8: Brain Development

Question 1

What does the notochordal process induce formation of?

With what molecule?

Answer 1

Neural plate

Sonic Hedge Hog (SHH)

Question 2

When does primary neurulation occur?

Answer 2

Day 22-23

Beginning of 4^th week

Question 3

What parts of the CNS form during primary neurulation?

Answer 3

Future Brain and lumbar Spinal Cord

Question 4

What neuropore closes on day 25?

Answer 4

Cranial/Rostra Neuropore

Question 5

What neuropore closes on day 27?

Answer 5

Caudal Neuropore

Question 6

What part of the neural tube forms the brain?

Answer 6

Neural tube cranial to 4^th somites

Question 7

What are the three primary brain vesicles?

Answer 7

• Proencephalon: forebrain
• Mesencephalon: midbrain
• Rhombencephalon: hindbrain

Question 8

What primary brain vesicles divide in the 5^th week?

Answer 8

Forebrain (Prosencephalon)

Hindbrain (Rhombencephalon)

Question 9

What does the prosencephalon give rise to?

Answer 9

• Telencephalon: cerebral hemipsheres and lateral venticles
• Diencephalon: thalami structures and 3^rd ventricle

Question 10

What are derivatives from the mesencephalon?

Answer 10

Midbrain and cerebral aqueduct

Question 11

What does the rhombencephalon give rise to?

Answer 11

• Metencephalon: pons, cerebellum, and upper part of 4^th ventricle
• Myelencephalon: medulla and lower part of 4^th ventricle

Question 12

What does the cervical flexure divide?

Answer 12

Hindbrain and spinal cord

Flexes forward

Question 13

What does the pontine flexure divide?

Answer 13

Divides hindbrain into rostral metencephalon and caudal myelecephalon (pons/cerebellum and medulla)

Extending

Question 14

What separates hindbrain from midbrain?

Answer 14

Isthmus Rhombencephali

Question 15

What does the mesencephalic flexure divide?

Answer 15

Midbrain and forebrain

Flexes forward

Question 16

What are some structures formed in the myelencephalon (medulla oblongata)?

Answer 16

• Nuclei Gracilus and Curneatus (sensory nuclei)
• Pyramids (white matter dealing with motor tracts)
• Alar and Basal Plates

Question 17

What gives rise to sensory neurons that remain contained within the CNS?

Answer 17

Alar plate

Question 18

What is the embryological origin of motor neurons that leave the CNS to go out to skeletal muscle?

Answer 18

Basal plate

Question 19

What is the division between the alar and basal plates?

Which plate is medial and lateral?

Answer 19

Sulcus limitans splits alar (lateral) and basal (medial) plates

Question 20

What gives rise to the cerebellum?

Answer 20

Dorsal parts of the alar plates

Eventually projects into 4th ventricle and overlaps pons and medulla

Question 21

What coveres teh ependymal roof of the 4^th ventricle?

Answer 21

Pia Mater

Question 22

What is tela choroidea?

Answer 22

• Very thin part of pia mater that coveres lower part of 4th venticle
• Will invaginate the ventricle to form choroid plexus

Question 23

How do the median and lateral apertures form?

Answer 23

Roof of 4th ventricle evaginates and those ruptures form the aperatures, allowing CSF to enter subarachnoid space

Question 24

What gives rise to the superior and inferior colliculi?

Answer 24

Neuroblasts from alar plate that make tectum

Colliculi deal with vision/hearing, which are sensory

Question 25

What gives rise to the tegmental nuclei? What are some examples of tegmental nuclei?

Answer 25

Neuroblasts from _basal plate_ that make tegmental nuclei * Red Nuclei * Reticular Nuclei * CN III Nuclei * CN IV Nuclei

Question 26

What gives rise to substantia nigra?

Answer 26

Basal or alar plate that migrate ventrally

Question 27

Are diencephalon structures grey or white matter?

Answer 27

Grey Matter

Question 28

What gives rise to the hypothalamus?

Answer 28

Neuroblasts in intermediate zone

Question 29

What gives rise to the pineal gland?

Answer 29

Median diverticulum of the caudal part of the epithalamus

Question 30

What major structure is the caudate nucleus located adjacent to?

Answer 30

Lateral ventricle

Question 31

What embryological layer gives rise to the anterior lobe of the pituitary gland?

Answer 31

Oral Ectoderm * Arises from the stomoedum, leading to Rathke's pouch * Hypophyseal diverticulum * When it fuses with posterior pituitary gland, rathke stalk degenerates

Question 32

What embryological layer gives rise to the posterior lobe of the pituitary gland?

Answer 32

Neuroectoderm * Arises from diencephalon (Neurohypophyseal diverticulum) * Infundibulum forms posterior pituitary and infundibular stalk

Question 33

What is holoprosencephaly?

Answer 33

Incomplete separation of cerebral hemispheres during development that can result in facial anomalies

Question 34

Patient presents with epilepsy, headache, abnormal movements. Upon examination, he has a reduced frontonasal prominence and a cleft lip as well as some developmental delay. What disorder does he most likely have?

Answer 34

Holoprosencephaly

Question 35

What can happen if there is agenesis of corpus callosum?

Answer 35

Seizures and mental deficiency

Question 36

What are the layers of the cerebral cortex?

Answer 36

From top to bottom: * Marginal Zone * Intermediate Zone * Ventricular Zone

Question 37

Where are the older and newer neurons in the cerebral cortex?

Answer 37

* Older Neurons: Deeper (Layer VI) * Newer Neurons: Superificial (Layer I)

Question 38

Failure of neuronal migration during weeks 12-24 can result in what brain disorder?

Answer 38

Lissencephaly (agyria, smooth brain)

Question 39

What is Lissencephaly characterized by?

Answer 39

Microcephaly Ventriculomegaly Minimal operculum of insula Complete/partial agenesis of corpus collosum

Question 40

What can cause microcephaly?

Answer 40

* Autosomal recessive primary microcephaly * Ionizing Radiation * Infectious Agents' * Cytomegalovirus * Rubella * Toxoplasma gondii * Maternal Alcohol Abuse