Overview
This lecture explains homeostasis, how feedback mechanisms (negative and positive) maintain it, and examines the roles of specific hormones and conditions like diabetes.
Biological Levels & Homeostasis
- The body is organized into cells, tissues, organs, and organ systems.
- Homeostasis is the body's maintenance of a stable internal environment.
- Examples include stable blood pH, glucose levels, and body temperature.
Warm-blooded vs Cold-blooded Animals
- Ectotherms ("cold-blooded") change body temperature with their environment.
- Endotherms ("warm-blooded") maintain a constant internal body temperature.
Negative Feedback Mechanisms
- Negative feedback counters a variable to return to a set point, supporting homeostasis.
- Hot environment: nerves signal the brain, causing sweating and blood vessel dilation to cool the body.
- Cold environment: shivering and blood vessel constriction help conserve heat and raise body temperature.
- Blood glucose regulation: high glucose triggers insulin release for glucose uptake; low glucose triggers glucagon release for glucose release.
Positive Feedback Mechanisms
- Positive feedback intensifies the original variable rather than counteracting it.
- Example: childbirth, where hormone release causes more contractions, leading to more hormone release and contractions.
Disorders of Feedback: Type 1 Diabetes
- Type 1 diabetes occurs when the pancreas cannot produce insulin.
- Without insulin, glucose cannot enter cells for energy production.
- Type 1 diabetics must monitor blood sugar and often take insulin since negative feedback is disrupted.
Key Terms & Definitions
- Homeostasis — A stable internal environment maintained by the body.
- Ectotherm — An animal whose body temperature changes with the environment.
- Endotherm — An animal that maintains a constant internal temperature.
- Negative feedback — A mechanism that counteracts a change to restore balance.
- Positive feedback — A process that amplifies a change or variable.
- Insulin — A hormone that helps cells take in glucose from the blood.
- Glucagon — A hormone that causes the liver to release glucose into the blood.
- Type 1 diabetes — A disorder where the pancreas does not produce insulin.
Action Items / Next Steps
- Review definitions and feedback examples.
- Understand the impact of disrupted feedback systems, such as in diabetes.