10.1 - Coordination

There are two main forms of coordination in mammals:

• The nervous system uses nerve cells to pass electrical impulses along their length. They stimulate their target cells by secreting chemicals, known as neurnotransmitters, directly onto them. This results in rapid communication between specific parts of an organism. The responses produced are often are often short-lived and restricted to a localised region of the body.
• The hormonal system produced chemicals (hormones) that are transported in the blood plasma to their target cells, which they then stimulate. This results in a slower, less specific form of communication between parts of an organism. The responses are often long-lasting and widespread.

Chemical Mediators

Chemical mediators are chemicals released from certain mammalian cells and have an effect on cells in their immediate vicinity. They are typically released by infected or injured cells and cause small arteries to dilate. This leads to a rise in temperature and swelling of the affected area - the so-called 'inflammatory response'. Two examples of chemical mediators are:

• histmine, which is stored…