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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. Neurons are the main components of nervous tissue in all animals except sponges and placozoans.
Since RNA encodes information [1] and living cells produce and modify RNA in reaction to external events, it might also be used in neurons to record stimuli. [2] [3] [4] This explained the results of McConnell's experiments in which planarians retained memory of acquired information after regeneration.
There are an estimated 100 billion neurons in the human brain. [1] Neurons are polarised cells that are specialised for the conduction of action potentials also called nerve impulses. [1] They can also synthesise membrane and protein. Neurons communicate with other neurons using neurotransmitters released from their synapses, and they may be ...
Human karyogram. Neurogenetics studies the role of genetics in the development and function of the nervous system.It considers neural characteristics as phenotypes (i.e. manifestations, measurable or not, of the genetic make-up of an individual), and is mainly based on the observation that the nervous systems of individuals, even of those belonging to the same species, may not be identical.
The synapse is the primary unit of information transfer in the nervous system, and correct synaptic contact creation during development is essential for normal brain function. Genetic mutations can disrupt synapse formation and function, contributing to the development of neurodevelopmental and neurodegenerative disorders. [46]
Neurons, however, are usually considered the most important cells in the brain. [8] In humans, the cerebral cortex contains approximately 14–16 billion neurons, [1] and the estimated number of neurons in the cerebellum is 55–70 billion. [2] Each neuron is connected by synapses to several thousand other neurons.
Neurotransmission implies both a convergence and a divergence of information. First one neuron is influenced by many others, resulting in a convergence of input. When the neuron fires, the signal is sent to many other neurons, resulting in a divergence of output. Many other neurons are influenced by this neuron. [citation needed]
Many neurons migrating along the anterior-posterior axis of the body use existing axon tracts to migrate along in a process called axophilic migration. [18] An example of this mode of migration is in GnRH-expressing neurons , which make a long journey from their birthplace in the nose, through the forebrain, and into the hypothalamus. [ 19 ]