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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]
The adult human brain weighs on average about 1.2–1.4 kg (2.6–3.1 lb) which is about 2% of the total body weight, [2] [3] with a volume of around 1260 cm 3 in men and 1130 cm 3 in women. [4] There is substantial individual variation, [ 4 ] with the standard reference range for men being 1,180–1,620 g (2.60–3.57 lb) [ 5 ] and for women ...
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]
Neurons may be termed by their associated neurotransmitter such as excitatory dopaminergic neurons and inhibitory GABAergic neurons. [ 5 ] Cortical interneurons only make up around a fifth of the neuronal population but they play a major role in modulating cortical activity needed for cognition and many aspects of learning and memory.
A biological neural network is composed of a group of chemically connected or functionally associated neurons. [2] A single neuron may be connected to many other neurons and the total number of neurons and connections in a network may be extensive.
There are 43 segments of nerves in the human body. [4] With each segment, there is a pair of sensory and motor nerves. 31 segments of nerves are in the spinal cord and 12 are in the brain stem. [4] Interneurons also known as association neurons are present throughout the central nervous system forming links between the sensory and motor fibres. [5]