Compare positive and negative feedback mechanisms.
Positive feedback mechanisms amplify or reinforce changes or deviations from a steady state. For example, during childbirth, the hormone oxytocin causes the muscles of the uterus to contract, which stimulates the production of more oxytocin. This positive feedback loop continues until the baby is born.
Negative feedback mechanisms, on the other hand, work to maintain a steady state or balance in a system. Negative feedback reduces or opposes deviations from a steady state. For example, when body temperature rises above a certain level, sweat glands are activated, and blood vessels dilate to release heat. This negative feedback loop results in a reduction in body temperature back to the normal range.
In summary, positive feedback mechanisms amplify a change from a steady state, while negative feedback mechanisms work to maintain or restore a steady state.
Positive Feedback Mechanism:
1. Definition: Positive feedback mechanisms amplify or reinforce a response or output, resulting in an exponential increase in the initial stimulus.
2. Process: When a specific event or stimulus occurs, it triggers a response that reinforces or intensifies the initial event, leading to further amplification.
3. Examples: Blood clotting, childbirth contractions, lactation in breastfeeding, and the release of oxytocin during labor.
4. Characteristics:
a. Self-amplifying: The response increases the original stimulus.
b. Temporary: The positive feedback loops are usually short-lived and end once the goal is achieved.
c. Exponential growth: The response continuously becomes stronger or larger.
d. Less common: Positive feedback loops are less common than negative feedback loops in biological systems.
Negative Feedback Mechanism:
1. Definition: Negative feedback mechanisms maintain homeostasis by counteracting or minimizing the deviation from a set point, resulting in a stabilizing effect.
2. Process: When a change occurs, negative feedback loops work to reverse the change and return the system to its original set point.
3. Examples: Regulation of body temperature, control of blood glucose levels, production of insulin, and regulation of blood pressure.
4. Characteristics:
a. Self-correcting: Negative feedback mechanisms work to restore the system's original state.
b. Stabilizing: The feedback process brings the system back to its set point, maintaining a stable internal environment.
c. Continuous operation: Negative feedback loops operate continuously to regulate and maintain homeostasis.
d. More common: Negative feedback loops are more common in living organisms and biological systems.