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Grey matter (which is only grey in preserved tissue, and is better described as pink or light brown in living tissue) contains a high proportion of cell bodies of neurons.

White matter is composed mainly of myelinated axons, and takes its color from the myelin.

The sympathetic nervous system is activated in cases of emergencies to mobilize energy, while the parasympathetic nervous system is activated when organisms are in a relaxed state.The enteric nervous system functions to control the gastrointestinal system.The sensory information from these organs is processed by the brain.In insects, many neurons have cell bodies that are positioned at the edge of the brain and are electrically passive—the cell bodies serve only to provide metabolic support and do not participate in signalling.It was in the decade of 1960 that we became aware of how basic neuronal networks code stimuli and thus basic concepts are possible (David H. The molecular revolution swept across US universities in the decade of 1980.

It was in the decade of 1990 that molecular mechanisms of behavioral phenomena became widely known (Eric Richard Kandel)." A microscopic examination shows that nerves consist primarily of axons, along with different membranes that wrap around them and segregate them into fascicles.

A protoplasmic fiber runs from the cell body and branches profusely, with some parts transmitting signals and other parts receiving signals.

Thus, most parts of the insect brain have passive cell bodies arranged around the periphery, while the neural signal processing takes place in a tangle of protoplasmic fibers called neuropil, in the interior.

Typically, each body segment has one ganglion on each side, though some ganglia are fused to form the brain and other large ganglia.

The head segment contains the brain, also known as the supraesophageal ganglion.

The nervous system derives its name from nerves, which are cylindrical bundles of fibers (the axons of neurons), that emanate from the brain and spinal cord, and branch repeatedly to innervate every part of the body.