Human Health and Diseases | Plus 2 Zoology| Exam Capsule Notes (Web and PDF)

HUMAN HEALTH AND DISEASES: 

CHAPTER AT A GLANCE

HUMAN INFECTIOUS DISEASES

Bacterial Diseases

Typhoid: 

• Pathogen: Salmonella typhi.
• Widal test: For confirmation of the disease.
• Transmission: Food & water → small intestine.
• Symptoms: High fever, weakness, stomach pain, constipation, headache & loss of appetite. Intestinal perforation.

Pneumonia: 

• Pathogen: Streptococcus pneumoniae & Haemophilus influenzae
• Transmission: Inhaling droplets from patients, Sharing contaminated objects.
• Symptoms: Respiratory problems, fever, chills, cough, headache. In severe cases, lips and finger nails turn gray to bluish colour.

Viral Diseases

Common cold: 

• Pathogen: Rhinovirus.
• Transmission: Inhaling droplets from cough or sneezes. Contaminated objects.
• Symptoms: Nasal congestion & discharge, sore throat, cough, hoarseness, headache, tiredness.

Protozoan Diseases

Malaria: 

• Pathogen: Plasmodium sp.
• Transmission: Female Anopheles mosquito.
• Symptoms: Haemozoin toxin causes chill and high fever recurring every 3-4 days.

Amoebiasis (Amoebic dysentery):

• Pathogen: Entamoeba histolytica
• Transmission: Houseflies transmit parasites from faeces to food & water.
• Symptoms: Constipation, abdominal pain & cramps, stools with mucus and blood clots.

Helminth Diseases

Ascariasis:

• Pathogen: Ascaris 
  
• Transmission: Soil, water, vegetables, fruits etc. contaminated with faeces.
• Symptoms: Internal bleeding, muscular pain, fever, anaemia, blockage of intestinal passage.

Filariasis (Elephantiasis):

• Pathogen: Wuchereria (Filarial worms)
• Transmission: Female Culex mosquito.
• Symptoms: Chronic inflammation and deformity of limbs & genital organs. 

Fungal Diseases

Ringworm:

• Pathogen: Microsporum, Trichophyton & Epidermophyton
• Transmission: From soil or towels, cloths, comb etc.
• Symptoms: Dry, scaly lesions on skin, nails, scalp etc. Itching.

IMMUNE SYSTEM

LYMPHOID ORGANS 

The organs where origin/ maturation & proliferation of lymphocytes occur.

2 types: Primary & Secondary.

1. Primary lymphoid organs: Here, immature lymphocytes differentiate into antigen-sensitive lymphocytes. E.g. Bone marrow & thymus.
2. Secondary lymphoid organs: The organs, to which matured lymphocytes migrate, interact with antigens and proliferate to effector cells. E.g. Spleen, lymph nodes, tonsils, Peyer’s patches, Mucosa associated lymphoid tissue (MALT) & appendix.

IMMUNITY 

2 types: Innate and Acquired.

1. Innate immunity

    Non-specific inborn immunity.

    It includes 4 types of Barriers:

• Physical barriers: E.g. Skin, Mucus.
• Physiological barriers: E.g. gastric HCl, saliva, tear etc.
• Cellular barriers: Phagocytes like WBC, macrophages etc.
• Cytokine barriers: Virus infected cells → interferon → protect non-infected cells from viral infection.

2. Acquired immunity

    Pathogen specific immunity developed during lifetime.

    First encounter of a pathogen → primary response in low intensity.

    Second encounter → strong secondary (anamnestic) response.

    These responses are carried out by

• B-lymphocytes (B-cells): Produce antibodies.
• T-lymphocytes (T-cells): Help B-cells to produce antibodies.

Types of Acquired immune response

1. Humoral immune response/ Antibody mediated immunity (AMI): It is mediated by antibodies.
2. Cell-mediated response / cell-mediated immunity (CMI): It is mediated by T-lymphocytes. 

Structure of antibody 

Types of Acquired immunity

• Active immunity: Here, antibodies are produced in host body. It is developed during natural infection by microbes or by injecting microbes during immunization.
• Passive immunity: Here, readymade antibodies are given to the body. E.g. Foetus gets antibodies from mother through Placenta, infants gets antibodies (IgA) in colostrum.

Types of Immunization

1. Active Immunization (Vaccination)

• Vaccine (inactivated pathogen or its antigenic proteins) is introduced into body for the development of antibodies.
• E.g. Polio vaccine, Hepatitis B vaccine, DPT vaccine etc.

2. Passive Immunization

• It is the direct injection of pre-formed antibodies or antitoxin. It requires for quick immune response.
• E.g. Immunization against Tetanus, snake venom etc.

Autoimmunity

Due to genetic and other unknown reasons, the body attacks self-cells resulting in damage to the body. It is called auto-immune disease. E.g. Rheumatoid arthritis.

Allergies

• Exaggerated response of the immune system to some antigens present in the environment.
• Allergens: E.g. mites in dust, pollens, animal dander etc.
• Symptoms: Sneezing, watery eyes, running nose, difficult breathing, wheezing etc.
• Antibodies produced against the allergens are IgE type.
• Asthma is a respiratory disease due to allergy.
• Treatment: Drugs like anti-histamine, adrenaline and steroids quickly reduce the symptoms.
• Modern-day life style & protected environment provided early in life results in low immunity and more sensitivity to allergens. So children in metro cities suffer from allergies and asthma.

AIDS (Acquired Immuno Deficiency Syndrome)

It is caused by HIV (Human Immunodeficiency Virus), a retrovirus having RNA genome.

Transmission: Sexual contact with infected person, Transfusion of contaminated blood, Sharing of infected needles, From mother to child through placenta.

Diagnosis: ELISA test (Enzyme-linked immuno-sorbent Assay).

Treatment: Anti-retroviral drugs.

Prevention: Educate people about AIDS, Make blood safe from HIV, Use disposable needles and syringes, Condoms, Control drug abuse.

Replication of retrovirus:

Life cycle of HIV:

HIV enters body → To macrophages (acts as HIV factory) → RNA becomes viral DNA in presence of Reverse transcriptase → Viral DNA incorporates into host DNA→ produce virus particles → HIV enters helper T-cells (TH lymphocytes) → Replicates & produce progeny viruses → Attack other TH cells → TH cells decrease → Weaken immunity.

CANCER

It is an abnormal and uncontrolled multiplication of cells to form tumour.

Normal cells show contact inhibition (contact with other cells inhibits their uncontrolled growth). Cancer cells do not have this property.

Types of Tumours: 

• Benign tumours: Confined to the place of its origin. Cause little damage.
• Malignant tumours: Tumour cells (neoplastic cells) invade and damage surrounding tissues. Cells from tumours reach other sites via blood and form a new tumour. It is called metastasis.

Causes of cancer (Carcinogens): 

• Physical agents: Radiations like X-rays, gamma rays, UV etc.
• Chemical agents: Tobacco smoke, vinyl chloride, nicotine, etc.
• Biological agents: Oncogenic viruses, c-onc (cellular oncogenes or proto oncogenes) etc.

Cancer detection and diagnosis:

• Biopsy: Histopathological studies of suspected tissue.
• Imaging techniques: Radiography, CT scan & MRI.
• Use of antibodies against cancer-specific antigens.
• Molecular biology technique: To detect cancer related genes.

Treatment of cancer: 

• Radiotherapy
• Chemotherapy
• Immunotherapy
• Surgery.

DRUGS, SMOKING & ALCOHOL ABUSE

DRUGS 

1. Opioids: 

• E.g. morphine, heroin, brown sugar.
• Morphine is extracted from latex of Papaver somniferum (poppy plant). It is a sedative & painkiller. Used in surgery.
• Heroin (smack or diacetylmorphine) is obtained by acetylation of morphine. It is a depressant.

2. Cannabinoids:

• Obtained from Cannabis sativa (Hemp plant).
• Includes marijuana, hashish, charas & ganja.
• They affect cardiovascular system.

3. Coca alkaloid or cocaine (coke or crack):

• It is obtained from coca plant Erythroxylum coca.
• It interferes with transport of neurotransmitter dopamine.
• It stimulates CNS producing euphoria & increased energy.

SMOKING

• Tobacco contains nicotine etc.
• Smoking causes cancers of lung, urinary bladder and throat, bronchitis, emphysema, coronary heart disease, gastric ulcer etc. Tobacco chewing causes oral cancer.
• Smoking increases CO content in blood and reduces oxyhaemoglobin. This causes O2 deficiency in the body.

ADOLESCENCE & DRUG/ALCOHOL ABUSE 

Causes of drug/alcohol use in Adolescence

• Curiosity and Experimentation.
• Need for adventure and excitement.
• To escape facing problems.
• Stress from pressure to excel in academics or examination.
• Television, movies, newspapers, internet etc.
• Unstable or unsupportive family structures & peer pressure.

Addiction: Psychological attachment with drugs & alcohol.

Dependence: Body manifests unpleasant withdrawal syndrome if drugs/alcohol is abruptly discontinued. This results in anxiety, shakiness, nausea and sweating.

Effects of Drug/alcohol abuse

• Reckless behaviour, vandalism and violence.
• Coma and death.
• Damage of nervous system and liver cirrhosis.
• Causes mental and social distress to family and friends.
• Social problems like stealing and spread of diseases.
• Misuse of drugs by athletes.

Warning signs of drug/alcohol abuse in Adolescence period

• Drop in academic performance and absence from school.
• Lack of interest in personal hygiene.
• Withdrawal and isolation.
• Depression, fatigue, aggressive and rebellious behaviour.
• Loss of interest in hobbies.
• Deteriorating relationships with family and friends.

Side effects of anabolic steroid abuse

In males:

• Acne, premature baldness
• Mood swings & depression, increased aggressiveness.
• Reduced testicles & decreased sperms.
• Kidney & liver dysfunction.
• Enlargement of Breast & prostate gland.

In females:

• Masculinisation, excessive hair growth
• Mood swings & depression, increased aggressiveness
• Abnormal menstrual cycle, deepening of voice
• Enlargement of clitoris

Prevention and control

• Avoid undue peer pressure.
• Education and counselling.
• Seeking help from parents and peers.
• Looking for danger signs.
• Seeking professional and medical help. 
  
  

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