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They are located in the brain and spinal cord and help to receive and conduct impulses. Neurons communicate with other cells via synapses, which are specialized connections that commonly use minute amounts of chemical neurotransmitters to pass the electric signal from the presynaptic neuron to the target cell through the synaptic gap.
In neuroanatomy, a nucleus (pl.: nuclei) is a cluster of neurons in the central nervous system, [1] located deep within the cerebral hemispheres and brainstem. [2] The neurons in one nucleus usually have roughly similar connections and functions. [3]
Duplication of DNA can lead to neuronal diversification in vertebrates, as seen in observations in the developing chick retina. These neurons re-enter the cell cycle as they travel to the ganglion cell layer when they are activated by p75NTR. These neurons are unable to enter mitosis and are stuck in a 4C DNA content state.
Neurons are diverse with respect to morphology and function. Thus, not all neurons correspond to the stereotypical motor neuron with dendrites and myelinated axons that conduct action potentials. Some neurons such as photoreceptor cells, for example, do not have myelinated axons that conduct action potentials. Other unipolar neurons found in ...
Glial stem cells are found in all parts of the adult brain. [1] Glial cells greatly outnumber neurons and apart from their supporting role to neurons, glia – astrocytes in particular have been acknowledged as being able to communicate with neurons involving a signalling process similar to neurotransmission called gliotransmission. [4]
The part of the soma without the nucleus is called perikaryon (pl.: perikarya). [4] There are many different specialized types of neurons, and their sizes vary from as small as about 5 micrometres to over 10 millimetres for some of the smallest and largest neurons of invertebrates, respectively. Animation in the reference
In this species, the nervous system is sexually dimorphic; the nervous systems of the two sexes, males and female hermaphrodites, have different numbers of neurons and groups of neurons that perform sex-specific functions. In C. elegans, males have exactly 383 neurons, while hermaphrodites have exactly 302 neurons. [29]
Axons transmit signals to other neurons by means of specialized junctions called synapses. A single axon may make as many as several thousand synaptic connections with other cells. [ 8 ] When an action potential, traveling along an axon, arrives at a synapse, it causes a chemical called a neurotransmitter to be released.