9. Development of the Nervous System

Question 1

Gastrulation occurs during week 3 and a primitive streak forms with a primitive node, groove, and pit along with the notochordal process. What does this become? (2)

Answer 1

Template for formation of vertebral column

Induce formation of the neural plate

Question 2

Neurulation begins day 22-23 and notochord release sonic hedge hog which induces formation of neural plate (ectoderm), including?

Answer 2

Neural groove, folds, and NEURAL TUBE (primary neurulation)

Question 3

As primary neurulation continues, the rostral and caudal neuropore form and fuse at what times?

Answer 3

Rostral at day 25
Caudal at day 28
Closure forms definitive neural tube

Question 4

Secondary neurulation occurs days 20-42, and is when the caudal eminence fuses with ________ to form what?

Answer 4

Caudal neuropore to make sacral/coccyx regions

Question 5

What will the neural tube/primary neurulation produce?

Answer 5

From brain to lumbar spinal cord

Question 6

The neural tube from neuroectoderm forms many things, including neurons, astrocytes, oligodendrocytes and ependymal cells/epithelium of choroid plexus. What is the only cell of the nervous system not made from this?

Answer 6

microglial cells, which is phagocytic and is made from mesoderm and derived from monocytes/mesenchymal cell

Question 7

The brain forms from the neural tube caudal to the fourth somite (mesoderm). What are the three primary brain vesicles?

Answer 7

Prosencephalon- forebrain
Mesencephalon - midbrain
Rhombencephalon - hindbrain

Question 8

During the 5th week, the prosencephalon and rhombencephalon (fore/hindbrain) will divide into?

Answer 8

Fore: telencephalong and diencephalon
Hind: metencephalon and myelencephalon

Question 9

The cervical flexure divides the hindbrain from the spinal cord, what does the pontine flexure divide?

Answer 9

the hindbrain into caudal myelencephalon and rostral metencephalon

Question 10

What does the cephalic flexure bend between?

Answer 10

midbrain and forebrain

Question 11

The basal ganglion and cortical structure inside is developing between what weeks?

Answer 11

6 to 32

Question 12

What forms the following: cerebral cortex, subcortical white matter (internal capsule), olfactory bulb and tract, basal ganglia, amygdala, and hippocampus?

Answer 12

telencephalon

Question 13

What forms the following: thalamus, hypothalamus, epithalamus, subthalamic nucleus and eyes (optic nerve)?

Answer 13

diencephalon

Question 14

What forms the following: cerebral peduncles, superior and inferior collilculus, and CN II?

Answer 14

Mesencephalon/Midbrain

Question 15

What forms the following: cerebellum and pons?

Answer 15

metencephalon

Question 16

What forms the following: medulla oblongata, olive, pyramid?

Answer 16

myelencephalon

Question 17

What results from incomplete separation of cerebral hemispheres, associated with facial abnormalities, reduction of FNP (frontonasal prominence) and hypotelorism (eyes close together)?

Answer 17

holoprosencepahly (HPE)

Question 18

What are the three main causes of holoprosencephaly?

Answer 18

genetic AND environmental factors
maternal diabetes
teratogens (alcohol)

Question 19

What are some of the common clinic features of HPE? 6

Answer 19

microcephalu, micropthalmia, cleft palate/lip, intellextual disability, epilepsy and hydrocephalus

Question 20

The pituitary gland is formed from first arch of surface ectoderm from the roof of the mouth. Which contributes to what part?

Answer 20

anterior lobe known as rathke’s pouch (hypophysial diverticulum)

Question 21

The posterior lobe of the pituitary gland is from neuroectoderm and is from the diencephalic floor. How do anterior and posterior meet?

Answer 21

Rathke’s pouch migrates up and fuses with neurohypophysial diverticulum, stalk of rathke’s pouch degrades

Question 22

The neural tube caudal to 4ths somite will form the neural/central canal as well as the sulcus limitans which separates what?

Answer 22

alar plate from basal plate

Question 23

What do the alar and basal plate form?

Answer 23

alar: dorsal horn/sensory neurons in CNS
Basal: motor neurons to skeletal M, presynpatic autonomics

Question 24

The neural/central canal has three different zones, ventricular (directly around canal), intermediate and marginal. What are the main contents of each?

Answer 24

Ventricular Zone: Stem cell, ependymal, choroid plexus cell
intermediate: neurons, glioblast, astrocyte (gray matt)
Marginal: Oligodendrocyte

Question 25

Sulcus limitans separates alar and basal plate, at the pontine flexure, it pushes what?

Answer 25

the alar laterl and basal plate medial | *this is why GVE/GSE/SVE are medial and GVA/SVA/SSA/GSA (sensory) are lateral

Question 26

Where do the hypoglossal nucleus, dorsal motor vagal nuclesu and nucleus ambiguus in the myelencephalon are from what?

Answer 26

basal plate

Question 27

the vestibular, cochlear nuclei, spinal trigeminal tract and nucleus, and solitary nucleus in the myelencephalon are from what plate?

Answer 27

Alar plate

Question 28

The facial, trigeminal, and superior salivatory nuclei and abducens nucleus in the metencephalon are from what?

Answer 28

basal plate

Question 29

Within the mesencephalon where do the red nucleus, oculomotor nucleus, trochlear nucleus and edinger westphal nucleus come from what plate?

Answer 29

Basal plate

Question 30

Where do the lateral ventricle, 3rd, 4th ventricles, and cerebral aqueduct come from?

Answer 30

lateral ventricle: telencephalon 3rd ventricle: diencephalon 4th ventricle: metencephalon AND myelencephalon Cerebral aqueduct: mesencephalon

Question 31

Choroid plexus lines all the ventricles and produces CSF, how does CSF leave the 4th ventricle?

Answer 31

2 lateral foramina of luschka | 1 medial foramen of magendie

Question 32

How does fluid go from lateral ventricle to 3rd ventricle?

Answer 32

interventricular foramen of monroe

Question 33

The lateral ventricle is split into 3 horns, what are they?

Answer 33

frontal/anterior horn temporal/inferior horn occiptal/posterior horn

Question 34

What abnormality is associated with chiari type 1 malformation, where there is excess fluid in the central canal, most commonly WITHIN the SC between C2-T9?

Answer 34

Syringomyelia

Question 35

What is characteristic of spastic cerebral palsy, due to excess fluid?

Answer 35

toe walking with a scissor gait, often with forearms out to gaurd from falling

Question 36

What is characteristic of athetoid cerebral palsy?

Answer 36

slow writhing movements of the extremities/trunk

Question 37

What is ataxic cerebral palsy?

Answer 37

incoordination, weakness and shaking during voluntary movement (drunken sailor)

Question 38

What malformation occurs when there is deformity of the hindbrain where herniation of cerebellar tonsils go through the foramen magnum, commonly seen with syringomyelia?

Answer 38

Arnold Chiari Type 1 malformation

Question 39

What malformation occurs when there is herniation of the medulla and cerebellum through the foramen magnum, ALWAYS has hydrocephalus (and spina bifida)?

Answer 39

Arnold Chiari Type II malformation

Question 40

Type 1 chiari is associated with head and neck pain and lower cranial nerve problems. What about Chiari type II?

Answer 40

Lower cranial nerve problems (tongue, facial M, lateral eye movement, decreased hearing, dizziness, sternocleidomastoid paralysis, and coordinating movements)

Question 41

What is most commonly seen with Chiari type I?

Answer 41

syringomyelia which is excess CSF within the SC in the spinal canal

Question 42

Chiari type II can be diagnosed via MRI, by herniation seen through the foramen magnum and what else?

Answer 42

Myelomeningocele (spina bifida with spinal cord and tissue)

Question 43

Dandy Walker Malformation (Cyst) is a large posterior fossa cyst continuous with the 4th ventricle, hypoplasia and atresia of what can be seen?

Answer 43

Hypoplasia of the cerebellum, and sometimes vermis | Atresia of foramina of luschka and magendie

Question 44

What has an unknown cause but is thought to be due to the obstruction of blood flow to the areas supplied by internal carotid arteries?

Answer 44

hydranencephaly (no cortex, SC in tact)

Question 45

Up until 5months, the brain is smooth and there are no sulci or gyri. What is the reason for gyri and sulci?

Answer 45

to increase SA while decreasing size

Question 46

What is the insula covered by?

Answer 46

operculum = frontal parietal and temporal lobes

Question 47

Lamina IV of the cerebrum receives the majority of what?

Answer 47

inputs from the thalamus (SENSORY)

Question 48

Lamina V of the cerebrum projects mostly to subcortical structures such as?

Answer 48

brainstem, spinal cord, and basal ganglia (MOTOR)

Question 49

Cytodifferentiation of the cerebrum is done from the inside-out. first neurons are produce in the ventricular zone. what are the next two steps?

Answer 49

1. From VZ, a superficial layer is formed called the Preplate 2. Axons from these neurons in VZ form intermediate zone

Question 50

Once the VZ, intermediate and preplate are made, neurons that are to be born migrate into the middle of the preplate and divide into three parts known as ?

Answer 50

marginal zone cortical plate subplate

Question 51

The to be born neurons migrate radially from VZ and intermediate zone using radial glial cells. What is the order of formation of the laminae of the cerebrum?

Answer 51

VI , V then IV , III , II, one is from the marginal zone

Question 52

Lissencephaly or agyria (smooth brain) is due to what?

Answer 52

incomplete or failure of neuronal migration during weeks 12-24

Question 53

What is characterized by microcephaly, ventriculomegaly, large sylvian fissures and agenesis of the corpus callosum?

Answer 53

Lissencephaly/agyria

Question 54

What sign has two major mechanisms of abnormal or lack of brain development or injust or insult to a previously normal brain?

Answer 54

microcephaly (SIGN NOT DX)

Question 55

What are some things that cause microcephaly? 4

Answer 55

genetic prenatal/perinatal brain injury craniosynostosis Postnala brain injury

Question 56

The cerebellum is old so there are only three layers. Cells from the ventricle migration and proliferate to form deep cerebellar nuclei and purkinje cells. What happens at the external germination center of the cerebellum during cytodifferentiation?

Answer 56

migrate over purkinje/deep cerebellar nuclei, then cells from external germ center migrate back in and form the granule cells, making the cerebellum

Question 57

What are the layers of the cerebellar cortex?

Answer 57

``` molecular layer purkinje cell layer granular layer white matter cerebellar nuclei ```

Question 58

While the alar plate gives sensory in the CNS via surface ectoderm, what gives rise to spinal ganglion cells and sensory neurons in the periphery?

Answer 58

Neural Crest cells

Question 59

What is the difference between length of spinal cord between newborn and adult?

Answer 59

Newborn: L2/L3 Adult: L1/L2

Question 60

Neural crest and ectodermal placode form the?

Answer 60

PNS

Question 61

What do these develop from: neurons of dorsal root ganglia, sensory ganglia of cranial nerves, schwann cells, and sympathetic ganglia?

Answer 61

NEURAL CREST | **preganglionic in CNS from Neuroectoderm**

Question 62

Myelination forms during late fetal period and continues through first postnatal year. What myelinates the CNS and PNS?

Answer 62

CNS: oligodendrocytes, starting in lower brain stem at mo 6 PNS: schwann cells, motor roots first at 4mo

Question 63

``` Spina bifida is due to failure of closure of caudal neuropore = no formation of vertebral lamina. What is characteristic of the following: Spina bifida oculta meningocele meningomyelocele myelocele ```

Answer 63

Spina bifida oculta: tuft of hair meningocele: sac with dura mater meningomyelocele: sac with dura mater and spinal cord outside the body myelocele: spinal cord is open to the back

Question 64

Anencephaly (no closure), encephalocele with brain tissue, encephalocele without brain tissue are all caused due to?

Answer 64

failure of the rostral neuropore to fuse/close during day 25