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

Peripheral nervous sytem

•Peripheral nervous sytem comprise peripheral nerves; afferent and efferent, recepors or sensory cell, and autonomic ganglia.
•Afferent nerves carry impulses from sensory cell to the spinal cord or brain.
•Efferent nerves carry impulses from spinal cord or brain to the effector organs (Muscle etc.).

•There are two kind of afferent nerves; somatic, visceral.
•Afferent nerves enter into the cord dorsally, efferent nerves leave the cord ventrally.
•There are two kind of afferent and efferent system.

peripheral nervous system.

Neuron structure

Neurons all have same basic structure, a cell body with a number of dendrites and one long axon

Nerve Tissue and Nerve cells in Animals

•Nervous systhem is composed of various cells having different function.
•Neuron is basic cell type.
•Other cells are; astrocyte, microglial cells, oligodendrocytes, shwann cells, ependimal cells

•Neurons have two extension: long one is called as axon, short one dentrites.
•Neurons can be classified acording to type of extension: Unipolar, bipolar, Multipolar.
•The majority of invertebrates interneurons and motorneurons are unipolar.


•Astrocytes provide connection between capillaries and neurons.
•Oligodendrocyte make myelin sheeth
•Microglia are phagocytic, motile cells that engulf and destroy cellular debris and microbes.

•Glial Cells are three type: Astrocyte, oligodentrocyte, microglia.


•In the peripheral nervous system, myelin is formed by Schwann cells.
•Each Schwann cell associates with only one axon, when forming a myelinated internode.

Vertebrate Nervous System

•The organization of the vertebrate nervous system is different from invertebrates.
•Vertebrates have a well-organized hollow dorsal nervous system.
•The central nervous sytem inclued a brain and spinal cord.
•The peripheral nervous sytem comprise peripheral nerves extending from spinal cord and peripheral ganglia

Nervous System Generally Informations

Nervous sytem of human body; tasting, smelling, seeing, hearing, thinking, dreaming, breathing, heart beating, moving, running, sleeping, laughing, singing, remembering, feeling pain or pleasure, painting, writing all of these activites are depend on nervous system of our body.

you couldn't do any of these things without your central and peripheral nervous system.

so what is the nervous system?

answer : composed of your brain, your spinal cord, and an enormous network of nerves.

it's the control center for your entire body.

The brain uses information it receives from your nerves to coordinate all of your action,reaction

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.