Friday, January 3, 2014

Neurons information

Neurons information
  1. Brain is a single organinternal structure and organization are quite complex.
  2. Contains about 1011 neurons,
  3. Mature neurons do not have the ability to go under Mitosis
  4. The "normal" loss of neurons has been estimated to be about 103 per hour,  in 75 years (660,000 hours), a loss of only 0.66 percent of the total number of neurons present at birth.
  5. People of advanced age
  6. less brain substance than their younger counterparts.
  7. brain shrinkage with age
  8. Environmental factors: accidents, drug use, can increase the rate of either cell shrinkage or cell loss.

Basic structural and functional units of the nervous system. They cannot divide by mitosis. The fully differentiated, post-mitotic cells cannot be replaced during the lifetime of the organism. As neurons die in the course of normal aging, they cannot be replaced. Therefore, the maximum number of neurons exists near the time of birth.  

Neurons respond to physical and chemical stimuli.These cells are able to produce and conduct electrochemical impulses. Electrical impulse move from one cell to another cell by the release chemical regulators.

Cell body (perikaryon):
·         “Nutrition center.”
·         Cell bodies within CNS clustered into nuclei,
and in PNS in  ganglia.
·         Dendrites:
        Provide receptive area.
        Transmit electrical impulses to cell body.
·         Axon:
        Conducts impulses away from cell body.
        Each neuron usually contains an axon
·         Synapses
        cell body of another neuron (axo-somatic synapses),
        contact dendrites (axo-dendritic synapses).
        one cell's axon and another cell's axon (axo-axonic, or presynaptic, synapses). 

Neurons are Excitable cells. They vary considerably in size and shape, Important biochemical and physiological properties are common.The dendrites are the short processes of the cell body. They conduct the nerve impulse toward the cell body.Axon is the largest process of the cell body. An axon conducts impulses away from the cell body. The majority of axons within the CNS, are only a centimeter or two in length. The dendrites and axons are often referred to as nerve fibers. Within the CNS, most axons make functional connections with other neurons at junctions called synapses.