nervous system pictures building

Building 
 
Schedule a nerve cell . Basic building block of the nervous system is the nerve tissue. It consists of interconnected nerve cells (neurons), whose cell body as Somata or Perikarya and their survival rates than nerve fibers (axons and dendrites) respectively. 

At higher organisms, the nerve tissue from a network of neurons and glial cells many places to dock. The latter support the activity of nerve cells, without directly to the transmission of stimuli to be involved.

nervous

Nervous 
 
Overview of the human nervous system 

The term nervous system (Systema nervosum lat) is the totality of nerve cells in an organism and describes how they arranged and connected. It is an organ system of higher animals, which has the task to provide information on the environment and the organism record, process and reactions of the organism action to optimal to react to changes. The nervous realized one of the basic properties of life, the irritability (irritability).

Anatomy of Vertebrate Nervous Systhem

•Nervous system of animals examined in two region
•Peripheral nervous system; sensory neurons, afferent and efferent nerves and ganglia
•Central Nervous system; Spinal cord and brain


•Somatic afferents and efferents innervate somatic organs that are voluntarily controlled.
•Autonomic afferents and efferents innervate autonomic organs such as heart and digestive channal.
•Cranial nerves innervate usually the muscle and gland of head. They originate from brain stem


•Sensory or receptor cells are stimulated by physical stimuli and localized in various sensory region of the body.
•Environmental information is only recieved by receptor cell or sometimes free afferent nerve endings

RESPONSE OF NERVE TISSUE TO INJURY

ØA. Damage to the Cell Body: Because mature neurons cannot divide, dead neurons cannot be replaced. Neurons not connected with otherfunctioning neurons or end organs are useless, and mechanisms have evolved to dispose of them. Thus, if a neuron makes synaptic contact with Only one other neuron and the latter is destroyed, the former undergoes autolysis, a process termed transneuronal degeneration. Most neurons, however, have multiple connections.
ØB. Damage to the Axon: Regeneration can occur in axons injured or severed Far enough from the soma to spare the cell. Such injuries are followed by partial degeneration and then regeneration. Nervous system
Ø1. Degeneration. A crushed or severed axon degenerates both distal and proximal to the injury. Distal to the site Of injury, both the axon and myelin sheath undergo complete degeneration connection with the soma has been lost. During this Wallerian, descendent, or secondary degeneration, whichusually lakes about 2-3 days, nearby Schwann cells proliferate, phagocytose degenerated tissue, and invade the remaining endoneurial channel. Proximal to the site of injury, degeneration of the axon and myelin sheath is similar but incomplete. This retrograde, ascendent, orprimary degeneration proceeds for about 2 internodes before the injured axon is sealed. The cell body also changes in response to injury. The perikaryon enlarges; chromatolysis, or dispersion of Nissl substance, occurs; and the nucleus moves to an eccentric position. Proximal degeneration and cell body changes fake about 2 weeks. 2. Regeneration. This begins in the third week after the injury. As the perikaryon gears up for increased protein synthesis, the Nissl bodies 'eappear. The axon's proximal stump gives off a profusion of smaller processes called neurites; one of these encounters and grows into the endoneurial channel, while the others degenerate. In the channel, the neurite grows 3-4 mm/d, guided and then myelinated by the Schwann cells. Growth is maintained by orthograde axoplasmic transport of material synthesized in the soma. When the tip of the neurite reaches its termination, it connects with its end organ or another neuron in the chain. If the cut ends of a severed nerve are matched by by fascicle size and arrangement and sutured together by their epineurial sheaths within 34 weeks after injury, sensory and motor innervation can often be restored. If the gap between the cut ends is too wide, the neurites may fail to find endoneurial sheaths to grow into and may grow out in a potentially painful disorganized swelling called a neuroma. Target organs deprived of innervation often atrophy.