Organ Systems and Homeostasis Part 2

Study Notes

Physiological control systems maintain the body's internal stability by monitoring and correcting disruptions.
Key functions must remain within specific operating ranges (setpoints) for optimal functioning.

Control systems consist of three main components: sensor, integrating center, and effector.
Sensors monitor environmental changes; integrating centers compare inputs with setpoints; effectors execute responses.

Local Control:
- Simplest form, involving paracrines and autocrines.
- Responses are restricted to the immediate area (e.g., tissue O2 decrease triggers local vasodilation).
Reflex Control:
- More complex, involving long-distance communication via nervous and endocrine systems.
- Changes affect wider systemic responses (e.g., baroreceptors detect low blood pressure, activating heart rate increase).

Stimulus: Initial disturbance triggering the response pathway.
Sensor/Receptor: Continuously monitors specific parameters.
Afferent Pathway: Carries input signals from sensors to integrating centers.
Integration Center: Compares input signals with setpoints to determine response.
Efferent Pathway: Sends output signals to target effectors (chemical, electrical, or both).
Effector: Executes the action to restore conditions within normal limits.

Negative Feedback: Homeostatic, slows stimulation and returns conditions to optimal range (e.g., regulating body temperature).
Positive Feedback: Non-homeostatic, promotes further stimulation (e.g., blood clotting cascade).
Feedforward Control: Anticipates changes and activates responses before disturbances occur (e.g., preparing for physical exertion).

Each regulated variable oscillates around a setpoint with a normal range allowing variability without triggering corrective action.
Setpoints can vary between individuals and change over time due to factors like inheritance, acclimatization, and biorhythms.

Biorhythms involve regular, predictable fluctuations (e.g., circadian rhythms influence blood pressure, body temperature, and metabolism).
Physiological adjustments accommodate differing requirements over time.

Negative feedback opposes inputs, keeping systems at or near setpoints.
Essential for restoring normal states but not for preventing deviations from setpoints.