Secretion Flashcards
What is the purpose of tubular secretion
Secretory mechanism transport substances from the peritubular capillaries into the tubule lumen, providing a second route into the tubule , so substances can be removed from the body
What is the importance of secretion
Important for substances that are protein bound because of the restrictions at the glomerulus
Ensures the removal of harmful substances as be eliminated more rapidly
How does secretion occur
Due to Tm-limitied carier mediators
How are Tm limited carrier mechanism able to secrete drugs
Carrier mechanisms aren’t very specific
What are substances that the body wants to gets rid of via secretion
Lactic, uric acid
Choline, Creatinine
Drugs
How are drugs such as penicillin, aspirin and para-amino hipputric acid sectreted
Through organic acid mechanism which secreted lactic and uric acid
How drugs such as are morphine and atropine secreted
Through organic base mechanism which secreted choline and creatinine
Why is K+ maintenance essential for life
Normal ECF = 4 moles /L used to maintain resting membrane potential
If increase above 5.5 moles = hypekalemia
If increase below 3.5 moles = hypokalaemia
What is the affect of hyperkalemia
Decreases the resting membrane potential of excitable cells, this results in ventricular fibrillation then death
What is the affect of hypokalaemia
Increases resting membrane potential, this hyperpolorizes muscle and cardiac cells, resulting in cardiac arrhythmias then death
What is the renal handling of K+
Filtered at the glomerulus then reabsorbed in proximal tubule due to following gradient and permeability, then excreted any active secretion in distal part of the tubule
What is K+ excretion dependant on
Changes in K+ secretion in distal part of the tubule
as secretion increases when potassium concentration increases (via ingestion)
and secretion reduces when potassium concentration decreases
What is the K+ secretion regulated by
Aldosterone - adrenal cortex hormone
What is the affect of aldosterone on K+ secretion
As potassium concentration increases in the ECF, it triggers aldosterone release which stimulates an increase in real tubule cell active potassium secretion
What also does aldosterone stimulate
Na+ reabsorption at the distal tubule by a different reflex pathway
