PSYC62H3 Chapter Notes - Chapter 8: Tegmentum, Delirium Tremens, Alcoholic Cardiomyopathy
Chapter 8: Alcohol
Alcohol: Most Commonly Used Depressant Substance
• Beverage alcohol = any drink containing ethyl alcohol (aka ethanol) → CNS depressant
• Methyl alcohol (methanol) = industrial solvent used in many products
o Antifreeze
o Acts as toxin for optic nerves
o If consumed → blindness
• Beverage alcohol widely consumed across the world, second to caffeine
• Highest alcohol consumptions levels occur in Europe, Russia, North America, South
America, and Australia
• Middle East reports lowest levels of alcohol consumption
Alcohol Production through Fermentation and Distillation
• Beer, wine, and spirits are primary sources of beverage alcohol
• Small amounts found in vinegar, and certain liquid medications (cough syrup)
• Amount of alcohol in a beverage labeled in two ways:
o Percentage
o Proof
• Percentage alcohol
o Number of grams of alcohol found in 100 mL of solution
• Proof of alcohol
o Numerical value that is double the actual % of alcohol
• Fermentation
o Process of alcohol production using yeast cells and some type of starch such as
grain/fruit
o Yeast interacts with sugars from starches creating alcohol
o Longer the yeast takes to metabolize the sugars, greater the percentage of
alcohol produced
o Higher alcohol percentages than 15% kill yeast cells → fermentation ends
• Beer
o Usually with 5% or less alcohol content
o Fermentation of barley, wheat, or rice
o During fermentation process, brewers add other ingredients to further promote
fermentation and provide flavouring
o Malt liquor
▪ Comes from malted barley
• Wine
o Usually with 12-15% alcohol content
o Fermentation of fruit
▪ Most use grapes
• Distilled alcoholic beverages
o Aka liquor or spirits
o Produced through distillation and have higher alcohol content
o Distillation: separates alcohol from a fermented mixture
▪ Highly alcoholic solution
o Contain at least 20% alcohol
▪ Brandy, gin, rum, tequila, vodka, and whiskey
o Everclear = highly filtered; contains high concentration of alcohol with few other
chemicals
▪ 75%-95% alcohol
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• Health officials compare beverages according to standard drink units
o Standard drink contains 14 grams of 100% alcohol
Pharmacokinetic Factors and Alcohol’s Effects
• Alcohol is highly soluble in water and fat → easy absorption into tissue
• Consume alcohol orally, after ingestion alcohol absorbs into bloodstream through
gastrointestinal tract
• Most alcohol absorbed through upper intestine because of large surface area
• Measure alcohol in the body by blood alcohol concentration (BAC)
o Number of grams of alcohol in a 100 ml volume of blood
o Max BAC from a drink occurs after approximately 45 min
• Enzymes in stomach, liver, and other parts of the body metabolize alcohol
o Alcohol dehydrogenase metabolizes 95% of alcohol → converts alcohol to
acetaldehyde (produces noxious effects)
o Brain also converts into acetaldehyde
o Metabolic process for alcohol
▪ Alcohol → acetaldehyde → acetic and acetate → water and CO2
• Polymorphisms that can affect rate of alcohol metabolism
o Alcohol dehydrogenase 1C*1 allele → more quickly converts alcohol to
acetaldehyde
• Both stomach and liver contain alcohol dehydrogenase enzymes
o Metabolism in stomach occurs 20% less in women
o After absorption, alcohol dehydrogenase in liver metabolize most of the
remaining alcohol
• Rate of alcohol elimination follows zero-order kinetics
o Rate remains the same regardless of the amount of alcohol consumed
o Zero order kinetics apply to alcohol’s elimination rate until all available enzymes
for metabolizing alcohol become saturated or completely occupied
o Although 95% of alcohol is metabolized, body eliminates remaining 5%
(unchanged) from the lungs
• Breathalyzer tests use ratio of alcohol concentration in expelled air to blood to accurately
determine amount of alcohol in blood
Alcohol and Central Nervous System Functioning
• Pharmacological actions of alcohol in the body involve GABA, glutamate, endogenous
opioid, dopamine, serotonin, and endocannabinoid systems
→ Alcohol and GABAa Receptors
• Alcohol acts directly on ionotropic GABAa receptors → inhibitory effects on neurons
o GABA activates GABAa receptors → channels open → negatively charged
chloride ions enter neuron → hyperpolarize neuron → inhibit neuron’s activity
o Alcohol binds and functions as positive modulator for GABAa receptors
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Document Summary
Alcohol: most commonly used depressant substance: beverage alcohol = any drink containing ethyl alcohol (aka ethanol) cns depressant, methyl alcohol (methanol) = industrial solvent used in many products, antifreeze, acts as toxin for optic nerves. If consumed blindness: beverage alcohol widely consumed across the world, second to caffeine, highest alcohol consumptions levels occur in europe, russia, north america, south. America, and australia: middle east reports lowest levels of alcohol consumption. Alcohol and central nervous system functioning: pharmacological actions of alcohol in the body involve gaba, glutamate, endogenous opioid, dopamine, serotonin, and endocannabinoid systems. Alcohol and glutamate receptors: alcohol also produces depressant effects by inhibiting excitatory glutamate nmda receptors, nmda receptors produce excitatory effects and facilitate learning and memory processes, alcohol binds to nmda receptors noncompetitively. Interfering with negative feedback loop involving a type of potassium channel called sk2, for the nmda receptor: chronic use inhibits function of sk2 channels diminishes effectiveness of negative feedback.
