CBSE Class 12 Biology Notes Chapter 8:
CBSE Class 12 Biology Notes for Chapter 8 Human Health and Disease are important resources for students preparing for their board exams. These notes provide a detailed overview of various aspects of human health, including the causes, types, and mechanisms of diseases, as well as the importance of maintaining health.
They simplify complex biological concepts, making it easier for students to grasp topics such as infectious diseases, non-communicable diseases, immunity and the role of various pathogens. By studying these notes, students can gain valuable insights into how human health is influenced by genetics, lifestyle and environmental factors.
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CBSE Class 12 Biology Notes Chapter 8 Overview
CBSE Class 12 Biology Notes for Chapter 8 Human Health and Disease are created by subject experts of Physics Wallah. These notes provide a clear overview of important topics related to health and diseases in humans.
These notes are a helpful study resource for students, making it easier for them to prepare for exams and understand the importance of health in our lives.
CBSE Class 12 Biology Notes Chapter 8 Human Health and Disease PDF
CBSE Class 12 Biology Notes for Chapter 8 Human Health and Disease are now available in PDF format.
With simplified explanations the PDF is designed to help students easily grasp complex topics and prepare effectively for their exams. You can access the PDF from the link provided below making it convenient to study anytime and anywhere. These notes are a great resource for mastering the chapter and ensuring success in the board exams.
CBSE Class 12 Biology Notes Chapter 8 Human Health and Disease PDF
CBSE Class 12 Biology Notes Chapter 8 Human Health and Disease
Here we have provided CBSE Class 12 Biology Notes Chapter 8 Human Health and Disease-
What Is Health?
Health, in simple terms, means being free from diseases and infections. However, according to the World Health Organization (WHO), health goes beyond just the absence of illness. It is a state of complete physical, mental, and social well-being. Maintaining good health requires a balanced diet and regular exercise. Several factors can affect health, such as:
-
Poor diet
-
Genetic disorders
-
Stress and anxiety
-
Infections caused by pathogens
-
Unhealthy and unhygienic food intake
-
Lack of physical activity
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What Are Diseases?
A disease is an abnormal condition that affects the health of a living organism. Diseases can be categorized into two main types:
Infectious diseases
: These are caused by pathogens like bacteria, viruses, fungi, and parasites. Infectious diseases can easily spread from one person to another, which is why they are also called contagious or communicable diseases. Examples include the common cold, tuberculosis, flu, ringworm and malaria.
Non-infectious diseases
: These cannot be transmitted from one person to another and are referred to as non-communicable diseases. They may result from genetic disorders, poor diets, lack of physical activity, or environmental factors. Examples include diabetes, heart disease and cancer.
Some Common Diseases in Humans
Pathogens such as bacteria, viruses, fungi, protozoa, and helminths can cause diseases in humans by entering the body, multiplying, and interfering with normal bodily functions. This often leads to damage, affecting both appearance and body functions. Below are some common diseases, their causative organisms, symptoms and effects:
|
Disease/Test
|
Causal Organisms
|
Symptoms
|
Effects
|
|
Typhoid
(Widal test)
|
Salmonella typhi
|
Sustained high fever, weakness, stomach pain
|
Interferes with intestinal functions, causing severe illness.
|
|
Pneumonia
|
Streptococcus pneumoniae, Haemophilus influenzae
|
Fever, chills, cough, headache
|
Alveoli fill with fluid, causing severe respiratory problems.
|
|
Common Cold
|
Rhino viruses
|
Nasal congestion, sore throat, cough, headache
|
Infects the nose and respiratory passages.
|
|
Malaria
|
Plasmodium (P. vivax, P. malariae, P. falciparum)
|
Recurring chills and high fever every 3–4 days
|
Parasites multiply in liver cells, then attack RBCs.
|
|
Amoebiasis
(Amoebic dysentery)
|
Entamoeba histolytica
|
Constipation, abdominal pain, stool with mucus and blood
|
Infects the large intestine.
|
|
Ascariasis
|
Ascaris (Helminth)
|
Internal bleeding, muscle pain, fever, anemia
|
Infected through contaminated water and food.
|
|
Elephantiasis
(Filariasis)
|
Wuchereria bancrofti, W. malayi
|
Inflammation in the lower limbs and genital organs
|
Lymphatic vessels of the lower limbs get blocked.
|
|
Ringworm
|
Microsporum, Trichophyton, Epidermophyton
|
Dry, scaly lesions on skin
|
Infects the skin, nails, and scalp.
|
Immunity
Immunity is the body's ability to defend and protect itself from harmful invaders like bacteria, viruses, and other foreign substances. There are two main types of immunity:
Innate Immunity
– This is the non-specific defense mechanism present from birth. It includes four types of barriers:
-
Physical barriers
: like the skin and mucous membranes that block pathogens.
-
Physiological barriers
: such as stomach acid and enzymes that destroy invaders.
-
Cellular barriers
: cells like white blood cells that engulf and destroy pathogens.
-
Cytokine barriers
: proteins that help regulate the immune response.
Acquired Immunity
– This is a pathogen-specific immunity developed over time. It is characterized by the body's ability to "remember" and respond more effectively to the same pathogen upon future exposure.
Active and Passive Immunity
-
Active Immunity
: In this type of immunity, the body produces its own antibodies in response to exposure to antigens, either through infection or vaccination (dead or weakened microbes). It is a slow process but provides long-lasting protection since the immune system develops memory cells.
-
Passive Immunity
: In passive immunity, ready-made antibodies are introduced into the body to provide immediate protection. This type of immunity is fast-acting but temporary, as the body does not produce its own antibodies or memory cells. Examples include antibodies passed from mother to baby or through antibody injections.
AIDS (Acquired Immuno Deficiency Syndrome)
AIDS is caused by the
Human Immunodeficiency Virus (HIV)
, which belongs to the retrovirus group. It weakens the immune system, making the body vulnerable to infections and certain cancers. HIV is primarily transmitted through:
-
Sexual contact with an infected person
-
Contaminated blood transfusions and blood products
-
Sharing of infected needles
-
Transmission from an infected mother to her child during pregnancy, childbirth, or breastfeeding
The
ELISA
(Enzyme-linked immunosorbent assay) test is commonly used to diagnose AIDS. This condition progresses over time, severely impairing the body's defense mechanisms.
Cancer
Cancer is one of the most feared diseases worldwide, being a major cause of death. In healthy individuals, normal cells exhibit
contact inhibition
, a property that prevents their uncontrolled growth upon coming into contact with other cells. Cancer cells lose this ability, leading to unchecked growth and tumor formation.
Differences Between Normal and Cancer Cells:
|
Characteristics
|
Normal Cells
|
Cancer Cells
|
|
Morphology
|
Uniform shape and size
|
Varied shapes and sizes with irregular nuclei and small cytoplasm
|
|
Reproduction & Cell Death
|
Stop dividing when cell numbers are sufficient, undergo apoptosis when damaged
|
Do not stop growing, resulting in tumors; fail to undergo apoptosis
|
|
Communication
|
Communicate for proper functioning
|
Do not communicate effectively with other cells
|
|
Adhesion & Invasion
|
Bond to other cells through external membranes
|
Lose adhesion molecules, spread via blood/lymphatic system (metastasis)
|
|
Specialization
|
Mature with specialized functions
|
Remain immature and lack specialization
|
|
Signal Recognition
|
Recognize signals to stop dividing
|
Ignore signals, causing unregulated division
|
Types of Tumors:
-
Benign Tumors
: Non-cancerous, confined to one organ, slow-growing, and non-invasive.
-
Malignant Tumors
: Cancerous, grow rapidly, spread (metastasis) to other parts of the body, and cause significant damage.
Causes of Cancer:
Cancer can be induced by physical, chemical, or biological agents called
carcinogens
.
Oncogenic viruses
contain viral oncogenes, while
cellular oncogenes
or
proto-oncogenes
in normal cells can be activated to transform into cancerous cells under specific conditions.
Detection & Diagnosis:
Cancer is detected through
biopsy
,
histopathological studies
,
blood tests
, and imaging techniques like
CT scans
,
MRI
, and
radiography
.
Treatment Options:
-
Surgery
: Removal of cancerous tissues.
-
Radiotherapy
: Lethal irradiation of tumor cells.
-
Chemotherapy
: Drugs to kill cancer cells (side effects include hair loss and anemia).
-
Immunotherapy
: Use of immune-boosting agents like
alpha-interferon
to help the body destroy tumors.
Drugs and Alcohol Abuse
Many commonly abused drugs include
opioids
,
cannabinoids
, and
coca alkaloids
, which are obtained from flowering plants and fungi.
-
Opioids
: These drugs bind to specific receptors in the central nervous system and the gastrointestinal tract. A well-known opioid is
heroin
, also called
smack
. Chemically known as
diacetylmorphine
, it is a white, bitter crystalline substance extracted from the poppy plant (
Papaver somniferum
). Heroin is taken by snorting or injection and acts as a depressant, slowing down the body's functions.
-
Cannabinoids
: This group of chemicals interacts with cannabinoid receptors in the brain. Natural cannabinoids are derived from the
Cannabis sativa
plant and include substances like
marijuana
,
hashish
,
charas
, and
ganja
. These drugs are consumed by inhalation or ingestion and primarily affect the cardiovascular system.
-
Coca alkaloids
: Cocaine, a powerful stimulant, is extracted from the
coca plant
(
Erythroxylum coca
), native to South America. Known as
coke
or
crack
, it is typically snorted and has a strong stimulating effect on the central nervous system, leading to euphoria and increased energy. Cocaine interferes with the transport of the neurotransmitter
dopamine
.
Adolescence and Drug Abuse
Adolescence, the transition period from childhood to maturity, occurs between the ages of 12 and 18. It is often during this time that individuals may encounter or experiment with drugs for reasons such as:
-
Curiosity
-
Adventure or excitement
-
Experimentation
-
Pressure to excel in exams
-
Stress
Effects of Drug and Alcohol Abuse:
-
Reckless behavior
-
Mischievous or violent actions
-
Decline in academic performance
-
Depression, isolation, and aggressiveness
When someone becomes dependent on drugs or alcohol, abruptly discontinuing them can lead to
withdrawal symptoms
, such as anxiety, shakiness, nausea, and sweating.
Prevention:
To prevent drug abuse, individuals should avoid
peer pressure
, seek
education and counseling
, get help from
family and friends
, and if needed, pursue
professional medical assistance
.
Benefits of CBSE Class 12 Biology Notes Chapter 8 Human Health and Disease
-
Comprehensive Understanding
: The notes provide a detailed overview of various aspects of human health and diseases helping students grasp important concepts.
-
Exam Preparation
: These notes cover important topics likely to be included in exams aiding students in effective revision and improving their chances of scoring well.
-
Clear Definitions and Explanations
: The notes break down complex terms and concepts, making them easier to understand for students.
-
Study Resource
: These notes are a reliable resource for quick reference, saving time during revision sessions.
-
Foundation for Advanced Studies
: A solid understanding of human health and disease provides a strong foundation for students interested in pursuing higher studies in medicine, biology or related fields.
-
Encouragement of Healthy Practices
: The notes often emphasize the importance of maintaining good health and preventing diseases promoting awareness of personal health management.
