Neurotransmitters are chemicals released by the brain that allow communication between nerve cells. The billions of nerve cells in the brain have no direct contact, so they send signals to each other by secreting neurotransmitters. Exercise has a direct effect on some neurotransmitters which can increase feelings of well-being and delay the effects of fatigue.

Boosting the Brain

When you exercise, the brain releases a combination of neurotransmitters -- such as serotonin, dopamine and endorphins -- which have a number of direct effects on the brain, according to a 1995 study conducted at Vrije University, Brussels. According to Rachael Seidler, associate professor of psychology and kinesiology at the University of Michigan, exercise can also boost brain power due to the increased flow of blood and oxygen to the brain.

Endorphins

Endorphins are one of the body's natural opioids. The concentration of endorphins in the blood plasma increases during exercise. Though few studies have been conducted on endorphins during exercise, according to a 1985 study published in "Medicine & Science, Sports & Exercise" showed that high-intensity exercise causes endorphins to adjust the rate of breathing and help to mask or lessen any pain or discomfort caused by the exercise.

The release of endorphins creates a pleasurable feeling known as "runner's high." This effect comes about after very intense workouts that tend to go a long way beyond the body's normal endorphin-activating threshold. Such strenuous exercise such as running and intense weightlifting boosts the brain's production of endorphins as the body attempts to deal with discomfort. The rush of endorphins may sometimes lead to an addiction to exercise.

Depression

Although jogging for a couple of miles may not enable you to throw away your antidepresssants, according to Harvard Health Publications, exercising on a regular basis can improve your mood if you suffer from mild to moderate depression. It may also complement the effects of medication in severe depression. In a study published in the "Archives of Internal Medicine" in 1999, one group of adults with depression took part in an aerobic exercise program, another group took anti-depression medication Zoloft and a third group did both. The results indicated that all three groups showed an improvement in their symptoms of depression. This suggests that exercise may be a reliable substitute for antidepressants if you wish not to or are unable to take them. You should consult your doctor if you are suffering from depression and you wish to stop taking your medication.

Memory and Learning

Exercise can help alleviate depression and benefit the brains of healthy people because it helps to increase dopamine D2 receptor levels in the brain, according to Astrid Bjornebekk at Karolinska Institutet. This reduces stress and anxiety and also helps to increase the growth of new brain cells in the areas related to learning and memory.