Next, picture the effects of movement-when a person sits up, stands up, or begins to walk or run. The heart rate increases and blood pressure rises. A group of pressure-sensitive nerves in the aorta respond to the changes in pressure by sending a message to the brain. The brain in turn sends a message back to the heart, which changes its rate and strength of contraction. Blood vessels also dilate to allow for the extra blood flow.
Age brings changes in the arteries.
Also at maximum exercise, the large arteries do not dilate as much as in the younger picture. These in brief outline are some of the major changes that occur in blood vessel hydraulics with age. One reason these changes intrigue scientists is that they could have a major impact on heart dynamics. Stiffening increases the amount of resistance the heart must overcome to eject blood into the arteries, and any resistance to flow places a load on the heart. The study in which Eileen Shields is a participant will show the impact of this load.