How do positive and negative feedback differ from each other? Explain.

Positive and Negative Feedback:

Positive Feedback:

• Definition: A positive feedback loop is a process in which the output of a system reinforces or amplifies the input, leading to a cumulative increase or decrease in the output.
• Characteristics:
  • The output of the system feeds back to the input in a way that strengthens or enhances the original input signal.
  • It results in an exponential increase or decrease in the output over time.
  • Positive feedback loops are typically unstable and can lead to runaway reactions or oscillations.
• Biological Examples:
  • Blood clotting: When a blood vessel is damaged, platelets aggregate at the site of injury and release factors that activate more platelets. This positive feedback loop leads to the formation of a stable blood clot, preventing further bleeding.
  • Muscle contraction: When a muscle fiber receives a nerve impulse, it releases calcium ions. These calcium ions bind to a protein called troponin, which initiates a series of events that leads to muscle contraction. The contraction itself generates more calcium ions, further enhancing the contraction. This positive feedback loop results in a strong and sustained muscle contraction.

Negative Feedback:

• Definition: A negative feedback loop is a process in which the output of a system counteracts or opposes the input, leading to a stable equilibrium or steady state.
• Characteristics:
  • The output of the system feeds back to the input in a way that weakens or reduces the original input signal.
  • It results in a stable output that is maintained within a specific range.
  • Negative feedback loops are typically stable and help regulate and maintain homeostasis in biological systems.
• Biological Examples:
  • Body temperature regulation: When body temperature rises, the hypothalamus triggers mechanisms such as sweating and vasodilation to release heat. Conversely, when body temperature drops, the hypothalamus initiates shivering and vasoconstriction to conserve heat. These negative feedback loops maintain body temperature within a narrow range, despite changes in the external environment.
  • Blood glucose regulation: After a meal, the increase in blood glucose levels triggers the release of insulin from the pancreas. Insulin promotes the uptake of glucose by cells, reducing blood glucose levels. As blood glucose levels decrease, insulin secretion is inhibited. This negative feedback loop maintains blood glucose levels within a healthy range.

Summary:

Feature	Positive Feedback	Negative Feedback
Output-Input Relationship	Output reinforces input	Output opposes input
Overall Effect	Cumulative increase/decrease	Stable equilibrium
Stability	Typically unstable	Typically stable
Biological Examples	Blood clotting, muscle contraction	Body temperature regulation, blood glucose regulation