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Introduction. Prof. K. Sivapalan. Function of the Nervous system. Organism responds to changes in the environment for survival. Changes occur in the internal and external environment. Responses can be reflex or planned.
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Introduction Prof. K. Sivapalan
Function of the Nervous system. • Organism responds to changes in the environment for survival. • Changes occur in the internal and external environment. • Responses can be reflex or planned. • Function of the human nervous system is highly sophisticated and it is very difficult to understand. • Experiments on animals cannot give full understanding as in other systems. Introduction to nervous System
Phylogeny of the Nervous system. • In one cell organism all activities have to be carried out by the same cell. • When multicellular animals evolved, some cells evolved as receptor cells and some as effecter cells. • Nerve cells developed at the next stage and this led to symmetrical nerve net. • When the animal became more complex, segmentation occurred. Each segment had a pair of collection of nerve cells- ganglions. Introduction to nervous System
Phylogeny of the Nervous system. • Ganglions functioned as coordinating bodies at the segmental level between receptors and effecters. • When the body structure needed movement of effectors from one segment to another, the structure dragged its nerve supply with it. • When activity in certain segment became more specialized, the ganglion also had to develop more than the others. • This occurred especially in the cephalic end and led to encephalization. • Certain receptors were pooled in strategic places and developed as special sense organs. Introduction to nervous System
Ontogeny of the Nervous System. • Development of the nervous system in human embryo goes through the process of stages in evolution. • Understanding this helps to understand the structure and function of the Nervous system. Introduction to nervous System
Formation of the neural tube. • Embryonic disc. • Formation of neural plate and neural crest in ectoderm. • Neural grove formation by depression. • The edges of the neural plate comes together to form neural tube. Introduction to nervous System
Development of Spinal cord • The neural tube develops into inner Ependymal layer and outer mantle layer. Marginal layer develops as nerve fibers grow. • Dorsal or posterior part is named Alar lamina and anterior or ventral part Basal lamina. • Alar lamina performs sensory function and the Basal lamina motor.functions. • Lateral or intermediate portion performs autonomic function. Introduction to nervous System
Spinal cord. Introduction to nervous System
Encephalization. • Cranial part enlarges – brain: and the rest remains tubular – spinal cord. • Three dilations become visible- Prosencephalon, mesencephalon and Rombencephalon. • Telencephalon and diencephalon from forebrain. • Metancephalon and Myelencephalon from hind brain. Introduction to nervous System
Organization of brain • Telencephalon- cerebral cortex and corpus striatum. • Diencephalon- thalamus, hypothalamus and neurohypophysis. • Mesencephalon- midbrain. • Metancephalon- pons and cerebellum. • Myelencephalon- medulla oblongata. Introduction to nervous System
Flexures. Introduction to nervous System
Development of Ventricles. Introduction to nervous System
Human brain development Introduction to nervous System
