~ PREAMBLE ~
This pamphlet is a synopsis of the topic: ‘Brain damage associated with alcohol abuse,’ from several perspectives. Firstly, a definition of alcohol, its potency; factors involved in ingestion and absorption. Secondly, an outline emphasising the anatomical and physiological components of the brain. The brain’s orientations and ensuing direct and indirect effects on the afferent neurones (that transmit impulses to the central nervous system (CNS)), and efferent fibres, e.g., the effectors of the muscle or glands. Concluding with a soupçon of information about behavioural effects, organ systems, anterograde amnesia, three consecutive phases in physical dependence syndrome; and Wernicke-Korsakoff’s syndrome.
ETHANOL.
Alcohol is known as ‘ethyl alcohol’ and ‘ethanol’. The word ‘ethanol’, rather than ‘alcohol’, is employed in this pamphlet, to conform with its approval by the International Union of Pure and Applied Chemistry (IUPAC). Ethanol is developed by either fermentation or distillation from agricultural products and comprises of Hydroxyl (OH) type organic compounds connected to a single carbon atom, viz., three hydrogen atoms adjoining a single carbon atom (CH 3 OH). The potency of ethanol beverages are variable. The Alcohol Drug Foundation (Victoria) report that ‘beer has an approximate ethanol content range between 2-5% x volume of 425 and 285 ml respectively, wine approximates between 10-20% x volume of 120 and 60 ml, and distilled spirits; 40% x volume of 30 ml’. 1.
Ingestion.
Ethanol is usually ingested orally and is absorbed into the body from both the upper and lower aspects of the alimentary canal at absorption levels of approximately 75% and 25% respectively. 2. Its rate of absorption is greater in the small intestine than the stomach. 3. Following ingestion, the blood ethanol (alcohol) level (BAL) may peak within 30 to 60 minutes. 4. The level of ethanol, and the determining factors in absorption are based on: the percentage level of ethanol per drink, the condition of the stomach, the variable time factors of absorption, and the rate of metabolism determined by liver mass, tolerance and genetic factors.
The absorption rate is less at the low level of the ethanol percentage range, whereas it is more at the high level. 5. A high level of ethanol in a void stomach may cause pylorospasms, viz., convulsions of the pyloric sphincter, that will obstruct the path into the small intestine; thus retarding the absorption rate. The rate is also determined by either presence or absence of food stuffs (solids/liquids) in the upper aspects of the gastrointestinal (GI) tract. 6.
Presence of food stuffs, particularly some fatty substances, slow down the rate of ethanol absorption, whereas its absence – or ethanol combined with carbonated fluids – may accelerate absorption by approximately 20% per dose. 7. Inflamed peptic ulcers may either inhibit or stimulate absorption. The rate of absorption is affected also by temperature. At environmental temperature, it is absorbed rather rapidly, whereas chilled, it absorbs slowly. 8.
Ethanol Molecule Infant’s Blood Brain Barrier (BBB).
The ethanol molecule (CH 3 CH 2 OH) is water and fat soluble and therefore absorb quite readily into all tissue including the brain. It also passes over the placenta – a structure that exchanges oxygen, nutrients, carbon dioxide and wastes between the foetal and maternal circulation – to an infant’s BBB. Pregnant women consuming several drinks per day expose their unborn infants to foetal alcohol syndrome (FAS). Foetal alcohol syndrome includes: anomalous cardiac function, arrested intellectual development, head and facial disfigurement. And abnormalities to the cartilaginous, fibrous and synovial joints, as well as the extremities (vide: Cox C. et al. ‘Drugs and Drug Abuse’, Addiction Research Foundation, 2nd ed, p. 283). The scientific community has not established safe levels of ethanol intake for pregnant women.
Inspiration and Excretion.
Diagram above by courtesy of the copyright owners: Microsoft(R) Encarta (R) 97 Encyclopaedia © 1993 – 1996 Microsoft Corporation.
Vaporized, ethanol can be absorbed by inspiration (inhalation of air into the lungs) into the blood stream, and small quantities can be excreted by expiration (exhalation of air from the lungs). The interchange of oxygen (O 2 > CO 2) from the left ventricle, and carbon dioxide (CO 2> O2) from the right ventricle of the pulmonary blood supply, ocurrs – during inhalation – between the capillary network and the alveoli; and during exhalation the carbon dioxide is removed from the lungs. Ethanol retards the rate of incoming atmospheric air and the interchange process between the alveoli and the pulmonary blood capillaries. Excretion, from the body via the kidney and urinary system, occurs following metabolic activity of the liver, viz., detoxification or catabolism.