Physiology Principles
Understand how the body maintains balance through feedback loops, fluid management, and acid-base regulation.
Visual learning
Physiology regulation flowchart
Follow how the body detects change, responds, and returns toward homeostasis.
Fast
Neural response
Sustained
Endocrine response
Local
Tissue response
Late
Compensation limit
- 1
Variable changes
Temperature, glucose, calcium, oxygen, pH, or pressure moves away from baseline.
- 2
Sensor detects change
Receptors or glands detect the shift and send a signal.
- 3
Control center compares
The brain, endocrine system, or local tissue compares current state with the target range.
- 4
Effector responds
Muscle, glands, kidneys, lungs, vessels, or cells change activity.
- 5
Feedback reduces imbalance
Negative feedback lowers the original stimulus once the variable improves.
Clinical connection
Physiology turns vital signs and symptoms into patterns: compensation, correction, or decompensation.
Negative Feedback Loops
The body's primary regulatory mechanism
Most physiological regulation uses negative feedback. The body detects a change, activates a response, and reverses the change to restore balance.
When you see a compensatory vital sign change in a patient (e.g., tachycardia in response to bleeding), you're witnessing negative feedback trying to maintain cardiac output.
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1Hypothalamus (control center) receives signal
2Effectors activated: vasodilation + sweating
3Body temperature decreases toward set point
4Negative feedback stops the response
5Thermoreceptors detect the change
6Body temperature rises above set point
Fluid Compartments
Where body water is distributed
~67%
Inside cells. Contains K+, Mg2+, PO4³⁻. The largest fluid compartment.
~33%
Outside cells. Includes intravascular (plasma) and interstitial (between cells). Contains Na+, Cl⁻, HCO3⁻.
'K+ stays IN the cell, Na+ stays OUT.' This is maintained by the Na+/K+ ATPase pump. When cells are damaged (trauma, burns), K+ leaks out → hyperkalemia risk.
1/2
Which electrolyte is the MOST abundant intracellular cation?