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The first list shows number of neurons in their entire nervous system. The second list shows the number of neurons in the structure that has been found to be representative of animal intelligence. [1] The human brain contains 86 billion neurons, with 16 billion neurons in the cerebral cortex. [2] [1]
Neurons are highly specialized for the processing and transmission of cellular signals. Given the diversity of functions performed in different parts of the nervous system, there is a wide variety in their shape, size, and electrochemical properties. For instance, the soma of a neuron can vary from 4 to 100 micrometers in diameter. [7]
There are nerve cells, also known as neurons, present in the human body. They are branched out. These cells make up nervous tissue. A neuron consists of a cell body with a nucleus and cytoplasm, from which long thin hair-like parts arise. [citation needed]
There are many types of neuron, and several types of glial cell. Neurons are the excitable cells of the brain that function by communicating with other neurons and interneurons (via synapses), in neural circuits and larger brain networks.
The enteric nervous system in humans consists of some 500 million neurons [11] (including the various types of Dogiel cells), [1] [12] 0.5% of the number of neurons in the brain, five times as many as the one hundred million neurons in the human spinal cord, [13] and about 2 ⁄ 3 as many as in the whole nervous system of a cat.
There is an anatomical convention that a cluster of neurons in the brain or spinal cord is called a nucleus, whereas a cluster of neurons in the periphery is called a ganglion. [20] There are, however, a few exceptions to this rule, notably including the part of the forebrain called the basal ganglia. [21]
In humans and many other mammals, new neurons are created mainly before birth, and the infant brain contains substantially more neurons than the adult brain. [71] There are, however, a few areas where new neurons continue to be generated throughout life.
Interneurons: Cells that form connections between neurons and whose processes are limited to a single local area in the brain or spinal cord; Structural classification: [5] Multipolar neurons: Have 3 or more processes coming off the soma (cell body). They are the major neuron type in the CNS and include interneurons and motor neurons.