If you are irritated by every rub, how will your mirror be polished? Rumi
Idea Transcript
Maintaining Life Chapter 1
Homeostasis Homeostasis-
the ability to maintain relatively constant internal conditions even though the outside world is changing continuously. Examples: Thermoregulation Glucoregulation Osmoregulation
Homeostasis Mechanism Receptor-
senses and responds to stimulus by sending a message to the control center. Control center- analyzes the information and determines the appropriate response or effect (usually the brain). Effector- acts on the stimulus and causes a response that either suppresses the stimulus or enhances it.
Feedback Negative
Feedback- a reaction in which the system responds to the stimulus in such a way as to reduce or shut off the original stimulus to maintain homeostasis. Example:
When the concentration of CO2 in the body increases, the lungs are signaled to increase their activity to expel more CO2
Positive
Feedback- the response is to increase the original stimulus, leading to de-stabilization. Less common. Example:
When you get a cut, the response is to amplify bleeding, eventually leading to a clot that will seal the wound and prevent further bleeding.
Quick Check When we begin to become dehydrated, we usually get thirsty, which causes us to drink liquids. Is the thirst sensation part of a negative or positive feedback control system?
Answer:
Thermoregulation Keeping
a constant body temperature Enzymes in the body work best at 37°C The hypothalamus monitors body temperature When body temperature drops too low or too high, the hypothalamus sends nerve impulses to the skin.
Glucoregulation Keeping
a constant blood sugar level Insulin- hormone that reduces the level of glucose in the blood. When blood sugar levels rise, the pancreas releases insulin into the blood. The presence of insulin causes the glucose level to decrease. When blood sugar levels are low, the pancreas stops producing insulin, allowing glucose to go into the blood.