Scientist long believed that two nerve cluster in the human hypothalam

Passage notes:
Passage 1: Scientists (long believed): 2 nerve clusters (SCNs) controlled rhythms (cycles-24 hours)
- Studies suggest something about animals : SCNs control BP, temp., activity, alertness, and melatonin.

- Furthermore (more info. on the same line): cells in retina discovered

Passage 2: 4 genes governing cycles are found in every tissue.
- However (some contrast)
-In addition- Experiment explained

Scientists (now believe): C. Clocks MAY respond to external cues other than light.

412. D
413. D
414. A



Thanks

4:54 sec.

Ans:
1. Scientists believe SCN controlled circadian rhythms. But later new discoveries have led to believe that other genes also regulate these cycles.
So answer is D) discuss evidence that has caused a longstanding belief to be revise

2. Passage mentions everything except vision. Answer D

3. Four critical genes governing circadian cycles have been discovered. Answer is B which says that the SCNs do not play an exclusive role in regulating circadian rhythms.

Hi Mike,

in above passage what does following sentence want to convey.

Four critical genes governing circadian cycles
have been found to be active in every tissue,
however, not just the SCNs, of flies, mice, and
humans.

Regards,
Ammu

I'm happy to respond.

So, the passage lets us know that the "suprachiasmatic nuclei (SCN)" is the place that runs the circadian cycles (that is, the 24-hour cycles of sleeping & waking). Naively, we would expect everything about circadian rhythms to be run from there. Then, this sentences surprises us.

Four critical genes governing circadian cycles have been found to be active in every tissue, however, not just the SCNs, of flies, mice, and humans.

Four of the genes that play crucial role in governing sleep/wake cycles are not just in the SCN, where we'd expect--instead, they're everywhere throughout the body!

My friend, if this sentence was a challenge to you, you need to practice reading. You need to read Scientific American every week for practice. See:
How to Improve Your GMAT Verbal Score

Does all this make sense?
Mike

Hi rajatbanik,

Carolyn from Magoosh here -- I can step in for Mike

This option is definitely tempting! Choice E) here states:

E) attempt to explain a commonly misunderstood biological phenomenon

Presumably, this "biological phenomenon" is the biological cycles, or circadian rhythms. Now, part of this fits, in a sense -- it seems reasonable to describe circadian rhythms as a "commonly misunderstood biological phenomenon". However, does the passage attempt to explain it? Not really -- it mostly just describes the existing theory, and the problems with the theory. It doesn't present any alternative explanation, it just says that something other than SCNs must also contribute to the phenomenon of circadian rhythms. The passage mentions a few things like temperature changes, but it definitely doesn't focus on any particular alternative explanation.

So, we can't say that attempting to explain this phenomenon is the primary purpose of this passage. Choice D fits better

Hope that helps!
-Carolyn

P1 - SCN, how it works
P2 - a theory around this, proof.

1. The primary purpose of the passage is to

(A) challenge recent findings that appear to contradict earlier findings - no
(B) present two sides of an ongoing scientific debate - no
(C) report answers to several questions that have long puzzled researchers - could be
(D) discuss evidence that has caused a longstanding belief to be revised - could be
(E) attempt to explain a commonly misunderstood biological phenomenon - no misunderstood

c- only one question snc alone controls or not .
d- yes, first line gave that belief, rest tried to proove it.

---------------------------

2. The passage mentions each of the following as a function regulated by SCNs in same animals EXCEPT

daily fluctuations in blood pressure, body temperature, activity level, and alertness, as well as the nighttime release of the sleep-promoting agent melatonin

(D) vision

---------------------------------------------

3. The author of the passage would probably agree with which of the following statement about the SCNs?

(A) The SCNs are found in other organs and tissues of the body besides the hypothalamus. - could be
(B) The SCNs play a critical but not exclusive role in regulating circadian rhythms. - could be
(C) The SCNs control clock genes in a number of tissues and organs throughout the body. - no
(D) The SCNs are a less significant factor in regulating blood pressure than scientists once believed. - no comparison defind.
(E) The SCNs are less strongly affected by changes in light levels than are by other external cues. - no comparison defind.

Scientist long believed that two nerve cluster in the human hypothalamus, called suprachiasmatic nuclei (SCNs) - SNC not found in other parts. A can be eliminated.

Took 5 minutes in answering....Though the passage was easy got 2/3 correct
I marked C in Question 3
Can anyone please explain how answer of the question 3 is Option B?
aragonn
Could you please explain?

Hello Vasuca10,

Though I am not the expert whom you requested for, I can help you out with this question. Passage 2 states, "While scientists do not dispute the role of the SCNs in controlling core functions such as the regulation of body temperature and blood pressure, scientists now believe that circadian clocks in other organs and tissues may respond to external cues other than light. This is essentially what option B is saying as in passage 1, we can deduce that scientists believed that SCNs had an exclusive role in the circadian rhythms. Hope this helps!

csaluja spot-on, vasuca10 - Sorry mate, I might have missed your request among other things. I will focus on approach. How to approach such type of questions. So
1. first thing is Para map - you have to be clear what para is saying what.
2. read the question carefully and understand what you need to answer.
3. read the choices, try to eliminate choices that you can. most cases one can eliminate 2-3 choices.
4. refer right para for remaining choices only. Para map will help you to find the correct or in correct choice. remember that if you have 2 choices left finding a right or wrong choice is going to help you. as remaining choice will be the correct one.
This approach will help you in solving these type of question faster.
This is what I did in my answer above. I left with A and B and then I referred for the passage.
Hope it is helpful.

Hi MagooshExpert, SajjadAhmad, workout,

My query is with regard to Q1. In it I eliminated option B, C, and E, for obvious reasons then left with A and D. A and D almost felt like same hence went ahead with A instead D. Could you please assist to find where I made error.

First of all analyze the wording used in both options A and D

(A) challenge recent findings that appear to contradict earlier findings
(D) discuss evidence that has caused a longstanding belief to be revised

Below is the explanation by "mikemcgarry"

In Par 1, he talks about the role of the SCN in regulating circadian rhythms.
Par. 2, he cites new evidence that is not entirely compatible with the SCN running everything. The first paragraph really sets the stage of what the author wants to say. The second paragraph is really the author's main point, the juicy point he want to make--- the first paragraph just sets the stage so we have context for the second paragraph. The "SCN runs the whole thing" theory was called "long believed," so it is a longstanding theory that the new evidence calls into question, causing scientist to revise the longstanding theory. This is what (D) says.

Thanks SajjadAhmad for response.

I felt that A also could be answer as

"Par. 2, he cites new evidence that is not entirely compatible with the SCN running everything" Which can be also inferred as "recent findings that appear to contradict earlier findings"

Not sure if I making any mistake in understanding it.

In RC, The correct answer should be correct on ALL grounds, i.e., 100% in line with the passage.

Excerpt from the passage:

While scientists do not dispute the role of the SCNs in controlling core functions such as the regulation of body temperature and blood pressure, scientists now believe that circadian clocks in other organs and tissues may respond to external cues other than light—including temperature changes—that recur regularly 24 hours.

The gist of the above lines:

Scientists (now believe): Apart from SCNs, Clocks MAY respond to external cues other than light.

The author agrees with the above-mentioned stance of the scientists. (the recent findings).

To answer your query:

True, the recent findings MAY appear contradicting to earlier findings.
However,
Reading entire Q in conjunction with Option A: challenge recent findings that appear to contradict earlier findings.

The primary purpose of the passage is to challenge recent findings that appear to contradict earlier findings

No where in the passage the author challenges the recent findings.
The author is not in disagreement with the recent findings.

Moreover, he emphasizes to add the recent findings to the earlier findings, suggesting longstanding belief to be revised.

For the main purpose question 1,I'm stuck between B and D. In p1, the author cites traditional belief and then he presents new belief in p2. Isn't it B? The option B deals with two sides of an ongoing scientific debate?

OE
Q1. The primary purpose of the passage is to
A. challenge recent findings that appear to contradict earlier findings
B. present two sides of an ongoing scientific debate
C. report answers to several questions that have long puzzled researchers
D. discuss evidence that has caused a long-standing belief to be revised
E. attempt to explain a commonly misunderstood biological phenomenon
Main idea
This question depends on understanding the passage as a whole. The passage begins by describing a longheld belief regarding humans’ circadian rhythms: that the SCNs control them. It then goes on to explain that new findings have led scientists to believe that other organs and tissues may be involved in regulating the body’s circadian rhythms as well.
A. The passage does not challenge the more-recent findings. Furthermore, the recent findings that the passage recounts do not contradict earlier findings; rather, when placed alongside those earlier findings, they have led scientists to reach additional conclusions.
B. The passage does not discuss a two-sided debate; no findings or conclusions are disputed by any figures in the passages.
C. There is only one question at issue in the passage: whether the SCN alone control human circadian rhythms. Furthermore, nothing in the passage suggests that researchers have been puzzled for a long time about this.
D. Correct. The new evidence regarding circadian rhythm–related gene activity in all the body’s tissue has led scientists to revise their long-standing belief that the SCN alone control circadian rhythms.
E. The biological phenomenon of circadian rhythms is not, at least as far as the passage is concerned, misunderstood. Its causes are being investigated and refined.
The correct answer is D.

Q2. The passage mentions each of the following as a function regulated by the SCNs in some animals EXCEPT
A. activity level
B. blood pressure
C. alertness
D. vision
E. temperature
Supporting idea
This question asks about what is NOT specifically mentioned in the passage with regard to functions regulated by the SCN. Those functions, as identified in the passage, are blood pressure, body temperature, activity level, alertness, and the release of melatonin.
A. The passage includes activity level in its list of functions regulated by the SCN.
B. The passage includes blood pressure in its list of functions regulated by the SCN.
C. The passage includes alertness in its list of functions regulated by the SCN.
D. Correct. While the passage does say that cells in the human retina transmit information to the SCN, there is no suggestion that the SCN reciprocally control vision.
E. The passage includes temperature in its list of functions regulated by the SCN.
The correct answer is D.

Q3. The author of the passage would probably agree with which of the following statements about the SCNs?
A. The SCNs are found in other organs and tissues of the body besides the hypothalamus.B. The SCNs play a critical but not exclusive role in regulating circadian rhythms.
C. The SCNs control clock genes in a number of tissues and organs throughout the body.
D. The SCNs are a less significant factor in regulating blood pressure than scientists once believed.
E. The SCNs are less strongly affected by changes in light levels than they are by other external cues.
Main idea
The author of the passage discusses the SCN in the passage in order to explain that they are most likely not, as long believed, solely responsible for the control of our circadian rhythms.
A. The author states that the SCN are nerve clusters in the hypothalamus, and nothing in the passage contradicts or undermines the supposition that they are only in the hypothalamus.
B. Correct. The author points out in the second paragraph that the SCN control core circadian function, but that circadian clocks found elsewhere in the body have an effect as well.
C. The evidence offered in the second paragraph about the activity of the clock gene in rat livers suggests that these clock genes are not under the SCN’s control. The passage does not suggest that the SCN control any of the non-SCN controllers of circadian rhythms.
D. The author states in the second paragraph that scientists do not dispute the idea that the SCN regulate blood pressure.
E. The first paragraph indicates that the SCN respond to light levels; clock genes in other tissues are the ones that may respond to other external cues.
The correct answer is B.

Two sides would be more suitable when both of them are of opposite ends exclusive of each other. IN this passage, one theory is not disputed but added some extra information on top it it. That's what makes D option better.





In summary: Before Belief: SCN: synchronization with the cycle of sunlight and darkness caused by Earth’s rotation
Later: SCNs control daily fluctuations in blood pressure, body temperature, activity level, and alertness etc.
Experiment: Peak activity of a clock gene in their livers shifted by 12 hours
Conclusion==> SCN may take inputs from other body functions ( new evidence) in addition to sunlight inputs ( earlier belief)

I hope it helps.

Can someone help me with option D in the 3rd question please?

3. The author of the passage would probably agree with which of the following statement about the SCNs?

(A) The SCNs are found in other organs and tissues of the body besides the hypothalamus.
(B) The SCNs play a critical but not exclusive role in regulating circadian rhythms.
(C) The SCNs control clock genes in a number of tissues and organs throughout the body.
(D) The SCNs are a less significant factor in regulating blood pressure than scientists once believed.
(E) The SCNs are less strongly affected by changes in light levels than are by other external cues.

While I agree that the 2nd paragraph says - "While scientists do not dispute the role of the SCNs in controlling core functions such as the regulation of body temperature and blood pressure", it also says that there are other organs and tissues that are performing this role as well. So doesn't it imply that SCNs are a less significant factor in regulating blood pressure than they used to be?