Nerve tissue

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Nerve Tissue


The nervous system is the most organized and sophisticated systems which are present in the human body. It is a cooprerating mechanism related to several other systems through reactions and adjustments of the organism.

The whole system is made of nervous tissue, which itself is made out of nervous cells. Nervous tissue is a communicating network which conducts and transmits impulses through the whole body. In fact the communication in the bodyoccurs through electrical impulses which are responsible for the information transfer. In other words it is kind of a language and the way how communication between parts of body can be done.

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Structure[✎ edit | edit source]

The nervous system of the body can be devided into two major parts which are:[1]

-The central nervous system (CNS)[✎ edit | edit source]

CNS consists of the brain and the spinal cord which are responsible for analysis and integration.

-Peripheral nervous system (PNS)[✎ edit | edit source]

PNS is the carrier and conductor of depolarization waves from and to the CNS through its branches.

These processes allow the body to function, coordinate and respond to stimuli. The PNS and CNS network together in the whole body by receiving and conducting electrical impulses through the structural and functional nerve cells, the neurons. Each neuron consists of an axon, a dendrite and soma which are extended like cables in the body and are responsible for our sensory and motoric abilities.

Types[✎ edit | edit source]

There are different types of neurons which can be classified into three major groups:[2]

Multipolar neurons[✎ edit | edit source]

These are mostly found in ithe alpha motor neurons in the spinal cord

Bipolar neurons[✎ edit | edit source]

They can be found in cells of retina

Unipolar neurons[✎ edit | edit source]

These are common in the first sensory neuron in the spinal ganglion.

More than 95% of neurons in the body are multipolar neurons. It can be said that our interacting with the world occurs through the electric impulses. These happen when the membrane potential of nerve cells change into positive or negative charges. Neurons are the first unit of the nervous system and transfer impulses with other cells through synapses. The transmitter substance at the synapses is responsible for the increase or decrease of the membrane potential. An Impulse van only be transmitted if the excitatory(decrease) potential predominates. Otherwise there won´t be any impulse.

Ionic gradient[✎ edit | edit source]

By resting and action potential all impulses can be transmitted through the body. [3]

The inward of the cell has a negative charge referred to the outside. This is a condition of the resting potential. Once the inside potential gets positive, it becomes an action potential. This the phase of depolarization through ion channels. This means that the concentration of ions inside and outside the cell determine the charge and condition of the nerve cells and contribute the required condition. Only if the threshold of -55mV is reached the action potential can be started. If the threshold value is not reached, there will not be any impuls. This happen ob the axon hill of the neuron and occure on the only due to the all or nothing rule.

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The depolarisation continues till the peak of +30m is reached. Now the repolarisation and hyperpolarisation can start to get the previous cell charge at the resting potential basement.. The most crucial ions around the cell membrane are Na+, K+, Cl, and Ca²+. Usually there are also negative proteins within the cell. There are much more K+ ions than Na+ inside the cell during the resting potential.

The process of action potential occurs around the axons through the membrane and Na+ and K+ channels when the inside potential of the cell changes from negative to positive.This depolarization stimulates and creates a condition which cause the rapid nerve impulses though the axons.

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  1. Atlas of histology from Domei Cui,page 118-120
  2. Atlas of histology from Victor P.Eroschenko, page 135-137
  3. Junqueira's basic hisology, page 160-172