Changes

Sensory neurones also enter the CNS through the dorsal root, with their nuclei in DRG. In contrast to the somatic nervous system, the motor component is in two parts; a preganglionic and postganglionic neurone. The preganglionic neurone has its cell body in the CNS. It exits via the ventral root and synapses with the postganglionic neurone. Cell bodies of the postganglionic neurone lie outside the CNS in ganglia. Ganglia of the ''sympathetic'' nervous system are near the '''spinal cord'''. Ganglia of the ''parasympathetic'' nervous system are near the '''target organ'''.  

Sensory neurones also enter the CNS through the dorsal root, with their nuclei in DRG. In contrast to the somatic nervous system, the motor component is in two parts; a preganglionic and postganglionic neurone. The preganglionic neurone has its cell body in the CNS. It exits via the ventral root and synapses with the postganglionic neurone. Cell bodies of the postganglionic neurone lie outside the CNS in ganglia. Ganglia of the ''sympathetic'' nervous system are near the '''spinal cord'''. Ganglia of the ''parasympathetic'' nervous system are near the '''target organ'''.  

== Neural Crest ==

== Neural Crest ==

[[Image:Neual crest.png|thumb|right|250px|Mithril 2010  Cross section scheme of vertebrate embryo. 1 – neural crest, 2 – neural tube, 3 – dorsal somite, 4 – notochord. Both paths of the neural crest cells migation marked by arrows: red one is the dorsolateral path, blue one signs the ventromedial path.]]  

[[Image:Neual crest.png|thumb|right|250px|Mithril 2010  Cross section scheme of vertebrate embryo. 1 – neural crest, 2 – neural tube, 3 – dorsal somite, 4 – notochord. Both paths of the neural crest cells migation marked by arrows: red one is the dorsolateral path, blue one signs the ventromedial path.]]  

The neuroectoderm is the region at the junction of epidermis and neural plate. When the neural tube closes, the epidermis is brought into contact with the crest neuroectoderm. This contact causes cells of the crest neuroectoderm to undergo an epithelial to mesenchymal transition. Cells that undergo this transition break away from the neuroectoderm and are called '''neural crest cells'''. The peripheral nervous system (PNS) develops from the neural crest. The undifferentiated neural crest cells migrate away from the neural tube along "pathways". These pathways are governed by repulsive cues from the cells, as well as proliferation and survival signals. They differentiate once they reach their destination. Other non - neural tissues also develop from the neural crest. The type of tissue that neural crest forms is dependant on the origination of the cell along the anterior - posterior axis:  

The crest neuroectoderm is the region at the junction of epidermis and neural plate. When the neural tube closes, the epidermis is brought into contact with the crest neuroectoderm. This contact causes cells of the crest neuroectoderm to undergo an epithelial to mesenchymal transition. Cells that undergo this transition break away from the neuroectoderm and are called '''neural crest cells'''. The peripheral nervous system (PNS) develops from the neural crest. The undifferentiated neural crest cells migrate away from the neural tube along "pathways". These pathways are governed by repulsive cues from the cells, as well as proliferation and survival signals. They differentiate once they reach their destination. Other non - neural tissues also develop from the neural crest. The type of tissue that neural crest forms is dependant on the origination of the cell along the anterior - posterior axis:  

'''Anterior Neural Crest''' forms:  

'''Anterior Neural Crest''' forms: