Human Health and Disease: Class 12 Biology NCERT Chapter 8

Key Features of NCERT Material for Class 12 Biology Chapter 8–  Human Health and Disease 

In the previous chapter 7: Evolution, you learned about human evolution. In this chapter: Human Health and Disease, you will learn about that Health is characterized as the condition of complete physical, mental and social prosperity and not only the nonattendance of disease or sickness.

The human body is a stunning creation. There are numerous frameworks inside a similar body that work so well in an all around facilitated and coordinated way. No big surprise it required some investment to truly comprehend the working of the human body and other related angles. Today we have a superior comprehension of what comprises health which additionally incorporates psychological wellness. Let us investigate.

As indicated by the World Health Organization, Health is characterized as the condition of complete physical, mental and social prosperity and not only the nonattendance of disease or sickness. Health additionally mirrors the metabolic and utilitarian productivity in living creatures. 

Health is considered as a fundamental boundary to life. There are numerous things that can influence the health of the living life form, including the physical condition of the body just as the brain and the psychological state. Being healthy compares to numerous positive properties. It implies more proficiency, greater profitability at work, a superior comprehension of the earth just as better life span. 

(Human Health and Disease: Class 12)

Quick Revision Notes

 The condition of complete physical, mental and social well creatures is called health. Health basically doesn’t just methods without disease condition or physical wellness. Health is influenced by- 

  1. Hereditary issues – the imperfection which kid acquires from it guardians. 
  2. Contamination from microorganisms or other living beings.
  3. Way of life incorporates food and water we take, exercise and rest. Great health can be kept up by
  •       Balanced diet. 
  •       Personal cleanliness 
  •       Regular work out 
  •       Awareness about the disease and their impact 
  •       Immunization against the irresistible disease
  •       Proper removal of wastage 
  •       Control of vectors
  •       Maintenance of clean food and water.

 Disease – Diseases can be extensively gathered into irresistible and non-irresistible.

  1. a) Infectious disease – Diseases which are effectively sent starting with one individual then onto the next, are called irresistible diseases e.g AIDS, regular cold, jungle fever, tuberculosis and so forth
  2. b) Non-irresistible disease – Diseases which can’t communicated starting with one individual then onto the next, are called non-irresistible diseases e.g cancer, hypertension, diabetes and so forth. 

(Human Health and Disease: Class 12)

Basic Diseases in Humans: 

  •       The disease-causing microorganisms like microscopic organisms, infection, growth, protozoa, helminthes are called microbe. 
  •       The microorganism can enter the body by different methods and duplicate and meddle with typical indispensable exercises bringing about morphological and useful harm.
Name of disease /test Causal organisms Symptoms Effects
Typhoid / Widal test Salmonella typhi Sustained high fever, shortcoming, stomach torment, 
Pneumonia Streptococcus pneumoniae and Haemophilus influenzae Fever, chills, hack and headache. Alveoli get loaded up with liquid prompting extreme issues in breath
Common cold Rhino viruses Nasal clog and release, sore throat, hack and headache Infect the nose and respiratory entry. 
Malaria Plasmodium (P. vivax, P. malaria and P. falciparum) The chill and high fever repeating 3 to 4 days. Parasite increase inside switch cells and afterward assault the RBCs.


Amoebiasis or Amoebic dysentery Entamoeba histolytica Constipation, stomach torment, cramps, stool with mucous and blood clot Infect the internal organ
Ascariasis Ascaris (Helminthes) Internal dying, strong agony, fever, weakness etc Healthy individual get tainted through water, vegetable and so on
Elephantiasis or filariasis Wuchereria (W. bancrofti and  W. malayi) Inflammation in the lower appendage and genital organs Lymphatic vessels of lower appendages get blocked
Ring worms Microsporum,

Trichophyton and Epidermophyton

Appearance of dry, layered sores on different piece of body. Infects the skin, nail and scalp. 

Life pattern of plasmodium : Plasmodium enters the human body as little sporozoites through the chomp of contaminated female anopheles mosquito and increases inside the switch cells. Later assaults the RBCs bringing about the joy with arrival of harmful substance, haemozoin, which is liable for high fever and chill repeating each three to four days.

Malarial parasite requires two hosts, human and anopheles mosquito to finish their life cycle. Female anopheles is vector of this disease to human creatures.

Flowchart to show lifecycle of Plasmodium 

Immunity – the capacity of host cells to battle the disease causing microorganism because of insusceptible framework is called immunity. There are two sorts of immunity-

Natural immunity – vague sorts of safeguard presents at the hour of birth and give various types of hindrances to the section of unfamiliar operators into the body. it comprises of four sorts of hindrance

  1. Physical boundary skin, bodily fluid covering of epithelium coating the respiratory, gastrointestinal and urogenital parcel.
  2. Physiological boundary corrosive in stomach and spit in mouth.
  3. Cell obstruction leucocytes, neutrophils, monocytes.

(Human Health and Disease: Class 12)

  1. Cytokine obstructions infection tainted cells secretes protein called interferon.
No Innate Immunity Acquired (Adaptive) Immunity
1 Present from birth itself Develops during life time
2 The immunity remains throughout life. Can be short lived or lifelong.
3 Contact or exposure with pathogen or its antigen is not essential. Contact with pathogen or its antigen is essential.
4 Innate immunity is inheritable. Acquired immunity can’t be passed to the cutting edge with the exception of a concise period to children. 
5 It shields the people from withdrawal of diseases of other organisms It shields the people from microorganisms present on other individuals from similar species. 

Obtained Immunity-microorganism explicit barrier described by memory. At the point when our body experiences a microorganism first time delivers a reaction called essential reaction of low power. Ensuing experience by same microorganism produce profoundly escalated reaction called optional reaction or anamnestic reaction because of memory of first experience. 

Essential and optional reactions are completed with the assistance of B-lymphocytes and T-lymphocytes. B-lymphocytes produce armed force of protein called antibodies each having two light and two overwhelming chains. 

It includes two sorts of lymphocytes –

  •       B lymphocytes: Show humoral invulnerable reaction (HI) 
  •       T lymphocytes: Show cell intervened immunity (CMI)

Structure of an Antibody:

  •       The antibodies are protein atoms called immunoglobulins and are of different sorts like IgA, IgM, IgE, IgG. 
  •       Each antibody atom comprises of four polypeptide chains, two are for quite some time called overwhelming chains and other two are short called light chains. Both are masterminded looking like ‘Y’, subsequently an antibody is spoken to as H2L2. 

Based on creation of antibodies, immunity can be additionally ordered as –

  •       Active immunity: Body delivers its own antibodies against antigens
  •       Passive immunity: Readymade antibody is moved starting with one individual then onto the next
  •       Colostrum (contains antibodies IgA) is a case of uninvolved immunity gave by the mother to her kid.

Various sorts of antibodies produce in blood incorporate IgA, IgM, IgEete. They are called humoral resistant reaction because of quality in blood.

Human invulnerable framework can recognize self and unfamiliar atoms or unfamiliar bodies. Some of the time, because of hereditary or obscure reasons, the body assault self-cells. This outcomes in harm to the body and called auto-resistant disease. Rheumatoid joint inflammation is because of this impact

Hypersensitivities – the misrepresented reaction of insusceptible framework to specific antigens present in the earth is called sensitivity. The substance to which such resistant reaction is created is called allergens. The antibodies delivered due to these are IgE types. Hypersensitivity is because of discharge of synthetics like histamine and serotonin from the pole cells.

Insusceptible framework in the body-the human safe framework incorporates lymphoid organs, tissue, cells and solvent particles like antibodies.

Lymphoid organs are where inception and development and expansion of lymphocytes happen. Essential lymphoid organs incorporate bone marrow and thymus.

After development lymphocytes relocate to auxiliary lymphoid organ like spleen, lymph hubs, tonsils, peyer’s patches of small digestive system and informative supplement. They give the locales to collaboration lymphocyte with antigens.

There is lymphoid tissue likewise situated inside the covering of respiratory, stomach related and urogenital plot called mucosal related lymphoid tissue ( MALT). It establish half of lymphoid tissues in human body.

Helps (Acquired Immuno Deficiency Syndrome) was first announced in 1981. It is brought about by HIV (human Immuno lack infection), a retrovirus. Transmission of HIV infection happens by-

  1. Sexual contact with contaminated individual
  2. Bonding of sullied blood and blood items
  3. Sharing contaminated needles as in intravenous medication victimizers
  4. Contaminated mother to her kid through placenta.

Replication of retrovirus in Macropahges

(Human Health and Disease: Class 12)

Helps/HIV doesn’t spread by physical contact. It spread uniquely through body liquids. There is consistently delay among contamination and presence of manifestations that may change from 5-10 years.

Demonstrative test for AIDS is ELISA (protein connected Immuno-sorbent test). The treatment of this disease with against retroviral tranquilize is somewhat viable and simply drawn out the life however not forestalls the demise.

Cancer is one of the most feared diseases of human creatures and is a significant reason for death everywhere throughout the world. Ordinary cells show a property called contact hindrance by uprightness of which contact with other cells restrain their uncontrolled development. Cancer cells lost this property. 

Cell Characteristics Normal Cells Cancer Cells
Morphology Normal cells have uniform  shapes and sizes Cancer cells have a large variety of sizes and shapes

The nucleuses have irregular structure and have relatively small cytoplasm.

Reproduction and Cell Death Cells stop dividing when too much of its kind are present.

These cells grow and divide in a controlled manner and follow a predictable life cycle.

Normal cells undergo the process of apoptosis – self destruction if they detect abnormalities and damage in their organelles.

Cancer cells don’t stop growing resulting to appearance of a tumor ( a cluster of mutant cells)
Communication Normal cells communicate with each other for proper functioning. Cancer cells do not communicate with each other
Adhesion and Invasion These cells have external membranes that allow them to bond with other cells. Cancer cells lose the molecules that keep cells bonded together.

These cells have the ability to invade or spread to other parts of the body by travelling through the blood stream or the lymphatic system – metastasis.

Specialization Normal cells start out as immature cells and mature with certain specialized functions. Cancer cells do not mature, and undergo apoptosis. Instead these cells become immature overtime.

Cancer cells are primitive and they don’t have specialized functions.

Signal Recognition Normal cells recognize signals. They know when there are enough new cells and stops dividing. Cancer cells don’t recognize signals. Hence these cells erratically reproduce mutated cells.

Cancerous cells keep on separating offering ascend to masses of cells called tumors. There are two kind so tumors-

(a) Benign tumors

(b) Malignant tumors 

Benign Tumor Malignant Tumor
  1. It remains confined to the affected organ.
  1. It also spreads to other organs of the body.
  1. Rate of growth is usually slow.
  1. Rate of growth is usually rapid.
  1. There is no latent stage.
  1. There is latent stage.
  1. It causes limited damage to the body.
  1. The cancer cells migrate to other sites of the body.
  1. There is no metastasis.
  1. There is metastasis.
  1. It is non-cancerous.
  1. It is cancerous.

Reasons for cancer – cancerous neoplastic cell might be initiated by physical, substance and natural specialists called cancer-causing agents. Cancer causing infections called oncogenic infection have quality called viral oncogenes. A few qualities called cell oncogenes (c-onc) or proto oncogenes have been distinguished in ordinary cells which, when enacted under specific conditions, could prompt oncogenic change of the cells.

Cancer identification and conclusion cancer recognition depends on biopsy and histopathological investigation of the tissues, blood and bone marrow test for expanded cell checks. Radiography, CT (figured tomography), MRI (attractive reverberation imaging) are extremely valuable to cancers of interior organs.

(Human Health and Disease: Class 12)

Treatment of Cancer-

  1.       Surgical – cancerous tissues are precisely expelled.
  2.       Radiotherapy – tumor cells are illuminated mortally by radiation.
  3.       Chemotherapy – drugs are utilized to murder cancerous cells, yet shows symptoms like going bald, paleness, and so forth.
  4.       Immunotherapy – patients are given with alpha-interferon which initiate their resistant framework and help in annihilating the tumor

Medications and Alcohol Abuse

Regularly mishandled drugs incorporate narcotics, cannabinoids and coca alkaloids got from blossoming plants and a couple from parasites.

Narcotics are the medications which tie to explicit narcotics receptors present in our focal sensory system and gastrointestinal parcel. Heroin usually called smack is artificially diacetylmorphine which is a white, unscented, severe translucent compound. It is separated from the latex of poppy plant (Papaversomniferum).Generally taken by grunting and infusion, heroin is a depressant and hinders body capacities.

Cannabinoids are a gathering of synthetic substances which communicate with cannabinoid receptors present in the mind. Normal cannabinoids are acquired from the inflorescence of the plant cannabis sativa. They incorporate weed, hashish, charas and gangja. They for the most part taken by inward breath and oral ingestion, these are known for their impacts on cardiovascular arrangement of the body.

Coca alkaloid or cocaine is gotten from coca plant Erythroxylum coca, local to South America. It meddles with the vehicle of the neuro-transmitter dopamine. Cocaine, regularly called coke or split is generally grunted. It has a strong invigorating activity on focal sensory system, creating a feeling of happiness and expanded vitality.

Puberty and Drug misuse

  •         Adolescence is the period during which the youngster gets developed.
  •         It is between 12 – 18 years old.

Reasons for sedate maltreatment –

  •         Curiosity
  •         Adventure
  •         Excitement
  •         Experimentation
  •         Stress or strain to exceed expectations in assessment

Impacts of medication/liquor misuse –

  •         Reckless conduct
  •         Malicious naughtiness
  •         Violence
  •         Drop in scholarly execution
  •         Depression, separation, forcefulness, and so forth.

Reliance is the inclination of the body to show a trademark and terrible withdrawal disorder if customary portion of medication/liquor is suddenly stopped that incorporates tension, flimsiness, sickness and perspiring.

Counteraction maintain a strategic distance from unjustifiable friend pressure, instruction and guiding, looking for helps from guardians and companions, looking for expert and clinical assistance and so on.


Q: Health is

  •         Weight of body as indicated by tallness
  •         Absence of disease or illness
  •         State of complete physical mental and social prosperity
  •         None of the abovementioned

Ans: The right alternative is “C”. Health is characterized as a condition of complete physical, mental and social prosperity. It relies upon three boundaries physical, mental and social. It is a powerful condition coming about because of a body’s consistent change and variation in light of stresses and changes in the earth for keeping up an inward balance called homeostasis.

(Human Health and Disease: Class 12)

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