Lecture 10: Dev't of CNS and PNS

• What develops from the ectoderm to form the central nervous system (CNS)?

  The CNS develops from the ectoderm specified into surface ectoderm and neuroectoderm.
• What is the role of the peripheral nervous system (PNS)?

  The PNS serves as the communication system between the CNS and the rest of the body.

  
• What signaling molecule is mentioned as important in the development of the CNS and PNS?

  Sonic hedgehog is a signaling molecule mentioned.
• What does Sonic hedgehog signal the notochord to do?

  Sonic hedgehog signals the notochord to induce ectodermal cells to differentiate into neuroectoderm.
• What are signaling molecules that act between cells within a close range called?

  They are referred to as paracrine factors or morphogens.
• What is the role of signaling molecules in embryonic development?

  They are involved in induction and embryonic cell patterning.
• What do cells from the primitive node eventually form?

  They will eventually form the notochord.

  
• What happens to the neural plate during development?

  • The neural plate is induced by the notochord.
  • It folds and forms the neural tube.

  
• What are neural crest cells needed for?


  Neural crest cells are needed for PNS formation.
• What does BMP4 do during the development of the ectoderm?

  BMP4 prevents the dorsal ectoderm from forming neural tissue.

  
• What molecules do the developing notochord secrete during neurulation?

  The developing notochord secretes noggin and chordin.

  
• What is the function of noggin and chordin during neurulation?

  They block the inhibitory influence of BMP4, allowing neural tissue formation.
• What is the composition of the neural plate and neural tube before neurogenesis?

  They are composed of a single layer of neuroepithelial cells (neuroepithelium).

  
• What happens to the neuroepithelium shortly after induction?

  It organizes into a pseudostratified epithelium.
• What does the term pseudostratified mean?


  Pseudostratified refers to closely packed cells that appear layered but are actually one layer.
• What occurs to the nuclei within the neuroepithelial cells as the cell cycle progresses?

  The nuclei shift extensively within the cytoplasm and migrate towards the lumen of the neural tube.
• How does the orientation of the mitotic spindle affect daughter cells during division?

  The orientation determines the fate of the daughter cells.
• What happens if the cleavage plane is perpendicular to the apical surface of the neural tube?

  The two daughter cells migrate towards the periphery of the neural tube.
• What is the fate of the daughter cell closer to the inner surface of the neural tube?

  It remains a proliferative progenitor cell capable of mitosis.
• What happens to the daughter cell closer to the basal surface of the neural tube?

  It inherits a high concentration of the Notch receptor and becomes a neuroblast.
• What are neuroblasts the precursor cells of?

  Neuroblasts are the precursor cells of neurons.
• What happens to neuroblasts during further differentiation?

  Several small cytoplasmic processes extend from their cell body, forming the primitive axon and dendrites.
• What type of neurons do multipolar neuroblasts eventually become?

  They become mature multipolar neurons.
• What are glioblasts formed from?

  Glioblasts are formed by neuroepithelial cells after the production of neuroblasts ceases.
• What can glioblasts differentiate into?

  They can become O2-A progenitor cells, leading to oligodendrocytes or astrocytes.

  
• What is the function of oligodendrocytes?

  Oligodendrocytes form the myelin sheath.
• What do radial glial cells do?

  They act as guide wires in the brain for the migration of young neurons.

  
• What types of cells can radial glial cells differentiate into?

  They can differentiate into astrocytes, ependymal cells, and neurons.

  
• What are microglial cells and their function?

  Microglial cells act as motile macrophages after damage to the CNS.
• What happens to the neuroepithelium as cellular differentiation begins in the neural tube?

  • The neuroepithelium thickens and appears layered.
  • Cells differentiate to become the ependyma of the central canal and the ventricular system of the brain.

  
• What are the layers formed during spinal cord development?

  1. Ventricular zone
  2. Intermediate layer (becomes grey matter)
  3. Marginal layer (becomes white matter)
• What are the basal and alar plates in spinal cord development?

  The ventral thickenings are called basal plates, and the dorsal thickenings are called alar plates.

  
• What connects the left and right alar plates?

  The roof plate connects the left and right alar plates.
• What is the function of the roof and floor plates?

  They primarily connect one side of the neural tube to the other and do not contain neuroblasts.
• What do neural crest cells give rise to?

  They give rise to sensory or spinal ganglia, Schwann cells, melanocytes, odontoblasts, and mesenchyme of the pharyngeal arches.
• What happens to the spinal cord as the vertebral column and dura grow?

  The spinal cord terminates in the vertebral column due to the faster growth of the vertebral column and dura.
• What is the phenomenon called when the spinal cord terminates at the level of L2 to L3 in adult animals?

  This phenomenon is called ascensus medullae spinalis.
• What develops from the anterior two-thirds of the neural tube?

  The anterior two-thirds develop into the brain.
• What results from the fusion of the neural folds in the anterior region?

  It results in the formation of the three primary brain vesicles.

  
• What is the first brain vesicle formed from the neural tube?

  The first brain vesicle is the prosencephalon or forebrain.