HOMEOSTASIS

Definition and Importance

Homeostasis is the state of steady internal, physical, chemical conditions maintained by living systems. This dynamic equilibrium allows organisms to function optimally despite changing external conditions.

Key regulated variables include:

• Body temperature: maintained around $37\,^\circ\text{C}$ in humans.

• Blood glucose concentration: maintained between $4.0\,mmol\,dm^{-3}$ and $7.0\,mmol\,dm^{-3}$.

• Blood $pH$: strictly regulated between $7.35$ and $7.45$.

Feedback Mechanisms

Homeostasis relies primarily on negative feedback loops to reverse deviation from a set point.

Components of a Feedback Loop

1. Stimulus: A change in the internal or external environment.

2. Receptor / Sensor: Detects the change and sends signals to the control center.

3. Control Center: Processes information and determines the response.

4. Effector: Executes the response to restore balance.

+----------------+       +------------------+       +-----------------+
|   Stimulus     | ----> | Receptor / Sensor| ----> | Control Center  |
| (Deviation)    |       | (Detects change) |       | (Processes info)|
+----------------+       +------------------+       +-----------------+
        ^                                                    |
        |                                                    v
+----------------+                                  +-----------------+
|  Set Point     | <------------------------------- |    Effector     |
| (Restored)     |       (Negative Feedback)        | (Response)      |
+----------------+                                  +-----------------+

Thermoregulation Example

When body temperature rises above $37\,^\circ\text{C}$:

• Sensors: Therm