Nervous and Hormonal Systems

• Nervous system:

  Speed of action: Very rapid

  Nature of message: Electrical impulses, travelling along nerves

  Duration of response: Usually within seconds

  Area of response: Localized response (only one area usually)

  Examples of process controlled: Reflexes such as blinking
• Endocrine system:

  Speed of action: Can be slow

  Nature of message: Chemical messenger (hormones) travelling in bloodstream

  Duration of response: May take years (puberty)

  Area of response: Widespread response (in many organs)

  Examples of process controlled: Development of reproductive system
• Hormones are used in food production, for example oestrogen is used to boost growth rate of chickens.

  • Advantage: chickens grow quickly meaning more profit.
  • Disadvantages: this may cause human males to develop feminine characteristics, and it is unnatural.