Nervous system development

Question 1

What is the diff b/w ganglion and nucleus?

Answer 1

Ganglion is a collection of cell bodies located outside of CNS (in PNS), while nucleus is located w/in the CNS

Question 2

What does the brainstem consist of?

Answer 2

Medulla, pons, midbrain

Question 3

The cerebellum has been largely viewed as a component of the __ sytem, but it has a wide range of functions including __ and __.

Answer 3

The cerebellum has been largely viewed as a component of the motor system, but it has a wide range of functions including learning and memory.

Question 4

What does the diencephalon consist of?

What about the telencephalon?

Answer 4

Thalamus, Hypothalamus, and epithalamus;

striatum and cerebral cortex

Question 5

What are the major lobes of the cerebral cortex/neo cortex?

Answer 5

occipital, parietal, temporal, frontal,

also post-central, orbito-frontal, cingulate

Question 6

The neocortex is a 6-layered structure. In the sensory cortex, inputs from the thalamus largely target cells in what layer?

Answer 6

layer 4

Question 7

The cerebral hemispheres are interconnected through what 3 major pathways?

Answer 7

Corpus callosum, anterior commissure, and posterior commissure.

Question 8

In the 3rd wk, inductive factors from where cause the transformation of the surface ectoderm into the neural plate?

Answer 8

Notochord and paraxial mesenchyme.

Question 9

What is primary neurulation and when does it happen?

Answer 9

Neural folds and a midline neural groove forms in the neural plate in the region of the 4th thru 6th somites. This happens in 4th wk days 22-23

Question 10

Closure of the neural tube proceeds bidirectionally. When and where is the first closure?

Answer 10

Day 22 in the region of the 5th somite.

NOTE: neural tube closure occurs at up to 5 diff places and abnormal closure of different sites results in neural tube defects.

Question 11

How is the caudal most portion of the neural tube formed?

When is this completed?

Answer 11

By secondary neurulation of the caudal eminence NOT the neural plate.

Secondary neurulation is completed by wk 8.

Question 12

Failure of fusion of the neural rube and vertebral arches are defects collectively known as…

Answer 12

Spina bifida

Question 13

Defects in the closure of the rostral neuropore results in what?

Defects in the closure of the caudal neuropore results in what?

Answer 13

Incomplete development of the brain, calvaria, and/or face;

Different types of spina bifida

Question 14

What is microencephaly?

Answer 14

A severe form of rostral neural tube defect in which portions of the cranium fail to form w/ resulting defects in brain development.

Typically forebrain, midbrain, and portions of hindbrain fail to form.

Question 15

Describe the different severities of spina bifida.

Answer 15

1. Spina bifida occulta: failure of fusion of vertebral arches (L5 or S1). Indicated by a small dimple w/ a patch of hair
2. Spina bifida cystica meningocele: spinal cord in normal position but a meningal sac protrudes thru the defect
3. Spina bifida cystica meningomyelocele: spinal cord and nerve roots also protrude thru the vertebral defect
4. Spina bifida myeloschisis: most severe form, the neural tube failed to fuse resulting in a flattened neural mass directly exposed to amniotic fluid.

Question 16

Which neural crest cells migrate just deep to the ectoderm w/in the loose mesoderm?

Answer 16

Cephalic neural crest cells

Question 17

What is neurofibromatosis?

What is neuroblastoma?

Answer 17

Peripheral nerve tumors;

Tumor of the adrenal medulla, autonomic ganglia

Question 18

The ___ of the neural plate forms the spinal cord.

Answer 18

Caudal 1/3

Question 19

What is the ventricular zone?

Answer 19

The neuroepithelial layer adjacent to the central canal (the lumen of the neural tube) and contains precursor cells that give rise to all of the neurons and macroglia of the spinal cord.

Question 20

The primordial neurons migrate from ___ to ___.

Answer 20

the ventricular zone to the intermediate zone.

Question 21

What is the sulcus limitans?

Where does it extend through?

Answer 21

It is a shallow longitudinal groove in the lateral walls of the neural tube that separate the developing gray matter into a dorsal alar plate and ventral basal plate.

The sulcus limitans extends the length of the spinal cord through the mesencephalon (midbrain).

Question 22

Neuronal cell bodies in the alar plate form:

Answer 22

nuclei that constitute the dorsal gray matter that receive and relay input from afferent (sensory, somatic, and visceral) neurons

Question 23

Neuronal cell bodies in the basal plate form:

Answer 23

The ventral gray matter or efferent neurons. Axons of these neurons project motor fibers to skeletal m. and form the ventral roots of the spinal n.’s

Question 24

Describe how ventral and dorsal roots of the spinal nerves come about.

Answer 24

The ventral roots are motor fibers that extend from the basal plate. The dorsal roots arise from the developing spinal ganglia and join w/ the ventral roots.

The spinal n.’s branch to form the dorsal and ventral primary rami.

Question 25

At wk __, the spinal cord extends the full length of the vertebral column. In adults, the spinal cord ends at the level of __. This results in the formation of the __.

Answer 25

At wk 8, the spinal cord extends the full length of the vertebral column. In adults, the spinal cord ends at the level of L1-L2. This results in the formation of the Cauda equina (which consists of the long dorsal/ventral roots that descend to their original vertebral levels.

Question 26

Where are SHH and BMP secreted?

Answer 26

SHH: by notochord and subsequently by the floor plate of the neural tube

BMP: by ectoderm over dorsal neural tube, which then sets up a secondary cetner in the roof plate of the neural tube

Question 27

How do the opposing gradients of BMP and SHH control the fate of neuroblasts in the developing neural tube?

Answer 27

Neuroblasts exposed to hight SHH and low BMP will differentitate into motor neurons.

Neuroblasts exposed to low SHH and high BMP will differentiate into sensory neurons

Question 28

What are the 3 primary vesicles of the brain and by what day are they apparent?

Answer 28

Prosencephalon (forebrain)

Mesencephalon (midbrain)

Rhombencephalon (hindbrain);

Day 26

Question 29

During the 5th wk, the prosencephalon (1,2)and rhombencephalon (4,5) each subdivide, contributing to 5 secondary vesicles. Name them and what the neural canal in each vesicle becomes definitively.

Answer 29

1. Telencephalon: lateral ventricles
2. Diencephalon: third ventricle
3. Mesencephalon: aqueduct of Sylvius
4. Metencephalon: (see 5)
5. Myelencephalon: fourth ventricle (w/ 4)

Question 30

What are the 3 main flexures and what do they become?

NOTE: They all appear during week 5.

Answer 30

1. Cervical flexure: forms b/w rhomboencephalon and spinal cord: develops thru wk 8 but doesn’t persist in adule
2. Cephalic flexure: forms at level of future midbrain: persists in adult as a bend b/w brainstem and forebrain
3. Pontine flexure (AKA dorsal flexure): forms b/w metencephalon and myelencephalon: causes walls of myelencephalon to spread apart and results in the thinned roof of the 4th ventricle, doesn’t persist in adult, but plays an important role in the development of the cerebellum and pons.

Question 31

A pair of dorsal root ganglia develops at every spinal segment, except at:

Answer 31

1st cervical, and 2nd & 3rd coccygeal levels

Question 32

What are postganglionic parasympathetic neurons derived from?

Answer 32

from neural crest cells originating from the occipito-cervical region of the neural tube

Question 33

Parasympathetic ganglion cells to the most inferior portion of the gut have 2 origins. What are they?

Answer 33

Occipito-cervical neural crest and sacral neural crest cells

Question 34

What are the sympathetic chain ganglia derived from?

How many sympathetic ganglia are there in the cervical and coccygeal region?

Answer 34

From spinal neural crest cells that migrate to a position ventral to the developing dorsal root ganglia.

3 ganglia in cervical, 1 gangion in coccygeal region.

Question 35

Which neurons are the first to send axons into the periphery?

Answer 35

Neurons in the ventral (motor) columns of the spinal cord

Question 36

cells of the neuroepithelium differentiate into:

Where does this occur?

Answer 36

neurons, glia, and ependyma of the CNS;

Differentiation begins in the rhombocephalic region just after neural tube closure in that region

Question 37

The layer of proliferating cells that line the central canal of the neural tube is called the __.

The first cells produced by the ventricular layer are the __ that migrate to from the __ layer. Processes that extend from this form a third layer, the __, which is a layer that contains no __ and becomes __.

Answer 37

The layer of proliferating cells that line the central canal of the neural tube is called the ventricular layer.

The first cells produced by the ventricular layer are the neuroblasts that migrate to from the mantle layer. Processes that extend from this form a third layer, the marginal__ zone, which is a layer that contains no cell bodies and becomes white matter.

Question 38

After neuroblast formation __ differentiate from the epithelial lining of the neural canal.

What do they become?

Answer 38

Glioblasts; They become astrocytes and oligodendrocytes

Question 39

After glioblast differentiation, the neuroepithelial layer will differentiate in place to form the __.

Answer 39

Ependymal cell lining of the ventricles and central canal of the spinal cord.

Question 40

Initially neuroblasts are __, and once they differentiate into neurons they lose their ability to __.

Answer 40

non-polar; divide

Question 41

What cells myelinate axons in the PNS and CNS?

Answer 41

Schwann cells; oligodendrocytes

Question 42

What becomes of the ependyma (which is from the neuroepithelium)?

Answer 42

It becomes the epithelium of choroid plexus.