Chapter 7: What Is Health?

Definition of Health:

Health, in its simplest form, can be defined as the state of being free from diseases and infections. However, this definition only scratches the surface. According to the World Health Organization (WHO), health is much more than the mere absence of disease or infirmity. It is a state of complete physical, mental, and social well-being. This broader definition emphasizes that health encompasses a dynamic state of overall wellness, which involves maintaining a balance in various aspects of life.



Factors Affecting Health:

Several factors can significantly influence an individual’s health. Some of these factors include:

1. Poorly Balanced Diet:

  - Nutrition plays a critical role in maintaining health. A balanced diet provides the necessary nutrients, vitamins, and minerals required for the body to function optimally. Conversely, a poorly balanced diet can lead to malnutrition, obesity, and a host of other health issues.

2. Genetic Disorders:

  - Genetic makeup can predispose individuals to certain health conditions. Disorders inherited from parents can affect an individual's health and require specialized medical intervention and lifestyle adjustments.

3. Stress and Anxiety:

Mental health is an integral component of overall health. Chronic stress and anxiety can lead to numerous physical health problems, such as heart disease, hypertension, and weakened immune function.

4. Infection from Pathogens:

  - Pathogens such as bacteria, viruses, fungi, and parasites can cause infectious diseases. Maintaining good hygiene and a strong immune system are vital to preventing infections.

5. Intake of Unhealthy and Unhygienic Food:

Consuming food that is unhealthy or unhygienic can lead to foodborne illnesses and long-term health issues like diabetes, cardiovascular diseases, and gastrointestinal disorders.

6. Lack of Exercise and Physical Activities:

Physical inactivity is a significant risk factor for various health conditions, including obesity, cardiovascular diseases, and musculoskeletal problems. Regular physical activity is essential for maintaining a healthy body weight, enhancing cardiovascular health, and improving mental well-being.

Maintaining Good Health:

To maintain good health, individuals should adopt the following practices:

1. Healthy and Balanced Diet:

A diet rich in fruits, vegetables, whole grains, lean proteins, and healthy fats ensures the body receives essential nutrients. Avoiding excessive intake of processed foods, sugar, and unhealthy fats is crucial.

2. Personal Hygiene:

Good personal hygiene practices, such as regular handwashing, oral care, and proper sanitation, can prevent infections and promote overall health.

3. Regular Exercise and Physical Activities:

Engaging in regular physical activities, such as walking, jogging, swimming, or yoga, helps maintain physical fitness, boosts mental health, and enhances immune function.

4. Awareness of Diseases:

Being informed about different types of diseases, their causes, symptoms, and preventive measures empowers individuals to take proactive steps in safeguarding their health.

Read Also: Class 11 Biology Notes on Cell Cycle and Cell Division

What Are Diseases?

Definition of Disease:

A disease is an abnormal condition that negatively affects the structure or function of part or all of an organism. Diseases are often characterized by specific signs and symptoms. They can be broadly categorized into infectious and non-infectious diseases.

Infectious Diseases:

Infectious diseases are caused by pathogens such as bacteria, viruses, fungi, and parasites. These diseases can be easily transmitted from one person to another, making them contagious or communicable. Common examples of infectious diseases include:

1. Common Cold:

  - Caused by Rhinoviruses, the common cold is one of the most prevalent infectious diseases. It spreads through respiratory droplets when an infected person coughs or sneezes.

2. Tuberculosis:

Caused by the bacterium *Mycobacterium tuberculosis*, tuberculosis primarily affects the lungs but can also impact other parts of the body. It spreads through the air when an infected person coughs or sneezes.

3. Flu:

Influenza, commonly known as the flu, is caused by influenza viruses. It spreads through respiratory droplets and can cause severe respiratory illness.

4. Ringworm:

A fungal infection of the skin, ringworm is highly contagious and spreads through direct contact with infected individuals or contaminated surfaces.

5. Malaria:

Caused by the protozoan parasite *Plasmodium*, malaria is transmitted through the bite of infected female Anopheles mosquitoes. It is characterized by fever, chills, and flu-like symptoms.

Non-infectious Diseases:

Non-infectious diseases cannot be transmitted from one person to another. They may result from genetic factors, lifestyle choices, environmental factors, or a combination of these. Examples include:

1. Genetic Disorders:

Diseases like cystic fibrosis, sickle cell anemia, and Down syndrome are caused by genetic mutations and are inherited from parents.

2. Lifestyle Diseases:

Conditions such as diabetes, cardiovascular diseases, and obesity are often linked to unhealthy lifestyles, including poor diet, lack of exercise, and excessive stress.

3. Environmental Diseases:

Exposure to environmental toxins, such as pollution and hazardous chemicals, can lead to diseases like lung cancer, asbestosis, and lead poisoning.

Some Common Diseases in Humans

1. Typhoid:

Typhoid fever is caused by the bacterium *Salmonella typhi*. It is a serious illness characterized by prolonged fever, weakness, stomach pain, headache, and loss of appetite. The Widal test is commonly used for its diagnosis.

2. Pneumonia:

Pneumonia is an infection that inflames the air sacs in one or both lungs. It can be caused by bacteria like Streptococcus pneumoniae and Hemophilus influenzae. Symptoms include cough, fever, chills, and difficulty breathing.

3. Common Cold:

The common cold is caused by various viruses, primarily Rhinoviruses. It is highly contagious and typically spreads through respiratory droplets. Symptoms include runny nose, sore throat, cough, and congestion.

4. Malaria:

Malaria is caused by Plasmodium parasites, which are transmitted through the bites of infected Anopheles mosquitoes. It presents with fever, chills, and flu-like symptoms.

5. Amoebiasis:

Caused by the protozoan Entamoeba histolytica, amoebiasis results in severe gastrointestinal issues, including diarrhea, stomach cramps, and dysentery.

6. Ascariasis:

  - Ascariasis is an infection caused by the intestinal roundworm Ascaris lumbricoides. It leads to symptoms like abdominal pain, nausea, and vomiting.

7. Filariasis (Elephantiasis):

  - Filariasis is caused by the filarial worm Wuchereria bancrofti. It results in chronic swelling of body parts, typically the legs, leading to a condition known as elephantiasis.

Immunity

Definition:

Immunity refers to the body's ability to defend against invading pathogens, such as bacteria, viruses, and other foreign bodies, as well as toxic substances. It is the body's defense mechanism to protect against diseases.

Types of Immunity:

1. Innate Immunity:

Innate immunity is the non-specific defense mechanism that an individual is born with. It provides the first line of defense against pathogens and includes various barriers and responses:

 Physical Barrier:

Skin and mucous membranes act as physical barriers to prevent the entry of pathogens.

Physiological Barrier:

Body fluids like saliva, tears, and gastric juices contain enzymes and acids that destroy pathogens.

Cellular Barrier:

White blood cells (leukocytes) such as neutrophils, macrophages, and natural killer cells engulf and destroy pathogens.

Cytokine Barrier:

Cytokines are signaling proteins that help regulate immune responses and inflammation.

2. Acquired Immunity:

Acquired immunity, also known as adaptive or specific immunity, develops over time as the body is exposed to various pathogens. It is characterized by the ability to remember and respond more efficiently to pathogens that the body has previously encountered.

Active and Passive Immunity:

Active Immunity:

Active immunity occurs when the body is exposed to an antigen and produces its own antibodies. This can happen through natural exposure to a pathogen or through vaccination. Active immunity provides long-lasting protection but takes time to develop fully.

Passive Immunity:

Passive immunity is provided when ready-made antibodies are transferred to an individual. This can occur naturally, such as through the transfer of maternal antibodies to a newborn, or artificially, through antibody-containing blood products. Passive immunity provides immediate protection but is short-lived.

AIDS

Acquired Immuno Deficiency Syndrome (AIDS):

- AIDS is a chronic, potentially life-threatening condition caused by the Human Immunodeficiency Virus (HIV). HIV attacks and weakens the body's immune system, making it vulnerable to infections and certain cancers.

Transmission:

HIV is transmitted through contact with infected body fluids, including blood, semen, vaginal fluids, and breast milk. Common routes of transmission include:

Sexual Contact:

Unprotected sexual intercourse with an infected person.

Blood Transfusion:

Receiving contaminated blood or blood products.

Sharing Needles:

Using needles or syringes that have been contaminated with infected blood.

Mother-to-Child:

Transmission from an infected mother to her child during pregnancy, childbirth, or breastfeeding.

Diagnosis

AIDS is diagnosed using the Enzyme-linked Immunosorbent Assay (ELISA) test, which detects the presence of HIV antibodies in the blood. Early diagnosis and treatment are crucial for managing the disease and improving the quality of life for affected individuals.

Important Questions Class 12 Biology Notes-Human Health and Disease

Q1: What is health according to WHO?

According to the WHO, health is not just the absence of disease or illness but a state of complete physical, mental, and social well-being.

Q2: What are the factors affecting health?

Factors affecting health include a poorly balanced diet, genetic disorders, stress and anxiety, infection from pathogens, intake of unhealthy and unhygienic food, and lack of exercise and physical activities.

Q3: How can one maintain good health?

Good health can be maintained by including a healthy and balanced diet, maintaining personal hygiene, engaging in regular exercise and physical activities, and being aware of different types of diseases and their effects.

Conclusion

The study of human health and disease in Class 12 emphasizes the comprehensive understanding of health as a state of complete physical, mental, and social well-being. It underscores the significance of a balanced diet, regular exercise, and good hygiene in maintaining health while highlighting the various factors that can affect it. By distinguishing between infectious and non-infectious diseases and exploring common illnesses, the chapter prepares students to recognize, prevent, and manage health issues effectively. Understanding immunity, particularly the roles of innate and acquired immunity, equips students with knowledge on the body's defense mechanisms. The section on AIDS provides crucial information on its transmission, diagnosis, and the importance of early intervention. Overall, these notes provide essential insights into maintaining health and preventing diseases, fostering a proactive approach to well-being.