A man is walking for a mile. A thorn pricks his leg so suddenly he bows down. At that time he gets sudden sparking pain at his back. This is due to sudden change in the position of back body muscles. Explain it.

This scenario explained in the question is related to reflex action. The stimulus by the prick of the thorn is received by the skin receptors. This stimulates the sensory neurons and carries the signals to the reflex arc present in the spinal cord. The interneurons carry this signal to the brain. The message is then interpreted in the brain and the motor neurons then send the signal to the effector organ. This response enables the person to remove his leg with a jerk to avoid pain due to pricking. However, this sudden jerk causes the spontaneous contraction of the muscles of the back which causes muscle spasm.

What is exogenous phase in the lifecycle of Ascaris ?

Ascaris belongs to Helminthes and is an intestinal endoparasite. Their primary host are humans. Exogenous phase in the lifecycle of Ascaris indicates the temporary stage outside the primary host body. They are released as embryonated eggs and through the food, water, and soil infect children and adults.

Explain the prevention of graft rejection in the clinical field.

Graft rejection occurs when the immune system of the recipient attacks the donated graft and begins destroying the transplanted tissue or organ. In this rejection response, the immune response is usually triggered by the presence of the donor's own unique set of proteins (HLA), which the recipient's immune system will identify as foreign. The degree of similarity between the HLA genes of the donor and recipient is known as histocompatibility or tissue compatibility; the more genetically compatible the donor and the recipient, the more tolerant the recipient’s immune system to the graft. Prevention of graft rejection can be achieved by inhibiting the action of immune cells towards the graff. As it is now known that T cells play a central role in the specific immune response, strategies to prevent T cell activation or function are thus all potentially useful for immunosuppression. Standard immunosuppressive therapy consists of baseline therapy to prevent rejection and short courses of high-dose corticosteroids or monoclonal or polyclonal antibodies. Triple-drug therapy with the combination of cyclosporin, corticosteroids and azathioprine is now the most frequently used immunosuppressive drug in certain transplantation (primarily kidney). Other compounds that are now entering routine clinical practice for immunosuppression are tacrolimus (mode of action similar to cyclosporin), mycophenolate mofetil and mizoribine (which inhibit the enzyme inosine monophosphate dehydrogenase, the rate-limiting enzyme for de no vo purine (a group of nitrogenous base) synthesis during cell division), and sirolimus.

How will a doctor identify that the host body has rejected a graft?

Grafting or organ transplantation is a medical procedure in which an organ is removed from one body and placed in the body of a recipient, to replace a damaged or missing organ. Graft rejection occurs when the recipient's immune system attacks the donated graft and begins destroying the transplanted tissue or organ. The immune response is usually triggered by the presence of the donor's own unique set of HLA (Human Leucocyte Antigen) proteins, which the recipient's immune system will identify as foreign. The following conditions indicate that the host body has rejected a graft: The organ's function may start to decrease. General discomfort, uneasiness. Pain or swelling in the area of the organ. Fever Flu-like symptoms, including chills, body aches, nausea, cough, and shortness of breath.

Explain the viral diseases in human beings.

The most common viral diseases encountered by humans are as follows: 1. Common cold Causative agent: Rhinovirus Symptoms: Nasal congestion and discharge, sore throat, cough and headache. 2. Mumps Causative agent: Paramyxovirus Symptoms: Enlargement of the parotid glands. 3. Measles Causative agent: Rubella virus Symptoms: Sore throat, running nose, cough, fever, reddish rashes on the skin, neck and ears. 4. Viral hepatitis Causative agent: Hepatitis A virus, hepatitis B virus, Hepatitis C virus Symptoms: Liver damage, jaundice, nausea, yellowish eyes, fever and pain in the abdomen. 5. Dengue fever Causative agent: Dengue virus or Flavi virus Symptoms: Headache, muscle and joint pain, onset of fever. 6. Chikungunya Causative agent: Alpha virus Symptoms: Fever, joint pain and swelling, headache. 7. Poliomyelitis Causative agent: Poliovirus Symptoms: Muscular stiffness, paralysis, respiratory failure, fever. 8. Encephalitis Causative agent: Herpes Simplex Virus Symptoms: Headache, mild flu-like symptoms (aches, fatigue, slight fever), sensitivity to light, neck stiffness, sleepiness or lethargy. 9. Chickenpox: Causative agent: Varicella-Zoster virus Symptoms: Fever with itchy skin, rashes and blisters. 10. AIDS: Causative agent: Human immuno virus Symptoms: Rapid weight loss, recurring fever or profuse night sweats, extreme and unexplained tiredness, prolonged swelling of the lymph glands in the armpits, groin, or neck, pneumonia, etc.