The greater the heart muscle is stretched, i.e the greater volume of blood that enters, the stronger the contraction, and the greater the volume of blood ejected in one stroke. A. Adrenal cortex. B. Cholesterol is needed there to synthesize steroid hormones such as cortisol. HDL may bring cholesterol to adrenal, 7. Without angiontensinII, the radius of the arterioles will increase.
Body regulates amount in different regions by vasoconstriction.
Usually some overall vasoconstriction, if suddenly have extensive vasodilation, the same amount of blood is now spread over a much larger area, leading to a decrease in blood pressure. The increase in blood pressure is sensed by the baroreceptor in the carotid sinus, which sends a message to the medulla oblongata to relax arteriolar smooth muscle, and to decrease rate of the heart beat, both of which will lead to a decrease in blood pressure. These effects are dependent on increased parasympathetic activity, and decreased sympathetic activity.