Reading ComprehensionDifficulty: Hard

PT125 S3 P4 Q24 Explanation

Neurotransmitter Theory

A free, expert breakdown of this official LSAT Reading Comprehension question.

TopicsMeaning in ContextScience

Keep going in LSAT Lab

  • Save & drill this skill — build targeted practice sets from questions like this one

  • Video walkthroughs — watch every question solved step by step

  • 81 official LSATs — as questions, timed sections & full-length tests

Start practicing free

Free to start

Full official LSAT questions are available through LawHub. This page provides LSAT Lab's explanation, strategy, and review tools without republishing the full official question.

Passage

Neurobiologists once believed that the workings of the brain were guided exclusively by electrical signals; according to this theory, communication between neurons (brain cells) is possible because electrical impulses travel from one neuron to the next by literally leaping across the synapses (gaps between neurons). But many neurobiologists puzzled over how this impulse that runs through the cell; the electrical impulse is thereby transmitted to the receiving neuron.

This theory has gradually won acceptance in the scientific community, but for a long time little was known about the mechanism by which neurotransmitters manage to render the receiving neuron permeable to ions. In fact, some scientists remained skeptical of the theory because they had trouble imagining how the binding of a of receptors plays the pivotal role in mediating the conversion of chemical signals into electrical activity.

The new evidence shows that receptors for neurotransmitters contain both a neurotransmitter binding site and a separate region that functions as a channel for ions; attachment of the neurotransmitter to the binding site causes the receptor to change shape and so results in the opening of its channel component. Several types of receptors display enough similarities to constitute a family, known collectively as neurotransmitter-gated ion channels.

It has also been discovered that each of the receptors in this family comes in several varieties so that, for example, a GABA receptor in one part of the brain has slightly different properties than a GABA receptor in another part of the brain. This discovery is medically significant because it raises any number of debilitating conditions, including mood disorders, tissue damage associated with stroke, or Alzheimer’s disease.

What this question is testing

Meaning in Context

Your task

Pin down exactly what the question asks about the passage — a detail, the author's view, the structure, or the main point — before looking at the choices.

Common trap

Answers that restate a true detail from the passage but don't answer the specific question being asked.

Winning move

Anticipate the answer in your own words from the passage, then find the choice that matches that prediction.

Reading along? Open the full official question in LawHub — we show a fragment here and keep the reasoning in our own words.

The question
24.

The author most likely uses the phrase “defined categories of neurons” in the fourth paragraph in order to

Answer choices

  1. Too Generic10% picked this

    possess channels for

    All neurons possess channels for ions. This passage is saying that we've discovered that the way electrical signals can be sent chemically from neuron to neuron is that a neuron's chemical receptor detects a neurotransmitter, which causes the receptor to open up its channel for ions. Since this answer describes a trait that applies to all neurons, it has nothing to do with what we're looking for: selectivity and specificity.

  2. Too Generic9% picked this

    respond to drug

    All neurons can potentially respond to drug treatment. The idea of making a drug for "defined categories of neurons" is the idea that it would only target specific neurons in specific areas of the brain. Since this answer describes a trait that applies to all neurons, it has nothing to do with what we're looking for: selectivity and specificity.

  3. Too Generic7% picked this

    contain receptor

    All neurons possess receptor molecules. The main point of the passage is that electrical signals are sent from neuron to neuron via a chemical reaction caused with each neuron's receptor molecule. Since this answer describes a trait that applies to all neurons, it has nothing to do with what we're looking for: selectivity and specificity.

  4. Correct64% picked this

    influence particular brain

    Why this is right

    This reinforces the context leading up to this phrase, "defined categories". The previous sentence said: This discovery is medically significant because it raises the possibility of the highly selective treatment of certain brain disorders. And our sentence says: Pharmacologists may be able to design drugs targeted to specific receptors on defined categories of neurons. Different brain functions happen in different areas of the brain, and the whole idea of these new targeted drugs is that they wouldn't affect the whole brain, just the area of the brain that's impacted by the disorder.

    Skill tested: Meaning in Context · how this choice captures the passage's function is the move to repeat next time.

  5. Too Generic10% picked this

    react to binding by

    All neurons act this way. The main point of the passage is that the way electrical signals can be sent chemically from neuron to neuron is that a neuron's chemical receptor reacts to a neurotransmitter by binding to it, which causes the receptor to open up its channel for ions. Since this answer describes a trait that applies to all neurons, it has nothing to do with what we're looking for: selectivity and specificity.

Continue the review in LSAT Lab

Save this question, watch the video walkthrough, and drill similar questions in your LSAT Lab account.

Save and practice this skill
LSAT Lab

Turn this review into a targeted study plan.

Save this question, drill more like it, watch the video walkthrough, and track your progress in your LSAT Lab account.

Start practicing free