why digoxin enhances automaticity but hyperkalemia reduce the automaticity ?

[DrXmIsH0]

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hi
every one know digoxin blocks na/k Atapase -->more k outside --> reduce resting membran potintion
In My bock Hyperkalemia reduce the automaticity because there is reducing in resting membrane potintion
but the same book say digoxin enhance automaticity and I don't way it should reduce the automaticity of heart ?
please help 🙁

 

[SAvoodoo]

hi
every one know digoxin blocks na/k Atapase -->more k outside --> reduce resting membran potintion
In My bock Hyperkalemia reduce the automaticity because there is reducing in resting membrane potintion
but the same book say digoxin enhance automaticity and I don't way it should reduce the automaticity of heart ?
please help 🙁

a) know one really knows how digoxin works, there are theories but no one's quite sure
b) it doesn't work how you think (think more towards Na+/Ca2+)

here, it even has a fun little cartoon!

http://pharmacologycorner.com/anima...ffects-at-molecular-tissue-and-system-levels/

 

[DrXmIsH0]

a) know one really knows how digoxin works, there are theories but no one's quite sure
b) it doesn't work how you think (think more towards Na+/Ca2+)

here, it even has a fun little cartoon!

http://pharmacologycorner.com/anima...ffects-at-molecular-tissue-and-system-levels/

I understand all functions of digoxin and I have study it perfectly
If the resting membrane potintion became less negative--> automaticity should reduced

can u tell me how digoxin enhance automaticity ?
thanks

 

[SAvoodoo]

I understand all functions of digoxin and I have study it perfectly
If the resting membrane potintion became less negative--> automaticity should reduced

can u tell me how digoxin enhance automaticity ?
thanks

as far as i can tell the eventual increase in Ca2+ intracellularlly leads to increased binding of troponin, facilitating coupling and contraction.

if anyone has a better explanation please correct me

 

[DrXmIsH0]

as far as i can tell the eventual increase in Ca2+ intracellularlly leads to increased binding of troponin, facilitating coupling and contraction.

if anyone has a better explanation please correct me

automaticity mean ectoic fucus or abnormal peace maker
I don't talk about contraction 😀

 

[donkeyboy]

I understand all functions of digoxin and I have study it perfectly
If the resting membrane potintion became less negative--> automaticity should reduced

can u tell me how digoxin enhance automaticity ?
thanks

can't understand exactly what you're saying, but your statement here is wrong

when resting potential becomes LESS negative (closer to zero), automaticity should be enhanced because the membrane is closer to deplolarization. when resting potential becomes MORE negative, automaticity is reduced. because digoxin reduces intracellular K+ levels, the membrane potential is less negative (closer to zero), thus automaticity is increased

 

[donkeyboy]

hi
every one know digoxin blocks na/k Atapase -->more k outside --> reduce resting membran potintion
In My bock Hyperkalemia reduce the automaticity because there is reducing in resting membrane potintion
but the same book say digoxin enhance automaticity and I don't way it should reduce the automaticity of heart ?
please help 🙁

digoxin caused hyperkalemia because it blocks K+ entry into the cell, and thus increases its concentration in the serum. by decreasing K+ in the cell the membrane potential becomes less negative and thus more depolarized which enhances automaticity. on the other hand digoxin slows the heart rate because it decreases conduction through the AV node via vagal stimulation for reasons unknown to me.

 

[kdavis04]

hi
every one know digoxin blocks na/k Atapase -->more k outside --> reduce resting membran potintion
In My bock Hyperkalemia reduce the automaticity because there is reducing in resting membrane potintion
but the same book say digoxin enhance automaticity and I don't way it should reduce the automaticity of heart ?
please help 🙁

Digoxin does not increase automaticity. It increases inotropy. It does so by inhibiting Na/K ATPase, leading to dysfunction of the Na/Ca exchanger. This leads to increased [Ca] Intracellularly--> increase in inotropy

 

[astrocreep96]

hi
every one know digoxin blocks na/k Atapase -->more k outside --> reduce resting membran potintion
In My bock Hyperkalemia reduce the automaticity because there is reducing in resting membrane potintion
but the same book say digoxin enhance automaticity and I don't way it should reduce the automaticity of heart ?
please help 🙁

I'm going to go against your book and say that (at therapeautic levels)...

A.) When discussing automaticity in the heart, outside of any other pathologies, you may want to discuss the SA node since it has the fastest rate of repolarization and therefore determines the heart rate, meaning you may want to post a graph demonstrating the potential of the SA node, not the myocardium.

B.) Automaticity (again, disallowing for something like a nodal block or toxic levels of digoxin) is determined in large part by the slope of phase 4 and phase 0 in the SA node. Phase 4 is the slow depolarization of the node, determined by activation of the spontaneously deplarizing sodium channels, that themselves do not open until repolarized.

Meaning, if digoxin increases the Calcium levels in the tissue, it reduces the probability of a funny sodium channel being open, which slows the rate of automaticity. A further mechanism of accomplishing the exact same thing is stimulation of the vagus nerve, increasing parasympathetic drive to the heart.

 

[BanBidil]

Next time you are in the hospital speak with a Pharmacist...