Action potential
From The Art and Popular Culture Encyclopedia
(Difference between revisions)
| Revision as of 11:02, 22 June 2012 Jahsonic (Talk | contribs) ← Previous diff |
Current revision Jahsonic (Talk | contribs) |
||
| Line 1: | Line 1: | ||
| {{Template}} | {{Template}} | ||
| - | + | In [[physiology]], an '''action potential''' is a short-lasting event in which the electrical [[membrane potential]] of a [[Cell (biology)|cell]] rapidly rises and falls, following a consistent trajectory. Action potentials occur in several types of [[animal cell]]s, called [[Membrane potential|excitable cells]], which include [[neuron]]s, [[myocyte|muscle cells]], and [[endocrine]] cells, as well as in some [[plant cell]]s. In neurons, they play a central role in cell-to-cell communication. In other types of cells, their main function is to activate intracellular processes. In muscle cells, for example, an action potential is the first step in the chain of events leading to contraction. In [[beta cell]]s of the [[pancreas]], they provoke release of [[insulin]]. | |
| - | The '''brain''' is the center of the [[nervous system]] in all [[vertebrate]] and most [[invertebrate]] animals—only a few invertebrates such as [[sponge]]s, [[cnidaria|jellyfish]], adult [[sea squirts]] and [[echinoderm|starfish]] do not have one, even if diffuse neural tissue is present. It is located in the head, usually close to the primary sensory organs for such senses as vision, hearing, balance, taste, and smell. The brain of a vertebrate is the most complex organ of its body. In a typical human the [[cerebral cortex]] (the largest part) is estimated to contain 15–33 billion [[neuron]]s, each connected by [[synapse]]s to several thousand other neurons. These neurons communicate with one another by means of long [[protoplasm]]ic fibers called [[axon]]s, which carry trains of signal pulses called [[action potential]]s to distant parts of the brain or body targeting specific recipient cells. | + | |
| - | + | ||
| - | From an evolutionary-biological point of view, the function of the brain is to exert centralized control over the other organs of the body. The brain acts on the rest of the body either by generating patterns of muscle activity or by driving secretion of chemicals called [[hormone]]s. This centralized control allows rapid and coordinated responses to changes in the environment. Some basic types of responsiveness such as [[reflex]]es can be mediated by the spinal cord or peripheral [[ganglion|ganglia]], but sophisticated purposeful control of behavior based on complex sensory input requires the information-integrating capabilities of a centralized brain. | + | |
| - | + | ||
| - | From a philosophical point of view, what makes the brain special in comparison to other organs is that it forms the physical structure that generates the [[mind]]. As [[Hippocrates]] put it: "Men ought to know that from nothing else but the brain come joys, delights, laughter and sports, and sorrows, griefs, despondency, and lamentations." In the early part of psychology, the mind was thought to be separate from the brain. However, after early scientists conducted experiments it was determined that the mind was a component of a functioning brain that expressed certain behaviours based on the external environment and the development of the organism. The mechanisms by which brain activity gives rise to consciousness and thought have been very challenging to understand: despite rapid scientific progress, much about how the brain works remains a mystery. The operations of individual brain cells are now understood in considerable detail, but the way they cooperate in ensembles of millions has been very difficult to decipher. The most promising approaches treat the brain as a biological computer, very different in mechanism from electronic computers, but similar in the sense that it acquires information from the surrounding world, stores it, and processes it in a variety of ways. | + | |
| - | + | ||
| - | This article compares the properties of brains across the entire range of animal species, with the greatest attention to vertebrates. It deals with the human brain insofar as it shares the properties of other brains. The ways in which the human brain differs from other brains are covered in the [[human brain]] article. Several topics that might be covered here are instead covered there because much more can be said about them in a human context. The most important is brain disease and the effects of brain damage, covered in the [[human brain]] article because the most common diseases of the human brain either do not show up in other species, or else manifest themselves in different ways. | + | |
| ==See also== | ==See also== | ||
| - | * [[Outline of neuroscience]] | + | * [[Bursting]] |
| - | * [[List of neuroscience databases]] | + | * [[Signals (biology)]] |
| - | * [[Brain–computer interface]] | + | * [[Single-unit recording]] |
| - | + | * [[Central pattern generator]] | |
| {{GFDL}} | {{GFDL}} | ||
Current revision
|
Related e |
|
Featured: |
In physiology, an action potential is a short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls, following a consistent trajectory. Action potentials occur in several types of animal cells, called excitable cells, which include neurons, muscle cells, and endocrine cells, as well as in some plant cells. In neurons, they play a central role in cell-to-cell communication. In other types of cells, their main function is to activate intracellular processes. In muscle cells, for example, an action potential is the first step in the chain of events leading to contraction. In beta cells of the pancreas, they provoke release of insulin.
[edit]
See also
Unless indicated otherwise, the text in this article is either based on Wikipedia article "Action potential" or another language Wikipedia page thereof used under the terms of the GNU Free Documentation License; or on research by Jahsonic and friends. See Art and Popular Culture's copyright notice.
