Life span of a neuron. is there a definite time?
Answers:
There is no definite lifespan for a neuron. They can live for a very long time.
In general, most of your neurons are born before you are two years old. After that age, only a very few specific types of neurons continue to be made in any appreciable numbers. Thus, in most cases, the neurons you have at age two have to last the rest of your life. The neurons that control your hand movements, for example, at age two are the very same cells that control your hands at age 102. Along the way, perhaps some of the neurons in the circuits have died, and that may be part of the reason why people are less coordinated at old ages, but the active living neurons may be over 100 years old.
The same would be true in even longer lived species like the galapagos tortoise which can live to be over 150 years old.
BTW: This is part of the reason why injuries to the central nervous system (brain and spinal cord) can be so devastating: neurons do not often replace themselves, and so there is no way to repair the losses.
One thing to note: although the cell lives, its component parts are replaced as needed to prevent the accumulation of damage: for example, the lipids of the cell membrane or cellular proteins are continously renewed.
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as far as I know, the lifespan of a neuron, provided there is no trauma, would be as long as they get enough oxygen
woldnt say theres a definate time,There are many type of neurons. They vary in size from 4 microns (.004 mm) to 100 microns (.1 mm) in diameter. Their length varies from a fraction of an inch to several feet.
They all carry electro-chemical nerve signals, but differ in structure (the number of processes, or axons, emanating from the cell body) and are found in different parts of the body.
Sensory neurons or Bipolar neurons carry messages from the body's sense receptors (eyes, ears, etc.) to the CNS. These neurons have two processes. Sensory neuron account for 0.9% of all neurons. (Examples are retinal cells, olfactory epithelium cells.)
Motoneurons or Multipolar neurons carry signals from the CNS muscles and glands. These neurons have many processes originating from the cell body. Motoneurons account for 9% of all neurons. (Examples are spinal motor neurons, pyramidal neurons, Purkinje cells.)
Interneurons or Pseudopolare (Spelling) cells form all the neural wiring within the CNS. These have two axons (instead of an axon and a dendrite). One axon communicates with the spinal cord; one with either the skin or muscle. These neurons have two processes. (Examples are dorsal root ganglia cells.)
Unlike most other cells, neurons cannot regrow after damage (except neurons from the hippocampus). Fortunately, there are about 100 billion neurons in the brain.
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