📊Cell Volume Regulation
Cells must maintain their volume within narrow limits to function properly. Volume regulation involves complex sensing mechanisms and coordinated activation of ion channels and transporters to restore cell size after osmotic challenges.
🔑 Osmotic Balance
Hypotonic Stress
Water enters → Cell swells
Response: RVD (lose solutes)
Isotonic
No net water movement
Normal cell volume
Hypertonic Stress
Water exits → Cell shrinks
Response: RVI (gain solutes)
📊Cell Volume Regulation Simulator
Status
RVI: NKCC brings in Na⁺, K⁺, 2Cl⁻ → water follows → volume increases.
⚙️Volume Regulatory Mechanisms
RVD (Regulatory Volume Decrease)
Activated when cells swell in hypotonic conditions.
RVI (Regulatory Volume Increase)
Activated when cells shrink in hypertonic conditions.
🔍Volume Sensing Mechanisms
How do cells detect volume changes? Several mechanisms have been proposed:
Membrane stretch
Mechanosensitive channels detect tension
Macromolecular crowding
Changes in protein concentration/interactions
Cytoskeleton
Actin network senses mechanical forces
Ionic strength
Changes in intracellular ion concentrations
🏥Clinical Relevance
Cerebral Edema
Brain cell swelling in hyponatremia, stroke, or trauma
Apoptotic Volume Decrease
Programmed cell shrinkage during apoptosis via K⁺/Cl⁻ loss
Sickle Cell Disease
Abnormal volume regulation contributes to sickling
Kidney Disease
Impaired tubular volume regulation affects reabsorption
Chapter Topics
🎓 Course Complete!
Congratulations on completing the Cell Physiology course! You've learned about: