individual, which disturbs the normal activities of the body.
• These microorganisms easily adapt to the body of the host for their survival. 

Types of Pathogens

• Algae: Algae are single-celled organisms that are formed due to a lack of chlorophyll.
• Bacteria: Bacteria are single-celled microorganisms that can pass through air, water, soil and physical touch.
• Virus: A virus is a form of microorganism that rapidly produces numerous identical copies of the original virus, thus damaging the host cells.
• Protozoans: Protozoans are single-celled organisms that cause diseases like malaria, amoebiasis, giardiasis and toxoplasmosis.

Types of Pathogens

Parasites causing Human Diseases

Various parasites causing human diseases are as follows:

Malaria

• Malaria is an infectious disease that is caused by protozoan Plasmodium vivax. 
• It is also popular with the name Roman Fever.
• Usage of shared and infected needles, transfusion, organ transplantation and malarial vector bite are common causes of malaria.
• Fever, nausea, vomiting, anemia, diarrhea and headaches are all symptoms of this disease.
• The first and foremost step for preventing malaria is using mosquito nets and repellents.

Malaria

Dengue

• Dengue is a mosquito-borne disease that is caused by the dengue virus or a female mosquito named Aedes aegypti. 
• These mosquitoes are mostly found during dawn and dusk. 
• Its symptoms are visible only after 6 to 10 days after being bitten.
• Loss of appetite, vomiting, nose bleedings, fatigue, nausea and sudden drop in blood pressure are symptoms of dengue.
• Dengue can be diagnosed by testing serum samples and isolation of the virus.
• Treatment of dengue includes drinking lots of water and taking proper rest.

Chikungunya

• Chikungunya is a form of viral infection that is caused by chikungunya virus (CHIKV)
• Its symptoms are visible only after 3 to 7 days after being bitten.
• Muscle pain, headache, fever, joint swelling and rash are common symptoms of chikungunya.
• Treatment of dengue includes drinking lots of water, taking proper medication on doctor consultations, and getting proper rest.

Filariasis

• Filariasis is a parasitic disease that is transmitted by mosquitoes and black flies.
• These parasites have a lifespan of around 5 to 7 years.
• Lymphatic filariasis, subcutaneous filariasis and severe cavity filariasis are three categories of filariasis.
• Fever, chills, skin lesions and headaches are symptoms of this disease.
• Applying insect repellents and using mosquito mats, coils, and nets are some common treatments for this disease.

Ascariasis

• Ascariasis is a type of disease that is caused by an intestinal parasite called Ascaris.
• Ascaris are white, long, slender, tube-like worms that are found in the intestines of humans.
• Fever, malnutrition, shortness of breath, abdominal swelling and diarrhoea are symptoms of ascariasis.
• Albendazole and Mebendazole are two treatments for the disease prescribed by the WHO.
• Wash your hands after using the restroom to prevent the spread of the disease.

Ascariasis

Typhoid

• Typhoid is a type of bacterial disease that is spread due to poor hygienic conditions and consumption of contaminated food or water.
• It is caused by the Salmonella typhi bacteria.
• The disease usually affects the small intestine.
• High fever, stomach ache, headache, loss of appetite, and constipation are symptoms of typhoid.
• Typhoid Conjugate Vaccine, Unconjugated polysaccharide Vaccine, and Ty21a Vaccine are three vaccines prescribed for the disease.

Typhoid

Pneumonia

• Pneumonia is a type of bacterial disease that is caused by Streptococcus pneumoniae and Haemophilus influenzae.
• The disease is spread by droplets emitted by infected people.
• It will cause inflammation of air sacs in one or both the lungs. 
• Bacterial Pneumonia, Viral Pneumonia and Mycoplasma Pneumonia are different types of pneumonia.
• Shortness of breath, fever, sweating, nausea and loss of appetite are common causes of this disease.
• Vaccination, proper hygiene and avoiding the consumption of alcohol are the common treatments for pneumonia.

Common Cold

• The common cold is a pathogen-borne disease that affects the nose, sinuses, ears, and bronchial tubes.
• Headache, runny nose, scratchy throat, fever, and non-stop sneezing are common symptoms of this disease.
• RSV, parainfluenza and Rhinovirus are different types of common colds.
• Diarrhoea, fever, fast heartbeat, shortness of breath, chest pain with difficulty in breathing, vomiting and nausea are other common cold symptoms.
• Vaccination, consuming vitamins, drinking lots of water, using masks, and maintaining hygiene are the treatments for disease.
• Human Health and Diseases Notes also have links that help students prepare to solve questions on AIDS and HIV.

Immunology

• Immunology is a branch of biology that studies the immune system and its humoral aspects.
• Immunity refers to the ability of the body to defend itself against infectious viruses and diseases.
• It protects the cells of the body, tissues, and organs by drawing lines of defense.
• Antibodies prevent viruses and bacteria from destroying the microbes in the body.
• Innate immunity and acquired immunity are two types of immunity.
• Acquired immunity or adaptive immunity is a form of immunity that an individual body acquires in a lifetime.
• Innate immunity protects our body from viruses and bacteria from the time of childbirth.

Cancer

• Cancer is a disease that causes infectious cells inside the human body to grow uncontrollably and spread to different parts of the body.
• This will result in the formation of tumors in the organs, thus causing organ failure.
• Carcinoma, sarcoma, melanoma lymphoma and leukemia are different types of cancer.
• Benign tumors are harmless tumors that do not spread to other parts of the body.
• A malignant tumor is a type of cancerous tumor that grows quickly and spreads to other normal tissues of the body. 
• Premalignant tumors appear like a benign tumor but have features of malignant tumors.
• Biopsy, histopathological studies of tissue, radiography techniques, and computed tomography are some methods used to diagnose cancer.
• Treatment of cancer includes surgery, chemotherapy and radiation therapy. 

AIDS

• AIDS stands for Acquired Immunodeficiency Syndrome, whose causative agent is the HIV virus.
• HIV stands for Human Immunodeficiency Virus, which attacks the immune system of the body.
• People who have AIDS will have a weak immune system, as a result of which they are not able to fight any infection or disease. 
• Pneumonia, thrush, fungal infections, and TB are health conditions that develop due to this disease.
• The disease is transmitted through unprotected sexual contact and contaminated blood transfusions.
• Fever, muscle pain, sore throat, night sweats and chills are initial symptoms of AIDS.
• Shortness of breath, blurred vision and white spots on the tongue or mouth are symptoms noticed during the later stages.
• Antiretroviral therapy (ART) is one of the treatments for AIDS.

AIDS

Drug and alcohol abuse

• Drug and alcohol abuse is a serious problem that is increasing continuously in our society.
• Alcohol abuse is a form of addiction that causes chronic, relapsing disorder, which is characterized by compulsive drug seeking and its adverse consequences.
• Heavy alcohol consumption can cause heart failure, coma, and death.
• It will damage the nervous system and liver of an individual.
• Drugs are also consumed from needles by injecting them into the body.
• Crack, cocaine and ecstasy are different types of drugs.

There are Some important List Of Top Biology Questions On Human Health and Diseases Asked In CBSE CLASS XII