Norepinephrine acts on the heart by . A) decreasing heart contractility B) causing a decrease in stroke volume C) blocking the action of calcium D) causing threshold to be reached more quickly

option d

Explanation:they are also normally called noradrenaline.

They do help by constant regulating of the blood pressure and to increase the sugar (glucose) level content in the blood. It help majorly to lift up (increase) the rate as well as the force of the contraction of the heart and also in do lead to an increase in muscle contraction due to the fact that they are push out(realeased) from the sympathetic nerve fibre ends.

using the scientific method.