question

[usmletoo]

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I am struggling with this silly point-
So skeletal muscle ,cardiac and smooth muscle ALL have dihydropyridine receptors bound to the rynodine receptors ? are the dihydropyridine receptors in called L ca channels in cardiac muscle? -
Because to my understanding :
in cardiac muscle there is calcium induce calcium release - so calcium gets in during phase 2 through L voltage calcium channels this activates rynodine receptors in SR and calcium gets out-
in Skeletal muscle according to my understanding you have
the AP travels till reaches T tubules this opens the dihydropyrine receptors that are linked to the rynodine receptors and calcium is released- no calcium involved-
in smooth muscle same as skeletal in terms of the dihydropyridine receptors
Lastly:
dihydropyrine calcium channel blocker group act more on vessels than in heart because of the presence or absence of these dihydropyridine receptors?
Thanks in advance

 

[GotTheSikhness]

I am struggling with this silly point-
So skeletal muscle ,cardiac and smooth muscle ALL have dihydropyridine receptors bound to the rynodine receptors ? are the dihydropyridine receptors in called L ca channels in cardiac muscle? -
Because to my understanding :
in cardiac muscle there is calcium induce calcium release - so calcium gets in during phase 2 through L voltage calcium channels this activates rynodine receptors in SR and calcium gets out-
in Skeletal muscle according to my understanding you have
the AP travels till reaches T tubules this opens the dihydropyrine receptors that are linked to the rynodine receptors and calcium is released- no calcium involved-
in smooth muscle same as skeletal in terms of the dihydropyridine receptors
Lastly:
dihydropyrine calcium channel blocker group act more on vessels than in heart because of the presence or absence of these dihydropyridine receptors?
Thanks in advance

Ok, hope this answers it . . .

L-type calcium channels have Dihydropyridine receptors in SKELETAL MUSCLE, which when stimulated, stimulate ryanodine receptors to open and release Ca+ from the SR.

In smooth muscle, the L-type calcium channels bring in extracellular calcium, which then stimulates the SR to release more calcium. I believe these channels do possess DHP receptors on the L-type calcium channels.

As for cardiac muscle, it also has L-type calcium channels on the surface to bring in extracellular calcium as smooth muscle does, but I don't believe it has DHP receptors.

This would explain why Verapamil (a non-DHP L-type calcium channel blocker) is more effective on the heart, whereas Nifedipine (and DHP-receptor mediated L-type calcium channel blocker) is more effective on smooth muscle.

 

[usmletoo]

Thank you

 

[FutureDoc4]

GotTheSikhness,

Where did you find that info? (just curious)

 

[GotTheSikhness]

Lippincott Pharm, classnotes, and wiki to confirm.

 

[McGillGrad]

Lippincott Pharm, classnotes, and wiki to confirm.

Possibly the funniest and most ******ed thing I have read today.

 

[Captopril]

Possibly the funniest and most ******ed thing I have read today.

no need for that, broseph

 

[Captopril]

Also, for the OP:

skeletal muscle: AP from NMJ-->T-tubule. Here, it stimulates DHPreceptors, which are linked to Ryanodine receptors that open up SR-->Ca2+ release from INSIDE the muscle cell (take home message: Ca2+ is from inside the cell in skeletal muscle).

cardiac muscle: Ca2+ enters the myocyte from OUTSIDE the cell through L-type channels. Once inside, the Ca2+ enters SR (through a pump). Inside the SR, the Ca2+ can just hang out, or it can stimulate the Ryanodine receptors to open up, releasing all the Ca2+ that has built up inside the SR (this is called Ca2+ mediated Ca2+ release). take home message: in cardiac myoctes, Ca2+ is from OUTSIDE of the cell.

I forget the exact source of Ca2+ in smooth muscle, but I know Myosin-Light chain Phosphyrlation is involved.

 

[GotTheSikhness]

Possibly the funniest and most ******ed thing I have read today.

Unlike most people, I'm guessing, I actually refer to the sources that are cited in the article and I'm pretty sure published journal articles and the NIH are reliable sources . . . do you have something condescending to say about those as well?

 

[McGillGrad]

Unlike most people, I'm guessing, I actually refer to the sources that are cited in the article and I'm pretty sure published journal articles and the NIH are reliable sources . . . do you have something condescending to say about those as well?

Yeah, rationalizing your actions is even funnier.

Next time use uptodate.com like a professional academic.

 

[GotTheSikhness]

Yeah, rationalizing your actions is even funnier.

Next time use uptodate.com like a professional academic.

Maybe when I get to clinicals and I have 500 bucks I'll spring for it, but for now I think my sources will suffice. Thanks for the tip. I actually had never heard of the site.