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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.
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 two main neuronal classes in the cerebral cortex are excitatory projection neurons (around 70-80%) and inhibitory interneurons (around 20–30%). [2]
Glial cells play a major role in brain metabolism by controlling the chemical composition of the fluid that surrounds neurons, including levels of ions and nutrients. [ 85 ] Brain tissue consumes a large amount of energy in proportion to its volume, so large brains place severe metabolic demands on animals.
Sensory neurons, also known as afferent neurons, are neurons in the nervous system, that convert a specific type of stimulus, via their receptors, into action potentials or graded receptor potentials. [1] This process is called sensory transduction. The cell bodies of the sensory neurons are located in the dorsal root ganglia of the spinal cord ...
Neuroscience is the scientific study of the structure and function of the nervous system. [1] [2] It encompasses the branch of biology [3] that deals with the anatomy, biochemistry, molecular biology, and physiology of neurons and neural circuits. It also encompasses cognition, and human behavior. [2]
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 ...
Neurons expressing certain types of neurotransmitters sometimes form distinct systems, where activation of the system affects large volumes of the brain, called volume transmission. Major neurotransmitter systems include the noradrenaline (norepinephrine) system, the dopamine system, the serotonin system, and the cholinergic system, among others.
The connections between neurons can form neural pathways, neural circuits, and larger networks that generate an organism's perception of the world and determine its behavior. Along with neurons, the nervous system contains other specialized cells called glial cells (or simply glia), which