L.11 Regulation of potassium Flashcards
What is the most abundant intracellular cation?
Potassium (K+)
Potassium accounts for 98% of the intracellular cation concentration.
What is the role of potassium in muscle and nerve function?
Potassium is essential for normal muscle and nerve function
It determines the resting membrane potential.
How is resting membrane potential defined?
It is the voltage difference across the cell membrane when the cell is at rest
This potential is influenced by the distribution of potassium ions.
What is the normal serum potassium concentration range?
3.5-5.0 mmol/L
Serum K+ levels are tightly regulated.
What is potassium homeostasis?
The balance of potassium intake and output
Intake comes from diet, while output is managed by the kidneys.
What stimulates potassium uptake in cells?
Insulin and β-adrenergic stimulation
Insulin is secreted in response to high blood glucose or potassium levels.
What effect does insulin have on potassium levels?
Stimulates K+ uptake into cells
Insulin activates the Na+/K+ pump, promoting potassium influx.
What are β-adrenergics?
Adrenaline and noradrenaline
These hormones stimulate the Na+/K+ pump, increasing cellular potassium uptake.
How does aldosterone affect potassium levels?
Stimulates K+ excretion
Aldosterone increases the quantity and activity of the Na+/K+ pump in kidney tubule cells.
Fill in the blank: Potassium intake comes from _______.
diet
This is a key aspect of maintaining potassium homeostasis.
Fill in the blank: Potassium output is regulated by the _______.
kidneys
The kidneys play a crucial role in potassium balance.
True or False: The resting membrane potential is influenced by potassium distribution.
True
Potassium distribution is critical for establishing the resting membrane potential.
What is the significance of potassium (K+) regulation?
Crucial for normal cell function, disturbances can lead to significant morbidity and mortality
Potassium is vital for various physiological processes, including muscle contraction and nerve transmission.
What are the sample types used for potassium measurement?
Serum or plasma
Both serum and plasma are commonly used in clinical settings to measure potassium levels.
How is potassium measured in the laboratory?
By ion selective electrode (ISE)
ISE is a common method for measuring the concentration of specific ions in solution.
List some pre-analytical issues that can affect potassium measurement.
- Age of sample
- Haemolysis
- EDTA interference
- Storage conditions
- Traumatic venepuncture
- Fragility of RBCs and WBCs
Pre-analytical errors can significantly impact the accuracy of potassium results.
What is hypokalaemia?
A serum/plasma K+ level below the reference range (< 3.5 mmol/L)
Hypokalaemia can lead to serious health issues if not addressed.
What are some symptoms of hypokalaemia?
- Muscle weakness/cramps
- Constipation
- Cardiac arrhythmias
Symptoms arise due to changes in membrane potential affecting muscle and nerve function.
What are the causes of hypokalaemia?
- Reduced intake (rare)
- Redistribution
- Increased loss
Common causes include medications, metabolic conditions, and gastrointestinal losses.
What treatment options are available for hypokalaemia?
Oral or IV K+ supplement
Treatment depends on the severity and cause of hypokalaemia.
What does redistribution of K+ into cells cause?
- Metabolic alkalosis
- Treatment with insulin
- Treatment of anaemia
- β-adrenergic stimulation
Redistribution can occur in various clinical scenarios, leading to lower serum potassium levels.
What role do diuretics play in potassium levels?
Increased K+ loss
Diuretics can lead to hypokalaemia through increased urinary potassium excretion.
What are examples of loop diuretics?
- Furosemide
Loop diuretics are often used for rapid diuresis and can cause significant potassium loss.
What are examples of thiazide diuretics?
- Bendroflumethiazide
Thiazide diuretics are typically used for long-term management of hypertension and fluid retention.
