biology

What is the main job of the First Line of Defence, and what are 3 examples of it?

• Main Job: To keep pathogens (germs) OUT of the body. It acts like a non-specific castle wall to block everything.

• Examples:

  1. Skin: A physical barrier that blocks germs.

  2. Stomach Acid / Tears: Chemical barriers that destroy germs.

  3. Mucus / Cilia: Microscopic traps and brooms that catch and sweep germs away.

2nd Line of Defence Flashcard

• Main Job: An active, non-specific response that destroys any pathogen that successfully breaks past the first line (like through a cut).

• 3 Main Weapons:

  1. Phagocytes: White blood cells that act like "Pac-Man" by engulfing and eating germs.

  2. Inflammation: Blood vessels widen so backup white blood cells can rush to the injury, causing redness and swelling.

  3. Fever: The brain turns up the heat to cook out pathogens and speed up your immune response.

What makes the Third Line of Defence different from the first two, and what are its main components?

• Difference: It is specific (targets a particular germ) and creates memory (gives you long-term immunity).

• Key Components:

  1. Antigens: The unique "name tags" on germs that the body detects.

  2. B Cells: White blood cells that create custom Y-shaped antibodies to bind and trap the germs.

  3. T Cells: White blood cells that hunt down and destroy infected cells.

  4. Memory Cells: Cells that stay in your body to wipe out the same germ instantly if it ever returns.

What is histamine and what does it do during the 2nd line of defence?

• What it is: A chemical emergency alarm released by damaged cells.

• What it does: It causes blood vessels to widen and become leaky.

• Why: This allows a massive rush of blood and "Pac-Man" white blood cells (phagocytes) to travel to the injury quickly to fight germs.

• Side effects: This rush of fluid causes inflammation (redness, heat, swelling, and pain).

what Are the 4 main pathogens

1. Bacteria (Living cells; killed by antibiotics; e.g., Strep throat)

2. Viruses (Non-living; hijacks cells; antibiotics don't work; e.g., Flu)

3. Fungi (Feeds on tissue in warm/damp places; e.g., Athlete's foot)

4. Parasites (Steal food/energy from inside or outside the host; e.g., Tapeworms)

non cellular pathogen

2. Non-Cellular Pathogen

A pathogen that is not made of cells and is considered non-living. It cannot reproduce on its own and must hijack a host cell to make copies of itself.

• Key word to remember: Non-living

• Examples: Viruses, Prions.

non-cellular: no cells (not alive)

cellular pathogen

1. Cellular Pathogen

A pathogen that is made up of living cells and has its own cellular machinery to reproduce and survive.

• Key word to remember: Living

• Examples: Bacteria, Fungi, Parasites.

Non-cellular = No cells (Not alive).

variation

Definition: Random genetic differences among pathogens that make some naturally weaker and others naturally stronger against medicine.

reproduction

Definition: When the surviving, tough pathogens multiply and pass their resistant genes to their offspring.

selection

• Definition: When a pressure (like an antibiotic) kills the weak pathogens, "selecting" the tough ones to survive.

evolution

Definition: A change in the pathogen population over time, where the whole group becomes resistant to a treatment.

how people become a immune to antibotics

 How it happens:

  1. Variation: A few bacteria randomly mutate to be naturally tough against the drug.

  2. Selection: Antibiotics kill the weak bacteria, leaving the tough ones alive (especially if you stop medicine early).

  3. Reproduction: The tough survivors multiply rapidly.

  4. Evolution: The entire population becomes a drug-resistant "superbug."

memory immunitiy

• Line of Defence: The 3rd Line of Defence.

• Specific: It creates custom-shaped antibodies to target one exact type of germ (using B and T cells).

• Memory: It leaves behind Memory Cells that remember the germ, allowing your body to destroy it instantly if it ever returns so you don't get sick twice.