Potassium Function in the Body

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Questions and Answers

What is the primary role of potassium (K+) in the body?

Muscle contraction and excitation (correct)
Metabolism of carbohydrates
Regulating blood pressure
Formation of blood clots

What happens to the resting membrane potential (RMP) with elevated plasma K+ levels?

It becomes less negative (correct)
It increases dramatically
It remains unchanged
It becomes more negative

What percentage of the body’s total K+ circulates in the plasma?

5%
10%
15%
2% (correct)

What can severe hyperkalemia lead to?

Lack of muscle excitability (D) Signup and view all the answers

Which of the following cellular functions is NOT significantly influenced by K+ levels?

Formation of ATP (B) Signup and view all the answers

What effect does a lower than normal difference between resting and action potential have on the cell?

Increases cell excitability (C) Signup and view all the answers

Flashcards

Potassium: Intracellular Dominance

Potassium (K+) is the main positive ion found inside cells, with 20 times higher concentration inside cells compared to outside.

Potassium's Tight ECF Control

The body tightly controls the amount of K+ in the fluid surrounding cells (ECF) to ensure proper cell function, keeping it low.

Plasma Potassium's Scarcity

Only a small fraction (2%) of the body's total K+ circulates in the blood (plasma), highlighting the importance of its regulation.

Potassium's Diverse Roles

Potassium plays crucial roles in various bodily functions, such as nerve and muscle activity, heart contractions, and maintaining cell fluid balance.

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Hyperkalemia: Muscle Weakness

A high level of K+ in the blood (hyperkalemia) makes cells more excitable, leading to weak muscles, as the difference between resting and action potential decreases.

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Severe Hyperkalemia: Paralysis

A very high K+ level can lead to paralysis or even fatal heart problems, as the cell's resting potential becomes higher than its action potential, preventing proper electrical activity.

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Study Notes

Potassium Function in the Body

Potassium (K+) is the main intracellular positive ion, 20 times more concentrated inside cells than outside.
Only 2% of total body potassium circulates in the plasma.
Potassium plays crucial roles in regulating neuromuscular excitability, heart contraction, intracellular fluid volume, and hydrogen ion concentration.
Potassium significantly affects skeletal and cardiac muscle contraction.

Effects of Elevated Potassium

Elevated plasma potassium (hyperkalemia) lowers the resting membrane potential (RMP) of cells, making it closer to zero.
This reduced difference between resting and action potentials increases cell excitability, potentially leading to muscle weakness.
Severe hyperkalemia can drastically raise the RMP above the action potential, causing a lack of muscle excitability, which may result in paralysis and fatal cardiac arrhythmias.