Bio Body Reponse Notes

Graph

Skin is broken. Non-specific immune response occurs. This is an example of mechanical damage.
Specialised leukocytes, mast cells, are activated and cause several chemicals to be released, such as:
- histamine:
  - Increases blood flow to the area through vasodilation.
  - Walls of capillaries become more permeable.
  - Result: Increased blood flow, indicated by redness and heat.
    - Escape of fluid causes swelling.
- heparin: Prevents clotting in the immediate area of injury.
Chemicals released by most cells increase phagocytes to the area
$\to$ engulf micro-organisms + cell debris.
Damaged tissue stimulate pain receptors causing pain.
Dead phagocytes and tissues fluid form pus (a yellowy fluid)
New cells are formed by mitosis repair tissue.

Pathogens infecting the body result in the elevation of high temperature, called a fever.
Due to infection, the hypothalamus sets the body temperature to a higher point (new set point)
The infected person feels cold causing:
- Shiver: Muscles contract + relax to generate heat
- Vasoconstriction(in the skin): blood vessels marrow to reduce blood flow and conserve heat.
- Result: body temperature increases.
Eventually the fever breaks, called the crisis, so the hypothalamus resets body temperature to normal ($36.4 \degree C$)
The person feels hot, so:
- Sweating: Evaporation of sweat cools the body down.
- Vasodilation in skin: blood vessels widen to increase heat loss by radiation, conduction (+2% convection)
Body cools down.
Purpose of the fever is to kill of the pathogens.