Development Of The Brain

Question 1

The neural plate and neural groove develop on the ____ at week ____. This is induce by the notochord.

Neurulation begins week ___.

Cranial 2/3 of the neural plate become ____ and caudal 1/3 becomes ____.

Answer 1

Posterior aspect of the trilaminar embryo; 3

4

4th pair of somites=future brain
Future SC

Question 2

The neural tube first forms at the ___.

It proceeds cranially and caudally until the neuropores remain. Cranial neuropore closes at ____ and caudal neuropore closes at ____.

Answer 2

5th somite

25 days; 27 days

Question 3

SC develops caudal to the ____.

The lateral walls of the neural tube thicken which reduces the size of the ____ until a small ____ exists at week ____.

The neural tube is composed of ____ neuroepithelium.

Answer 3

4th pair of somites

Neural canal; central canal (canals will form the ventricles); 9-10

Pseudostratified columnar

Question 4

What are the three zones of the neural tube and what cells do they contain?

Answer 4

Ventricular zone: neuroepithelial cells closed to the lumen that will divide and migrate

Intermediate zone: cells that differentiate into neurons and/or glia

Marginal zone: decreased cell bodies that contain axons that will eventually be myelinated

Question 5

There are five closure sites involved in the formation of the neural tube. Failure of a site to close during week ___ leads to ____.

____ results from the failure of closure of site 2.

____ results from failure of closure of sites 1, 2, 4.

Closure of site 5 occurs via ____.

Answer 5

4; spina bifida cystica

Meroencephaly

Craniorachischisis

Secondary neurulation

Question 6

Four types of spina bifida?

Answer 6

SB occulta: infused neural (vertebral) arch, skin remains intact

SB with meningocele: meninges extrude

SB with menigomyelocele: meninges and neural tissue extend

SB with myeloschisis: open neural tissue

Question 7

___ differentiate from neuroepithelial cells. After neuronal formation ceases, glioblasts become ____ and ____.

When glial production stops -> neuroepithelial cells differentiate into ____.

Microglia are derived from ___.

___ controls the proliferation and patterning of neuroepithelial cells via GLI transcription factors.

Answer 7

Glioblasts; astrocytes and oligodendrocytes

Ependymal cells

Mesenchyme

SHH

Question 8

Differentiation of the SC produces thick walls, but thin roof and floor plates. It produces a shallow longitudinal groove on each side called a ____.

Fx?

Answer 8

Sulcus limitans: separates the alar plate (dorsal) form the basal plate (ventral)

Regional separation of plates has a fundamental importance: each become associated with afferent and efferent functions

Question 9

Cell bodies in the alar plates form a ____, constitute afferent nuclei and groups of them form the _____.

____ forms with enlargement of alar plates.

Answer 9

Dorsal gray column; dorsal gray horns

Dorsal median septum

Question 10

Cell bodies in the basal plate form ventral and lateral gray columns. They form the efferent nuclei -> _____.

Axons will grow out to form ____.

As the basal plates enlarge, they bulge ventrally on each side forming ____.

A deep longitudinal groove develops on the ventral surface called ____.

Answer 10

Ventral gray horns and lateral gray horns

Ventral roots of spinal nerves

Ventral median septum

Ventral median fissure

Question 11

Basal and alar cranial nerve nuclei are organized into seven columns?

Answer 11

1. Somatic efferents
2. Branchial efferents (special visceral efferents
3. General visceral efferents
4. General visceral afferents
5. Special visceral afferents
6. General somatic afferents
7. Special somatic afferent

Question 12

Brian develops during the ___ week from the ____, cranial to the 4th pair of somites.

Fusion of neural folds in cranial region and closure of rostral neuropore form _____.

Answer 12

3rd; neural tube

Primary brain vesicles

Question 13

During the ____ week, the secondary brain vesicles form.

Forebrain divides into ____.

Midbrain does not divide but becomes the ____.

Hindbrain divides into ____.

Answer 13

5th

Telencephalon: cerebral hemispheres/lateral ventricles
Diencephalon: thalamus/3rd ventricle

Mesencephalon: midbrain/cerebral aqueduct

Metencephalon: pons and cerebellum?upper 4th ventricle
Myelencephalon: medulla/lower 4th ventricle

Question 14

During the ___ week, the embryonic brain grows rapidly and bends ventrally with the ____.

Bending produces the ____ and ____.

Unequal growth produces the ____ that folds in the opposite direction.

Answer 14

5th; head fold

Midbrain flexure (mesencephalic flexure); cervical flexure (midbrain-SC junction)

Pontine flexure (meten-myelencephalon junction)

Question 15

Cervical flexure demarcates the ____ from the SC. The junction is defined as the level of the superior rootlet of ____ (foramen magnum).

The pontine flexure divides the hindbrain into the ____ and ____.

Myelencephalon -> _____.

Metencephalon -> ____.

Cavity of hindbrain -> ____ and ____.

Answer 15

Hindbrain; C1

Metencephalon and myelencephalon

Medulla oblongata

Pons and cerebellum

4th ventricle and central canal in medulla

Question 16

In the caudal myelencephalon, neuroblasts in alar plates migrate into the marginal zone and form the ____ and ____.

_____ consist of the crossing of CST fibers.

Answer 16

Nuceli gracilus and cuneatus

Pyramids

Question 17

The rostral myelencephalon forms the ______, ______, and _____.

Basal plates become medial to the ____ and motor nuclei develop medially to ___.

Answer 17

Pontine flexure (causes walls of the medulla to move laterally/flatten), roof plate, and cavity (part of the future 4th ventricle)

Alar plates; sensory nuclei

Question 18

Neuroblasts in the basal plate develop into ____. Nuclei organize into cell columns on each side and contain _____.

Neuroblasts in the alar plate of the medulla form neurons arranged in columns on each side and contain ____.

Some migrate ventrally and form neurons in the ____.

Answer 18

Motor neurons; efferents

Afferents

Olivary nuclei

Question 19

Metencephalon forms the ____ ventrally and the ____ dorsally.

Cavity of metencephalon forms the superior part of the ____.

The pontine flexure forces walls of the pons laterally -> spreading the gray matter in the floor of the ____.

Neuroblasts in each basal plate develop into ____.

Answer 19

Pons; cerebellum

4th ventricle

4th ventricle

Motor nuclei

Question 20

Cerebellum develops from the ____.

____ project into the 4th ventricle and fuse in the medial plate.

Then they overgrow the rostral 4th ventricle and overlap the _____.

Answer 20

Dorsal parts of the alar plates

Cerebellar swellings

Pons/medulla.

Question 21

Neuroblasts of alar plates migrate into the tectum to form the _____ and ____.

Neuroblasts of basal plates form the ____ which include what?

Fibers growing from the cerebral cortex form ____.

The neural canal narrows and forms ____ connecting what?

Answer 21

Superior and inferior colliculi

Tegmental nuclei: red nuclei, reticular nuclei, CN III and IV nuclei

Cerebral peduncles

Cerebral aqueduct: connecting 3rd-4th ventricles

Question 22

Swellings in the lateral walls of the 3rd ventricle form the diencephalon including the ____, _____, ____.

What does the epithalamus sulcus separate?

What does the hypothalamic sulcus separate?

Answer 22

Thalamus, hypothalamus, and epithalamus

Separates thalamus and epithalamus

Separates thalamus and hypothalamus

Question 23

The thalamus develops on each side of the ____, bulges into its cavity, and fuses at the midline forming the _____ connecting the two halves.

Hypothalamus arises from ____ in the intermediate zone. Endocrine and homeostatic nuclei develop. ____ form on the ventral surface.

Answer 23

3rd ventricle; interthalamic adhesion

Neruroblasts

Mammillary bodies

Question 24

Pituitary gland develops from the _____ to become the pars anterior and pars tuberalis. The _____ develops to become the median eminence, infundibulum, and pars nervosa.

The hypophyseal diverticulum lies near the floor of the ____ and forms during the ___ week. Its connection to the oral cavity degenerates during the ____ week.

The infundibulum passes between the developing bones of the ____.

Answer 24

Hypophyseal diverticulum: (Rathke’s pouch) upgrowth of the roof of the stomodeum

Neurohypophyseal diverticulum: downgrowth from diencephalon

Diencephalon; 3rd; 6th

Cranium

Question 25

The telencephalon splits to contain a median part and two _____ which become the ____.

The medial cavity of the telencephalon forms the anterior ____.

As closure of the rostral neuropore occurs, the ____ appear which become ____.

Communication of the cerebral hemispheres with the 3rd ventricle is via the ____.

Answer 25

Two telencephalon/cerebral vesicles ->cerebral hemispheres

3rd ventricle

Optic vesicles -> retinae and optic N

Interventricular foramina

Question 26

The medial wall of the cerebral hemisphere becomes thin and is continuous with the roof of the 3rd ventricle to become the ___.

Cerebral hemispheres expand and cover the ____.

The mesenchyme trapped in the longitudinal fissures give rise to the _____.

The cavities of the telencephalon and diencephalon form the ____.

Answer 26

Choroid plexus

Diencephalon, midbrain, hindbrain

Falx cerebri

3rd ventricle

Question 27

The cerebral hemispheres initially have three zones in the neural tube? What is the 4th layer that appears after?

The proliferating cells of the ____ layer undergo a series of regulated divisions to produce waves of neurons that migrate peripherally, this becomes the ____.

Cortical layers are laid down in a sequence ____.

Answer 27

Ventricular, intermediate, and marginal zones; subventricular zone

Ventricular; neuronal layers of the cortex

Deep to superficial (inside out): neurons migrate through the deeper layer and exit to establish more superficial layers (inside out development)

Question 28

The 1st neurons from the ventricular zone form a ____ that underlies the developing pia.

The axons extend on the inner side of the preplate and establish the ____.

The next set of neurons migrate into the preplate, split it, and produce the ____.

Answer 28

Preplate

Intermediate zone

Cortical plate: in between the marginal zone and the subplate

Question 29

Neurons migrate on the processes of the ____ that span the cortex to get to their final destination.

Axons from the neurons in the cortical plate and subplate join those in intermediate zone and will later form the _____ of the cortex.

Early neurons from the deepest layers of the cortex including layers ___.

Answer 29

Radial glial cells

White matter

VI and V

Question 30

Late neurons migrate through intermediate zone and subplate. They pass through layers _____ and establish layers _____.

What is the subventricular zone?

Answer 30

VI and V

IV -> III -> II

New neurons in an extra germinative layer

Question 31

Groups of never fibers interconnecting the cerebral hemispheres are _____. The rostral end of the forebrain is the ____.

What two commissures form first?

Answer 31

Cerebral commissure

Lamina terminalis

Anterior commissure: interconnects the olfactory bulb within the hemispheres

Hippocampal commissure: connects the hippocampal formations

Question 32

_____ forms and links hemispheres.

Lamina terminalis is stretched and forms the ____.

Answer 32

Corpus callosum (anterior portion forms first then posterior)

Septum pellucidum (thin plate of brain tissue containing nerve cells and fibers)

Question 33

____ is the complete or partial absence of the corpus callosum.

Cause what?

Answer 33

Agensis of corpus callosum

Seizures

Question 34

____ is the incomplete neuronal migration to cerebral cortex during _____ months of gestation.

What does this cause?

Answer 34

Lissencephaly; 3-4

Pachygyria: broad thick gyri

Agyria: lacks of gyri (smooth surface)

Neuronal heterotopia: cells in aberrant position compared to a normal brain

Enlarged ventricles and malformation of the corpus callosum

Initially appear normal but later develop seizures, mental deficiencies, spastic quadriplegia

Question 35

____ is a neurodevelopmental disorder where the calvaria and the brain are small but the face is normal sized.

What does it cause?

What causes it?

Answer 35

Microcephaly

Mental deficiencies due to brain underdevelopment.

Low pressure from a reduction in brain growth leads to a small neurocranium

Ionizing radiation, maternal EtOH use, infections agents (cytomegalovirus, rubella virus, toxoplasma Gondi), autosomal recessive

Question 36

Hydrocephalus is caused by _____.

What causes this?

Answer 36

Impaired production and absorption of CSF -> excess CSF in the ventricular system

Increased CSF by choroid plexus adenoma
Intraventricular hemorrhage causing obstruction of the lateral or median aperture
Congenital aqueductal stenosis

Question 37

Hydrocephalus results in the dilation of the ventricles ____ to the obstruction, internal accumulation of CSF, and increased pressure on cerebral hemispheres.

What are the two types and what causes them?

Answer 37

Proximal

Obstructive (noncommunicating): ventricles are enlarged

Nonobstructive (communicating): no subarachnoid cisterns or malformation of arachnoid villi

Question 38

____ is the incomplete separation of the cerebral hemispheres and are associated with facial abnormalities.

Defects in the forebrain development often cause facial anomalies resulting from a reduction of the ____.

Causes what?

What genes are involved?

Answer 38

Holoprosencephaly (HPE)

FNP

Cyclopes, premaxillary agenesis, proboscis, single nostril, hypotelorism, facial clefts

SHH, GLI, IHH, SIX3, TGIF, ZIC, PTCH

Question 39

_____ is a structural defect of the cerebellum.

Causes what?

What are the two types?

Answer 39

Chiari malformation

Tongue like projection of the medulla of the cerebellum; inferior displacement of the cerebral tonsil through the foramen magnum into the vertebral canal; small posterior cranial fossa; noncommunicating hydrocephalus

Type I: inferior part of the cerebellum herniated through the foramen magnum

Type II (Arnold-Chiari malformation): cerebellar tissue and brainstem herniate through the foramen magnum; accompanied by occipital encephalocele and lumbar myelomenigocele