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 are involved in the adrenergic reaction called "FIGHT OR FLIGHT", or fight or run. As can be understood from its name, this reaction has the purpose of preparing the body for an important psychophysical effort in a very short time:

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

Adrenaline

Functions:

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

Adrenaline is secreted in response to very low intensity stimuli and peaks around 60% of VO2 max.

Factors that stimulate the secretion of catecholamines Anxiety
Freddo
Ache
Trauma
Physical efforts Hypotension
Fear
Hypercapnia
Intense pleasure
Hunger

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

Noradrenaline

Functions:

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

Norepinephrine, on the other hand, is 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 norepinephrine secretion.