Biology: Health and Diseases

Here are some study notes

• Biology, though younger than physics and chemistry, significantly contributes to human welfare, notably in health and agriculture since the 20th century.
• Discoveries such as antibiotics, synthetic drugs, and anesthetics have reshaped medical practices, improved human health, and increased life expectancy.
• Changes in agriculture, food processing, and diagnostics have led to socio-cultural shifts in communities.
• Health is defined as complete physical, mental, and social well-being.
• Good health improves work efficiency, boosts economic prosperity, increases longevity, and reduces infant and maternal mortality.
• A balanced diet, personal hygiene, and regular exercise, including Yoga, are vital for maintaining health.
• Disease is when one or more bodily systems are adversely affected, marked by signs and symptoms.
• Diseases are broadly classified as infectious and non-infectious, with infectious diseases being easily transmittable.
• AIDS and cancer are major causes of death.
• Drug and alcohol abuse negatively impact health.

Common Diseases in Humans

• Diseases in humans are caused by a wide range of organisms, including bacteria, viruses, fungi, protozoans, and helminths, which are known as pathogens.
• Pathogens, often parasites, harm the host by living in or on them and must adapt to the host environment to survive.
• Salmonella typhi, a pathogenic bacterium, causes typhoid fever.
• Symptoms of typhoid include sustained high fever (39° to 40°C), weakness, stomach pain, constipation, headache, and loss of appetite.
• Severe cases of typhoid can result in intestinal perforation and death, and typhoid fever is confirmed through the Widal test.
• "Typhoid Mary" (Mary Mallon) was a cook who spread typhoid fever for years through contaminated food.
• Bacteria like Streptococcus pneumoniae and Haemophilus influenzae are responsible for pneumonia.
• Pneumonia infects the alveoli of the lungs, causing them to fill with fluid and leading to respiratory problems; Symptoms include fever, chills, cough, and headache.
• Pneumonia is transmitted through inhaling droplets/aerosols or sharing utensils with an infected person.
• Viruses, such as rhinoviruses, cause the common cold, which affects the nose and respiratory passage but not the lungs; Symptoms include nasal congestion, sore throat, cough, and headache.
• The common cold typically lasts 3-7 days and spreads through inhaled droplets or contaminated objects.
• Malaria is caused by the protozoan Plasmodium, with different species (P. vivax, P. malaria, P. falciparum) causing different types of malaria.
• Malignant malaria, caused by Plasmodium falciparum, is the most serious and potentially fatal form.
• Plasmodium's life cycle involves the human body and female Anopheles mosquitoes.
• Plasmodium enters humans as sporozoites through mosquito bites, multiplies in liver cells, and then attacks red blood cells (RBCs), leading to their rupture.
• The rupture of RBCs releases haemozoin, causing recurring chills and high fever, and the parasite then enters the mosquito's body through a bite on an infected person, completes development, and forms sporozoites in salivary glands.
• Female Anopheles mosquitoes transmit the sporozoites to new human hosts, and acts as the vector because it transmits the disease.
• Entamoeba histolytica is a protozoan parasite that causes amoebiasis (amoebic dysentery) in the large intestine.
• Amoebiasis symptoms include constipation, abdominal pain, cramps, and stools with excess mucous and blood clots.
• Houseflies act as mechanical carriers to transmit the parasite from faeces of an infected person to food.
• Ascaris and Wuchereria are helminths pathogenic to humans, where Ascaris causes ascariasis through intestinal parasite.
• Ascariasis symptoms include internal bleeding, muscular pain, fever, anemia, and blockage of the intestinal passage.
• Infection occurs through contaminated water, vegetables, and fruits. Wuchereria (W. bancrofti and W. malayi) causes elephantiasis or filariasis, leading to chronic inflammation, typically affecting lymphatic vessels in lower limbs, and spreads through mosquito vectors.
• Ringworm, caused by fungi (Microsporum, Trichophyton, and Epidermophyton), is a common infectious disease characterized by dry, scaly lesions on skin, nails, and scalp, accompanied by intense itching.

Hygiene for Disease Prevention

• Maintaining personal and public hygiene is crucial for preventing infectious diseases.
• Personal hygiene involves keeping the body clean and consuming clean water, food, vegetables, and fruits.
• Public hygiene includes proper waste disposal, periodic cleaning and disinfection of water reservoirs, and observing hygiene practices in public catering.
• Close contact with infected individuals should be avoided.
• Controlling and eliminating insect vectors and their breeding places is important for vector-borne diseases like malaria and filariasis.
• Advancements in biological science, such as vaccines and immunization programs, have helped eradicate or control infectious diseases like smallpox, polio, diphtheria, pneumonia, and tetanus.
• Biotechnology is developing newer and safer vaccines, while antibiotics and other drugs have enhanced the treatment of infectious diseases.

Immunity

• Immunity is the overall ability of a host to fight disease-causing organisms, conferred by the immune system which is of two types: (i) Innate immunity and (ii) Acquired immunity.
• Innate immunity is non-specific and present from birth, involving various barriers like physical, physiological, cellular and cytokine barriers:
• Physical barriers: Include skin and mucus coating in the respiratory, gastrointestinal, and urogenital tracts.
• Physiological barriers: Involve acid in the stomach, saliva in the mouth, and tears from the eyes.
• Cellular barriers: Involve leukocytes like neutrophils, monocytes, natural killer cells, and macrophages.
• Cytokine barriers: Involve virus-infected cells secreting interferons.
• Acquired immunity is pathogen-specific and characterized by memory.
• The first encounter produces a low-intensity primary response, while subsequent encounters elicit a highly intensified secondary response.
• B-lymphocytes produce antibodies to fight pathogens, while T-cells assist B-cells, recognizing pathogens quickly and overwhelming invaders through massive antibody production.
• Antibodies are of different types: IgA, IgM, IgE, IgG - each antibody molecule has four peptide chains, two light and two heavy chains, and is represented as H2L2.
• The response is called a humoral immune response.
• T-lymphocytes mediate CMI (cell-mediated immunity).
• Grafts from just any source cannot be made since the grafts would be rejected sooner or later.
• Tissue matching and blood group matching are essential for organ transplantation, and patients require immunosuppressants to prevent graft rejection.
• The body differentiates between ‘self' and ‘nonself,’ with cell-mediated immune response responsible for graft rejection.
• Active immunity develops when the body produces antibodies in response to antigens found in microbes/proteins.
• This process is slow and takes time that comes from immunisation or natural infection.
• Passive immunity is when ready-made antibodies are directly given to protect against foreign agents.
• Mother's milk (colostrum) has abundant antibodies (IgA) to protect the infant.
• The foetus also receives antibodies from the mother during pregnancy.
• Immunisation or vaccination relies on the immune system's memory; antigenic proteins or weakened pathogens (vaccine) are introduced to stimulate antibody production.
• Vaccines generate memory B and T-cells to quickly recognize and neutralize pathogens upon subsequent exposure
• In critical cases like tetanus or snakebites, preformed antibodies (antitoxin) or antibodies against the venom are directly injected.
• Passive immunisation occurs with the injection of preformed antibodies
• Recombinant DNA technology has facilitated large-scale production of antigenic polypeptides in bacteria or yeast, such as the hepatitis B vaccine produced from yeast.

Allergies and Autoimmunity

• Allergy is an exaggerated immune response to environmental antigens (allergens), such as pollen and mites.
• Antibodies produced are of the IgE type, leading to symptoms like sneezing, watery eyes, and difficulty in breathing.
• Allergy results from the release of chemicals like histamine and serotonin.
• Determining the cause involves exposing the patient to small doses of possible allergens, and antihistamines, adrenalin, and steroids are used to quickly reduce symptoms.
• Modern lifestyle has lowered immunity, increasing sensitivity to allergens.
• The ability to differentiate foreign organisms from self-cells underlies acquired immunity.
• Higher vertebrates can distinguish foreign molecules, which is dealt with in experimental immunology.
• Due to genetic or unknown reasons, the body attacks self-cells, resulting in autoimmune diseases like rheumatoid arthritis.

Immune System in the Body

• The human immune system consists of lymphoid organs, tissues, cells, and soluble molecules like antibodies.
• The immune system recognizes foreign antigens, responds to them, and remembers them, playing roles in allergic reactions, autoimmune diseases, and organ transplantation.
• Lymphoid organs are where lymphocytes originate, mature, and proliferate, including primary lymphoid organs like bone marrow and the thymus.
• Immature lymphocytes differentiate in the bone marrow and thymus into antigen-sensitive lymphocytes.
• After maturation, lymphocytes migrate to secondary lymphoid organs like the spleen, lymph nodes, tonsils, Peyer's patches in the small intestine, and the appendix.
• Secondary lymphoid organs facilitate lymphocyte interaction with antigens, which then proliferate into effector cells.
• The bone marrow is the main lymphoid organ where all blood cells, including lymphocytes, are produced.
• The thymus, a lobed organ near the heart, reduces in size with age and provides micro-environments for T-lymphocyte development.
• The spleen, a bean-shaped organ, mainly contains lymphocytes and phagocytes and acts as a blood filter and erythrocyte reservoir.
• Lymph nodes trap micro-organisms or antigens and activate lymphocytes, triggering an immune response.
• Mucosa-associated lymphoid tissue (MALT) is located within the lining of major tracts (respiratory, digestive, urogenital) and accounts for approximately 50% of the body's lymphoid tissue.
• AIDS (Acquired Immuno Deficiency Syndrome) is a deficiency of the immune system acquired during an individual's lifetime.
• AIDS was first reported in 1981 and has killed over 25 million people worldwide.

AIDS (Acquired Immuno Deficiency Syndrome)

• AIDS is caused by the Human Immuno deficiency Virus (HIV), which is a retrovirus containing RNA and spreads through:
  • Sexual contact with an infected person.
  • Transfusion of contaminated blood and blood products.
  • Sharing infected needles.
  • From infected mother to child through the placenta.
• High-risk individuals include those with multiple sexual partners, IV drug users, transfusion recipients, and children born to infected mothers.
• HIV/AIDS is not spread by mere touch but through body fluids, requiring the infected to not be isolated from society.
• There is a lag between infection and AIDS symptom appearance, varying from months to years (typically 5-10 years).
• After entering the body, HIV infects macrophages, using reverse transcriptase to create viral DNA from its RNA genome.
• Macrophages act as HIV factories, while also infecting helper T-lymphocytes (Tʜ cells), causing a progressive decline in their numbers.
• As Tʜ cell counts decrease, infected individuals suffer from fever, diarrhoea, weight loss, and become susceptible to infections.
• A diagnostic test for AIDS is enzyme-linked immuno-sorbent assay (ELISA), and treatment with anti-retroviral drugs is only partially effective, prolonging but not preventing death.
• AIDS prevention includes safe blood transfusions, disposable needles, condom distribution, drug abuse control, safe sex promotion, and regular check-ups.
• National AIDS Control Organisation (NACO) and WHO educate people about AIDS.
• HIV/AIDS-infected individuals need support, and society must address the issue collectively to prevent its spread.

Cancer

• Cancer is a leading cause of death worldwide due to the mechanisms underlying oncogenic transformation.
• Cancer research focus is on treatment and control.
• Cell growth and differentiation is regulated, and cancer cells disrupt this regulation by losing contact inhibition, leading to tumor formation.
• Tumors are benign (localized) or malignant (invading and damaging surrounding tissues), dividing continuously and starving normal cells.
• Metastasis occurs when cells from malignant tumors spread to distant sites, forming new tumors which serves as one of the most feared aspects of it.
• Carcinogens (physical, chemical, biological agents) induce transformation of normal cells, where ionising and non-ionizing radiations cause DNA damage.
• Chemical carcinogens in tobacco smoke are a major cause of lung cancer.
• Oncogenic viruses have viral oncogenes, and cellular oncogenes can lead to oncogenic transformation.
• Early detection of cancer is based on biopsy, histopathological studies, blood and bone marrow tests, radiography, CT scans, and MRI.
• Biopsy involves examining stained tissue under a microscope.
• CT scans use X-rays for three-dimensional imaging, and MRI uses magnetic fields to detect pathological changes.
• Antibodies against cancer-specific antigens and molecular biology techniques are used for cancer detection.
• Cancer treatments: Surgery, radiation therapy, and immunotherapy.
• Radiotherapy uses lethal irradiation of tumor cells, and chemotherapy uses drugs to kill cancer cells.
• Most cancers require a combination of surgery, radiotherapy, and chemotherapy.
• Biological response modifiers like α-interferon activate the immune system to destroy tumors.

Drugs and Alcohol Abuse

• Drug and alcohol use, on the rise among youth, is a cause for concern, requiring education and guidance.
• Common abused drugs include opioids, cannabinoids, and coca alkaloids, mostly from flowering plants or fungi.
• Opioids bind to receptors in the central nervous system and gastrointestinal tract.
• Heroin (smack) is a diacetylmorphine obtained from acetylation of morphine, derived from the opium poppy (Papaver somniferum).
• Heroin is a depressant, slowing down body functions, and generally taken by snorting or injection.
• Cannabinoids, from Cannabis sativa, affect the brain and are used to produce marijuana, hashish, charas, and ganja.
• They are generally taken by inhalation or oral ingestion, and cause effects on the cardiovascular system.
• Coca alkaloids (cocaine) from Erythroxylum coca interfere with dopamine transport.
• Cocaine (coke/crack) is snorted and acts as a CNS stimulant, producing euphoria and increased energy with hallucinogenic effects causing hallucinations.
• Other hallucinogens include Atropa belladona and Datura.
• These days cannabinoids are also being abused by some sportspersons.
• Barbiturates, amphetamines, and benzodiazepines are also often misused, alongside morphine and other plants/seeds with hallucinogenic properties.
• Drug abuse involves using these substances outside of medicinal use, which impairs physical, physiological, and psychological functions.
• Smoking also paves the way to hard drugs, and tobacco use has been around for over 400 years.
• Tobacco contains chemicals including nicotine (an alkaloid) which stimulates the adrenal gland, increasing blood pressure and heart rate.
• Smoking increases the risk of cancers (lung, bladder, throat), bronchitis, emphysema, heart disease, and gastric ulcer, and oral cancer from chewing.
• Smoking increases blood carbon monoxide, reducing oxygen levels, and cigarette packets contain statutory warnings.

Adolescence and Drug/Alcohol Abuse

• Adolescence is the period (12-18 years) and process of maturing towards societal participation, bridging childhood and adulthood.
• Adolescence is accompanied by biological/behavioural changes, representing a vulnerable phase.
• Experimentation is motivated by the need for adventure and excitement to be able to escape facing problems.
• Significant role is played from the stress from academics or exams.
• The perception that it is cool uses drugs and alcohol is also a cause that are also affected by TV, movies, newspapers, and internet.
• Influencing factors include unstable family structures and peer pressure
• Addiction is a psychological attachment to effects like euphoria linked with drugs/alcohol and can be self-destructive.
• Repeated use increases tolerance, requiring higher doses and leading to addiction, with potential for addiction occurring even once.
• Dependence causes withdrawal syndrome(anxiety and sweating)
• Dependence can cause social adjustment problems as well.
• Immediate drug/alcohol effects: reckless behaviour, vandalism, and violence, to heart failure/cerebral hemorrhage.
• Drug/alcohol abuse effects: declining grades, absence, lack of hygiene, aggressive/rebellious behaviour, and deteriorating relationships.
• Long-term effects: addiction and brain failure.
• Long-term results can be seen with stealing.
• Sharing needles intravenously lead to higher risks of contracting AIDS or hepatitis B.
• Teenage drinking leads to long-term use, resulting damages to the nervous and liver systems, affecting foetal development in pregnancy.
• Muscle bulk and promoting more energy causes athletic to misuse drugs.
• Side-effects: Increase in more aggressive, body acne, and early end of the long bones.

Prevention and Control

• "Prevention is better than cure" as stated years prior.
• More prevalent at a young age, taking alcohol or smoking.
• Should identify problems for more assistance over that process and remedial actions as soon as one can detect it.
• Associated family's should discipline and parenting for lowers of substance or alcohol abuse.
• It is important to avoid peer pressure - every child have the same as the others.
  • Educating and counselling should accept failures/disappointments.
  • There are also good ways to push that kind of energy, channeling them into healthy hobbies such as reading, music, sports, yoga, etc.
• Should immediately let the parents/peers know about something to find them the right solution.
• It can be friends/close.
  • It'll give advises to sort out problems to vent more anxiety or pain that needs to be released. Looking For Danger Signs - Identify and find the symptoms.
• It better that they let know, instead of using drug or using alcohol.
• You can help with appropriate steps or medical solutions. Seeking professional and medical help
• Helpful with getting psychologists to help rehabilitate the person
• Medical support is also good with them getting the power to do so that it won't happen again.