Tag: nervous system of man

The central nervous system (CNS) controls most functions of the body and mind. It consists of two parts: 

Neural crest cells of ectoderm migrate downward to form the dorsal root ganglia of the spinal nerves and the postganglionic sympathetic neurons. The sensory cells in the dorsal root ganglia give rise to dendrites extending to sense organs and axons extending into the spinal cord. Some other neural crest cells form parts of certain sense organs and parts of the head. Few head derivatives of the neural crest give rise to sensory nerves and other parts of the peripheral nervous system and ganglia of the autonomic nervous system. Thus, the correct answer is option C.

• The meninges are three layers of protective tissue called the dura mater, arachnoid mater, and pia mater that surround the neuraxis. 
• The meninges of the brain and spinal cord are continuous, being linked through the magnum foramen. 
• In order from the outermost to innermost layer, the meninges are dura mater, arachnoid mater, subarachnoid space, and pia mater. Hence, The innermost layer of meninges is Pia mater.

•  The central nervous system CNS is responsible for integrating sensory information and responding accordingly. 
• The major divisions of the brain are the forebrain (telencephalon), midbrain (mesencephalon), and hindbrain (rhombencephalon).
•  It consists of two main components: The spinal cord serves as a conduit for signals between the brain and the rest of the body. It also controls simple musculoskeletal reflexes without input from the brain. Hence, Rhombencephalon, Mesencephalon and Telencephalon are the components of central nervous system. 

Lymph is the fluid having the same composition as tissue fluid and is carried in lymph vessels. Osteocytes, the bone cells are the longest-lived cells. Chromatophores with black pigment present in certain parts of brain and retina are one of the largest cells at maturity; however, not it does not hold true for all chromatophores. Neurons are the largest cells that can be several feet long. Each neuron consists of the dendrite, axon and soma. Thus, the correct answer is option C.

Metamorphosis is the process by which an organism changes its form or habits during normal development after embryonic stage.
Gastrulation is the process, where there are cell movements, which result in the reorganization of the embryo from blastula to gastrula.
Neurulation is the process of folding in the embryos of vertebrates, where there is the transformation of neural plate into the neural tube. This process induces the formation of the central nervous system.
Invagination is the infolding of one part within another part and it involves the morphogenetic processes by which an embryo takes form and is the initial step of gastrulation.
Thus, the correct answer is the option (C), 'Neurulation'.