Defence Mechanisms

• What are defence mechanisms in the body?

  They are the body's ways to fight pathogens.
• How does surface area influence the rate of diffusion in cells?

  A larger surface area increases the rate of diffusion.
• What happens to a plant cell placed in a solution with a lower water potential?

  The plant cell loses water and becomes flaccid.
• What role does sodium play in glucose transport in the ileum?

  Sodium ions create a gradient for glucose transport.
• What are the main defence mechanisms of the body?

  • General immediate defences: skin, phagocytosis
  • Specific defences: lymphocytes
  • Cell-mediated responses (T lymphocytes)
  • Humoral responses (B lymphocytes)
• Why do some people survive infectious diseases while others do not?

  Differences occur due to interactions with pathogens.
• What happens if pathogens overpower the body's defences?

  The individual may die from the infection.
• What occurs if the body's defences overpower pathogens?

  The person recovers and gains immunity.
• How do lymphocytes distinguish between self and non-self cells?

  They recognize unique surface molecules on cells.
• What happens if lymphocytes cannot distinguish self from non-self?

  They would attack the body's own tissues.
• What are the unique surface molecules on cells primarily made of?

  They are primarily made of proteins.
• What types of harmful threats does the immune system identify?

  Pathogens, toxins, and abnormal body cells.
• How does the immune system respond to transplant tissues?

  It identifies them as non-self and tries to destroy them.
• How can rejection of donor tissues be minimized?

  By closely matching donor tissues to recipients.
• What is the role of immunosuppressant drugs?

  They reduce immune responses to transplants.
• How many different types of lymphocytes exist?

  Approximately ten million different types.
• What happens when a specific lymphocyte binds to a pathogen?

  It undergoes clonal selection and divides rapidly.
• Why is there a time lag between pathogen exposure and immune response?

  Due to the time taken for clonal selection.
• How do lymphocytes recognize self-cells in the fetus?

  They encounter mainly self-cells due to maternal protection.
• What happens to lymphocytes with receptors matching self-cells?

  They are eliminated or suppressed.
• What occurs to lymphocytes reacting to self-antigens in adults?

  They undergo apoptosis before maturing.
• What is the result of eliminating self-reactive lymphocytes?

  Only non-self-reactive lymphocytes circulate in blood.
• How do lymphocytes recognize foreign material in adults?

  They encounter self-antigens in the bone marrow.
• What happens to lymphocytes that react to self-antigens?

  They undergo apoptosis before maturing.
• What is the significance of lymphocytes not appearing in the bloodstream?

  It ensures only non-self-reactive lymphocytes are present.
• How do lymphocytes primarily encounter the body’s own cells in the fetus?

  Through constant collisions with cells in a protected environment.
• What happens to self-reactive lymphocytes in the fetus?

  They either die or are suppressed.
• What is the outcome for lymphocytes that only recognize foreign material?

  They remain active and respond to non-self.
• How do lymphocytes recognize unique chemical shapes?

  Each lymphocyte has specific surface proteins.
• What is the role of apoptosis in lymphocyte maturation?

  It eliminates self-reactive lymphocytes.
• How does the immune system ensure effective responses to pathogens?

  By maintaining a diverse population of lymphocytes.
• What is the significance of lymphocyte diversity in the immune response?

  It allows recognition of various pathogens.