Most people know that exercise is good for us. "Use it or lose it" is a phrase used in connection with musculo-skeletal health. Also, with worries about obesity, heart disease and diabetes, a large proportion of health education budgets go on promoting healthy lifestyles, a key feature of which is exercise.
However, for some time now, neuroscientists have been aware of other benefits of exercise, namely those related to improving brain health. Much of this awareness has grown from a diversity of research areas including Alzheimer's disease, Parkinson's disease, drug addiction, sports psychology and attention deficit disorder (ADD).
What Keeps the Brain Healthy?
Like any other organ in the body, the brain needs oxygen, energy in the form of glucose, and nutrients. Good oxygen and glucose supply are dependent on efficient blood circulation and severe damage and loss of function can occur if this is impaired, resulting in a stroke.
Nutrients from food are also needed to build and repair the nerve cells, which transmit information throughout the brain and the rest of the nervous system. These mostly come from the diet and are transported to the brain via the blood. A vital role for nutrients supplied to brain is the manufacture of neurotransmitters. These are specialised chemical compounds which play a crucial role in the nervous system.
Role of Neurotransmitters in Nerve Transmission
Nerve impulses travel through the nervous system - to, from and within the brain – through nerve fibres (axons) which extend from the nerve cell body. These carry nerve signals to other nerve cells, not through a direct connection of fibres but via a synapse which is essentially a tiny gap between the end of the axon and the next cell.
When a nerve signal reaches the end of the fibre, it has to "jump" this gap to the next nerve cell. Neurotransmitters make this jump. When the impulse reaches the end of the axon, it causes a neurotransmitter to be secreted into the synaptic gap, travel across and enter the membrane of the next cell and so continue the impulse.
Different neurotransmitters have different functions: some can have a stimulatory effect on the impulse and others an inhibitory effect. Clearly then, the amount and type of neurotransmitter being secreted in the brain at any one time has a profound effect on function.
Neurotransmitters and Exercise
All the brain's neurotransmitters are being studied but three have been shown to be of particular interest. They are serotonin (5 hydroxytryptamine), dopamine and norepinephrine.
Serotonin is the principle mood neurotransmitter. People with low levels are more inclined to suffer from depression. Modern antidepressants act by increasing the amount of serotonin available.
Dopamine is involved in control of movement and its deficiency is implicated in Parkinson's disease. With norepinephrine, dopamine also increases alertness. Physical exercise seems to increase concentrations of these neurotransmitters.
It's been known for some time that regular exercise improves mood and this is consistent with exercise producing higher levels of serotonin.
The increase in levels of dopamine and norepinephrine through exercise has been postulated as the reason for the beneficial effects of exercise on ADD. Dr John Ratey, Associate Clinical Professor of Psychiatry at Harvard Medical School, suggests in his book Spark: The Revolutionary New Science of Exercise and The Brain, that regular exercise might be as effective as Ritalin in controlling ADD in some people.
Dementia and Exercise
Numerous studies have shown that physical exercise has a protective effect on the brain, probably due to both increased cerebral blood flow and enhanced neurotransmitter production.
Studies on the effect of exercise on brain disorders show that only moderate exercise is required for beneficial effect. Twenty minutes brisk walking three times per week is sufficient to provide a high degree of neuroprotection for most people.
Brain Plasticity
None of this will be a surprise for evolutionary psychologists. Humans evolved to be much more active than we are today, children especially so. The brain is constantly changing in response to internal and external stimuli - this inherent plasticity, evolved over millennia, requires a minimum level of stimulation to keep the nervous system healthy.
This article is for information only. If you have any health concerns, you should consult your doctor.
Sources:
Optimal Ageing and Cognition. American Psychological Association Annual Convention. August 11 2008.
Human Anatomy and Physiology by Carola, Harley and Noback. Pub. McGraw Hill 1992
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