Nervous systemIn biology, the nervous system is the highly complex part of an animal that coordinates its actions and sensoryinformation by transmitting signals to and from different parts of its body. The nervous system detects environmental changes that impact the body, then works in tandem with the endocrine system to respond to such events. Nervous tissue first arose in wormlike organisms about 550 to 600 million years ago.
Nervous tissueNervous tissue, also called neural tissue, is the main tissue component of the nervous system. The nervous system regulates and controls body functions and activity. It consists of two parts: the central nervous system (CNS) comprising the brain and spinal cord, and the peripheral nervous system (PNS) comprising the branching peripheral nerves.
SynapseIn the nervous system, a synapse is a structure that allows a neuron to exchange (receive or send) signals with another cell in its immediate vicinity. Synapses can be classified as either chemical or electrical, depending on the mechanism of signal transmission between neurons. In the case of electrical synapses, neurons are coupled bidirectionally with each other through gap junctions and have a connected cytoplasmic milieu.
Central nervous systemThe central nervous system (CNS) is the part of the nervous system consisting primarily of the brain, and the spinal cord. The retina is also technically part of the CNS. The CNS is named so because the brain integrates the received information and coordinates and influences the activity of all parts of the bodies of bilaterally symmetric and triploblastic animals—that is, all multicellular animals except sponges and diploblasts.
Membrane potentialElectric potential difference between interior and exterior of a biological cell The electrical charge across a cell membrane resulting from different concentrations of ions on the inside of the cell vs. the outside of the cell. Key: Blue pentagons – sodium ions; Purple squares – potassium ions; Yellow circles – chloride ions; Orange rectangles – membrane-impermeable anions (these arise from a variety of sources including proteins).
NeurotransmitterA neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a synapse. The cell receiving the signal, or target cell, may be another neuron, but could also be a gland or muscle cell. Neurotransmitters are released from synaptic vesicles into the synaptic cleft where they are able to interact with neurotransmitter receptors on the target cell. Some neurotransmitters are also stored in large dense core vesicles.
Action potentialAn action potential (also known as a nerve impulse or "spike" when in a neuron) is a series of quick changes in voltage across a cell membrane. An action potential occurs when the membrane potential of a specific cell rapidly rises and falls. This "depolarization" (physically, a reversal of the polarization of the membrane) then causes adjacent locations to similarly depolarize.
SpongeAnimals of the phylum PoriferaSponges or sea sponges are primarily marine invertebrates of the animalphylumPorifera (; meaning 'pore bearer'). They are filter feeders that are typically bound to the seabed, being sessile. Sponges are one of the most ancient members of living seabed community (macrobenthos), with many species being important reef-builders. Some sponge species inhabit freshwater.
Neural network (biology)A neural network, also called a neuronal network, is an interconnected population of neurons typically containing multiple neural circuits. Biological neural networks are studied to understand the organization and functioning of nervous systems. Artificial neural networks, which are defined as machine learning models, are loosely inspired by biological neural networks.
Cell (biology)Basic unit of life formsThe cell is the basic structural and functional unit of all forms of life or organisms. The term comes from the Latin word cellula meaning 'small room'. A biological cell basically consists of a semipermeablecell membrane enclosing cytoplasm that contains genetic material. Most cells are only visible under a microscope.
American EnglishAmerican English, sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States. English is the most widely spoken language in the U.S., as well as the common language used in government, education, and commerce in all 50 states, the District of Columbia, and in all U.S. territories except Puerto Rico. Since the late 20th century, American English has become the most influential form of English worldwide.British EnglishBritish English is the set of varieties of the English language native to the United Kingdom, especially Great Britain. More narrowly, it can refer specifically to the English language in England, or, more broadly, to the collective dialects of English throughout the United Kingdom taken as a single umbrella variety, for instance additionally incorporating Scottish English, Welsh English, and Northern Irish English.
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