Potassium Physiology Flashcards
Serum [K] is the main determinant of the __ __ Potential
Serum [K] is the main determinant of the Resting Membrane Potential
- both low and high potassium has increased risk of mortality
what parts of this action potentiall is mediated by K+?
resting membrane potential determines how far e are from the threshold potential.
The efflux of potassium ions decreases the membrane potential or hyperpolarizes the cell. For small voltage increases from rest, the potassium current exceeds the sodium current and the voltage returns to its normal resting value, typically −70 mV.
why is the inside of the cell negatively charged?
because of the Na+/K+ ATPAse. 3 Na out for every 2K in.
at resting membrane potential, individual Na+ channels are ___, and K+ channels are ___.
at resting membrane potential, individual Na+ channels are CLOSED, and K+ channels are OPEN.
K+ can flow freely at resting state, keeping it negative (since theres more K+ in the cell, it will flow out. After depolarization, the Na+ K+ atpase pumps K+ back in.
determinants of intra/extracellular K+ concentration in any cell
- the cell membrane. keeps K+ in and Na+ out (for themost part). if there was a flaw in the membrane, K+ and Na+ would go every which way, and the cell would be neutral to the extracellular space
- at rest, Na+ is in closed state. Na+ can’t get into the cell, keeping the outside positive. K+ continues to efflux based on concentration, and the RMP is stable.
- potassium channel is Open iat rest
- inside the cell is negatively charged, and equally important (NOT MOBILE) because they are usually trapped/ex/ phosphates, proteins).
5 Na+/K+ ATPase.
- Na+/H+ exchanger.
Na+/K+ atpase is increaed by __ stimualtion and ___, and inhbited by ___ and __
Na+/K+ atpase is increaed by BETA2 stimualtion and ALDOSTERONE, and inhbited by ALPHA1 STIMULATION and DIGOXIN
what hormone turns on the sodium-hydrogen exchanger in cells, promoting Na+ intake into the cells, and H+ release?
insulin
the ___ regulates total body potassium
kidney
like sodium and water, most of the K+ is reabsorbed at the level of the ___.
there is no absorption of K+ at the ___ LOH.
in the Ascendign LOH, there is ___ K+ via the ___ transporter.
by the time you get to DCT, the K+ in filtrate is pretty similar to blood. Can be exreted by the distal. nephron if there is excess K+ in the blood. the. kdiney regulates the total body potassium by secretion that is regulated by ___
like sodium and water, most of the K+ is reabsorbed at the level of the PCT.
there is no absorption of K+ at the DESCENDING LOH.
in the Ascendign LOH, there is ABSORPTION K+ via the NKCC2 transporter
by the time you get to DCT, the K+ in filtrate is pretty similar to blood. Can be exreted by the distal nephron if there is excess K+ in the blood. the. kdiney regulates the total body potassium by secretion that is regulated by ALDOSTERONE at the level of the PIRNCIPLE CELL
at the DCT:
the principle cell has a ____ atpase transporter on the cell-vessel side, which is also the side where aldosterone moves in.
on the tubular lumen side, the ___ Na+ transporter gets turned on by aldosterone, making sodium flow in. the K+ transporter on the luminal side brins K+ ___, allowing for fine tuning regulationi of total body potassium.
the principle cell has a NA+/K+ atpase transporter on the cell-vessel side, which is also the side where aldosterone moves in.
on the tubular lumen side, the ENAC Na+ transporter gets turned on by aldosterone, making sodium flow in. THIS CREATES A NEGATIVE CHARGE IN THE LUMEN. the K+ transporter on the luminal side brins K+ OUT TO OFFSET THE NA+MEDIATED NEGATIVE CHARGE, allowing for fine tuning regulationi of total body potassium.
OUtline the trans-tubular potassium gradient equation
interpretation of the TTKG;
Hyperkalemia but ttkg= < 7 is abnormal, blame the principal cell
Hypokalemia but ttkg = > 4 is abnormal, blame the principal cell
Hyperkalemia but ttkg= < 7 is abnormal, blame the principal cell
Hypokalemia but ttkg = > 4 is abnormal, blame the principal cell
