Noradrenaline

Noradrenaline is an example of a Neurotransmitter and also a Hormone. It is also known by the name Norepinephrine, mostly in the United States. This catecholamine is mostly responsible for concentration, and are released in response to physical or mental stress. This hormone affects many parts of the brain. The hormone affects adrenergic receptors, which are transmembrane proteins spanning across the plasma membrane of many cell types.

Noradrenaline (norepinephrine) is often referred to as a 'fight or flight' chemical, as it is responsible for the body's reaction to stressful situations.

Noradrenaline normally produces effects such as increased heart rate, increased blood pressure, dilation of pupils, dilation of air passages in the lungs and narrowing of blood vessels in non-essential organs. This enables the body to perform well in stressful situations.

Noradrenaline works by stimulating receptors (adrenoceptors) which are found all over the body. When injected into a vein, noradrenaline acts mostly on a type of adrenoceptor known as an alpha receptor. These are present in the muscle within the walls of blood vessels of the extremities. By stimulating these alpha receptors, noradrenaline causes the muscle to contract. This results in narrowing of the blood vessels.

Narrowing the blood vessels in the extremities redirects blood to essential organs such as the heart and brain. It also produces greater resistance for the heart to beat against, and this increases blood pressure.

Noradrenaline is used to restore blood pressure to normal in emergency situations when blood pressure has dropped dangerously low.