Correct answers are in bold, but be sure to read why the other answers are not correct.

1. Which of the following statements describes how ethanol crosses the blood-brain-barrier?
   1. It moves by filtration through fenestrae (pores) in capillary endothelial cells membranes.
      Sorry, try again. While most capillaries in the body have fenestrae (pores) through which water, ions, and small solutes move, the brain capillaries do not have these fenestrae.
   2. It diffuses passively across the endothelial cell membranes.
      Terrific! The brain capillaries have endothelial cells that are tightly packed together and do not have the fenestrae (pores) found in capillaries elsewhere in the body. But, it’s small size and relatively non-polar character allows ethanol to cross the brain capillary endothelial cell membrane by simply diffusing across with its concentration gradient (in either direction).
   3. It moves by filtration through spaces between the endothelial cells.
      Sorry, try again. The brain capillaries have endothelial cells that are tightly packed together unlike endothelial cells found in capillaries elsewhere in the body. The packing is tight enough to exclude the passage of ethanol between the endothelial cells.
   4. It is transported by a special carrier protein across the endothelial membrane.
      Sorry, that is incorrect. Ethanol is not transported by special proteins across membranes. It’s relatively non-polar character enables is to diffuse passively through the endothelial cell membrane, with the concentration gradient.
2. Which symptoms of alcohol intoxication are most likely to emerge first?
   1. slurred speech
      Sorry, you got it wrong. Slurred speech occurs after one has had several drinks because it takes more alcohol to suppress motor control.
   2. loss of balance
      Sorry, try again. The loss of balance occurs at blood levels of alcohol that are higher than those that produce incoordination.
   3. impaired memory
      Not likely. Impaired memory in the form of a blackout occurs when people drink a lot of alcohol in a few hours—this is called binging. Or, impaired memory results from repeated use of smaller amounts of ethanol.
   4. impaired judgement
      Yes, you are correct! One of the first areas of the brain to be affected by alcohol is the cerebral cortex. Judgment is governed by the frontal part of the cerebral cortex, along with thinking and decision-making. Risky and impulsive behavior is also under the control of the frontal cortex.
3. To produce the signs of intoxication, ethanol must interact with specific membrane proteins called GABA and glutamate receptors. These receptors normally regulate the electrical excitability of neurons. Which of the following occurs when alcohol causes the signs of intoxication?
   1. alcohol increases the firing rate of neurons all over the brain
      Well, only part is true. Alcohol decreases the firing rate of neurons wherever in the brain alcohol has access (i.e., everywhere!). It increases chloride ion entry through GABA receptors and blocks sodium ion entry through glutamate receptors. Either way, the more negative interior of the cell reduces the flow of an electrical impulse.
   2. alcohol decreases the firing rate of neurons all over the brain
      Fantastic! Alcohol decreases the firing rate of neurons wherever in the brain alcohol has access (i.e., everywhere!). It increases chloride ion entry through GABA receptors and blocks sodium ion entry through glutamate receptors. Either way, the more negative interior of the cell reduces the flow of an electrical impulse.
   3. alcohol increases the firing rate of neurons in specific parts of the brain
      Sorry. Alcohol decreases the firing rate of neurons wherever in the brain alcohol has access (i.e., everywhere!), but the actual symptoms are due to alcohol’s actions in specific brain regions. It increases chloride ion entry through GABA receptors and blocks sodium ion entry through glutamate receptors. Either way, the more negative interior of the cell reduces the flow of an electrical impulse.
   4. alcohol decreases the firing rate of neurons in specific parts of the brain
      You’re close, but not perfect. Alcohol decreases the firing rate of neurons wherever in the brain alcohol has access (i.e., everywhere!), but the actual symptoms are due to alcohol’s actions in specific brain regions. It increases chloride ion entry through GABA receptors and blocks sodium ion entry through glutamate receptors. Either way, the more negative interior of the cell reduces the flow of an electrical impulse.
4. With repeated alcohol use, GABA receptors adapt to the presence of the alcohol by down-regulating, or decreasing their number in the neurons. What effect would this have if one keeps drinking alcohol?
   1. the person would need more alcohol to become intoxicated (i.e., become tolerant)
      Great! People develop tolerance to alcohol when they drink it repeatedly—this means they need more alcohol to produce the same effect they had originally. Tolerance is due, in part, to a down-regulation of GABA receptors in the brain, the target of ethanol’s action.
   2. the person would need less alcohol to become intoxicated (i.e., become tolerant)
      Sorry, it’s backwards. People develop tolerance to alcohol when they drink it repeatedly—this means they need more alcohol to produce the same effect they had originally. Tolerance is due, in part, to a down-regulation of GABA receptors in the brain, the target of ethanol’s action.
   3. the person would metabolize more alcohol (i.e., become tolerant)
      Not quite. Actually, this is a trick question. People develop tolerance to alcohol when they drink it repeatedly—this means they need more alcohol to produce the same effect they had originally. There are two reasons for the tolerance development; 1) there is a down-regulation of GABA receptors in the brain, the target of ethanol’s action and 2) people metabolize alcohol faster after drinking repeatedly, so they need more of it.
   4. the person would metabolize less alcohol (i.e., become tolerant)
      Wrong. People develop tolerance to alcohol when they drink it repeatedly—this means they need more alcohol to produce the same effect they had originally. There are two reasons for the tolerance development; 1) there is a down-regulation of GABA receptors in the brain, the target of ethanol’s action and 2) people metabolize alcohol faster after drinking repeatedly, so they need more of it.
5. A friend of yours drank some alcohol and had a really bad reaction; she had nausea, rapid heart rate, sweating, and her face got really red. You knew what probably caused the bad reaction. What was it?
   1. Her liver metabolized the alcohol into a toxic compound
      True, but there’s more to the answer. Her liver enzyme alcohol dehyrogenase or ADH metabolized the alcohol into acetaldehyde, a toxic compound that produces the symptoms described. See the other answers for the reason why this happens.
   2. Her liver enzymes were too slow to metabolize acetaldehyde, causing it to accumulate.
      True, but there’s more to the answer. Her liver enzyme acetaldehyde dehyrogenase or ALDH was not very active, so it couldn’t metabolize the acetaldehyde very well. The acetaldehyde, a toxic compound, accumulated in her blood to produce the symptoms described. See the other answers for the reason why this happens.
   3. She carried a polymorphism for the ALDH gene that reduced the activity of the ALDH enzyme
      Great! Because she carried a polymorphism for the acetaldehyde dehydrogenase (ALDH) gene, she synthesized a poorly active form of the ALDH enzyme. Thus, her liver couldn’t metabolize the acetaldehyde very well. The acetaldehyde, a toxic compound, accumulated in her blood to produce the symptoms described. See the other answers for the reason why this happens.
   4. All of the above
      Perfect! See the answers to 1-3.