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Questions and Answers
What percentage of extracellular cations does sodium Na+ represent?
What percentage of extracellular cations does sodium Na+ represent?
- 100%
- 50%
- 70%
- 90% (correct)
What is the primary mechanism that prevents sodium Na+ from reaching equilibrium between the extracellular fluid and inside the cell?
What is the primary mechanism that prevents sodium Na+ from reaching equilibrium between the extracellular fluid and inside the cell?
- Active transport via ion pumps (correct)
- Osmosis
- Facilitated diffusion
- Passive diffusion
How many sodium Na+ ions are moved out of the cell by the Na+,K+ ATPase ion pump?
How many sodium Na+ ions are moved out of the cell by the Na+,K+ ATPase ion pump?
- 1
- 4
- 3 (correct)
- 2
What happens to water when sodium Na+ is actively removed from the cell?
What happens to water when sodium Na+ is actively removed from the cell?
What is the normal plasma osmolality value approximated in mmol/L?
What is the normal plasma osmolality value approximated in mmol/L?
Which of the following statements is true regarding potassium K+ compared to sodium Na+?
Which of the following statements is true regarding potassium K+ compared to sodium Na+?
Flashcards
Sodium (Na+)
Sodium (Na+)
The most abundant cation found outside of cells (ECF), making up 90% of all extracellular cations.
Plasma Osmolality
Plasma Osmolality
A measure of the concentration of dissolved particles in a solution, primarily determined by sodium in the plasma.
Na+, K+ ATPase Pump
Na+, K+ ATPase Pump
A specialized protein pump embedded in cell membranes responsible for actively moving sodium and potassium ions across the cell membrane.
Potassium (K+)
Potassium (K+)
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Osmosis
Osmosis
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Homeostasis
Homeostasis
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Study Notes
Sodium (Na+) in Extracellular Fluid (ECF)
- Sodium (Na+) is the most abundant cation in the ECF, making up 90% of all extracellular cations.
- It significantly influences plasma osmolality.
- Normal plasma osmolality is approximately 295 mmol/L, with 270 mmol/L contributed by Na+ and associated anions.
- The concentration of Na+ is much higher outside cells compared to inside.
- Passive diffusion of Na+ across cell membranes would lead to equilibrium.
- Cells utilize active transport systems, like ATPase ion pumps, to maintain this concentration gradient.
Potassium (K+) in Intracellular Fluid
- Potassium (K+) is the major intracellular cation.
- Like Na+, K+ would eventually diffuse across the cell membrane to reach equilibrium.
- The Na+/K+ ATPase ion pump actively transports ions.
- This pump moves three Na+ ions out of the cell for every two K+ ions moving in, using ATP. This process converts ATP to ADP.
Osmotic Balance and Cell Integrity
- Water follows the movement of electrolytes across cell membranes.
- Continuous removal of Na+ from the cell prevents osmotic rupture of the cell by drawing water out.
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