Human Health and Disease — NCERT Solutions

NACO stands for National AIDS Control Organisation.

HIV stands for Human Immuno deficiency Virus.

(a) Innate immunity and acquired immunity

• Innate immunity: Present from birth; it is non-specific. It provides barriers such as skin, mucus, stomach acid, saliva, tears, phagocytic cells and interferons.

Example: Skin preventing entry of microbes; stomach acid preventing microbial growth.

• Acquired immunity: Develops after exposure to a pathogen; it is pathogen-specific and has memory. It involves B-lymphocytes and T-lymphocytes.

Example: Immunity developed after vaccination or after recovering from an infection.

(b) Active immunity and passive immunity

• Active immunity: The body itself produces antibodies when exposed to an antigen. It is slow to develop but long-lasting.

Example: Immunity after natural infection or vaccination.

• Passive immunity: Ready-made antibodies are given directly to the body. It acts immediately but is short-lived.

Example: Colostrum from mother’s milk, antibodies passed through the placenta, or anti-toxin injection in tetanus.

(b) Active immunity and passive immunity

So, active immunity is produced by the host’s own immune response, while passive immunity is obtained from outside in the form of antibodies.

HIV is transmitted by:

• sexual contact with an infected person
• transfusion of contaminated blood and blood products
• sharing infected needles and syringes, as in intravenous drug abuse
• from infected mother to child through placenta

It is not spread by mere touch or casual physical contact.

The AIDS virus (HIV) causes immune deficiency by infecting macrophages and helper T-lymphocytes. In macrophages, its RNA is converted into DNA by reverse transcriptase, and this viral DNA integrates into the host DNA and produces new virus particles. HIV also enters helper T-cells and multiplies, causing a progressive decrease in helper T-lymphocytes. As these cells fall, the body cannot mount proper immune responses, so the person becomes highly susceptible to other infections.

A cancerous cell differs from a normal cell in that:

• it loses contact inhibition
• it shows uncontrolled division
• it forms masses of cells called tumours
• malignant cancer cells invade surrounding tissues and may spread to distant parts of the body
• normal cells divide in a controlled manner and remain regulated by the body's mechanisms

Metastasis is the spread of malignant tumour cells from the original site to distant parts of the body through the blood. These cells get lodged elsewhere and start a new tumour there. It is the most feared property of malignant tumours.

The harmful effects of alcohol/drug abuse include:

• reckless behaviour, vandalism and violence
• coma and death due to respiratory failure, heart failure or cerebral haemorrhage
• overdosing, especially when drugs are taken with alcohol
• drop in academic performance, absence from school/college, lack of hygiene, withdrawal, isolation, depression, fatigue, aggression and rebellious behaviour
• deterioration of relationships with family and friends
• risk of AIDS and Hepatitis B from shared needles
• damage to the nervous system and liver (cirrhosis)
• harm to the foetus during pregnancy

Yes, friends can influence one to take alcohol or drugs through peer pressure. To protect oneself:

• avoid undue peer pressure
• choose friends wisely
• get education and counselling
• talk to parents, teachers or trusted friends when facing problems
• stay engaged in healthy activities like sports, music, yoga and reading
• seek professional help if needed

Youngsters are motivated towards alcohol or drugs by curiosity, need for adventure and excitement, experimentation, stress, the idea that it is cool or progressive, and peer pressure. Unstable or unsupportive family structures and influence of media also contribute.

This can be avoided by:

• education and counselling
• avoiding undue peer pressure
• seeking help from parents and peers
• looking for and acting on danger signs early
• involving professional and medical help when necessary
• channelising energy into healthy pursuits like sports, reading, music and yoga