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Quiz: Parkinson's, Alzheimer's, and the Gut

Test your understanding of Chapter 14. Choose the best answer, then click Show Answer to check.

Question 1

What is the main cause of the movement symptoms of Parkinson's disease?

  1. Loss of dopamine-making neurons in the substantia nigra
  2. Amyloid beta plaques building up in the hippocampus
  3. Damage to the muscles of the arms and legs
  4. Too much serotonin made in the gut
Show Answer

The correct answer is A. Movement symptoms come mainly from the death of dopamine-making neurons in the substantia nigra; NINDS says most people have lost 60 to 80% or more of them by the time symptoms appear. Option B describes a hallmark of Alzheimer's disease, not Parkinson's.

Concept Tested: Dopamine Neuron Loss Bloom's Level: Remember

Question 2

What is a Lewy body?

  1. A bundle of vagus nerve fibers in the gut wall
  2. A plaque of amyloid beta between neurons
  3. An abnormal clump, made mostly of misfolded alpha-synuclein, inside a nerve cell
  4. A group of gut bacteria found in people with Parkinson's
Show Answer

The correct answer is C. Lewy bodies are clumps of misfolded alpha-synuclein found inside damaged nerve cells in most people with Parkinson's. Option B mixes up Lewy bodies with the amyloid plaques of Alzheimer's disease, which form between neurons rather than inside them.

Concept Tested: Lewy Body Bloom's Level: Remember

Question 3

In Braak's 2003 staging system, where does Lewy pathology first appear in the brain?

  1. In the outer cortex, then it moves down to the brainstem
  2. In the substantia nigra only
  3. In the hippocampus and memory areas
  4. In the brainstem vagus nucleus and a smell-processing area
Show Answer

The correct answer is D. Braak's team reported that pathology first shows up in the dorsal motor nucleus of the vagus and an olfactory (smell) area, then climbs upward, reaching the substantia nigra in middle stages and the cortex last. Option A reverses the direction of the proposed spread.

Concept Tested: Braak Hypothesis Bloom's Level: Remember

Question 4

A 2016 meta-analysis found that people with constipation had an odds ratio of about 2.27 for a later Parkinson's diagnosis. What is the best interpretation?

  1. Most people with constipation will develop Parkinson's disease.
  2. Constipation is linked to about double the odds of a later diagnosis, but because Parkinson's is uncommon, most constipated people never develop it.
  3. Constipation causes Parkinson's disease by damaging the substantia nigra.
  4. Treating constipation prevents Parkinson's disease.
Show Answer

The correct answer is B. An odds ratio near 2 is a relative comparison between large groups; doubling a small chance still leaves a small chance. Option A is the most common misreading, and options C and D claim cause, which observational studies can't show.

Concept Tested: Constipation Bloom's Level: Understand

Question 5

What does "prion-like spread" mean in Parkinson's research?

  1. Parkinson's can be caught from another person, like an infection.
  2. Gut bacteria travel through the blood to the brain.
  3. Misfolded alpha-synuclein may pass to connected neurons and make normal copies misfold, so damage moves along nerve pathways.
  4. Dopamine leaks out of the brain into the gut.
Show Answer

The correct answer is C. Prion-like spread describes misfolding moving from neuron to connected neuron inside one person's nervous system, like falling dominoes. Option A is a common misunderstanding of the word "prion"; Parkinson's is not contagious between people.

Concept Tested: Prion-Like Spread Bloom's Level: Understand

Question 6

How do the gut-first and brain-first subtypes differ in what they predict before diagnosis?

  1. Gut-first predicts constipation and REM sleep behavior disorder years before movement symptoms; brain-first predicts movement symptoms earlier, with those problems usually absent before diagnosis.
  2. Gut-first predicts memory loss first; brain-first predicts constipation first.
  3. Both predict exactly the same order of symptoms.
  4. Brain-first predicts that cutting the vagus nerve will prevent the disease.
Show Answer

The correct answer is A. In the gut-first idea, body nerves and brainstem sleep circuits are damaged before the dopamine system, so constipation and dream-acting come first. In the brain-first idea, the dopamine system is hit early. Option D gets it backward: the vagus route matters only in the gut-first idea.

Concept Tested: Gut-First Subtype Bloom's Level: Understand

Question 7

A man has had trouble with his Parkinson's medicine kicking in late, especially after large, protein-heavy meals and on days when he is constipated. Which explanation fits the chapter best?

  1. Protein and constipation destroy levodopa in the brain.
  2. Levodopa can't cross the blood-brain barrier at all, so it never works.
  3. His dopamine neurons grow back after meals.
  4. Slow gut movement delays levodopa's trip to the small intestine, and amino acids from protein compete with it for absorption.
Show Answer

The correct answer is D. Levodopa is absorbed from the upper small intestine, so slow stomach emptying and constipation can delay it, and dietary amino acids share its transport system. Option B is wrong because levodopa does reach the brain, where it is converted into dopamine; it's dopamine itself that doesn't cross easily. Any changes should be made by his care team.

Concept Tested: Levodopa Absorption Bloom's Level: Apply

Question 8

A headline says: "Cutting the appendix slashes Parkinson's risk!" Based on the evidence in this chapter, what is the best response?

  1. It's true, so people should consider having their appendix removed.
  2. One 2018 study found lower risk, but a Danish study found slightly higher risk and two meta-analyses found no overall link, so the claim is not supported.
  3. It's true only for people with constipation.
  4. It's proven in mice, so it must be true in people.
Show Answer

The correct answer is B. The Killinger 2018 finding was not confirmed when studies were pooled: Lu 2020 found a relative risk of 1.02 and Chin 2025 found 1.01, both meaning no overall link. Option A turns a disputed association into a medical recommendation, which no evidence supports.

Concept Tested: Appendix and Parkinson's Bloom's Level: Apply

Question 9

The Danish truncal vagotomy study found a hazard ratio of 0.53 (95% CI 0.28 to 0.99) for people followed more than 20 years, while the larger Swedish study found no overall link (hazard ratio 0.96). What is the most reasonable conclusion?

  1. Cutting the vagus nerve is proven to prevent Parkinson's.
  2. The vagus nerve has nothing to do with Parkinson's.
  3. The human evidence is mixed: some subgroup results fit the gut-first idea, but they are imprecise and observational, so they can't prove cause.
  4. The Swedish study must be wrong because it was larger.
Show Answer

The correct answer is C. The Danish result came from a subgroup, with a confidence interval that nearly reached 1.0, and the Swedish study found no overall effect. Both are observational, so differences between people who had surgery and those who didn't could explain the results. Option A overstates a weak, mixed signal.

Concept Tested: Truncal Vagotomy Studies Bloom's Level: Analyze

Question 10

A 2017 study compared stool samples from 25 people with Alzheimer's and 25 matched people without it and found differences in gut bacteria. Which statement best analyzes what this study can show?

  1. It shows a correlation in a small snapshot; the disease, diet, medicines, or activity could explain the bacterial differences.
  2. It proves gut bacteria cause amyloid beta plaques in people.
  3. It shows that probiotics prevent Alzheimer's.
  4. It shows nothing at all because it studied people instead of mice.
Show Answer

The correct answer is A. This cross-sectional study of 50 people found an association, but it can't tell which came first, and people with dementia often differ in diet, activity, and medicines. Option B confuses correlation with cause; experts describe this research area as still in its infancy.

Concept Tested: Alzheimer's Disease Bloom's Level: Analyze