Physiology Principles

Understand how the body maintains balance through feedback loops, fluid management, and acid-base regulation.

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.

Negative feedback loop for thermoregulation - homeostasis diagram - NurseNest pre-nursing

Clinical Connection

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.

Thermoregulation Sequence

Arrange the steps of the negative feedback loop for body temperature regulation

Arrange the steps in the correct physiological order:

1Hypothalamus (control center) receives signal

2Effectors activated: vasodilation + sweating

3Thermoreceptors detect the change

4Negative feedback stops the response

5Body temperature rises above set point

6Body temperature decreases toward set point

Fluid Compartments

Where body water is distributed

Intracellular Fluid (ICF)

~67%

Inside cells. Contains K+, Mg2+, PO4³⁻. The largest fluid compartment.

Extracellular Fluid (ECF)

~33%

Outside cells. Includes intravascular (plasma) and interstitial (between cells). Contains Na+, Cl⁻, HCO3⁻.

Memory Aid

'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.

Physiology Check

1/2

Which electrolyte is the MOST abundant intracellular cation?

Pre-nursing comprehensive review

1/20

Which organelle contains its own DNA and is inherited exclusively from the mother?