PHYSIOLOGICAL EFFECTS OF AGING
Cardiovascular Effects
This Cardiovascular system includes the heart and the blood vessels. Due to an increase in the size of
individual heart muscle cells, the heart tends to enlarge resulting in thicker walls, slightly larger chambers
and reduced elasticity of the heart muscle resulting in a reduced cardiac output. Heart valves can thicken
and not fully seat (murmur). The heart's natural pacemaker cells decrease causing arrhythmias or
irregular heartbeats.
The older heart functions at a lower heart rate at rest. However, during exertion, it is not able to increase
the amount of blood flow as compared to a younger heart. The heart cannot respond as quickly, or as
forcefully, to an increased workload. Blood vessels can become brittle and the passages narrow due to
arterial plaque (arteriosclerosis) resulting in a decreased blood flow and higher blood pressures
(hypertension). An increased risk of aneurysms can be a result of lost elasticity.
A reduction in blood flow results in a decrease in the amount of oxygen that can be delivered to the other
systems. This is measured as VO2 MAX and defined as the maximum amount of oxygen that can be
utilized per minute. Reduced blood flow can result in shortness of breath, dizziness and in extreme cases
Cyanosis characterized by a bluish discoloration of the skin. Many of these effects can be reduced by
exercise.
Higher blood pressures are also a result of the heart's inability to fully relax (diastole) in order to fill with
blood before the next contraction (systole). High blood pressure causes the left ventricle to work harder to
push blood into narrowed and inflexible pathways. It may enlarge and outgrow its blood supply and thus
becomes weaker. Blood pressure is normal during the diastolic phase and high during the systolic phase.
This is common condition in the elderly and is called Isolated Systolic Hypertension. Almost half of all
heart failures are due to failure of the heart in the diastolic phase. During diastolic heart failure, heart
function appears normal, but the stiffened heart muscle causes excess fluid to build up in the lungs, feet,
ankles, and legs. Blood may pool in the veins of the legs because the valves are not able to function
correctly. This can also cause swelling of the lower extremities.
Reduction in hematocrit, which is a measure of both the number of red blood cells and the size of red
blood cells, which can lead to anemia. Constriction or blockages of peripheral veins can cause the
formation of clots, which can then dislodge causing an embolism in the lungs or stopping circulation in
extremities. Phlebitis, which is an inflammation of the vein also occurs more often in the elderly. Blood
glucose levels increase with age but not because of changes in the blood. Rather, it is the result of age-
related insulin changes. Bone marrow decreases with age, causing a decrease in the number of new
blood cells. As a result, bleeding will not stop as quickly.
The liver receives a smaller supply of blood due to shrinkage. This reduces the rate of drug detoxification,
which can exaggerate the effects of drugs predisposing the elderly to drug overdose. By age 70, the
weight of the liver has decreased by roughly 20%.
Specially adapted nerve fibers in the larger blood vessels and heart called beta adrenergic
(^) receptors
(bAR) become less sensitive and, as a result, cardiovascular adjustments to changes in position are
slowed, causing an increase in dizziness and falling. Fluid balance or pH usually remains constant unless
there is an incidence of disease or damage to a particular organ.