* not completed

. In the development of the nervous system, which is the correct order of events?

First, cells must be specified to be neurons, second, these neurons must make connections with their targets, third, the neurons must migrate to their final position, and fourth, the neurons refine their synaptic connections. correct incorrect

First, cells must be specified to be neurons, second, the neurons must migrate to their final position, third, these neurons must make connections with their targets, and fourth, the neurons refine their synaptic connections. correct incorrect

First, cells must migrate to their final position, second, these cells must be specified to be neurons, third, the neurons must make connections with their targets, and fourth, the neurons refine their synaptic connections. correct incorrect

There is no fixed order of events; different portions of the nervous system do things in different ways. correct incorrect

* not completed

. Schwann cells

are glial cells correct incorrect

are responsible for myelination of axons in the peripheral nervous system correct incorrect

are related to the oligodendrocytes of the central nervous system correct incorrect

are all of the options given correct incorrect

* not completed

. The vertebrate central nervous system (brain and spinal cord) is derived from

cells of the neural tube correct incorrect

neural crest cells that migrate along the dorso-lateral route correct incorrect

neural crest cells that migrate through the anterior half of the somites correct incorrect

somitic mesoderm correct incorrect

* not completed

. Local organizers of brain pattern

are of mesodermal origin correct incorrect

cease functioning after the neural plate closes correct incorrect

may signal bidirectionally correct incorrect

have high rates of cell proliferation correct incorrect

* not completed

. The use of segments as a developmental strategy in vertebrates is evident in:

the endoderm correct incorrect

the axial skeleton, only correct incorrect

the hindbrain, only correct incorrect

both the axial skeleton and the hindbrain correct incorrect

* not completed

. Which of the following is a determined neuronal cell type?

pre-migratory neural crest cells correct incorrect

floor plate cells correct incorrect

commissural cells correct incorrect

roof plate cells correct incorrect

* not completed

. What is the relationship between dorso-ventral patterning of the neural tube and patterning of the somites?

The somites pattern the neural tube after they form. correct incorrect

The neural tube plays the role of organizer in being the sole influence on patterning in the somites correct incorrect

Sonic hedgehog from the notochord and floor plate of the neural tube confers ventral fates on both the neural tube and the somite, whereas BMPs confer more dorsal fates. correct incorrect

Both the neural tube and the somites acquire their dorso-ventral patterning during gastrulation correct incorrect

* not completed

. Axons of spinal cord neurons from the lateral motor column in the chick embryo innervate

muscles of the body wall correct incorrect

muscles of the limb buds correct incorrect

muscles attached to the spine correct incorrect

muscles in the gut wall correct incorrect

* not completed

. What part, if any, do Hox genes play in specification of neuronal fate?

Different Hox genes are activated along the dorso-ventral axis by the gradient of Shh. correct incorrect

Different combinations of Hox genes specify the identities of neurons along the antero-posterior axis correct incorrect

Hox genes determine the identity of the segments along the axis of the vertebrate spinal cord correct incorrect

Hox genes determine the different subtypes of neurons that form along the dorso-ventral axis. correct incorrect

Hox genes have no role in nervous system development. correct incorrect

* not completed

. In Drosophila, the neuroectoderm is located ventrally during gastrulation, whereas in mice or frogs, the neuroectoderm is located dorsally. Which statement best describes how the two systems are similar or different?

There are no similarities between flies and vertebrates in development of the nervous system. correct incorrect

Although gastrulation is completely different in invertebrates and vertebrates, the formation of a neural tube is identical in the two types of animals. correct incorrect

There is little similarity, since the neurectoderm of invertebrates forms their nervous system with no further morphological changes, while in vertebrates, the neural tube forms a bundle of neurons running along the antero-posterior axis called the spinal cord. correct incorrect

Although the invertebrate nervous system is a ventrally located nerve cord, and the vertebrate spinal cord is located dorsally, homologous genes have a role in their patterning, and neurons are ultimately specified through a process of lateral inhibition in both cases. correct incorrect

* not completed

. How does lateral inhibition work to specify individual neurons in the neural epithelium of invertebrates and vertebrates?

Prospective neurons first arise in a cluster, but then, by chance, one cell will come to signal more strongly through Delta and Notch than its neighbors and become the only neuron in the cluster, by inhibiting its neighbors' specification as neurons. correct incorrect

Stripes of prospective neurons will inhibit formation of neurons in stripes lateral to themselves. correct incorrect

A gradient of inhibition spreads from the cells lateral to the neural epithelium, inhibiting their specification of neurons until a threshold is reached, at which point a single neuron is permitted to develop. correct incorrect

Only one cell in each cluster of prospective neurons is fated to become a neuron, and it does so by inhibiting neural development in its lateral neighbors. correct incorrect

The epidermal cells in the neural epithelium inhibit the laterally adjacent cells from being epidermis, thus promoting neuronal identity. correct incorrect

* not completed

. What would be the consequence of reducing Delta expression in the developing vertebrate neural tube?

Excess neurons are produced, because reduced Delta prevents the inhibition of neurogenesis in neighboring cells. correct incorrect

Excess neurons are produced, because the reduction in Delta expression increases neurogenin expression. correct incorrect

Fewer neurons are produced, because Delta signaling is required for neurogenesis. correct incorrect

There is no change in neurogenesis unless Delta expression is eliminated completely. correct incorrect

* not completed

. The ventricular zone is:

a region of cell division in the neural plate correct incorrect

a region of cell division in Henson's node correct incorrect

a region of cell division in the neuroectoderm of Drosophila correct incorrect

a region of cell division in the neural tube correct incorrect

* not completed

. In the developing cerebral cortex

layer VI is the layer nearest to the ventricular zone correct incorrect

excitatory neurons have local connections whereas inhibitory neurons project over long distances correct incorrect

the outermost layer of neurons is born before those of layer VI correct incorrect

areal identity is conferred by incoming axons from the thalamus correct incorrect

* not completed

. Cortical neurons migrate to their final positions in the cortex along

Schwann cells correct incorrect

commissural neurons correct incorrect

radial glia correct incorrect

roof-plate cells correct incorrect

* not completed

. What is the role of semaphorins and Eph ligands in the development of the nervous system?

The semaphorins and Eph ligands are growth factors that stimulate cell division of neurons. correct incorrect

The semaphorins and Eph ligands act as signals for the outgrowth of neuronal growth cones; in general, both lead growth cones to turn away. correct incorrect

The semaphorins and Eph ligands act as signals for the outgrowth of neuronal growth cones; in general, both lead growth cones to come toward them. correct incorrect

The semaphorins and Eph ligands are cell-cell adhesion molecules that bind adjacent neurons together. correct incorrect

* not completed

. Which of these is a cell-surface adhesion molecule that mainly attracts axons during their outgrowth?

neurotrophins correct incorrect

cadherins correct incorrect

netrins correct incorrect

semaphorins correct incorrect

* not completed

. What is the consequence for the ability of motor neurons to find their correct targets, if a section of the spinal cord is rotated, so that the antero-posterior axis is reversed?

Anterior motor neurons enter the limb in a bundle in the posterior instead of the anterior, but then take novel pathways to find the correct anterior muscles to innervate. correct incorrect

Anterior motor neurons enter the limb in a bundle in the posterior instead of the anterior, and follow pathways intended for posterior neurons to make contacts with posterior muscles. correct incorrect

Anterior motor neurons change their course to enter the limb in the anterior, but take their usual pathways to find the correct anterior muscles. correct incorrect

The motor neurons grow over to the other side of the spinal cord and resume their normal pathways into muscles on their normal side of the body. correct incorrect

* not completed

. Knock-outs of the mouse netrin-1 gene have a phenotype similar to that of knock-outs of what other gene or gene product?

the DCC receptor correct incorrect

the Robo1 receptor correct incorrect

the semaphorin signaling molecule correct incorrect

the Slit signaling molecule correct incorrect

* not completed

. Neurons in the anterior (nasal) region of the right retina will project axons to

the anterior portion of the left tectum correct incorrect

the anterior portion of the right tectum correct incorrect

the posterior portion of the left tectum correct incorrect

the posterior portion of the right tectum correct incorrect

* not completed

. What does the experiment in which a frog's eye is rotated tell us about the normal spatial relationships between the retina and the tectum?

The retina in the right eye makes connections to the right tectum; nasal (anterior) neurons go to the anterior tectum, and temporal (posterior) neurons go to the posterior tectum. correct incorrect

The retina in the right eye makes connections to the right tectum; nasal (anterior) neurons go to the posterior tectum, and temporal (posterior) neurons go to the anterior tectum. correct incorrect

The retina in the right eye makes connections to the left tectum; nasal (anterior) neurons go to the posterior tectum, and temporal (posterior) neurons go to the anterior tectum. correct incorrect

The retina in the right eye makes connections to the left tectum; nasal (anterior) neurons go to the anterior tectum, and temporal (posterior) neurons go to the posterior tectum. correct incorrect

* not completed

. The synapses formed between motor neurons and muscles are called

myotomes correct incorrect

neuromuscular junctions correct incorrect

Nieuwkoop centers correct incorrect

retino-tectal projections correct incorrect

* not completed

. The "synaptic cleft" of a neuromuscular junction is

a groove in the muscle cell plasma membrane through which neurons grow correct incorrect

that portion of the cell surface receptor molecule on the surface of a muscle cell, into which the ligand binds correct incorrect

a depression at the end of an axon from which neurotransmitters are secreted correct incorrect

the space between the plasma membrane of a neuron on the pre-synaptic side of the synapse, and the plasma membrane of the muscle cell on the post-synaptic side of the synapse correct incorrect

* not completed

. Do neurons make synapses with other neurons?

No, the only role of neurons is to cause muscles to contract correct incorrect

No, neurons can innervate tissues other than muscle, but there is no need for them to synapse with other neurons correct incorrect

Yes, neurons make contacts with other neurons that are identical to those they make with muscle cells correct incorrect

Yes, but the connections neurons make with each other differ from those they make with muscle cells in that cell-cell adhesion molecules link the pre-synaptic and post-synaptic membranes correct incorrect

* not completed

. The neurotransmitter used in the communication between motor neurons and muscles is

serotonin correct incorrect

dopamine correct incorrect

epinephrine correct incorrect

acetylcholine correct incorrect

* not completed

. Why can't babies see well when they are first born?

The multiple connections between the retina and the visual cortex present at birth become refined in response to visual stimuli, through changes in connectivity and cell death. correct incorrect

At birth, the eyes are not yet connected to the visual cortex, and processing of visual stimuli occurs only at the level of the geniculate nucleus. correct incorrect

Synapses have formed at birth, but are not functional until visual stimuli begin to occur. correct incorrect

The lens of the eye is not fully formed at birth. correct incorrect