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).
Norepinephrine Epinephrine. Norepinephrine, also known as noradrenaline, is a neurotransmitter found in the sympathetic nervous system. The sympathetic nervous system stimulates the heart, blood vessels, sweat glands, the large internal organs, and the adrenal medulla in the brain.he amino acid tyrosine, found in high concentrations in cheese, is converted by specific reactions into at least two neurotransmitters â norepinephrine and dopamine. Norepinephrine is produced from dopamine, with the help of the amino acids phenylalanine, lysine, and methionine.