BHSC 301
Homeostasis
Maintaining the Internal Environment
Basic Health Sciences (BHSC) Program
Academic Year 2024–2025
, 1. The Concept of Homeostasis
Homeostasis is the maintenance of a stable internal environment within narrow
physiological ranges, despite changes in the external environment. The term was
coined by Walter Cannon in 1932.
Definition Homeostasis: The tendency of biological systems to maintain relatively
constant conditions in the internal environment while continuously
interacting with and adjusting to changes originating within or outside the
system.
2. Components of Homeostatic Control
Every homeostatic control system has three components:
2.1 Receptor (Sensor)
• Detects changes in a specific variable (the stimulus)
• Examples: baroreceptors (blood pressure), osmoreceptors (blood osmolality),
thermoreceptors (temperature)
2.2 Control Center (Integrating Center)
• Receives input from the receptor
• Compares the detected level to a set point
• Determines the appropriate response
• Examples: hypothalamus (temperature), medullary cardiovascular center (blood
pressure)
2.3 Effector
• Carries out the response to restore the variable to the set point
• Examples: sweat glands, blood vessels, muscles, glands
Homeostasis
Maintaining the Internal Environment
Basic Health Sciences (BHSC) Program
Academic Year 2024–2025
, 1. The Concept of Homeostasis
Homeostasis is the maintenance of a stable internal environment within narrow
physiological ranges, despite changes in the external environment. The term was
coined by Walter Cannon in 1932.
Definition Homeostasis: The tendency of biological systems to maintain relatively
constant conditions in the internal environment while continuously
interacting with and adjusting to changes originating within or outside the
system.
2. Components of Homeostatic Control
Every homeostatic control system has three components:
2.1 Receptor (Sensor)
• Detects changes in a specific variable (the stimulus)
• Examples: baroreceptors (blood pressure), osmoreceptors (blood osmolality),
thermoreceptors (temperature)
2.2 Control Center (Integrating Center)
• Receives input from the receptor
• Compares the detected level to a set point
• Determines the appropriate response
• Examples: hypothalamus (temperature), medullary cardiovascular center (blood
pressure)
2.3 Effector
• Carries out the response to restore the variable to the set point
• Examples: sweat glands, blood vessels, muscles, glands
