Deck 8: Activity-Guided Neural Development

Question 1

Apoptosis that occurs in motor neurons during vertebrate development can be postponed by

A) removing a limb bud.
B) removing motor units.
C) stopping electrical activity in motor neurons.
D) lesioning the muscle fiber.

Answer 1

C

Question 2

Unlike in adult rats, muscle fibers in newborn rats

A) each are innervated by more than one motor neuron.
B) each are innervated by a single motor neuron.
C) express acetylcholine receptors.
D) do not respond to action potentials.

Answer 2

A

Question 3

The elimination of polyneuronal innervation in the neuromuscular junction is mediated by

A) apoptosis.
B) competitive synapse refinement.
C) a random process of axon branch retraction.
D) synchronous activation of motor neurons.

Answer 3

B

Question 4

What type of activity in motor neurons drives the elimination of polyneuronal innervation in the neuromuscular junction?

A) Asynchronous
B) Disynchronous
C) Synchronous
D) Random

Question 5

Sympathetic and parasympathetic neurons typically have _______ effects on their target organ.

A) synergistic
B) opposing
C) excitatory
D) inhibitory

Question 6

Sympathetic and parasympathetic neurons have different effects on a target organ because they

A) innervate the organ in different locations.
B) have different numbers of synapses on the organ.
C) release different neurotransmitters.
D) use asynchronous activity.

Question 7

In developing autonomic ganglia,

A) the number of afferent inputs per target neuron increases.
B) afferent inputs compete for synaptic space on the target neuron.
C) synapses are eliminated, resulting in a net loss in total number of synaptic inputs.
D) synaptic rearrangement is driven by apoptosis.

Question 8

A Hebbian synapse becomes _______ when it causes the _______ neuron to fire.

A) weaker; postsynaptic
B) weaker; presynaptic
C) stronger; postsynaptic
D) stronger; presynaptic

Question 9

Subjecting neurons in the perforant pathway to tetanus stimulation strengthens activity in the dentate gyrus, indicating that

A) long-term potentiation does not occur in the hippocampus.
B) the hippocampus is involved in memory.
C) synapses in the brain do not behave like Hebbian synapses.
D) synapses in the brain can behave like Hebbian synapses.

Question 10

Which neurotransmitter does the hippocampus primarily use?

A) Glutamate
B) Acetylcholine
C) GABA
D) Dopamine

Question 11

Long-term potentiation in the hippocampus is mediated by

A) ionotropic glutamate receptors.
B) acetylcholine receptors.
C) metabotropic glutamate receptors.
D) Hebbian receptors.

Question 12

AMPA receptors produce stable excitatory responses at _______ rates of stimulation, and NMDA receptors produce increased synaptic responses at _______ rates of stimulation.

A) fast; fast
B) slow; slow
C) fast; slow
D) slow; fast

Question 13

When hippocampal afferents are stimulated at a slow rate,

A) NMDA receptors depolarize the target neuron.
B) NMDA receptors are blocked by magnesium ions.
C) more AMPA receptors are added to the postsynaptic membrane.
D) AMPA receptors are blocked by magnesium ions.

Question 14

In long-term potentiation, pre-synaptic glutamate release can be increased by

A) slow-rate stimulation of afferent inputs.
B) magnesium blockage of NMDA receptors.
C) a retrograde messenger released from the postsynaptic cell.
D) a retrograde messenger released from the presynaptic cell.

Question 15

In vertebrates, the right visual cortex receives information from the

A) left eye only.
B) right eye only.
C) left visual field only.
D) right visual field only.

Question 16

By which pathway does visual information travel to be interpreted by the vertebrate brain?

A) Retinal ganglion cells; optic tract; lateral geniculate nucleus; visual cortex
B) Optic tract; retinal ganglion cells; lateral geniculate nucleus; visual cortex
C) Visual cortex; retinal ganglion cells; optic tract; lateral geniculate nucleus
D) Retinal ganglion cells; optic tract; visual cortex; lateral geniculate nucleus

Question 17

In what way is the organization of the lateral geniculate nucleus and layer IV of the adult primary visual cortex similar?

A) Input from one eye is evenly distributed across both regions.
B) Both are organized into regions that receive input from both visual fields.
C) Both are organized into regions that receive input from both eyes.
D) Both are organized into regions that receive input from only one eye.

Question 18

Ocular dominance bands appear in layer IV of the visual cortex in mice even before rods and cones in the retina can respond to light, suggesting that _______ required for the segregation of input from the two eyes.

A) visual experience is
B) neuronal activity is not
C) visual experience is not
D) neuronal activity is

Question 19

The segregation of input from the two eyes in the developing lateral geniculate nucleus is driven by

A) spontaneous neuronal activity.
B) visual experience.
C) apoptosis.
D) synchronous neuronal activity between the two eyes.

Question 20

In visual system development, axons travel from the retina to their approximate correct position in the lateral geniculate nucleus by

A) spontaneous neuronal activity.
B) axonal pathfinding mechanisms.
C) random neuronal outgrowth.
D) visual experience.

Question 21

The number of synapses in the human cortex _______ rapidly from adolescence to adulthood and _______ from adulthood to old age.

A) increases; decreases rapidly
B) decreases; increases gradually
C) decreases; decreases gradually
D) increases; decreases gradually

Question 22

The net loss of cortical synapses during childhood is

A) due to a thinning of gray matter.
B) greatest in males.
C) due to a loss of white matter.
D) unique to humans.

Question 23

The last region to fully mature in the human brain appears to be the

A) hippocampus.
B) prefrontal cortex.
C) sensory cortex.
D) temporal lobe.

Question 24

In the development of the human cortex, neuronal activity leads to an increase in

A) the density of synapses.
B) the total number of synapses.
C) gray matter.
D) myelination.

Question 25

Refer to the figure.
Curare is a toxin that blocks acetylcholine receptors, including those at the neuromuscular junction (NMJ). Based on the experimental data from chick embryos that were treated with curare (red line) and control chick embryos (blue line), what happens to motor neurons when the communication between motor neurons and muscles is silenced? What would you expect to happen when curare is removed? What does this suggest about normal motor system development?

Question 26

What evidence suggests that changes in muscles are responsible for the extent of apoptosis in motor neurons? How may neurotrophic factors mediate this process?

Question 27

Some motor units are large, with a single motor neuron stimulating thousands of individual muscle fibers; some motor units are small, with a single motor neuron stimulating less than a hundred individual muscle fibers. What is one potential benefit of this variety in motor unit size?

Question 28

How do autonomic ganglia in newborn mammals differ from those in adult mammals?

Question 29

In addition to existing synapses simply getting stronger or weaker, what else drives Hebbian synaptic plasticity? Why must Hebbian competition require communication between inputs to a given neuron?

Question 30

What is long-term potentiation (LTP), and what is one region in the brain where this occurs?

Question 31

Name three classes of ionotropic glutamate receptors. Which one(s) participate in long-term potentiation?

Question 32

Describe the mechanism by which magnesium interacts with NMDA receptors when hippocampal afferents are stimulated at slow versus fast rates. What three changes occur after fast rate stimulation that contribute to long-term potentiation in the hippocampus?

Question 33

Refer to the figure.
Using the number labels in shown the visual fields of the figure, list which parts of the visual field would be affected by a lesion in right optic tract (marked in red).

Question 34

What mechanisms allow spontaneous neuronal activity to spread across the developing retina?