Overview
The lecture explains positive and negative feedback loops in biology, focusing on homeostasis, examples in animals and plants, and the consequences of disrupted feedback such as diabetes.
Homeostasis and Feedback Loops
- Homeostasis is maintaining a stable internal environment.
- Feedback loops regulate variables like temperature, blood glucose, and osmolarity.
- A target set point is the ideal value the body tries to maintain using feedback mechanisms.
Negative Feedback Loops
- Negative feedback brings the variable closer to its target set point.
- Example: Body temperature regulation in mammals operates via negative feedback.
- If body temperature rises, the body sweats and vasodilates to lose heat; if it falls, it vasoconstricts and causes goosebumps to conserve heat.
- Blood glucose regulation is controlled by insulin (lowers glucose) and glucagon (raises glucose).
Positive Feedback Loops
- Positive feedback amplifies changes and moves the variable away from its set point.
- Example: Ethylene hormone in fruit ripening triggers nearby fruit to ripen, accelerating the process.
- Example: Childbirth contractions intensify due to pressure from the baby’s head, speeding up delivery.
Disruptions in Feedback Loops: Diabetes
- Type 1 diabetes results from beta cell destruction in the pancreas, leading to no insulin production.
- Type 2 diabetes arises from body cells not recognizing insulin, usually linked to lifestyle.
- Both types cause blood glucose to remain dangerously high, leading to serious health impacts.
- Insulin therapy or pumps can help regulate glucose in diabetic patients.
Key Terms & Definitions
- Homeostasis — maintenance of a stable internal environment.
- Negative Feedback Loop — process that decreases deviation from a set point.
- Positive Feedback Loop — process that increases deviation from a set point.
- Insulin — hormone that lowers blood glucose.
- Glucagon — hormone that raises blood glucose.
- Beta Cells — pancreatic cells that produce insulin.
- Alpha Cells — pancreatic cells that produce glucagon.
- Ectotherm — organism matching body temperature to environment.
- Endotherm — organism maintaining constant internal temperature.
Action Items / Next Steps
- Review examples of positive and negative feedback in your textbook.
- Understand the differences between type 1 and type 2 diabetes.
- Be able to explain feedback mechanisms using body temperature and blood glucose as examples.