> [!infobox] <s class="aside-in"><em>mentioned in 21 topics, 21 evergreens, 7 sources</em></s> #### <s class="topic-title">[[brain]]</s> > [!wikipedia] [brain](https://en.wikipedia.org/wiki/Brain) > > A brain is an organ that serves as the center of the [[nervous system]] in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for [[senses]] such as [[vision]]. It is the most complex organ in a vertebrate's body. In a human, the [[cerebral cortex]] contains approximately 14–16 billion [[neuron]]s, and the estimated number of neurons in the cerebellum is 55–70 billion. Each neuron is connected by synapses to several thousand other neurons. These neurons typically communicate with one another by means of long fibers called axons, which carry trains of signal pulses called action potentials to distant parts of the brain or body targeting specific recipient cells. > > [[physiology|Physiologically]], brains exert centralized control over a body's other organs. They act on the rest of the body both by generating patterns of muscle activity and by driving the secretion of chemicals called hormones. This centralized control allows rapid and coordinated responses to changes in the environment. Some basic types of responsiveness such as reflexes can be mediated by the spinal cord or peripheral ganglia, but sophisticated purposeful control of behavior based on complex sensory input requires the information integrating capabilities of a centralized brain. > > The operations of individual brain cells are now understood in considerable detail but the way they cooperate in ensembles of millions is yet to be solved. Recent models in modern [[neuroscience]] treat the brain as a biological computer, very different in mechanism from an electronic computer, but similar in the sense that it acquires [[information]] from the surrounding world, stores it, and processes it in a variety of ways. > **See**:: #### Related - [[Anxiety is a defense-mechanism of the brain]] - [[Emotions are how our brain stores thought processes]] - [[How to understand the brain]] - [[Our brain actively inhibits us from processing repressed emotions]] - [[Our brains are built around survival]]