In the heart there are two different subtypes of beta-adrenergic receptors—beta1 and beta2—which are activated by the stress hormones adrenaline and noradrenaline. They both trigger the strongest stimulation of the heart rate and pumping capacity that we know of. The two subtypes are highly similar biochemically, but differ substantially in terms of their functional and therapeutic relevance.
Click here for original story, Receptor location in heart plays a key role in their function
Source: Phys.org