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Human Body Systems

Sodium, blood pH and oxygen saturation

  • 3 things to know
  • AS 2

Overview

Sodium balance and imbalance, the normal range of blood pH, buffering by blood, lungs and kidneys, acidosis and alkalosis, oxygen saturation and how a pulse oximeter works.

What you need to know

Answer each one before you reveal it.

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Key term

How is sodium balance regulated in the body?

Key term

Why are sodium and chloride ions important for health?

Key term

What happens if blood sodium is too high or too low?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    How is sodium balance regulated in the body?

    Model answer

    The kidneys adjust how much sodium is reabsorbed or excreted in urine. Aldosterone from the adrenal glands increases sodium reabsorption.

  2. 2

    Why are sodium and chloride ions important for health?

    Model answer

    Sodium and chloride ions control the balance of water between body fluids. Sodium ions are also essential for nerve impulses and muscle contraction.

  3. 3

    What happens if blood sodium is too high or too low?

    Model answer

    High sodium draws water from cells and is linked to high blood pressure. Low sodium can cause confusion, cramps and, in severe cases, seizures.

  4. 4

    What is the normal range of blood pH?

    Model answer

    Normal blood pH is between 7.35 and 7.45. The narrow range is needed for enzymes and proteins to work properly.

  5. 5

    How is blood buffered to keep its pH stable?

    Model answer

    The hydrogencarbonate buffer system mops up excess hydrogen ions or releases them as needed. Plasma proteins and haemoglobin also act as buffers.

  6. 6

    How do the lungs and kidneys help control blood pH?

    Model answer

    The lungs remove carbon dioxide, which forms acid in the blood. The kidneys excrete hydrogen ions and retain hydrogencarbonate.

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Acidosis means blood pH falling below 7.35.
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