Development of the Nervous System

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Questions and Answers

During the development of the spinal cord, what is the key factor that leads to the formation of the ventral motor horn cells?

  • The presence of the floor plate, which provides pathways for nerve fibers crossing from one side to the other.
  • Formation of the sulcus limitans, which separates the basal and alar plates.
  • Continuous addition of neuroblasts to the mantle layer, resulting in ventral thickening known as the basal plates. (correct)
  • Migration of neuroblasts into the mantle layer and subsequent differentiation into bipolar neuroblasts.

What is the primary role of the sulcus limitans in the development of the spinal cord?

  • It plays a critical role in the migration of neuroblasts from the neuroepithelial layer to the mantle layer.
  • It marks the boundary between the basal and alar plates, indicating the future locations of motor and sensory areas. (correct)
  • It serves as a pathway for nerve fibers to cross from one side of the cord to the other.
  • It defines the boundary between the ventral motor horn and dorsal sensory horn.

Which of the following statements accurately describes the relationship between the mantle layer and the white matter of the spinal cord?

  • The mantle layer forms the gray matter, and the white matter develops from the marginal layer surrounding it. (correct)
  • The mantle layer and white matter are separate structures with no direct developmental relationship.
  • The mantle layer forms the white matter, while the gray matter develops from the neuroepithelial layer.
  • The mantle layer differentiates directly into the white matter, forming the myelinated axons of nerve fibers.

Which of the following statements is TRUE about the relationship between the notochord and the neural plate?

<p>The notochord induces the neural plate to form by stimulating overlying surface ectoderm to convert into neuroectoderm. (A)</p> Signup and view all the answers

Which of the following correctly identifies a key characteristic of the floor plate and roof plate in the spinal cord?

<p>They are devoid of neuroblasts and act as pathways for nerve fibers to cross from one side of the cord to the other. (A)</p> Signup and view all the answers

How does the differentiation of neuroblasts within the mantle layer contribute to the formation of the spinal cord's structure?

<p>Neuroblasts differentiate into different types of neurons, including those found in the intermediate horn, forming parts of the autonomic nervous system. (D)</p> Signup and view all the answers

What is the correct sequence of events during neurulation?

<p>Neural plate formation -&gt; neural groove formation -&gt; neural fold fusion -&gt; neural tube closure. (D)</p> Signup and view all the answers

Which of the following is NOT a correct statement about the neural tube?

<p>The neural tube develops into the peripheral nervous system, including the nerves and ganglia. (B)</p> Signup and view all the answers

Which of the following INCORRECTLY matches a neural tube defect with its description?

<p>Exencephaly: Brain exposed outside the skull. (B)</p> Signup and view all the answers

Which of the following is a derivative of the neural crest?

<p>Melanocytes (pigment cells) (C)</p> Signup and view all the answers

What is the primary function of the notochord during embryonic development?

<p>To provide support for the developing embryo. (D)</p> Signup and view all the answers

Which of the following statements regarding the early development of the brain vesicles is TRUE?

<p>The forebrain vesicle develops into the cerebrum and diencephalon. (B)</p> Signup and view all the answers

What is the primary structure formed from the caudal part of the neural tube?

<p>Spinal cord (C)</p> Signup and view all the answers

On which day does the anterior neuropore close during neurulation?

<p>Day 24 (B)</p> Signup and view all the answers

Which neural tube defect is characterized by the closure failure of the anterior neuropore?

<p>Exencephaly (A)</p> Signup and view all the answers

What condition is a precursor to anencephaly?

<p>Exencephaly (C)</p> Signup and view all the answers

Where do neural crest cells reside?

<p>Along the neural plate border (A)</p> Signup and view all the answers

What is commonly associated with spina bifida?

<p>Incomplete closing of vertebrae (A)</p> Signup and view all the answers

Which part of the neural tube is responsible for forming the brain?

<p>Anterior part (D)</p> Signup and view all the answers

When does neurulation start according to developmental timelines?

<p>Day 17 (A)</p> Signup and view all the answers

What does microcephaly refer to?

<p>Presence of a small brain in a small cranium (B)</p> Signup and view all the answers

What do neural crest cells give rise to?

<p>Bones of the face and skull (D)</p> Signup and view all the answers

Which brain vesicle develops into structures such as the cerebral cortex and basal ganglia?

<p>Telencephalon (A)</p> Signup and view all the answers

What structures are derived from the neural tube?

<p>CNS components including brain and spinal cord (C)</p> Signup and view all the answers

Which of the following structures are classified as part of the ectoderm?

<p>Epidermis and hair (D)</p> Signup and view all the answers

What is the primary function of Schwann cells?

<p>Produce myelin sheath in the PNS (D)</p> Signup and view all the answers

What is the role of the optic vesicles in early development?

<p>Form the optic cups which develop into the retina (B)</p> Signup and view all the answers

Which cranial nerve is primarily associated with the optic vesicle?

<p>Optic nerve (CN II) (D)</p> Signup and view all the answers

Which secondary brain vesicle gives rise to the medulla oblongata?

<p>Myelencephalon (C)</p> Signup and view all the answers

What do dorsal root ganglia primarily contain?

<p>Sensory nerve cell bodies (C)</p> Signup and view all the answers

Which structure does NOT originate from the neural crest?

<p>Epidermis of the skin (A)</p> Signup and view all the answers

Which of the following statements accurately describes the development of the mantle layer in the spinal cord?

<p>The mantle layer develops from the neuroepithelial layer and contains both neuroblasts and glial cells. (D)</p> Signup and view all the answers

What is the primary function of the neuroepithelial layer in spinal cord development?

<p>To generate the neuroblasts and glial cells that make up the mantle layer. (D)</p> Signup and view all the answers

Which of the following accurately reflects the relationship between the marginal layer and the white matter of the spinal cord?

<p>The marginal layer develops into the white matter, containing primarily myelinated nerve fibers. (B)</p> Signup and view all the answers

Which of the following best describes the neuroepithelial cells during the early stages of spinal cord development?

<p>Neuroepithelial cells proliferate rapidly, giving rise to both neuroblasts and glial cells. (B)</p> Signup and view all the answers

Based on the provided information, what is the primary function of the neuroblasts during spinal cord development?

<p>To differentiate into neurons and contribute to the grey matter. (B)</p> Signup and view all the answers

What is the primary difference between the mantle layer and the marginal layer in the developing spinal cord?

<p>The mantle layer forms the grey matter, while the marginal layer forms the white matter. (C)</p> Signup and view all the answers

Which of these accurately describes the development of the optic nerve (CN II)?

<p>It develops as a direct outgrowth of the neuroepithelium of the forebrain. (C)</p> Signup and view all the answers

Which of the following statements is TRUE about the neuroepithelial cells?

<p>Neuroepithelial cells are present in the developing brain and spinal cord. (A)</p> Signup and view all the answers

After the closure of the neural tube, what happens to the neuroepithelial cells?

<p>Neuroepithelial cells begin to divide rapidly and give rise to neuroblasts. (B)</p> Signup and view all the answers

What is the fate of the neuroblasts formed from the neuroepithelium?

<p>Neuroblasts migrate to the mantle layer and differentiate into neurons (D)</p> Signup and view all the answers

Flashcards

Marginal layer

The outer region of the developing spinal cord that eventually forms the white matter.

Mantle layer

The middle layer of the developing spinal cord that gives rise to the gray matter.

Neuroepithelial layer

The inner layer of the developing spinal cord, composed of neuroepithelial cells that divide to form neuroblasts.

Basal plate

A thickening in the ventral region of the mantle layer that develops into the motor horns of the spinal cord.

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Alar plate

A thickening in the dorsal region of the mantle layer that develops into the sensory horns of the spinal cord.

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Neurulation

The process of the neural tube formation.

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Neural Canal

A hollow space within the neural tube, eventually developing into the brain's ventricles and the spinal cord's central canal.

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Anencephaly

A defect in the neural tube's closure at the cranial end, often resulting in a missing or incomplete brain.

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Spinal Bifida

A defect in the neural tube's closure at the caudal end, resulting in a gap in the vertebrae, often affecting the spinal cord.

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Ectoderm

The outermost layer of the embryo, which gives rise to the nervous system, skin, and other structures.

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Notochord

A long rod-like structure that forms along the back of the embryo, guiding the formation of the neural tube.

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Neural Crest

A group of cells that arise from the neural tube and migrate outwards, giving rise to various cell types, including neurons, glial cells, and pigment cells.

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Anterior Neuropore

The front opening of the neural tube, which needs to close by day 24.

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Posterior Neuropore

The back opening of the neural tube, fully closing by day 26.

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Cephalic part of the neural tube

The part of the neural tube developing into the brain.

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Caudal part of the neural tube

The part of the neural tube developing into the spinal cord.

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Microcephaly

A birth defect characterized by a small brain within a small skull.

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Neural Crest Cells

A group of cells that develop from the ectoderm during embryonic development, giving rise to various structures in the body.

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Neural Tube

The central canal of the developing embryo, which will eventually develop into the central nervous system (brain and spinal cord).

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Neuroectoderm

The part of the ectoderm that develops into the brain and spinal cord.

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Surface Ectoderm

The part of the ectoderm that forms the skin and other structures like hair and nails.

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Primary Brain Vesicles

The three primary divisions of the developing brain: prosencephalon (forebrain), mesencephalon (midbrain), and rhombencephalon (hindbrain).

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Secondary Brain Vesicles

The five secondary brain vesicles that develop from the three primary vesicles.

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Cranial Nerves

The twelve pairs of nerves that connect the brain to different parts of the body.

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Optic Cup

A specialized structure that develops from the forebrain during embryonic development, forming the retina of the eye.

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Neuroblasts

Undifferentiated cells that form the basis of the nervous system.

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Closure of the neural tube

Process where the neural tube closes, marking the beginning of spinal cord development.

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Formation of the mantle zone

The process of a rapidly dividing neuroepithelial layer forming a structure called the mantle zone.

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Neural Groove Stage

The stage of development where neuroepithelial cells rapidly divide.

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Neuroepithelial cell division

Special type of cell division occurring in the neuroepithelial layer during early development of the spinal cord.

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Grey matter development

The grey matter of the spinal cord develops from the mantle layer.

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White matter development

The white matter of the spinal cord develops from the marginal layer, formed by nerve fibers emanating from the mantle layer.

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Study Notes

Development of the Nervous System

  • The nervous system develops from the ectoderm, one of the three germ layers that form during embryonic development.

  • Neurulation is the process by which the neural tube forms. This process begins at day 17 after fertilization.

  • Overlying ectoderm is induced by the notochord to form the neural plate.

  • The neural plate then folds to form the neural groove.

  • The neural folds fuse to form the neural tube.

  • The neural canal is a cavity inside the neural tube, which will later develop into the ventricles, a series of cavities in the brain.

  • The neural tube is separated from the surface ectoderm.

  • The closure of the neural tube disconnects the neural crest from the surface ectoderm.

  • The neural crest cells migrate to numerous locations and give rise to many different structures, including the peripheral nervous system.

  • The cephalic part of the neural tube develops into the brain, and the caudal part develops into the spinal cord.

  • The neural canal develops into the ventricular system and the central canal.

  • Neural tube defects, including anencephaly, exencephaly, and microcephaly, can result from incomplete closure of the neural tube.

  • Spina bifida is a neural tube defect that results from incomplete closing of the vertebrae.

  • The three primary brain vesicles are the prosencephalon (forebrain), mesencephalon (midbrain), and rhombencephalon (hindbrain).

  • The five secondary brain vesicles are the telencephalon, diencephalon, mesencephalon, metencephalon, and myelencephalon.

  • The brainstem is a direct continuation of the spinal cord and has a similar organization but shows accentuation of the alar plate and regression of the basal plate in higher centers.

  • 12 pairs of cranial nerves arise from the brainstem.

  • The optic nerve (CN II) is an extension of the forebrain.

  • During the neural groove stage and immediately after closure of the neural tube, neuroepithelial cells divide rapidly, forming neuroepithelial layers.

  • The mantle layer forms the grey matter of the spinal cord and contains neuroblasts.

  • The marginal layer develops into the white matter of the spinal cord.

  • The neural tube is divided into three main layers: neuroepithelial layer, mantle layer, and marginal layer.

  • Neuroblasts arise from the division of neuroepithelial cells.

  • Neuroblasts migrate into the mantle layer.

  • Multipolar neuroblasts develop from bipolar ones which develop from apolar ones.

  • Axons of neurones in the basal plate break through the marginal layer and become visible on the ventral aspect of the spinal cord.

  • Axons of neurones in the alar plate penetrate into the marginal layer – ascend to either higher or lower levels to form association neurones (interneurons).

  • Glial cells, also known as glial blasts, are formed from neuroepithelial cells after the neuroblasts cease to form.

  • Glial cells include protoplasmic astrocytes, fibrillar astrocytes, oligodendrocytes, and microglia.

  • Different types of glial cells migrate to different locations, and perform different metabolic functions in the spinal cord and brain.

  • Ependymal cells line the central canal of the spinal cord and ventricles.

  • Glial cells develop into Schwann cells which are responsible for myelination in the peripheral nervous system.

  • Oligodendrocytes are responsible for myelination in the central nervous system.

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