Regulation From Internal Stimuli

• Each organ system affects other organ systems

• Organ systems must work together to keep the organism healthy and keep the internal environment constant.

• The body must regulate:

  • Temperature

  • Amount of water

  • Amount of salts

  • pH levels

  • Nutrients (like glucose)

  • Gases (oxygen, carbon dioxide

Stimulus Response

• Stimulus: a change in the environment (internal or external) of an organism that results in a response

• Internal stimuli: body temperature, changes in body fluid levels, hormone changes, blood sugar

• External stimuli: changes in light, external temperature, injury/danger

• Response: action/ reaction an organism exhibits as a result of detecting stimulus

Homeostasis

• KEY CONCEPT: Homeostasis - regulation and maintenance of a CONSTANT environment within the body

Fight or Flight Response

• Pain, physical injury and/or emotional upset send signals to nerves that there is a threat

• The adrenal glands are stimulated to release epinephrine (adrenaline)

• Heart rate and blood pressure increase to move nutrients and oxygen to muscles

• Liver breaks down glycogen and releases glucose into the blood (to be used for quick energy)