07Class 12 Biology
Human Health and Disease short notes
Short notes on common diseases, immunity, AIDS, cancer and drugs. Pathogen and symptom pairs get asked often.
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Common diseases
- Typhoid: Salmonella typhi, tested with the Widal test.
- Pneumonia: Streptococcus pneumoniae and Haemophilus influenzae.
- Common cold: rhinoviruses.
- Malaria: Plasmodium, spread by the female Anopheles mosquito. Sporozoites are the infective stage, and haemozoin causes the fever. P. falciparum is the most serious type.
- Amoebiasis: Entamoeba histolytica, with houseflies as carriers.
- Ascariasis: Ascaris, and filariasis: Wuchereria.
- Ringworm: fungi such as Microsporum, Trichophyton and Epidermophyton.
Immunity
- Innate immunity is non-specific, and includes physical, physiological, cellular and cytokine barriers.
- Acquired immunity is specific and has memory. B cells make antibodies (humoral), and T cells give cell-mediated immunity.
- Antibodies have two heavy and two light chains (H₂L₂). Types are IgA, IgM, IgE and IgG.
- Active immunity: your body makes antibodies. Passive immunity: you receive ready-made antibodies, as with colostrum.
- Allergies involve IgE, and histamine causes the symptoms.
- Bone marrow and thymus are primary lymphoid organs. Spleen, lymph nodes and MALT are secondary ones.
AIDS and cancer
- HIV is a retrovirus that uses reverse transcriptase and attacks helper T cells. The test is ELISA.
- Cancer cells lose contact inhibition and can spread by metastasis.
- Detected by biopsy and imaging, and treated by surgery, radiation, chemotherapy or immunotherapy.
Drugs
- Opioids (heroin, from poppy) depress the nervous system.
- Cannabinoids come from Cannabis, and affect the heart and blood vessels.
- Coca alkaloids (cocaine) stimulate the nervous system, by interfering with dopamine.
- Nicotine stimulates the adrenal glands, raising blood pressure and heart rate.
Where students slip up
- Mixing up the Plasmodium stage that infects humans (sporozoite) with others.
- Thinking a vaccine gives passive immunity. It gives active immunity.
- Saying HIV attacks all T cells. It targets helper T cells first.
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