beta blockers

[Blind date18]

Does beta blockers decrease the slope of phase 4 and phase 0 in slow fibers (by influencing ca)?,if it does so would it have same effect even on the phase 2 of fast fibers...? i know this is kind off stupid question but my brain is at saturation point . thanx in advance for the input

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[Rahas]

It decreases the slope of phase 4 in slow fibers by inhibiting the funny current. No funny current in fast fibers, so phase 4 is unaffected.

It decreases the slope of phase 0 in slow fibers by inhibiting L type Ca channels. Phase 0 in fast fibers is due to fast Na channels, so it remains unaffected.

But the inhibition of L type Ca channels in fast fibers leads to diminished Ca influx -> diminished Ca-dep-Ca release from the SER -> lower than normal intracellular Ca levels -> negative inotropy

 

[Blind date18]

thanks mate,it helped a lot