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Quiz: The Vagus Highway

Test your understanding of Chapter 2. Choose the best answer, then click Show Answer to check.

Question 1

Which statement best describes an afferent signal?

  1. A command sent from the brain to make gut muscle contract
  2. A signal carried toward the central nervous system, usually sensory information
  3. A hormone released into the blood by the stomach
  4. A signal that travels only between neurons inside the gut wall
Show Answer

The correct answer is B. Afferent signals travel toward the brain or spinal cord ("afferent arrives") and usually carry sensory information. Option A describes an efferent signal, an easy mix-up.

Concept Tested: Afferent Signal Bloom's Level: Remember

Question 2

Where do the sensory signals carried by the vagus nerve first arrive in the brain?

  1. The dorsal motor nucleus
  2. The nodose ganglion
  3. The cerebral cortex
  4. The nucleus tractus solitarius in the brainstem
Show Answer

The correct answer is D. Vagal sensory fibers end mainly in the nucleus tractus solitarius (NTS) in the medulla. The nodose ganglion (B) holds their cell bodies, but it sits in the neck outside the brain, and the dorsal motor nucleus (A) sends signals out, not in.

Concept Tested: Nucleus Tractus Solitarius Bloom's Level: Remember

Question 3

Which cell type is a rare, hormone-releasing sensor scattered among the cells lining the intestine?

  1. Enteroendocrine cell
  2. Enteric glial cell
  3. Interstitial cell of Cajal
  4. Nodose neuron
Show Answer

The correct answer is A. Enteroendocrine cells make up about 1% of intestinal lining cells and release gut hormones such as CCK and GLP-1. Interstitial cells of Cajal (C) are pacemaker cells in the muscle layer, not hormone-releasing sensors.

Concept Tested: Enteroendocrine Cell Bloom's Level: Remember

Question 4

Why does this book say "Most vagus nerve fibers carry signals from the body to the brain. Classic fiber counts in animals put the figure at about 80%" instead of simply "80% of vagus fibers are sensory"?

  1. Because the true figure in humans is known to be exactly 90%
  2. Because the vagus nerve has no motor fibers at all
  3. Because the 80% figure comes from old animal counts, and careful studies show the exact share varies
  4. Because sensory fibers can't be counted under a microscope
Show Answer

The correct answer is C. The 80% figure traces back to fiber counts in cats, and a careful 1990 rat study found that motor fibers in the abdominal vagus may be over a quarter of the total. The majority-sensory point is solid; the exact number is approximate. Option A is wrong because no modern human count settles the figure.

Concept Tested: Vagus Nerve Bloom's Level: Understand

Question 5

How does a vago-vagal reflex help the stomach handle a meal?

  1. The ENS sends a signal to the spinal cord, which tells the stomach to empty faster.
  2. Stretch signals travel up the vagus to the NTS, and the DMV sends a command back down that relaxes the upper stomach.
  3. The brain's cortex decides consciously to relax the stomach after every bite.
  4. Gut hormones travel to the heart, which slows down to make room for food.
Show Answer

The correct answer is B. In gastric accommodation, afferent stretch signals reach the NTS, and efferent signals from the dorsal motor nucleus travel down the vagus to relax the upper stomach. Option C is wrong because this reflex runs in the brainstem without conscious decisions.

Concept Tested: Dorsal Motor Nucleus Bloom's Level: Understand

Question 6

Which statement about heart rate variability (HRV) matches the evidence in this chapter?

  1. HRV directly records electrical activity in the vagus fibers to the gut.
  2. HRV is unaffected by breathing, posture, or caffeine.
  3. A high HRV proves that someone's gut is healthy.
  4. HRV is an indirect estimate of vagal tone at the heart and is easy to misinterpret.
Show Answer

The correct answer is D. Researchers use HRV to index cardiac vagal tone, but it changes with breathing, posture, caffeine, and measurement methods, and it says nothing direct about the vagus fibers to the gut. Option A is the common smartwatch misconception.

Concept Tested: Vagal Tone Bloom's Level: Understand

Question 7

A 70-year-old had his main vagal trunks cut decades ago to treat an ulcer. He now feels full after a few bites. Which explanation fits best?

  1. Without efferent vagal signals, his upper stomach can't relax as well to make room for food.
  2. His enteric nervous system was removed during the surgery.
  3. His spinal nerves can no longer carry any gut sensations.
  4. Cutting the vagus made his stomach produce much more acid.
Show Answer

The correct answer is A. Vagotomy removes the efferent part of the vago-vagal reflex that relaxes the upper stomach during a meal, so it fills up quickly. Option B is wrong because the ENS stays in the gut wall and keeps running local reflexes, and option D is backwards: vagotomy was done to reduce acid.

Concept Tested: Vagotomy Bloom's Level: Apply

Question 8

Riya has strong lower-belly pain and urgency during a Crohn's flare. A classmate says, "That pain must travel only through the vagus nerve." What is the best response?

  1. That's right, because the vagus is the only nerve connecting the gut to the brain.
  2. That's right, because pain signals can't travel through the spinal cord.
  3. Not quite: spinal afferent nerves carry many gut sensations, including much of gut pain, especially from the colon and rectum.
  4. Not quite: gut pain is created entirely inside the gut and never reaches the brain.
Show Answer

The correct answer is C. Gut sensory signals travel by three pathways, one vagal and two spinal, and spinal afferents to the colon and rectum give rise to discomfort, urgency, and pain. Option A is the misconception that the vagus is the only gut-brain route.

Concept Tested: Spinal Afferent Nerve Bloom's Level: Apply

Question 9

In 2018, researchers showed that some gut sensor cells form synapses with vagal neurons and signal within milliseconds. Which is the most accurate way to describe this evidence?

  1. Strong evidence that human gut cells are wired directly to the brain
  2. Careful experiments in mice that test cause, but that have not yet been confirmed in humans
  3. A correlation study in people that can't show cause
  4. A marketing claim with no lab experiments behind it
Show Answer

The correct answer is B. The neuropod cell study switched gut cells on and off and blocked glutamate in mice, which tests cause, but it was done in mice and found a connection to vagal neurons, not straight to the brain. That's why the Hype Meter grade is Preliminary. Option A overstates both the species and the wiring.

Concept Tested: Neuropod Cell Bloom's Level: Analyze

Question 10

Rats given CCK before a meal eat less. Suppose an experiment finds that in rats whose vagus nerves were cut, CCK has a much smaller effect. What would this comparison suggest?

  1. CCK has no effect on eating at all.
  2. CCK works only by traveling to the brain through the blood.
  3. Cutting the vagus makes rats hungrier for every food.
  4. CCK's satiety effect depends largely on vagal afferent signals.
Show Answer

The correct answer is D. If removing the vagal route weakens the effect, that suggests the vagus carries much of CCK's satiety signal to the brainstem. Option B is the opposite conclusion; if CCK worked only through the blood, cutting the vagus wouldn't matter much.

Concept Tested: Cholecystokinin Bloom's Level: Analyze