Question 1

A 13-year-old girl develops a tumor of the anterior pituitary gland.What is the embryologic origin of the anterior pituitary gland?

Accepted Answer

The anterior pituitary gland is derived from Rathke's pouch, an outgrowth of the oral ectoderm that invaginates to form a pocket that eventually separates from the oral cavity and becomes the anterior pituitary gland.

Question 2

A 3-year-old boy with spina bifida develops hydrocephalus.What is the likely cause of this?

Accepted Answer

Blockage of the median or lateral apertures can lead to obstruction of the flow of cerebrospinal fluid (CSF) out of the ventricles and result in hydrocephalus. Spina bifida, a neural tube defect, can cause malformation of the brain and its structures, leading to hydrocephalus. Blockage of the subarachnoid space, enlargement of the choroid plexus, constriction of the foramen magnum, or degeneration of the choroid plexus are not commonly associated with hydrocephalus in individuals with spina bifida.

Question 3

A researcher labels a small area of the neural tube at the future cerebellar level.It is later noted that cells in the deep cerebellar nuclei are labeled.What portion of the neural tube was labeled in this experiment?

Accepted Answer

D

Question 4

A 4-year-old girl is diagnosed with cerebellar heterotopia.What developmental process likely went awry,accounting for heterotopia?

Accepted Answer

Cerebellar heterotopia is caused by abnormal cell migration during development. The cells destined to become part of the cerebellum migrate to the wrong location, resulting in heterotopia.

Question 5

Weaver mice provide insight into mechanisms of cerebellar development.What gene is mutated in these mice?

Accepted Answer

The gene mutated in weaver mice is Girk2 (G protein-activated inward rectifier potassium channel 2). This mutation leads to the characteristic neurological defects observed in these mice, providing insights into cerebellar development and function.

Question 6

A researcher knocks out the Soho gene in the rudiment of the developing mouse eye.What aspect of eye development will be affected?

Accepted Answer

The Soho gene is involved in the formation of the nasal-temporal axis of the neural retina. Knocking it out would specifically affect the development of this axis, but not the other axes or the induction of the lens or cornea.

Question 7

A researcher interested in patterning of the early neural tube identifies a new secreted factor expressed in the floor plate.Assuming that the newly identified factor plays a role in patterning,which axis of the developing neural tube would you expect to be perturbed if this factor is inactivated?

Accepted Answer

The floor plate is a key signaling center in the dorsal-ventral patterning of the neural tube. Inactivation of a secreted factor expressed in the floor plate would likely perturb the dorsal-ventral axis of the developing neural tube.

Question 8

A surgeon operates on the lumbar nervous system to relieve intractable pain in a terminal cancer patient.What specific part of the nervous system would be cut?

Accepted Answer

The dorsal root of a spinal nerve contains sensory fibers which transmit impulses from the body's sensory receptors to the spinal cord. By cutting the dorsal root, the surgeon could eliminate pain signals from reaching the central nervous system and provide relief for the terminal cancer patient.

Question 9

A researcher interested in patterning of the early neural tube identifies a new secreted factor expressed in the isthmus signaling center.Assuming that the newly identified factor plays a role in patterning,which axis of the developing neural tube would you expect to be perturbed if this factor is inactivated?

Accepted Answer

The isthmus signaling center is crucial for patterning along the cranial-caudal (anterior-posterior) axis of the developing neural tube, influencing the development of midbrain and hindbrain structures. Inactivating a factor expressed in this region would likely disrupt cranial-caudal patterning.

Question 10

An investigator injects a cell lineage marker into the developing ventricular zone of the ganglionic eminence of the developing forebrain.Cells in which region of the neonatal brain will be labeled?

Accepted Answer

The ganglionic eminence gives rise to the basal ganglia, so cells in the basal ganglia region of the neonatal brain will be labeled.

Question 11

A 20-year-old woman suffers a stroke after a drug overdose that causes localized damage to the brain stem special somatic afferent column on one side.Sensation from which structure(s) will be compromised?

Accepted Answer

The inner ear is responsible for the sensation of balance and spatial orientation, which is transmitted through the vestibular nerve, a component of the special somatic afferent column. Therefore, damage to this column on one side would compromise sensation from the inner ear on the same side.

Question 12

A child is diagnosed with Kallmann syndrome.Genetic evaluation revealed a mutation in the patient of the KAL1 gene.What does this gene encode?

Accepted Answer

The KAL1 gene encodes for anosmin-1, a protein crucial for normal development of the olfactory and reproductive systems. Mutations in this gene are responsible for Kallmann syndrome, which is characterized by hypogonadotropic hypogonadism and anosmia (lack of sense of smell).

Question 13

A researcher knocks out Ephrin-B2 in the developing visual system.What effect will this have on retinal ganglion cell (RGC) axon projection?

Accepted Answer

Ephrin-B2 is involved in guiding retinal ganglion cell (RGC) axons to their correct targets in the visual system. Normally, Ephrin-B2 and its receptors help to establish the correct balance of ipsilateral and contralateral projections. Knocking out Ephrin-B2 disrupts this guidance, leading to RGC axons projecting contralaterally instead of their normal ipsilateral or contralateral projection pattern.

Question 14

A 45-year-old man develops Bell's palsy in which function of the facial (VII) cranial nerve is compromised.What specific level of the central nervous system does the facial nerve connect to?

Accepted Answer

The facial nerve (cranial nerve VII) connects to the brainstem at the level of the metencephalon, which includes the pons and the cerebellum. This area is responsible for transmitting nerve signals that control facial expressions, among other functions.

Question 15

A researcher treats an early neural-tube-stage embryo with a 1-hour pulse of colchicine,which arrests proliferating cells in metaphase.Where will the arrested cells be found?

Accepted Answer

Colchicine arrests cells in metaphase of mitosis, which occurs in the ventricular layer of the neural tube where cell division occurs. Therefore, the arrested cells will be found throughout the ventricular layer of the neural tube.

Quiz 10: Development of the Central Nervous System