Alcohol and cars – a volatile mix
Box 1 | Ethanol and the brain
The brain is a large and highly complex organ made up of a tangled mass of nerve cells, or neurons. These cells carry messages in the form of electrochemical impulses throughout the brain and the body’s nervous system. The messages are transmitted from one neuron to another, across a tiny gap called a synapse, by chemical messengers called neurotransmitters. These are released from the axon of one neuron and then bind to receptors on the surface of another neuron.
Different neurotransmitters have different effects on the transmission of nerve impulses. Some promote this transmission while others inhibit it. Scientists have so far found hundreds of neurotransmitters, and the list is still growing.
Ethanol appears to affect various neurotransmitters. One of these is glutamate, the major promoter of nerve impulses in the brain. Scientists believe that one of the main effects of ethanol on nerve ‘firing’ is a decrease in the activity of glutamate neurotransmitters, leading to a slowing down of brain activity.
In addition, ethanol might increase the activity of another important neurotransmitter, gamma-aminobutyric acid (GABA). GABA’s role is quite different from that of glutamate in that it inhibits neuronal activity. When ethanol molecules bind to GABA receptors, the ethanol further inhibits neuronal activity. The parts of the brain that have GABA receptors include those responsible for movement, memory, and judgment.
Long-term effects of ethanol
Studies into the effects of ethanol on the brain are also increasing our understanding of longer-term problems, such as alcoholism and the effects of alcohol on health. These might be quite different from the short-term effects. For example, animals subject to long-term exposure to ethanol have been shown to have a reduced number of GABA receptor sites. As a result, the synapses of such animals are less effective in inhibiting nervous reactions such as seizures - perhaps explaining why chronic alcohol users experience more seizures than the rest of the population.
Related sites
How the body responds to alcohol (How Stuff Works, USA)
Neurotransmitters and neuroactive peptides (Neuroscience for kids, University of Washington, USA)
Neurotransmission (The Merck Manual of Diagnosis and Therapy, USA)
What are the effects of alcohol on the brain? (Ask the experts, Scientific American)
Related Nova topic
Getting our heads around the brain
Page updated June 2010.