Term
| What are the basic steps of early embryonic neural development? |
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Definition
1) Ectoderm on dorsal side of embryo thickens to become NEURAL PLATE via the action of the underlying mesoderm (induction)
2) Two sides of neural plate fold up, fusing at the midline and forming the NEURAL TUBE (transiently overlaid by the NEURAL CREST) in between (rostral becomes brain, caudal becomes spinal chord)
3) Neural crest cells migrate ventro-laterally to form sensory and autonomic ganglia, as well as cranio-facial structures in the head, melanocytes and Schwann Cells. |
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Term
| What structures do neural crest cells give rise to? |
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Definition
Overlay neural tube, underneath Ectoderm
1) Sensory and Autonomic ganglia
2) Melanocytes
3) Schwann cells (myelinate PNS) |
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Term
| What is the developmental basis for the basic organization of the spinal chord? |
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Definition
Chord comes from Caudal neural tube!
1) Sulcus limitans separates ventricular proliferative zone of neural tube into the dorsal alar plate (sensory neurons) and ventral basal plate (somatic and visceral).
2) Neurons from alar plate occupy dorsal (sensory) horn and Nuerons from basal plate occupy ventral (somatic) and lateral (visceral) horns.
3) After 3rd fetal month, vertebral column grows faster than spinal chord (reaches L3- creating lumbar cistern for CSF tap), and as lumbar and sacral nerve roots are stretched, they form cauda equina. |
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Term
| What types of neurons form spinal nerves? |
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Definition
1) Sensory (dorsal root ganglia and horns)
2) Motor and Autonomic (ventral and lateral horns and ganglia) axons |
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Term
| What is the developmental basis for the basic, "5-ventricle" organization of the brain? |
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Definition
Under influence of mesoderm, the Rostral neural tube enlarges to become
1) Prosencephalon (telencephalon and diencephalon),
2) Mesencephalon (mid brain)
3) Rhombencephalon (metencephalon and myelencephalon). |
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Term
| What is the developmental trajectory of the Telencephalon? |
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Definition
- Telencephalon becomes lateralized and gives rise to cerebral hemispheres
- Young neurons (previously ventricular zone epithelial cells) migrate to become gray matter structures-cerebral cortex, olfactory bulb, hippocampus and basal ganglia (caudate, putamen and globus pallidus)
- The cavity becomes the lateral ventricles of the central hemisphere.
- Rapid growth of telencephalon gives rise to 4 lobes (as well as insula) and causes sulci and gyri to form. |
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Term
| What is the developmental course of the Diencephalon? |
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Definition
| Diencephalic vesicle gives rise to epithalamus, thalamus (form wall of third ventricle), hypothalamus (with mammary bodies) and subthalamus |
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Term
| What is the developmental course of the Mesencephalon? |
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Definition
Mesencephalon gives rise to superior and inferior colliculi (dorsally) and oculomotor and trochlear nerve nuclei (ventrally).
- Embryonic thickening gives rise to cerebral aqueduct, which separates superior and inferior colliculi (alar plate) from oculomotor and trochlear nerve nuclei (basal plate).
- CN III and IV innervate superior colliculi. |
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Term
| What is the developmental course of the Hindbrain ventricles? |
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Definition
1) Metencephalon gives rise to pons (bridge) and cerebellum, which is important for coordinated movement
2) Myelencephalon is rostral continuation of spinal chord and develops into medulla
3) Cavity of metencephalon and myelencephalon become 4th ventricle, which expands and pushes rostral medulla, opening it like a book, and causing the alar plate to sit dorsolateral to the basal plate. |
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Term
What happens when fusion of the rostral neural folds fails?
What about caudal fusion? |
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Definition
1) Rostral is brain so you get Anencephaly and death.
2) Caudal is chord so you get Spina Bifida, and oftentimes increased ICP from Arnold-Chiari Malformation. |
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Term
| What is "Megacolon" and how does it arise? |
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Definition
Huge, engorged colon with lack of defecation.
Lack of innervation of colon because of poor migration of neural crest cells |
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Term
Match the following brain region with its appropriate ventricle.
1) Telencephalon
2) Diencephalon
3) Mesencephalon
4) Metencephalon and Myelencephalon |
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Definition
1) Lateral ventricles (CSF produced here)
2) Walls of 3rd ventricle (CSF produced here)
3) Cerebral Aqueduct (CSF produced here)
4) 4th ventricle (CSF produced here) |
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Term
| What is Mesencephaly and how does it arise? |
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Definition
1) "Smooth brain" because abnormal Telencephalon development
2) Failure of neurons to migrate from ventricle to Pia |
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