The is the region of the eye where photoreceptors are most highly concentrated.

activity

the category "activity" includes exercise, rest and sleep. there is much confusion about the role that exercise and sleep play in health. like diet, activity is an area where each person can take control.    

vigorous physical activity puts demands on all body systems to work harder. the body responds to these demands by becoming stronger and more efficient. the health benefits of exercise include improved metabolism, increased muscle and bone strength, more efficient cardiovascular (heart and blood vessel) function, larger lung capacity, tension reduction, and improved sleep.

the most efficient way to obtain these benefits is through regular aerobic exercise. aerobic exercise involves the large muscles of the body, particularly the legs. examples include brisk walking, jogging, swimming and bike riding. exercise is most enjoyable when it is incorporated into recreation and becomes a regular part of your normal daily activities.

the benefits of regular aerobic activity are becoming more widely understood and accepted; however, the benefits of sleep are often ignored. sleep deprivation can suppress the body's immune system, and has been associated with depression. healing activity is accentuated during sleep. two aspects of sleep must be considered: quality and quantity.

many people just don't allow enough time for sleep. they regard it as a waste of time and use drugs such as caffeine to stimulate their exhausted bodies into action. some people allow plenty of time for sleep, but the quality of their sleep is poor. regular exercise is often effective in people improve their ability to fall asleep. physically fit people spend more of their sleeping time in deep sleep, and in rem (rapid eye movement), or dreaming sleep, the more restorative stages of sleep. people who are getting enough sleep wake spontaneously and feel refreshed.

psychology

psychological health is characterized by high self-esteem and is dependent on two primary features: productive activity and effective interpersonal skills.

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