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Refractory Period (physiology)
Refractoriness is the fundamental property of any object of autowave nature (especially excitable medium) not to respond on stimuli, if the object stays in the specific ''refractory state''. In common sense, refractory period is the characteristic recovery time, a period that is associated with the motion of the image point on the left branch of the isocline \dot = 0 (for more details, see also Reaction–diffusion and Parabolic partial differential equation). In physiology, a refractory period is a period of time during which an organ or cell is incapable of repeating a particular action, or (more precisely) the amount of time it takes for an excitable membrane to be ready for a second stimulus once it returns to its resting state following an excitation. It most commonly refers to electrically excitable muscle cells or neurons. Absolute refractory period corresponds to depolarization and repolarization, whereas relative refractory period corresponds to hyperpolarization ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Autowave
Autowaves are self-supporting non-linear waves in active media (i.e. those that provide distributed energy sources). The term is generally used in processes where the waves carry relatively low energy, which is necessary for synchronization or switching the active medium. Introduction Relevance and significance In 1980, the Soviet scientists G.R. Ivanitsky, V.I. Krinsky, A.N. Zaikin, A.M. Zhabotinsky, B.P. Belousov became winners of the highest state award of the USSR, Lenin Prize "''for the discovery of a new class of autowave processes and the study of them in disturbance of stability of the distributed excitable systems''." A brief history of autowave researches The first who studied actively the self-oscillations was Academician AA Andronov, and the term "''auto-oscillations''" in Russian terminology was introduced by AA Andronov in 1928. His followers from Lobachevsky University further contributed greatly to the development of ''autowave theory''. The s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Autowave
Autowaves are self-supporting non-linear waves in active media (i.e. those that provide distributed energy sources). The term is generally used in processes where the waves carry relatively low energy, which is necessary for synchronization or switching the active medium. Introduction Relevance and significance In 1980, the Soviet scientists G.R. Ivanitsky, V.I. Krinsky, A.N. Zaikin, A.M. Zhabotinsky, B.P. Belousov became winners of the highest state award of the USSR, Lenin Prize "''for the discovery of a new class of autowave processes and the study of them in disturbance of stability of the distributed excitable systems''." A brief history of autowave researches The first who studied actively the self-oscillations was Academician AA Andronov, and the term "''auto-oscillations''" in Russian terminology was introduced by AA Andronov in 1928. His followers from Lobachevsky University further contributed greatly to the development of ''autowave theory''. The s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cardiac Electrophysiology
Cardiac electrophysiology is a branch of cardiology and basic science focusing on the electrical activities of the heart. The term is usually used in clinical context, to describe studies of such phenomena by invasive (intracardiac) catheter recording of spontaneous activity as well as of cardiac responses to programmed electrical stimulation - clinical cardiac electrophysiology. However, cardiac electrophysiology also encompasses basic research and translational research components. Specialists studying cardiac electrophysiology, either clinically or solely through research, are known as cardiac electrophysiologists. Description Electrophysiological (EP) studies are performed to assess complex arrhythmias, elucidate symptoms, evaluate abnormal electrocardiograms, assess risk of developing arrhythmias in the future, and design treatment. These procedures include therapeutic methods (typically radiofrequency ablation, or cryoablation) in addition to diagnostic and prognostic proced ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physiology
Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemical and physical functions in a living system. According to the classes of organisms, the field can be divided into medical physiology, animal physiology, plant physiology, cell physiology, and comparative physiology. Central to physiological functioning are biophysical and biochemical processes, homeostatic control mechanisms, and communication between cells. ''Physiological state'' is the condition of normal function. In contrast, ''pathological state'' refers to abnormal conditions, including human diseases. The Nobel Prize in Physiology or Medicine is awarded by the Royal Swedish Academy of Sciences for exceptional scientific achievements in physiology related to the field of medicine. Foundations Cells Although there are differ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reaction–diffusion System
Reaction–diffusion systems are mathematical models which correspond to several physical phenomena. The most common is the change in space and time of the concentration of one or more chemical substances: local chemical reactions in which the substances are transformed into each other, and diffusion which causes the substances to spread out over a surface in space. Reaction–diffusion systems are naturally applied in chemistry. However, the system can also describe dynamical processes of non-chemical nature. Examples are found in biology, geology and physics (neutron diffusion theory) and ecology. Mathematically, reaction–diffusion systems take the form of semi-linear parabolic partial differential equations. They can be represented in the general form :\partial_t \boldsymbol = \underline \,\nabla^2 \boldsymbol + \boldsymbol(\boldsymbol), where represents the unknown vector function, is a diagonal matrix of diffusion coefficients, and accounts for all local reactions. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Action Potential
An action potential occurs when the membrane potential of a specific cell location rapidly rises and falls. This depolarization then causes adjacent locations to similarly depolarize. Action potentials occur in several types of animal cells, called excitable cells, which include neurons, muscle cells, and in some plant cells. Certain endocrine cells such as pancreatic beta cells, and certain cells of the anterior pituitary gland are also excitable cells. In neurons, action potentials play a central role in cell-cell communication by providing for—or with regard to saltatory conduction, assisting—the propagation of signals along the neuron's axon toward synaptic boutons situated at the ends of an axon; these signals can then connect with other neurons at synapses, or to motor cells or glands. 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 l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neuron
A neuron, neurone, or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous tissue in all animals except sponges and placozoa. Non-animals like plants and fungi do not have nerve cells. Neurons are typically classified into three types based on their function. Sensory neurons respond to stimuli such as touch, sound, or light that affect the cells of the sensory organs, and they send signals to the spinal cord or brain. Motor neurons receive signals from the brain and spinal cord to control everything from muscle contractions to glandular output. Interneurons connect neurons to other neurons within the same region of the brain or spinal cord. When multiple neurons are connected together, they form what is called a neural circuit. A typical neuron consists of a cell body (soma), dendrites, and a single axon. The soma is a compact structure, and the axon and dend ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Autowave Reverberator
In the theory of autowave phenomena an autowave reverberator is an autowave vortex in a two-dimensional active medium. A reverberator appears a result of a rupture in the front of a plane autowave. Such a rupture may occur, for example, via collision of the front with a nonexcitable obstacle. In this case, depending on the conditions, either of two phenomena may arise: a ''spiral wave'', which rotates around the obstacle, or an ''autowave reverberator'' which rotates with its tip free. Introduction The ''reverberator'' was one of the first autowave solutions, researchers found, and, because of this historical context, it remains by nowadays the most studied autowave object. Up until the late 20th century, the term "''auto-wave reverberator''" was used very active and widely in the scientific literature, written by soviet authors, because of active developing these investigations in USSR (for more details, see "A brief history of autowave researches" in Autowave). And, inasmuc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Voltage-gated Potassium Channel
Voltage-gated potassium channels (VGKCs) are transmembrane channels specific for potassium and sensitive to voltage changes in the cell's membrane potential. During action potentials, they play a crucial role in returning the depolarized cell to a resting state. Classification Alpha subunits Alpha subunits form the actual conductance pore. Based on sequence homology of the hydrophobic transmembrane cores, the alpha subunits of voltage-gated potassium channels are grouped into 12 classes. These are labeled Kvα1-12. The following is a list of the 40 known human voltage-gated potassium channel alpha subunits grouped first according to function and then subgrouped according to the Kv sequence homology classification scheme: Delayed rectifier slowly inactivating or non-inactivating *Kvα1.x - Shaker-related: Kv1.1 (KCNA1), Kv1.2 (KCNA2), Kv1.3 (KCNA3), Kv1.5 (KCNA5), Kv1.6 (KCNA6), Kv1.7 ( KCNA7), Kv1.8 (KCNA10) *Kvα2.x - Shab-related: Kv2.1 (KCNB1), Kv2.2 (KCNB2) *Kvα3.x - ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Excitable Medium
An excitable medium is a nonlinear dynamical system which has the capacity to propagate a wave of some description, and which cannot support the passing of another wave until a certain amount of time has passed (known as the refractory time). A forest is an example of an excitable medium: if a wildfire burns through the forest, no fire can return to a burnt spot until the vegetation has gone through its refractory period and regrown. In chemistry, oscillating reactions are excitable media, for example the Belousov–Zhabotinsky reaction and the Briggs–Rauscher reaction. Cell excitability is the change in membrane potential that is necessary for cellular responses in various tissues. The resting potential forms the basis of cell excitability and these processes are fundamental for the generation of graded and action potentials. Normal and pathological activities in the heart and brain can be modelled as excitable media. A group of spectators at a sporting event are an excitable ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sodium Channel
Sodium channels are integral membrane proteins that form ion channels, conducting sodium ions (Na+) through a cell's membrane. They belong to the superfamily of cation channels and can be classified according to the trigger that opens the channel for such ions, i.e. either a voltage-change ("voltage-gated", "voltage-sensitive", or "voltage-dependent" sodium channel; also called "VGSCs" or "Nav channel") or a binding of a substance (a ligand) to the channel (ligand-gated sodium channels). In excitable cells such as neurons, myocytes, and certain types of glia, sodium channels are responsible for the rising phase of action potentials. These channels go through three different states called resting, active and inactive states. Even though the resting and inactive states would not allow the ions to flow through the channels the difference exists with respect to their structural conformation. Selectivity Sodium channels are highly selective for the transport of ions across cell membr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neurons
A neuron, neurone, or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous tissue in all animals except sponges and placozoa. Non-animals like plants and fungi do not have nerve cells. Neurons are typically classified into three types based on their function. Sensory neurons respond to stimuli such as touch, sound, or light that affect the cells of the sensory organs, and they send signals to the spinal cord or brain. Motor neurons receive signals from the brain and spinal cord to control everything from muscle contractions to glandular output. Interneurons connect neurons to other neurons within the same region of the brain or spinal cord. When multiple neurons are connected together, they form what is called a neural circuit. A typical neuron consists of a cell body (soma), dendrites, and a single axon. The soma is a compact structure, and the axon and dend ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
