Normal resting heart rates range from 60â100 bpm. Bradycardia is defined as a resting heart rate below 60 bpm. However, heart rates from 50 to 60 bpm are common among healthy people and do not necessarily require special attention.achycardia is a fast heart rate, defined as above 100 bpm at rest. Bradycardia is a slow heart rate, defined as below 60 bpm at rest. During sleep a slow heartbeat with rates around 40â50 BPM is common and is considered normal.
The adrenergic receptors (or adrenoceptors) are a class of G protein-coupled receptors that are targets of the catecholamines, especially norepinephrine (noradrenaline) and epinephrine (adrenaline).
Beta blockers, also known as beta-adrenergic blocking agents, are a class of drugs that works by blocking the neurotransmitters norepinephrine and epinephrine from binding to receptors.There are three known types of beta receptors, known as beta 1 (Î² 1), beta 2 (Î² 2) and beta 3 (Î² 3).1  Î² 1 -adrenergic receptors are located commonly in the heart and kidneys.here are three known types of beta receptors, known as beta 1 (Î² 1), beta 2 (Î² 2) and beta 3 (Î² 3). 1  Î² 1 -adrenergic receptors are located commonly in the heart and kidneys.