Development of the Nervous System

Transcript

0:00 – 0:30  [Basic Definition]  The development of the nervous system includes the processes through which the embryonic ectoderm produces the neural tube and neural crest which are structures that contain the stem cells that differentiate to produce all neurons in the nervous system.  The neural tube expands into the prosencephalon which develops into the forebrain, the mesencephalon which develops into the midbrain, and the rhombencephalon which develops into the hindbrain – remaining parts of the neural tube give rise to the spinal cord. The neural crest gives rise to all neurons with cell bodies in the peripheral nervous system.

0:30-2:30  

We step forward a little bit and the edges of the neural plate start to sort of fold up, and the center sort of drops down, forming this groove called the neural groove.

And some other structures begin to appear. There are these specialized cells at the bottom along the ventromedial part of the neural groove that are called the floor plate.

Like the notochord, the floor plate is transiently important during development. They both will release cues that are going to be important for differentiation of cells within the developing neural tube.

And at the extremes of the neural groove, we have the beginning of the neural crest, another specialized population of cells. These cells are not actually going to stay in the neural tube.They’re going to eventually migrate away and turn into a number of peripheral structures, In the peripheral nervous system.

They’re going to turn into a sensory ganglia.They’re going to turn into visceral ganglia that that innervate our viscera, our organs. There are a portion of secretory cells in the adrenal medulla that come from neural crest cells, and cells in what’s called the enteric nervous system, which controls our GI tract. So a number of peripheral structures will emerge from the neural crest..

The notochord and the floor plate are important because of their release of diffusible ligands that induce cell fate in other cells in the developing nervous system.

There are other structures, other midline structures, more rostral, that are important for the formation of the forebrain. But notochord and the floor plate are important in the spinal cord and in the hindbrain. But really the idea is the same. You have these specialized structures along the midline that induce the fates of cells within the nervous system.

2:30-3:00  [Parallel Vocabulary] In introductory classes you learned about the development of the nervous system.  But Neuroscience is an interdisciplinary field, so there are many words for this term – For example, it may be shortened to neurodevelopment.  Moreover, there are technical terms for distinct steps in the process.  For example, neurulation is the process of forming the neural tube.  Neurogenesis is the process of creating new neurons.  And neurodifferentiation is the process through which stem cells give rise to more specialized nerve cells.  So….“neurulation”, “neurogenesis”, and “neurodifferentiation” may all refer to steps in the overall process of neurodevelopment.

3:00-4:00  [Here’s a real world example]  When development proceeds typically, the neural tube and neural crest give rise to all neurons in both the central and peripheral nervous system.  However, when development proceeds atypically, and the process of neurulation is disrupted, this can produce birth defects that range from mild to severe.  One of the most common neural tube defects is spina bifida, which occurs when a caudal region of the neural tube does not fully close. While spina bifida can affect any caudal part of the neural tube, it often manifests in regions of the lower back.  One major complication of spina bifida is incomplete closure or the spinal canal, which is the hollow space within the vertebrae that houses the spinal cord. Mild cases may cause no symptoms at all, while severe cases are associated with a large opening in the spinal canal through which the spinal cord and spinal nerves can protrude.  While not all causes are known, vitamin B reduces the risk.  Treatments include surgery to reposition the spinal cord and surgery to redirect the flow of cerebrospinal fluid.

4:00-6:00 [Follow along with this example]

6:00-6:30 [Here are a few readings to help you review]
1) Basic Clinical Neuroscience (Young)

• Chapter 24: “Development of the Nervous System: Congenital Anomalies”

2) Neuroscience (Purves)

• Chapter 22: “Early Brain Development”

Media attributions

Neural tube by OpenStax is licensed under an Attribution 4.0 International license (CC BY 4.0).