Question

Chronology of events occurring during nervous system development are
(A). Neural plate formation
(B). Change of ectodermal cells of embryonic disc to pseudostratified columnar neuroepithelial cells
(C). Neural tube formation
(D). Neural fold formation
Choose the correct answer from the options given below:

• A. (A), (B), (C), (D).
• B. (A), (D), (C), (B).
• C. (B), (A), (D), (C).
• D. (B), (A), (C), (D).

Hint:

To remember the sequence of neurulation:
Cells must change shape first (B), which forms the flat plate (A).
The plate then folds upward (D), and those folds fuse into the tube (C).

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Neurulation is the early developmental process in vertebrate embryos where the neural tube is formed, laying the foundation for the central nervous system (brain and spinal cord).
This process is driven by inductive signals from the underlying notochord.

Step 2: Detailed Explanation:
Let us trace the sequential steps of neurulation:
1. Cellular elongation (B): In response to chemical signals from the notochord, the simple ectodermal cells along the midline of the embryonic disc elongate to become pseudostratified columnar neuroepithelial cells.
2. Neural plate formation (A): This localized thickening of the ectoderm forms the neural plate.
3. Neural fold formation (D): The lateral edges of the neural plate elevate to form neural folds, creating a central neural groove.
4. Neural tube formation (C): The neural folds migrate toward the midline and fuse together, closing the neural groove to form the hollow neural tube, which is covered by overlying ectoderm.
This chronological sequence corresponds to the order: (B) \(\rightarrow\) (A) \(\rightarrow\) (D) \(\rightarrow\) (C).

Step 3: Final Answer:
The correct chronological sequence of events is (B), (A), (D), (C). This corresponds to option (C).