Answer to Question 1
Aging often results in the reduction of the size of the hippocampus, a brain region associated with memory. When that happens, memory decline can occur. The hippocampus begins to decrease in mass by 0.5 each year beginning as early as age 40. Recent studies have shown that regular physical activity, aerobic exercise, and strength-training increase the size of the hippocampus and decrease the rate of brain shrinkage. Maintaining a high level of fitness in mid-life can reduce a person's chances of developing Alzheimer's by 50 and dementia by 60. Even becoming physically active later in life can produce measureable gains in the weight of the hippocampus after just a few months of training.
Answer to Question 2
Smoking greatly decreases the ability of the blood to transport oxygen to working muscles. Oxygen is carried in the circulatory system by hemoglobin, the iron-containing pigment of the red blood cells. Carbon monoxide, a by-product of cigarette smoke, has 210-250 times greater affinity for hemoglobin over oxygen. Consequently, carbon monoxide combines much faster with hemoglobin, decreasing the oxygen-carrying capacity of the blood. Chronic smoking also increases airway resistance, requiring the respiratory muscles to work much harder and consume more oxygen just to ventilate a given amount of air. If a person quits smoking, exercise does help increase the functional capacity of the pulmonary system.
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