How does norepinephrine act on B1 receptors when it can only act on ALPHA adrenoreceptors?

[StrongBeliever]

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So, I know that epinepherine acts on both ALPHA and BETA adrenorecptors.
But, norepeniphrine acts only on ALPHA adrenoreceptors.

Then in my other book it says, in the pacemaker of the heart, sympathetic releases noradrenaline (norepinephrine) and acts on B1 receptor of the heart. But why??

 

[StrongBeliever]

bump

 

[StrongBeliever]

bump

 

[KVBane]

It works on beta receptors, just less actively than alpha receptors

 

[just_SAIYAN]

NE works alpha 1 alpha 2 and Beta 1
Alpha > beta 1


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