Homeostasis and Exercise Overview

Homeostasis

• Homeostasis is the maintenance of a constant internal environment, crucial for a healthy body.
• Claude Bernard first proposed this concept (1813-1878).
• Walter Cannon later termed it homeostasis in 1932.
• The word comes from Greek: homoios (same) and stasis (stay or stand).

Dynamic Constancy

• Blood pressure fluctuates, but the average pressure remains steady.
• This fluctuation is dynamic.
• The mean pressure is constant over time.

Steady State

• A steady state is a constant internal environment, but doesn't require the body to be at rest or normal.
• During submaximal exercise, body temperature plateaus.

Disturbances Outside Thermoneutral Range

• When not in a thermoneutral environment, body temperature increases steadily.
• This happens when exercising in hot/humid climates.

Homeostasis During Exercise

• Exercise disrupts homeostasis by changing pH, O2, CO2, and temperature.
• Control systems keep the body in steady state during light exercise.
• Intense exercise or prolonged exercise in extreme conditions can challenge this steady state and lead to exhaustion.

Biological Control Systems

• Within the body, proteins are broken down and synthesized.
• Energy is produced from stored nutrients.
• The pulmonary and circulatory systems work together to regulate oxygen and carbon dioxide levels.

Components of a Biological Control System

• A control system includes a sensor, integrating center, and effector.
• The sensor detects changes in the internal environment (stimulus).
• The integrating center processes the signals from the sensor and determines the required response.
• The effector carries out the response to return the system to normal (negative feedback).

Negative Feedback

• Negative feedback reverses the initial disturbance in homeostasis.
• An example is the body's response to an increase in CO2. CO2 triggers a receptor and leads to an increase in breathing, returning the CO2 levels to normal.
• Most systems in the body use negative feedback.

Gain of a Control System

• The capacity of a control system to maintain homeostasis is measured by its gain.
• Systems with high gain are better at maintaining it.
• The pulmonary and cardiovascular systems have high gain.

Examples of Homeostatic Control

• Body Temperature: The body regulates temperature through negative feedback loops involving blood vessel dilation or constriction, sweating, and shivering.
• Blood Glucose: The pancreas regulates blood sugar levels by producing insulin, which facilitates glucose uptake by cells. The pancreas works as both a sensor and effector.

Failure of Biological Control Systems

• Failure in any part of a biological control system can cause a disruption in homeostasis.
• Type 1 diabetes is an example, caused by damage to beta cells in the pancreas, preventing insulin release and causing hyperglycemia.

Example Exam Questions

• Students should be prepared to define and describe homeostasis.
• Differentiating homeostasis from steady state.
• Describing the role of the sensor, integrating center, and effector in biological control systems.
• Understanding negative feedback mechanisms.
• Discussing the concept of gain in a biological control system.

Reading

• Powers and Howley's "Exercise Physiology" is a good resource for more in-depth study.
• Consulting other exercise physiology textbooks can provide alternative viewpoints.