Physiology Principles

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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.

components.interactiveLearning.arrangeTheStepsInThe

1Hypothalamus (control center) receives signal

2Thermoreceptors detect the change

3Effectors activated: vasodilation + sweating

4Body temperature decreases toward set point

5Negative feedback stops the response

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?

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