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Quiz: The Developing and Teenage Brain

Test your understanding of Chapter 8. Choose the best answer, then click Show Answer to check.

Question 1

According to NINDS, when does the neural tube typically fold and close?

  1. During the last month of pregnancy
  2. About three to four weeks after conception
  3. Right after birth, during the first week of life
  4. Around the middle of pregnancy, at about 20 weeks
Show Answer

The correct answer is B. The neural tube typically closes during the third and fourth weeks after conception, often before a person knows they are pregnant. That is why folic acid is recommended for anyone who could become pregnant. It does not happen at mid-pregnancy or after birth. By then the brain is already far along.

Concept Tested: Neural Tube Bloom's Level: Remember

Question 2

Which cells act like guide ropes that many newborn neurons climb along to reach their place in the developing cortex?

  1. Microglia
  2. Oligodendrocytes
  3. Radial glia
  4. Schwann cells
Show Answer

The correct answer is C. Radial glia stretch from the inner wall of the neural tube to the outer surface, and many migrating neurons crawl along them. Radial glia also act as neural stem cells. Microglia help prune synapses, and oligodendrocytes and Schwann cells make myelin, but none of them is the main migration guide.

Concept Tested: Neuronal Migration Bloom's Level: Remember

Question 3

What is a teratogen?

  1. Something in the environment that can cause or raise the risk of a birth defect
  2. A gene that controls when the neural tube closes
  3. A glial cell that removes unused synapses
  4. A hormone that rises during puberty and increases reward-seeking
Show Answer

The correct answer is A. A teratogen is an environmental factor, such as alcohol, some medicines, street drugs, or some infections, that can interfere with development before birth. It is not a gene, a cell, or a puberty hormone. Alcohol is the best-studied teratogen affecting the brain.

Concept Tested: Teratogen Bloom's Level: Remember

Question 4

Why can synaptic pruning make the brain work better, even though it removes connections?

  1. Pruning removes neurons that have stopped firing, freeing space for new neurons to be born
  2. Pruning removes the myelin from slow axons so they can be rebuilt thicker
  3. Pruning happens only in sensory cortex, which leaves the prefrontal cortex free to grow
  4. Pruning removes weak or unused synapses and keeps the active ones, leaving more efficient circuits
Show Answer

The correct answer is D. Synaptic pruning follows "use it or lose it": active synapses are strengthened and kept, while unused ones are removed, like closing roads nobody drives on so traffic flows better. Pruning removes synapses, not myelin, and it isn't about making room for new neurons. It also happens in the prefrontal cortex, just later than in sensory cortex.

Concept Tested: Synaptic Pruning Bloom's Level: Understand

Question 5

Why does the CDC recommend daily folic acid for anyone who could become pregnant, rather than only after pregnancy is confirmed?

  1. Folic acid is needed mainly during the teen years, when the prefrontal cortex is pruning
  2. Neural tube defects form in the first few weeks of pregnancy, often before a person knows they are pregnant
  3. Folic acid speeds up myelination, which begins in the first week after conception
  4. Folic acid prevents all birth defects, so it should be taken as early as possible
Show Answer

The correct answer is B. The neural tube closes so early that waiting for a positive pregnancy test can miss the window when folic acid helps. Folic acid helps prevent neural tube defects, not all birth defects. Myelination begins months later, starting in the spinal cord, and peaks in the first year after birth.

Concept Tested: Neural Tube Bloom's Level: Understand

Question 6

Which statement best describes what research shows about when the brain "finishes" developing?

  1. The brain is fully mature at exactly age 25, when the prefrontal cortex switches on
  2. Brain development is essentially complete by age 18
  3. Development, especially of the prefrontal cortex and white matter, continues gradually into the mid-to-late twenties, with large differences between people
  4. The brain reaches its adult size and maturity at the same time, in early adolescence
Show Answer

The correct answer is C. NIMH says the brain finishes maturing in the mid-to-late twenties, prefrontal pruning continues through the twenties, and white matter volume peaks at about 29. There is no single finish line, and people vary. "Exactly 25" is a slogan, not a cutoff. The brain reaches adult size in early adolescence, but it keeps fine-tuning long after.

Concept Tested: Prefrontal Maturation Bloom's Level: Understand

Question 7

A 5-year-old is diagnosed with amblyopia ("lazy eye"). Her uncle had the same problem but was not treated until age 30. Based on critical periods, what outcome is most likely?

  1. The 5-year-old is likely to respond better to patching, because the visual system is more changeable in childhood
  2. Both will respond equally well, because the visual cortex never loses plasticity
  3. The uncle will respond better, because an adult brain has more myelin to support learning
  4. Neither can improve, because amblyopia is caused by damage to the eye itself
Show Answer

The correct answer is A. The visual system has a critical period early in life. The National Eye Institute says early treatment works well and treatment is usually less effective in adults. Plasticity declines with age (it doesn't vanish), and amblyopia is a problem of how the brain and eye work together, not eye damage.

Concept Tested: Critical Period Bloom's Level: Apply

Question 8

A 7-year-old has attention and memory problems, is below the 10th percentile for height, weight, and head size, and has a smooth philtrum and a thin upper lip. Records show his birth mother drank alcohol during pregnancy. Which diagnosis best fits?

  1. Lissencephaly caused by a neuronal migration error
  2. A neural tube defect such as spina bifida
  3. Attention-deficit/hyperactivity disorder (ADHD) alone
  4. Fetal alcohol syndrome, a condition on the fetal alcohol spectrum
Show Answer

The correct answer is D. Prenatal alcohol exposure plus characteristic facial features, growth problems, small head size, and neurobehavioral problems fits fetal alcohol syndrome. ADHD can share attention symptoms, but it doesn't explain the growth problems, facial features, and exposure history. Spina bifida and lissencephaly have different causes and signs.

Concept Tested: Fetal Alcohol Spectrum Bloom's Level: Apply

Question 9

In the Synaptic Pruning Over a Lifetime MicroSim, you set the age to 16. Which comparison matches what the research-based curves show?

  1. Both regions are still adding synapses, and white matter has already peaked
  2. Sensory cortex is pruning heavily, while prefrontal cortex has finished pruning
  3. Sensory cortex pruning is mostly done, while prefrontal cortex is still pruning and white matter is still rising
  4. Both regions finished pruning at the same age, around 12
Show Answer

The correct answer is C. Net synapse loss in auditory cortex ends by about age 12, but prefrontal pruning continues through adolescence and into the twenties, and white matter volume keeps rising to a peak near 29. The two regions follow different schedules, sensory first and prefrontal last.

Concept Tested: Synaptic Pruning Bloom's Level: Analyze

Question 10

In one experiment, adolescents, young adults, and adults did a risk-taking task either alone or with two peers present. Everyone took more risks with peers, but the effect was much stronger in adolescents and young adults. What is the best conclusion?

  1. Teens take risks because they don't understand danger as well as adults do
  2. The presence of peers has a bigger effect on risky decisions in younger people than in adults
  3. Peers make adults safer drivers but make teens more dangerous
  4. Risk-taking is caused entirely by peer pressure and has nothing to do with the brain
Show Answer

The correct answer is B. The study found a peer effect in every age group, but it was stronger for younger participants. Brain imaging later showed peers boost activity in teens' reward regions. Option A is a common myth. Other research shows teens' logical reasoning reaches adult levels around 16, while self-control in emotional moments matures later.

Concept Tested: Reward Sensitivity in Teens Bloom's Level: Analyze