NEET Biology Notes Structural Organisation in Animals Nervous Tissue
Nerve cells originate from embryonic ectoderm. Nervous system consists of two kinds of cells namely neurons and neuroglia. Neurons form the structural and functional unit of the nervous system. Neuroglia is non-excitable, supporting component of nervous tissue.
These are of following types :
- Neuroglial cell — In CNS
- Ependymal cells — In internal cavities of brain and spinal cord
- Capsular cells — Surrounding autonomic ganglion
- Schwann cells — Forming sheath
- Supporting cells — Sheathing nerve terminals
The glial cells are protective and supporting in function.
Organ and Organ Systems
Tissues organise to form organs, which in turn associate to form organ systems in the multicellular organisms. Such an organisation is essential for more efficient and better coordinated activities of millions of cells constituting an organism.