Human Health and Diseases

What is Health?

Health is the state of complete physical, mental, and social well being; increases productivity and ensures longevity

Ways to Ensure Good Health

Balanced diet

Personal hygiene

Exercise

Awareness about prevention and control of diseases

Proper waste disposal and control of vectors

Vaccination

Why do Diseases Occur?

Genetic reasons- innate deficiencies and inheritable defects

Infections

Sedentary life style- junk food; consumption of alcohol/drugs; lack of exercise

Pathogenic Diseases

Pathogens are the parasites that enter the human body through various means, then multiply, and interfere with normal vital activities

Typhoid (Bacterial)

Pathogen- Salmonella typhi

Transmission- Contaminated food and water

Site of Infection- small intestine

Symptoms- high fever, stomach pain, headache, loss of appetite, constipation, and intestinal perforations in severe cases

Diagnostics- Widal test

Pneumonia (Bacterial)

Pathogen- Streptococcus pneumoniae and Haemophilus influenzae

Transmission- Droplets/aerosols released from infected person, sharing of utensils or glasses

Site of Infection- Alveoli (gets filled with pus, dyspnea)

Symptoms- Fever, chills, cough, headache, lips and nails become grey in severe cases

Common cold (Viral)

Pathogen- Rhinovirus

Transmission- Nose and respiratory passage

Site of Infection- droplets released from coughing or sneezing, or fomites

Symptoms- nasal congestion and discharge, sore throat, cough, headache, tiredness

Malaria (Protozoan)

Pathogen- Plasmodium sps. (P. vivax, P. falciparum, P. malaria)

Transmission- Vector: Female Anopheles mosquito

Symptoms- high fever, chills

Amoebiasis (Protozoan)

Pathogen- Entamoeba histolytica

Transmission- Vector: housefly

Site of Infection- large intestine

Symptoms- constipation, abdominal pain, cramps, stools w/ mucous and blood clots

Ascariasis (Worm)

Pathogen- Round worm, Ascaris

Transmission- Water, vegetables, fruits contaminated by feces of infected person

Symptoms- internal bleeding, muscular pain, fever, anemia, blockage of intestinal passage

Elephantiasis/filariasis (Worm)

Pathogen- Wuchereria (W. malayi and W. bancrofti)

Transmission- Bite of female mosquito vector

Symptoms- chronic inflammation of the organs, usually the lymphatic vessels of lower limb

Plasmodium

requires 2 hosts to complete its life cycles

Step 3 of Plasmodium life cycle

parasites multiply via asexual reproduction in liver cells finally burst in liver cell; sporozoites are released in blood

Step 4 of Plasmodium life cycle

Parasites enter RBCs; sporozoites —→ gametocytes multiply; burst RBCs which releases toxic substance called haemozoin which gives fever and chills

Step 1 of Plasmodium life cycle

Female Anopheles mosquito bites healthy human being, releasing plasmodium which lives in body as sporozoite (infectious form); gametocytes are introduced to mosquito

Step 2 of Plasmodium life cycle

Gametocytes fertilise and develop inside the intestine of mosquito to form sporozoites which are stored in salivary glands of mosquito and are released into healthy person bitten by mosquito

What is immunity?

body’s ability to fight the disease causing organisms

Innate immunity

it is present from the time of birth; it is non-specific; consists of 4 barriers

Physical barriers

skin and mucus coating of respiratory, gastrointestinal, and urogenital tract prevent entry of microbes into body

Physiological barriers

stomach acid; saliva in mouth; tears from eyes

Cellular barriers

Blood has leukocytes such as polymorpho nucleur leukocytes, monocytes, etc., and tissue has macrophages which phagocytose the microbes

Cytokine barriers

special proteins called interferons are secreted by virus-infected cells that prevent the further spread of viral infection

Acquired Immunity

is produced in response to an encounter with a pathogen based on memory; pathogen specific

Primary response

when a pathogen for the first time infects a person —→ low intensity immune response is generated

Secondary response

when the same pathogen attacks again, intensified immune response is generated thereby preventing the occurrence of disease

B-lymphocytes

secrete proteins called antibodies in response to pathogens

Antibodies

specialized proteins w/ 4 peptide chains (2 light and 2 heavy) denoted as H2L2; e.g. IgA, IgM, IgE which generate humoral immune response found in blood

T-lymphocytes

help B-cells to produce antibodies; generate cell mediated immune response

Cell mediated immune response

response helps the body to differentiate between self and nonself as occurs in case of graft rejection

Active immunity

naturally acquired immunity produced in the host body in response to an antigen; e.g. immunization and body naturally getting immune to a microbe that had caused infection previously

Passive immunity

when ready made antibodies are provided to an individual to protect against foreign agents; colostrums present in mother’s milk contains IgA; fetus gets antibodies from mother thru placenta

How do vaccinations help?

Vaccines = inactivated pathogens; produce primary response when introduced into body and are produced against the pathogen —→ memory B-cells and T-cells are produced —→ when pathogen attacks again the memory cells generate massive immune response and pathogen is destroyed

Allergies

exaggerated immune response to certain antigens present in the environment; histamines and seratonins are released; symptoms include sneezing, watery eyes, dyspnea

Allergens

substances in response to which allergy is produced; e.g. dust, pollen

Allergy test

Patient is injected with small doses of allergens to monitor his response

Autoimmunity

body generates immune response against its own cells; reasons-genetic and other unknown reasons; e.g. rheumatoid arthritis is AI disease

Primary lymphoid organs

consist of bone marrow and thymus; immature lymphocytes are differentiated to form antigen sensitive lymphocytes

Bone marrow

all RBCs including lymphocytes are produced

Thymus

responsible for maturation of T-lymphocytes; lobed organ is situated near the heart and keeps on reducing in size as the age increases

Secondary lymphoid organs

Lymphocytes migrate here after attaining maturity; includes spleen, lymph nodes, tonsils, Peyer’s patches, and appendix

Spleen

large, bean shaped organ containing lymphocytes and phagocytes, which acts as a filter for blood

Lymph nodes

located at different points throughout the immune system; trap the antigens present in lymph or tissue fluid and these antigens cause activation of lymphocytes and generation of immune response

MALT

Mucousal-associated lymphoid tissue; lines major tracts (respiratory, digestive, urogenital); constitutes 50% of lymphoid tissue in body

How does AIDS spread?

Virus enters body and enters macrophages

Virus replicates; viral RNA reverse transcribes to viral DNA which gets incorporated into hosts DNA and subsequently new particles are produced

Macrophages become HIV factory

HIV enters T-lymphocytes, replicates, and produces progenies

As progenies release —→ T-lymphocytes are attacked

T-lymphocytes start decreasing in number and immune response of the person becomes weak

Diagnosis and Treatment of AIDS

ELISA; Enzyme Linked Immuno Sorbent Assay; no permanent care- antiretroviral therapies can prolong the life of patient

Oncogenic Transformation

normal cells have the property of contact inhibition (stoppage of growth on coming in contact w/ other cells) but cancer cells lose this property; uncontrollable division of cancer cells —→ tumors

Carcinogens

physical, chemical, and biological agents that cause cancer; e.g. ionizing radiations (X-rays and gamma rays), non ionizing radiations (UV)

Oncogenic

cancer-causing viruses; have viral cancer causing genes; sometimes normal genes in our body called proto-oncogenes get converted into cellular oncogenes that cause cancer

CT

computerized tomography; 3-D imaging of internals of an organ is generated by X-rays

MRI

magnetic resonance image; pathological and physiological changes in a living tissue are detected by using magnetic fields and non ionizing radiation

Radiotherapy

tumour cells are irradiated to death; proper care is taken for protecting surrounding normal tissues

Chemotherapy

drugs specific for particular tumors are used to kill cancer cells; have side effects like hair loss, anemia

Immunotherapy

biological response modifiers such as a-interferons are used; activate the immune system of patient and helps in destroying the tumor

Opioids (Heroin)

Source: Acetylation of morphine extracted from the latex of poppy plants (Papaver somniferum)

Consumed by: snorting or injection

Properties: white, bitter, and odorless

Mode of action: binds to opioid receptors present in the CNS and GI tract

Effect: depressant and slows down body function

Cannabinoids

Source: inflorescences of the plant Cannabis sativa

Consumed by: inhalation or oral inhalation

Mode of action: binds to cannabiniod receptors present in the brain

Effect: affects the cardiovascular system

Cocaine

Source: Coca plant Erythroxylum coca, found in South America

Consumed by: snorting

Mode of action: interference with transfer of neurotransmitter, dopamine

Effect: stimulates the CNS, producing a sense of euphoria and increased energy; excessive dosages cause hallucinations

Drugs normally used as meds

medicines used to help patients w/ mental illness and insomnia; e.g. barbiturates. amphetamines, benzodiazepines, LSD (Lysergic acid diethyl amides)

Morphine

pain killer for patients who have undergone surgery; also abused

Nicotine

Source: present in tobacco which is smoked, chewed, or snuffed

Mode of action: stimulates the adrenal gland to release adrenaline and nor-adrenaline

Effect: increases blood pressure and heart rate

Effects of smoking

Increased risk of diseases like bronchitis, emphysema, coronary heart disease, gastric ulcer, and cancer (throat, lung, and urinary bladder); increased CO levels in blood —→ O₂ deficiency

Anabolic steroidal effects in women

increase of masculinity, aggressiveness, depression, abnormal menstrual cycle, facial hair growth, enlargement of clitoris, deepening of voice

Anabolic steroidal effects in men

acne, aggressiveness, depression, reduction in size of testicles, decreased sperm production, enlargement of prostate gland, breast enlargement, premature baldness