Catecholamines: Adrenaline and Noradrenaline

Catecholamines: what they are

Adrenaline and noradrenaline are two hormones secreted by the medullary layer of the adrenal gland and some nerve endings (noradrenaline).

These two hormones intervene in the adrenergic reaction called "FIGHT OR FLIGHT", or you fight or run away. As can be guessed from its name, this reaction aims to prepare the organism for an important psychophysical effort in a very short time:

facilitating the use of muscle energy substrates
removing the catabolites (increases renal flow)
increasing energy intake to vital organs
facilitating the reconstruction of energy reserves

Adrenaline

Functions:

increases cardiac output
increases systolic blood pressure
diastolic blood pressure decreases
increases muscle blood flow
increases renal and cutaneous blood flow
increased glycogenolysis and lipolysis
peripheral vasoconstriction
splanchnic vasoconstriction
vasodilation in the hepatic and muscular areas
increased metabolism
bronchiolar dilation
increased vigilance

Adrenaline is secreted in response to very low stimuli and reaches a peak around 60% of VO2 max.

Factors that stimulate catecholamine secretion

Anxiety

Cold

Ache

traumas

Physical efforts

Hypotension

Fear

Hypercapnia

Intense pleasure

Hunger

During a static muscle exercise the adrenaline secretion prevails over the norepinephrine secretion.

Norepinephrine

Functions:

increases cardiac output
increases the total peripheral resistance
increases blood pressure
increases coronary flow

Norepinephrine is instead secreted in response to high intensity stimuli and its secretion is proportional to the intensity of the exercise. Around 70-75% of VO2max there is a peak in noradrenaline secretion.