Session 6 - Part II Flashcards
What effect does Hypokalaemia have on the cell memebrane?
Makes it more negative
Cells are hyperpolarised so Na+ more readily activated
What effect does Hyperkalaemia have on the cell membrane?
Makes it more positive
Higher than normal resting potential so depolarises membrane potential
What are the 2 processes of K+ handling?
Short term (Cells change how much is let in and out. K+ into cell = Na/K ATPase. K+ into ECF = K+ channels) Long term (Kidneys adjust how much they secrete into lumen to excrete into the urine)
What 3 hormones make K+ go into cells?
Insulin
Aldosterone
Catacholamines eg Adrenaline
How does the Pancreas effect K+ levels?
Increased K+ in splanchnic blood causes it to release Insulin
This makes K+ go into cells and the liver by increasing activty of Na/K ATPase channels
In the Kidney nephron, what 2 factors effect K+ secretion by the principle cells into the urine?
Tubular factors
Luminal factors
What are the Tubular factors effecting K+ secretion by Principle cells?
Increase transcription of Na channels (Apical) and Na/K ATPase (Always basolateral) and ENac in apical.
All due to aldosterone which increases transcription of them.
What are the Luminal factors effecting K+ secretion by Principle cells?
Increased delivery of Na to DCT lose more K+ (as go in opposite directions)
Increased flow so less time to go back in.
What are some of the symptoms of Hyperkalaemia?
Acidosis
Heart block
Arrhythmias
Heart less excitable
What are some of the symptoms of Hypokalaemia?
Muscle weakness
Paralytic ilius.
Nephrogenic diabetes insipidus caused by CD cells not responding to ADH
Heart more excitable
How can Cell lysis cause an increase in plasma K+ concentration?
Trauma to skeletal muscle cells causes necrosis and will release K+.
How can exercise cause an increase in plasma K+ concentration?
Exercise promotes K+ to leave cells as skeletal muscle contracts and releases K+ during the recovery phase
This is buffered by surrounding cells taking up the K+ to prevent Hyperkalaemia. Once exercise stopped it goes back into the skeletal cells
How can Acidosis cause high plasma K+ concentration?
High H+ concentration outside cell causes it to go into the cell and K+ will leave to maintain cell electroneutrality
How do Aldosterone antagonists cause increased plasma K+ concentration?
(Aldosterone usually makes you secrete K+ and absorb Na+)
Less K+ secretion so we retain more
*ACEi also prevent Aldosterone formation)
How does Alkalosis cause Hypokalaemia?
Low H+ concentration outside the cell causes H+ to leave the cell. K+ will have to enter the cell to maintain the electroneutrality
