Overview
This lecture covers how the body uses energy to maintain homeostasis, introduces feedback loops, and provides biological examples of negative and positive feedback.
Homeostasis and Set Points
- Homeostasis is the maintenance of stable internal conditions (temperature, water, solutes, etc.) necessary for optimal physiological function.
- Set points are average values around which the body keeps certain variables, such as body temperature (37°C) and blood glucose (90 mg/dL).
- The body responds to deviations from set points to restore homeostasis.
Components of Homeostatic Regulation
- A stimulus is any change in internal conditions that disrupts homeostasis.
- Sensors or sensory receptor cells detect changes in internal conditions.
- Information about the stimulus is sent via afferent pathways to the control center (central nervous system).
- The control center processes information and sends commands through efferent pathways.
- Effectors (muscles or glands) carry out responses that restore homeostasis.
Negative Feedback Loops
- Negative feedback loops counteract changes, restoring values to the set point.
- Example: Increased blood glucose after a meal triggers insulin release, lowering blood glucose back to the set point.
- When blood glucose drops, glucagon is released to increase blood glucose.
- In negative feedback, the response opposes the initial stimulus.
Positive Feedback Loops
- Positive feedback loops amplify changes, moving the system further from homeostasis to achieve a goal.
- Example: During childbirth, stretching of the cervix triggers oxytocin release, causing more uterine contractions and more stretching until delivery.
- In positive feedback, the response reinforces the initial stimulus.
Key Terms & Definitions
- Homeostasis — maintenance of stable internal conditions within narrow limits.
- Set Point — target value the body tries to maintain (e.g., temperature, glucose).
- Stimulus — change that disrupts homeostasis.
- Sensor (Receptor Cell) — detects changes in internal conditions.
- Afferent Pathway — carries information to the control center.
- Control Center — processes information (usually brain or spinal cord).
- Efferent Pathway — sends commands from the control center.
- Effector — muscle or gland that carries out the corrective response.
- Negative Feedback — response that reverses or reduces the effect of the stimulus.
- Positive Feedback — response that amplifies the stimulus.
Action Items / Next Steps
- Prepare for upcoming lecture on basic anatomical principles and language of anatomy and physiology.