How Alcohol affects the Brain
Normal GABA Functions |
The gap where an electrical signal jumps from one neuron to another is called the synaptic cleft. This is a closeup of the cleft between one neuron and another. Since the impulse cannot cross a gap as electricity, it crosses as a "message" by means of chemical messengers called neurotransmitters. This animation shows the action of a neurotransmitter called GABA, which acts to quiet electrical activity in parts of the brain. The GABA is produced in one neuron, here the one shown at the top. It is stored in packages called vesicles that move to the cell membrane and release the GABA into the cleft. The GABA crosses the gap between the neurons, and then binds to receiver sites, or receptors, on the neighboring neuron, shown at the bottom. When GABA occupies a receptor, it decreases the neuron's electrical activity. (That is, the neuron's electrical activity "quiets down.") After a while, the GABA comes off the receptor and is removed from the synapse by reuptake pumps that return it to the first neuron. |
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When GABA binds to its receptors, channels in the neuron flicker open and closed, allowing negatively charged molecules called ions (shown here in white) to move into the neuron. This decreases the neuron's activity. This close-up shows the opening of the ion channels in normal GABA binding, and then when alcohol is added. For another view of the "GABA rings" can be found in the Neurotransmitter Section on this site. Alcohol, shown in black, also binds to the GABA receptors, and increases the quieting effect that GABA has on neurons. Researchers are not sure exactly how it does so, but one theory holds that it causes the ion channels to stay open longer, thus increasing the ion flow. The result is a much greater quieting effect on the brain. Because there are GABA receptors in many parts of the brain, many different parts are affected. This accounts for alcohol's sedating effect on many functions controlled by the brain--judgment, movement, and even breathing. Unfortunately, prolonged alcohol use may cause the brain to adapt, so it comes to depend on the presence of alcohol to function normally. Then, if the person stops drinking, he or she experiences anxiety, jitteriness, emotional discomfort, insomnia, possibly tremors, and, in severe alcoholism, sometimes convulsions and/or death. Even long after the person has stopped drinking alcohol, brain abnormalities can persist, causing feelings of discomfort and craving for more alcohol to relieve these feelings. |
GABA Function When Alcohol is Added |
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| What is GABA and why is it important? It is the body's natural control mechanism for managing stress and nervous tension. | |||||
