Читать книгу Understanding Anatomy and Physiology in Nursing - John Knight - Страница 132

Adrenaline increases the heart rate and cardiac output by binding to beta (β) adrenergic receptors at the pacemaker (SAN). The drugs termed β blockers block adrenaline and noradrenaline from binding, thereby slowing the heart rate and reducing cardiac output and BP. Until recently β blockers such as atenolol were frequently prescribed to treat hypertension, but their use in treating this condition has now been largely superseded by ACE inhibitors (see below).

Adrenaline promotes vasoconstriction of blood vessels in the skin and gut: during periods of adrenaline release, the skin may take on an ashen appearance and many people complain of a feeling of butterflies in the stomach, which is thought to correspond to vasoconstriction in the gut. Simultaneously, adrenaline promotes vasodilation of blood vessels in the lungs and muscles, ensuring that blood is diverted to the key areas required for a fight-or-flight response.

The net result of increased cardiac output and changes in vascular tone mediated through adrenaline is a sudden increase in BP.