Module 4 Neuroanatomy

Which parts of neuroectoderm gives gives to the brain and SC, and then the PNS?

brain and spinal cord = neural tube

PNS = neural crest cells

What are the three cardinal signs of morphogenesis in the early stage embryo?

polarity, bilateral symmetry, regionalization (think about how the cranial side grows faster and first)

What is the influence of the notochord in dorsoventral patterning in the early stage embryo?

notochord released a soluble factor, sonic hedge hog, and then this will act to differentiate the floor plate and motor neurons

How does the shape of the neural folds change to form the neural tube?

Notochord is the most deep thing, and this is under the neural plate. The two ends will meet in the middle, and once they meet fully and close off, they will become the neural tube and it breaks off from the ectoderm. The neural crest cells migrate to sit underneath the ectoderm, and then the neural tube will be under these cells. The neural crest cells will then be acted upon by another inducible factor that will then cause it to stimulate the growth and formation of the PNS.

What are the three primary brain ventricles that appear in early stage embryos?

forebrain --> proencephalon

midbrain --> mesencephalon

hindbrain --> rhombencephalon

Where do the cephalic and cervical flexures fall?

cephalic = by the mesencephalon

cervical = between the myelencephalon and spinal cord

How do the three primary brain vesicle form into the five brain ventricles later in development?

forebrain --> telencephalon and diencephalon

midbrain --> mesencephalon

hindbrain --> metencephalon and myelencephalon

What structures develop from the embryonic telencephalon?

olfactory bulbs, basal ganglia, cerebral cortex, cortical white matter, corpus callosum, internal capsule

William's syndrome

cerebral cortex defect, deletion of chromosome 7 band 7q11.23

tend to have a smaller amygdala --> no fear of situations! central sulcus stops before reaching midline

strengths: tend to be dramatic storytellers, outgoing social abilities, language and face processing

impairments: spatial recognition

Where is the neural crest in the embryonic brain?

ectoderm --> neural crest cells --> neural tube

What are some neural derivatives of neural tube?

dorsal root ganglia, sympathetic chain ganglia enteric ganglia, sympathetic ganglia of cranial nerve 5-10, pre-aortic ganglia

What are some non-neural derivatives?

schwann cells, odontoblasts, melanoctyes, ciliary and pupillary muscles, satellite cells of peripheral ganglia, cartilages of the pharyngeal arches, chromaffin cells of adrenal medulla, leptomeninges

What is the most important reason why chimeras are good with fate mapping?

we are able to input something and then watch where those cells go

What happens when neural crest cells are cultured with and without glial growth factor (GGF2)?

absence: 80% of the cells will be neurons and the rest are glia

presence: 20% of the cells will be neurons and the rest are glia

What parts of the skull receive neural crest cells during development?

temporal bone, stapes, orbital bones, maxilla, mandible, hyoid, nasal bones, frontal bone, hard palate

What are some peripheral ganglia that are formed due to contributions from migrating neural crest cells?

sensory neurons and neural cell bodies in the dorsal root ganglion, sympathetic ganglia, pre-aoritic ganglia, into tissue of adrenal medulla, ganglia in the intestines

Where do the neural crest cells go in regards to the adrenal gland?

chromaffin cells in the adrenal medulla

What disrder arises when neural crest cells contract and won't relax?

Hirschsprung's disease --> the smooth muscle will constantly stay contracted, meaning that they won't relax and then let food through, so the intestines will become distended

What mutation is responsible for DiGeorge's syndrome?

gene mutation of chromosome 22 q11

What are some derangements of DiGeorge's syndrome

thymic aplasia --> no thymus = dangerous because this is what houses immune cells

cardiac abnormalities

neonatal hypocalemia, cleft palate, smal mouth, and low set ears

What is a technique that can correct for DiGeorge's syndrome?

thymus transplant

Neurulation

formation of the neural tube

What are the relative locations of the ectoderm, mesoderm, endoderm, neural fold, sulcus limitans?

Ectoderm - first layer, most superficial

Mesoderm - middle, sandwiched between ecto and endo

Endoderm - deep layer

Neural fold - when the two sides come together and meet, they form what looks like a fold

Sulcus limitans - the inner part of the neural tube that is formed (almost kind of outlines it)

Describe the transient zone of neurons formed during neuronal migration.

Primitive neurons start in the ventricular zone (VZ), along with primitive glial cells. Radial glial cells will help guide neurons to their destination, by using their processes that extend to the layers that will be created. There is an intermediate and pre-plate zones. Once the neurons start migrating up, the cortical plate will settle in between the sub-plate and the marginal zone. Then the neurons will have a bottom up approach where they will migrate up and settle at the bottom first, and then will continue layering themselves on top of each other to create the layers.

Describe periventricular heterotopia

Gene mutation of FLN1 gene, which codes for neuronal migration out of the ventricular zone. On X chromosomes, so will be lethal for males compared to females. Some alleles have it, some don't, so the ones that have it will be unable to leave the VZ, and will cluster around the ventricles.

Describe lissencephaly

Gene mutation of LIS-1 gene, which codes for progressing of the neuronal migration. Some of these have it, while some don't. The ones that don't will make it out of the ventricular zone, but will half at some point. This allows for no formation of the 6 layers and no gyrus formation.

Describe double cortex.

Gene mutation of the DCX gene, which codes for progressing of the neural migration. Neurons make it out of the VZ, but will stop halfway, forming what looks like a double layer of cerebral cortex.

What structures develop from the diencephalon?

thalamus, hypothalamus, pineal gland, optic vesicle

What structures develop from the mesencephalon?

tetum --> inferior and superior colliculi; tegmentum --> substantia nigra, red nucleus; cerebral aqueduct

What structures develop from the metencephalon?

pons, cerebellum, 4th ventricle

What structures develop from the myelencephalon?

medulla

What are the locations of the longitudinal groove, sulcus limitans, alar and basal plates?

longitudinal groove = line found in the middle of the inner surface of the neural tube

sulcus limitans = inner surface of the neural tube

alar plate = dorsal part, contains sensory neurons

basal plate = ventral part, contains motor neurons

Describe the pattern of CSF.

CSF is made by the choroid plexus, and this lines the ventricles. CSF starts in the lateral ventricles, then makes its way to the third ventricles via the interventricular foramen. Then it will go to the fourth ventricle via the cerebral aqueduct. Then it goes to the spinal cord or the sub-arachnoid space, where then arachnoid grandulations can re-absorb it.

Communicating vs. non-communicating hydrocephalus.

communicating = there is no blockage of CSF, but arachnoid granulations cannot re-absorb it

non-communicating = there is a blockage along the pathways that CSF takes, such as by a tumor in the brain that is along the ventricles

What are some risk factors to developing a neural tube defect?

vitamin deficiencies: vitamin a, folic acid, pantothenic acid, riboflavin, nicotinamide viral illness, x-rays, vitamin a excess, hypoxia

Differentiate between spina bifida oculta, meningocele, meningomyelocele, meningohydroencephalocele

spina bifida oculta - the fusion of the vertebral lamina doesn't occur

meningocele - meninges protrude out

meningomyelocele - meninges and SC/brain tissue protrude out

meningohydroencephalocele - meninges, brain tissue, and ventricular luman protrude out

Chiari type I malformation

"small posterior fossa" where the is defect of the foramen magnum (occipital bone); this is too small, so the brain almost slips out of the cranium and into the vertebral column

Chiari type II malformation

the defect occurs lower, where the spinal cord stays outside the spinal limits and the SC and will cause the brain to be pushed out

What are the features associated with Dandy-Walker syndrome?

"large posterior fossa" where there is aplasia of the normal cerebellum, an enlargement of the fourth ventricle that is roofless. a cyst is midline that is lined with ependyma and is contiguous with leptomeninges on its outer surface.

Describe features associated with semi-lobar and alobar holoprosencephaly, and then anencephaly.

semi-lobar --> there was the start of separation of the hemispheres, but a full one never occurred

alobar --> there was no separation of the hemisphere, so it is one big hemisphere with one large ventricle on the side. also, there is no gryus present = lissencephaly

anencephaly --> malformation of anterior end of the neural tube with absence of the brain and calvaria. forebrain development is disrupted, and all that remains in place is area cerbrovasculosa

What is the rate of neural tube defects such as anencephaly with and without folic acid vitamins?

before supplementation: 1 in 5 in 100 live births

after supplementation: 1 in 10,000 live births

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