Human Health and Disease

SYNOPSIS

•  Health is defined as a state of complete physical, mental and social well-being.
• Disease is a condition where malfunctioning of the body organs occurs leading to uneasiness and discomfort.
  
  
• Differences between Infectious Diseases and Non-Infectious Diseases
  
  

• Disease-causing organisms are called pathogens.

• Common Diseases in Humans
  
  

  Diseases	Pathogen	Signs and Symptoms
  Typhoid	Salmonella typhi	High fever, low pulse rate, abdominal pain, frequent stools
  Pneumonia	Streptococcus pneumoniae, Haemophilus influenzae	Lymph and mucus collect in the alveoli and bronchioles
  Common cold	Viruses like Rhino viruses	Nasal congestion and discharge, sore throat, hoarseness, cough, headache, tiredness
  Malaria	Plasmodium	Fever, restlessness, less appetite, slight sleeplessness, muscular pains, headache and feeling of chilliness
  Amoebiasis	Entamoeba histolytica	Blood along with faeces and abdominal pain
  Ascariasis	Ascaris	Obstruction of intestinal passage, abdominal discomfort
  Elephantiasis	Wuchereria bancrofti	Inflammation of lymphatic vessels of the lower limbs
  Ringworms	Microsporum, Trichophyton, Epidermophyton	Appearance of dry, scaly lesions on various parts of the body such as skin, nails and scalp

• Immunology is a branch of science which deals with the study of the immune system.

• Differences between Innate and Acquired Immunity
  
  

• Barriers of Innate Immunity
  
  

• Differences between B-cells and T-cells
  

• Differences between Antigen and Antibody
  
  

  Antigen	Antibody
  It is a substance which induces an immune response when introduced into an organism. It is a large molecule of protein or polysaccharide.	It is a plasma protein that is produced in response to the entry of an antigen in the body. It is a plasma protein.

• Humoral immune response: It operates by the production of humoral antibodies which circulate in the blood and lymph and react with foreign substances, thereby promoting their destruction.

• Cell-mediated immunity: It operates by the production of lymphocytes and macrophages which move in the blood and tissue and collectively destroy pathogenic organisms.

• Inflammation is the reaction of local tissue or blood to an injury or an infection.

• Primary immune response is developed as a result of the first encounter of the body with an antigen which is of low intensity.

• Secondary immune response is developed as a result of the subsequent encounter of the body with the same antigen.

• Active immunity is the immunity induced when a host is exposed to antigens, which may be in the form of living or dead microbes or other proteins and antibodies are produced in the host body.

• Passive immunity is the immunity induced when ready-made antibodies are directly given to protect the body against foreign agents.

• Difference between Active Immunisation and Passive Immunisation
  

  Active Immunisation	Passive Immunisation
  A person’s own body cells produce antibodies in response to the introduction of weakened or killed bacteria into the body by vaccination.	The antibodies produced in some other vertebrates are injected into the human body at the time of need to counteract antigens.
  This immunity arises slowly but lasts for a longer duration.	This immunity arises rapidly but lasts for a shorter duration.

• Vaccination is a preparation of antigenic proteins of pathogen or inactivated/weakened pathogen (vaccine) introduced into the body that produces antibodies against these antigens to neutralise the pathogenic agents during actual infection.

• Vaccines are weakened or dead pathogens which are injected into a person to stimulate the synthesis of antibodies against the antigen.

• Allergy is the hypersensitivity of the body to certain foreign substances.

• In autoimmunity, the immune system goes off track and turns against ‘self’ which leads to diseases called autoimmune diseases.

• Lymphoid organs are the organs where the maturation and proliferation of the lymphocytes take place. 
  
  Examples: Bone marrow, thymus, spleen, lymph nodes, mucosa-associated lymphoid tissue (MALT).

• AIDS – Acquired immunodeficiency syndrome
  

• Cancer is characterised by uncontrolled multiplication of cells. Cancerous cells continue to divide giving rise to masses of cells called tumours.

• Difference between Benign Tumour and Malignant Tumour:
  
  

• Metastasis is the transference of malignant tumour from a primary part to a secondary part of the body through the blood stream or lymph.

• Factors or agents which cause cancer are called carcinogens. Examples: X-rays, UV rays, chemicals like nicotine, tobacco etc.

• Interferons are the proteins released by the host cells in response to viral infections which make the unattacked cells less susceptible to viral infection.

• Diagnosis of cancer is done by monoclonal antibodies, blood tests, non-invasive techniques like X-rays, CT scans and MRI scans.

• Treatment of cancer includes surgery, radiation therapy, chemotherapy and immunotherapy.

• Addiction is the physical and mental dependence of the body on the certain substances like drugs.

• Opioids are drugs which bind to specific opioid receptors present in our central nervous system and gastrointestinal tract.

• Cannabinoids are a group of chemicals which interact with cannabinoid receptors present principally in the brain.

• Preventive Control Measures of Alcohol and Drug Abuse