The following answers correspond to the questions from CYU 3.6 in the Science Probe textbook.
Protecting The Body – CYU 3.6
1) Pathogens are a threat to the body because they interfere with the normal functioning of body cells or they produce toxins that prevent normal functioning of body systems. Pathogens = a micro-organism such as bacteria that causes disease.
2) The 3 lines of defense the body uses to fight infection are:
1st : Physical Barriers such as the skin and ear wax, hairs, and mucus. The skin also produces acidic secretions and sweat that prevent micro-organisms from growing.
2nd: Circulatory System and White Blood Cells – the white blood cells patrol the body and seek out pathogens to destroy.
3rd: Immune System – all foreign organisms contain or produce a chemical called an antigen. The antigen signals the body to produce antibodies. Each antigen causes the production of a specific antibody that attaches only to this antigen. The use of antibodies to fight a pathogen is called an IMMUNE RESPONSE.
3) The electron micrograph in Fig. 9 shows a white blood cell attacking bacteria with its pseudopods. The bacteria will eventually become engulfed as the body’s second line of defense completes its mission to destroy the pathogen.
4) Both Amoeba and specialized white blood cells in the human defense system use projections of their cytoplasm called pseudopods (false feet), to capture, engulf and destroy micro-organisms.
5) Antibodies protect the body from attack by locking onto markers/antigens on the surface of the bacteria, virus or toxin. This prevents the bacteria or virus from attacking the cells and it prevents the toxin from interfering with the normal functioning of cells.
6) We can become immune to a disease by becoming exposed to the pathogen that causes the disease and developing antibodies or by being vaccinated so that our bodies can produce the antibodies before we are exposed to the disease. Vaccinations expose your body to a small amount of a particular pathogen – not enough to do damage – just enough to stimulate your body to produce antibodies that will lock onto the antigens and destroy the invader. Mothers pass on certain immunities to their children in the womb and through breast milk.