Practice Passage Test - 4 | Practice Passages for MCAT PDF Download

"The condition known as ischemic stroke occurs when there is reduced blood flow to a specific area of the central nervous system, leading to focal dysfunction of the affected tissue. This dysfunction arises because the neurons in that area require a continuous supply of oxygen and glucose from the blood to maintain their high metabolic demands and limited energy reserves. The lack of energy supply causes the death of many neurons, and additional damage occurs later due to secondary cellular and molecular events that are detrimental to vulnerable neurons. In a study, a researcher is investigating the impact of ischemic stroke on the composition of interstitial fluid in the brain using an animal model. By inducing focal ischemia in the brain and collecting interstitial fluid samples at different time intervals after the stroke, the researcher aims to analyze the concentrations of ions and other substances. The researcher proposes that the extracellular concentration of potassium ions will increase after the stroke and eventually return to normal. Similarly, the researcher predicts that the concentration of the protein albumin, which is normally found in lower amounts in the brain compared to the blood, will exhibit a similar pattern to potassium ions. Additionally, the researcher plans to examine brain tissue sections near the injured area to quantify the different types of cells present."