homeostasis

• negative feedback - when there is too much / little of something, it triggers a response that brings back the level to normal (reaction is opposite to stimulus)
• homeostasis is the maintenance of a constant, stable internal environment
• internal environments must stay the same as much as possible
• things to manage internally include: body temperature, blood pressure levels, blood glucose levels
• the normal limit of blood pressure is usually 120/80mmHg
• the normal limit of resting heart rate is usually 60-100 beats per minute
• organs in the body work together to achieve homeostasis
• the key systems involved in maintaining homeostasis are the nervous and endocrine system
• constant external environmental changes = constant changes to internal environment
• negative feedback: response is opposite to the stimulus
• positive feedback: response is the same direction as the stimulus (forces organism out of homeostasis by amplifying stimulus)
• internal environment is managed by the automatic control system
• if homeostasis is not maintained, things like toxic wastes can accumulate in the body or cells may not get what they need, causing an imbalance. this imbalance could lead to things like diseases or death.
• when an imbalance is corrected (bringing back to homeostasis):

  1. sensory receptors pick up stimulus (change detected)
  2. control centre is alerted (input sent via afferent pathway)
  3. effectors are fired to manage stimulus (output sent via efferent pathway)
  4. stimulus corrected to bring back homeostasis (response to change)