Question

In development, nervous system (brain, spinal cord, nerve cells) is
A. Ectodermal
B. Endodermal
C. Ecto Mesoderm
D. Endomesoderm

Answer 1

Hint: Structurally, the nervous system is divided into central nervous system and peripheral nervous system. Central nervous system includes the brain and the spinal cord and peripheral nervous system cranial and spinal nerves, ganglia, plexuses, and sensory receptors. Nervous system is derived from one of the three germ layers.

Complete answer:
The early stages of embryonic development begin with fertilization. The fertilization is a controlled process which ensures that only one sperm fuses with one egg to form zygote. The zygote undergoes a series of mitotic divisions to form the blastula. The blastula is a hollow ball of cells which undergoes a process called gastrulation. During gastrulation the three germ layers are formed. This is the beginning of an early embryonic development. The three germ layers are endoderm (the innermost layer), mesoderm (the middle layer and the ectoderm (outermost layer).
The nervous system begins to form in the third week of development and it continues after birth. The nervous system (brain, spinal cord, nerves) is derived from the ectoderm, which is the outermost layer embryonic germ layer. Along with the nervous system, ectoderm forms the epidermal skin cells, ears, nails and hair.
The mesoderm gives rise to the muscle cells, heart, kidneys, gonads, genital ducts, cartilage, blood cells and connective tissue in the body.
The endoderm gives rise to the digestive organs such as colon, stomach, intestines, liver, lungs, pancreas and other internal organs.

Thus, option A. ectoderm is the correct answer.

Note: The inner cell mass of the blastocyst differentiates into three germ layers, an outer ectoderm, middle mesoderm and inner endoderm. Formation of organs (organogenesis) takes place from the germ layers. Each germ layer gives rise to specific tissue types.