Defence against diseases Flashcards
(18 cards)
What is a disease?
A particular kind of illness with characteristic symptoms
Three types of causes of disease
Genetic, environmental and infection with a pathogen
All bacterial pathogens belong to the domain __________
Eubacteria
Describe the body’s primary defense mechanisms
Skin - a hard layer of dead cells made of protein keratin. Hard for pathogens to pass through.
Sebaceous glands - secrete sebum lower pH and keep skin moist. Low pH inhibits bacterial growth
Mucous membranes - trap foreign particles and prevent them from entering the body
How does the process of blood clotting take place
Platelets aggregate at the site of cut or injury and release clotting factors such as the enzyme thrombin. Thrombin converts fibrinogen ( soluble) to insoluble fibrin which forms a mesh-like structure which traps platelets to form a plug. Clot is gel and then hardens on exposure to air
Differences between innate and adaptive immune system
Innate - inbuilt, broad and general, does not change. Phagocytes
Adaptive - Specific pathogen protection on the basis of memory from previous infections. Antibody producing lymphocytes
Why is pus a sign of infection
Pus consists of a large number of phagocytes. When a wound is infected phagocytes squeeze out through the walls of capillaries and engulf pathogens through endocytosis.
Lymphoctyes shape and function
Circular nucleus little cytoplasm produce antibodies - large proteins that help destroy pathogens
Parts of an antibody
Hypervariable region - recognises and binds to molecule
Other region which prevents infection by
- making pathogen easily recognisable for phagocytes to engulf
Preventing viruses from binding onto host cells
Describe the process of antigen-antibody binding
Specific antibodies are produced in reaction the presence of an antigen. The antibodies bind to an antigen. The binding is dependant on matching shapes and sizes and chemical properties. There is extreme specificity in binding. One antibody for one antigen. Irreversible binding. Binds to hypervariable region which varies from antibody to antibody.
Describe the process of reaction to pathogen
Pathogen ingested by macrophage and antibodies displayed
- T-helper cells with the right receptor proteins bind and get activated
- B lymphocytes with the right receptor proteins bind and get activated
- Theu divide and clone and grow in size and develop an extensive endoplasmic reticulum and large golgi. These are called Plasma B cells.
- Some B cells don’t activate and act as memory cells for future infection
How does the HIV virus destroy the immune response
The HIV virus invades and destroys helper T-cells leading to progressive loss of the capacity to produce antibodies. The body’s antibody production becomes so ineffective that it can contract a number of diseases and infections that could easily be fought off by someone HIV-negative. Leads to AIDS
How do antibiotics not harm human cells and why do they not work against viruses?
Antibiotics are used to combat bacterial infections. It blocks the processes of prokaryotic cells without harming eukaryotic cells therefore doesn’t harm human cells. It targets replication processes of bacteria. Saprotorphic fungi produce antibodies to sabotage bacterial competition for nutrition.
Cannot work against viruses because they use human cells to function.
What is bacterial resistance
Bacteria are becoming resistant to antibiotics. They are evolving and developing new strains that can fight or evade the antibiotics used.
How can we fight bacterial resistance
- Prescription of antibiotics should not be given casually
- Hospital staff must maintain hight standards of hygiene to prevent cross-infection.
- Farmers should avoid use of antibiotics for fodder
- new classes of antibiotics should be developed
What is zoonosis
a disease that can be transmitted to humans from other animals in natural circumstances
What is immunization
Vaccination uses live, weakened or dead bacteria to trigger an immune response.
What is herd immunity
Herd immunity occurs when a significant portion of a population has already been vaccinated. ( 1 - 1/R) x 100. With R being average number of people that an infected person infects.
