The immune system functions to protect against microscopic organisms and foreign substances that enter from outside the body and against some cancer cells that arise within.
Learning Goal 3
Communication between cells is required to coordinate their diverse activities. Cells may secrete molecules that spread locally to nearby cells or that are carried in the bloodstream to cells throughout the body. Nerve cells transmit electrochemical signals that carry information much more rapidly than is possible by diffusion or blood flow.
Learning Goal 5
Some drugs mimic or block the molecules involved in communication between cells and therefore affect operations of the brain and body.
Learning Goal 6
The human body is a complex system of cells, most of which are grouped into organ systems that have specialized functions. These systems can best be understood in terms of the essential functions they serve for the organism: deriving energy from food, protection against injury, internal coordination, and reproduction.
For Grades: 9-12
Learning Goal 1
Some allergic reactions are caused by the body's immune responses to usually harmless environmental substances. Sometimes the immune system may attack some of the body's own cells.
Learning Goal 2
Faulty genes can cause body parts or systems to work poorly. Some genetic diseases appear only when an individual has inherited a certain faulty gene from both parents.
Learning Goal 3a
New medical techniques, efficient health care delivery systems, improved diet and sanitation, and a fuller understanding of the nature of health and disease give today's human beings a better chance of staying healthy than their ancestors had.
Learning Goal 3b
Conditions now are very different from the conditions in which the species evolved. But some of the differences may not be good for human health.
Learning Goal 4
Some viral diseases, such as AIDS, destroy critical cells of the immune system, leaving the body unable to deal with multiple infection agents and cancerous cells.