Inflammation and Innate Defenses

Inflammation

• Hitting your finger with a hammer leads to:
  • Swelling
  • Redness
  • Heat
  • Pain
  • Temporary loss of function due to pain and swelling.

Cardinal Signs of Inflammation

• Four Cardinal Signs:
  • Swelling (Edema)
  • Redness (Erythema)
  • Heat
  • Pain
• Fifth Cardinal Sign:
  • Temporary loss of function

Causes of Redness and Heat

• Increase in blood flow due to vasodilation.
  • Vasodilation: Relaxation of smooth muscles around capillaries.

Causes of Swelling (Edema)

• Leakage in blood vessels leading to fluid accumulation in the interstitial fluid (IF).
  • Plasma proteins leak out of the vessel into the ICF (Intracellular fluid).
  • Excess fluid in the ICF causes swelling due to osmotic pressure.

Chemical Messengers and Pain

• White blood cells (specifically basophils) signal for help by releasing:
  • Histamine
  • Prostaglandins
• Histamine and Prostaglandins:
  • Chemical messengers trigger pain receptors.
  • Action potentials travel to pain receptors, causing the feeling of pain.

Swelling Explained

• Swelling is due to:
  • Leaky capillaries.
  • Plasma proteins exiting the capillaries and entering the ICF.
  • Increased osmotic pressure in the ICF, leading to increased fluid volume and swelling.

Innate Defenses

• Two types of defenses:
  • Innate
  • Adaptive

Innate Defenses: Surface Barriers

• Surface barriers:
  • Skin
  • Mucous membranes

Innate Defenses: Internal Defenses

• Internal defenses:
  • Phagocytes
  • Antimicrobial proteins
    • Interferons
    • Complements

Interferons

• Interferons: Block viral replication.
  • Secreted when a cell dies due to a virus.
  • Signals nearby cells to stop replicating the virus.
  • Binds to nearby cells to block viral replication.

Complements

• Complements: Membrane Attack.
  • Punctures a hole in the cell membrane of the target cell.
  • Lyses the target cell (breaks it down) by allowing water to enter and cell contents to leave.
  • H_2O enters, cell contents leave.

Innate vs. Adaptive Defenses

• Innate:
  • Born with it.
  • No significant changes.
  • Rapid response.
  • No memory.
  • Includes surface barriers and internal defenses.
• Adaptive:
  • Slow