LSAT 141 – Section 4 – Question 20

LSAT 141 - Section 4 - Question 20

September 2014

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Question
QuickView		 Type Tags Answer
Choices		 Curve Question
Difficulty		 Psg/Game/S
Difficulty		 Explanation
PT141 S4 Q20
+LR
Strengthen +Streng
Causal Reasoning +CausR
A
11%
160
B
1%
151
C
24%
160
D
59%
165
E
5%
162
145
158
171
 +Harder 147.542 +SubsectionMedium

In a recent study of stroke patients, those who exhibited continuing deterioration of the nerve cells in the brain after the stroke also exhibited the highest levels of the protein glutamate in their blood. Glutamate, which functions within nerve cells as a neurotransmitter, can kill surrounding nerve cells if it leaks from damaged or oxygen-starved nerve cells. Thus glutamate leaking from damaged or oxygen-starved nerve cells is a cause of long-term brain damage resulting from strokes.

Summarize Argument: Phenomenon-Hypothesis
The author concludes that glutamate leaking from damaged or oxygen-starved nerve cells is a cause of long-term brain damage resulting from strokes. This is based on the fact that in a study of stroke patients, those who showed deterioration of nerve cells in the brain also exhibited the highest levels of glutamate in the blood. In addition, glutamate can kill surrounding nerve cells if it leaks from damaged or oxygen-starved nerve cells.

Notable Assumptions
The author assumes that the glutamate observed in the blood leaked from damaged or oxygen-starved nerve cells (as opposed to originating from another source). The author assumes there’s no other explanation for the continued deterioration of nerve cells in the patients observed.

A
Any neurotransmitter that leaks from a damaged or oxygen-starved nerve cell will damage surrounding nerve cells.
If anything, this might undermine the argument by raising the possibility that some other neurotransmitter besides glutamate might be the cause of damaged nerve cells in stroke patients.
B
Stroke patients exhibit a wide variety of abnormal chemical levels in their blood.
The presence of other chemicals in blood does not help establish a connection between glutamate and the damaged brain nerve cells in stroke patients. We want to know that the glutamate leaked from damaged/oxygen-starved nerve cells. (B) doesn’t establish this.
C
Glutamate is the only neurotransmitter that leaks from oxygen-starved or physically damaged nerve cells.
We care about where the glutamate in the blood came from, not whether there are other kinds of chemicals that could come from damaged/oxygen-starved cells.
D
Leakage from damaged or oxygen-starved nerve cells is the only possible source of glutamate in the blood.
This strengthens by establishing that the glutamate observed in the blood of stroke patients must come from damaged/oxygen-starved nerve cells. This makes the premise concerning damage/oxygen-starved nerve cells more supportive of the conclusion.
E
Nerve cells can suffer enough damage to leak glutamate without being destroyed themselves.
We want to know that the glutamate leaked from damaged/oxygen-starved nerve cells. (E) doesn’t establish this. It simply tells us that nerve cells can leak glutamate without destroying themselves. But did the glutamate leak from damaged cells? We don’t know.

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LSAT PrepTest 141 Explanations

Section 1 - Reading Comprehension

Section 2 - Logical Reasoning

Section 3 - Reading Comprehension

Section 4 - Logical Reasoning

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