![]() Most neurons receive signals via the dendrites and soma and send out signals down the axon. The term neurite is used to describe either a dendrite or an axon, particularly when the cell is undifferentiated. Neurons may lack dendrites or have no axon. ![]() At the farthest tip of the axon's branches are axon terminals, where the neuron can transmit a signal across the synapse to another cell. It branches but usually maintains a constant diameter. The axon leaves the soma at a swelling called the axon hillock and travels for as far as 1 meter in humans or more in other species. Dendrites typically branch profusely and extend a few hundred micrometers from the soma. The soma is a compact structure, and the axon and dendrites are filaments extruding from the soma. When multiple neurons are functionally connected together, they form what is called a neural circuit.Ī typical neuron consists of a cell body ( soma), dendrites, and a single axon. Interneurons connect neurons to other neurons within the same region of the brain or spinal cord. Motor neurons receive signals from the brain and spinal cord to control everything from muscle contractions to glandular output. Sensory neurons respond to stimuli such as touch, sound, or light that affect the cells of the sensory organs, and they send signals to the spinal cord or brain. Neurons are typically classified into three types based on their function. Non-animals like plants and fungi do not have nerve cells. The neuron is the main component of nervous tissue in all animals except sponges and placozoa. Neurons communicate with other cells via synapses - 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. PMID 24672457.Within a nervous system, a neuron, neurone, or nerve cell is an electrically excitable cell that fires electric signals called action potentials across a neural network. "Evolutionary appearance of von Economo's neurons in the mammalian cerebral cortex". ^ Cauda, Franco Geminiani, Giuliano Carlo Vercelli, Alessandro (2014).Annals of the New York Academy of Sciences. "The von Economo neurons in fronto-insular and anterior cingulate cortex". Park, Soyoung Goubert, Virginie Hof, Patrick R. ![]() ^ "David Hubel's Eye, Brain and, Vision".^ Bipolar+cell Archived at the Wayback Machine at eMedicine Dictionary.Nolte's The Human Brain : An Introduction to Its Functional Anatomy. Von Economo neurons, also known as spindle neurons, found in a few select parts of the cerebral cortex of apes and some other intelligent animals, possess a single axon and dendrite and as such have been described as bipolar. In some cases where two fibers are apparently connected with a cell, one of the fibers is really derived from an adjoining nerve cell and is passing to end in a ramification around the ganglion cell, or, again, it may be coiled helically around the nerve process which is issuing from the cell. Sometimes the extensions, also called processes, come off from opposite poles of the cell, and the cell then assumes a spindle shape. In the spinal ganglia īipolar cells are also found in the spinal ganglia, when the cells are in an embryonic condition. The majority of the bipolar neurons belonging to the vestibular nerve exist within the vestibular ganglion with axons extending into the maculae of utricle and saccule as well as into the ampullae of the semicircular canals. In the vestibular nerve īipolar neurons exist within the vestibular nerve as it is responsible for special sensory sensations including hearing, equilibrium and motion detection. On-center bipolar cells have inhibitory synapses with the photoreceptors and therefore are excited by light and suppressed in the dark. ![]() The excitatory synapses thus convey a suppressive signal to the off-center bipolar cells. The off-center bipolar cells have excitatory synaptic connections with the photoreceptors, which fire continuously in the dark and are hyperpolarized (suppressed) by light. Bipolar cells come in two varieties, having either an on-center or an off-center receptive field, each with a surround of the opposite sign. Rather, they pass the information by graded signal changes. Bipolar cells in the retina are also unusual in that they do not fire impulses like the other cells found within the nervous system. The specific location of the bipolar cells allow them to facilitate the passage of signals from where they start in the receptors to where they arrive at the amacrine and ganglion cells. Often found in the retina, bipolar cells are crucial as they serve as both direct and indirect cell pathways. ![]()
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