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Afterhyperpolarization
Afterhyperpolarization, or AHP, is the hyperpolarizing phase of a neuron's action potential where the cell's membrane potential falls below the normal resting potential. This is also commonly referred to as an action potential's undershoot phase. AHPs have been segregated into "fast", "medium", and "slow" components that appear to have distinct ionic mechanisms and durations. While fast and medium AHPs can be generated by single action potentials, slow AHPs generally develop only during trains of multiple action potentials. During single action potentials, transient depolarization of the membrane opens more voltage-gated K+ channels than are open in the resting state, many of which do not close immediately when the membrane returns to its normal resting voltage. This can lead to an "undershoot" of the membrane potential to values that are more polarized ("hyperpolarized") than was the original resting membrane potential. Ca2+-activated K+ channels that open in response to th ... [...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 event ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Slow Afterhyperpolarization
Slow afterhyperpolarisation (sAHP) refers to prolonged periods of hyperpolarisation in a neuron or cardiomyocyte following an action potential or other depolarising event. In neurons, trains of action potentials may be required to induce sAHPs; this is unlike fast AHPs that require no more than a single action potential. A variety of ionic mechanism may contribute to sAHPs, including potassium efflux from calcium- or sodium- activated potassium channels, and/or the electrogenic response of the sodium-potassium ATPase.A.T. Gulledge, S. Dasari, K. Onoue, E.K. Stephens, J.M. Hasse, and D. Avesar, A sodium-pump-mediated afterhyperpolarization in pyramidal neurons., Journal of Neuroscience 33:13025-13041 (2013). Depending on neuron type and stimulus used for induction, slow afterhyperpolarisations can last for one second to several tens of seconds, during which time the sAHP effectively inhibits neural activity. Fast and Medium AHPs have shorter durations and different ionic mechanisms ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Afterdepolarization
Afterdepolarizations are abnormal depolarizations of cardiac myocytes that interrupt phase 2, phase 3, or phase 4 of the cardiac action potential in the electrical conduction system of the heart. Afterdepolarizations may lead to cardiac arrhythmias. Afterdepolarization is commonly a consequence of myocardial infarction, cardiac hypertrophy, or heart failure. It may also result from congenital mutations associated with calcium channels and sequestration. __TOC__ Early afterdepolarizations Early afterdepolarizations (EADs) occur with abnormal depolarization during phase 2 or phase 3, and are caused by an increase in the frequency of abortive action potentials before normal repolarization is completed. EADs most commonly originate in mid-myocardial cells and Purkinje fibers, but can develop in other cardiac cells that carry an action potential. Phase 2 may be interrupted due to augmented opening of calcium channels, while phase 3 interruptions are due to the opening of sodium channel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Calcium-activated Potassium Channel
Calcium-activated potassium channels are potassium channels gated by calcium, or that are structurally or phylogenetically related to calcium gated channels. They were first discovered in 1958 by Gardos who saw that calcium levels inside of a cell could affect the permeability of potassium through that cell membrane. Then in 1970, Meech was the first to observe that intracellular calcium could trigger potassium currents. In humans they are divided into three subtypes: large conductance or BK channels, which have very high conductance which range from 100 to 300 pS, intermediate conductance or IK channels, with intermediate conductance ranging from 25 to 100 pS, and small conductance or SK channels with small conductances from 2-25 pS. This family of ion channels is, for the most part, activated by intracellular Ca2+ and contains 8 members in the human genome. However, some of these channels (the KCa4 and KCa5 channels) are responsive instead to other intracellular ligands, such as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cellular Processes
The cell is the basic structural and functional unit of life forms. Every cell consists of a cytoplasm enclosed within a membrane, and contains many biomolecules such as proteins, DNA and RNA, as well as many small molecules of nutrients and metabolites.Cell Movements and the Shaping of the Vertebrate Body in Chapter 21 of Molecular Biology of the Cell '' fourth edition, edited by Bruce Alberts (2002) published by Garland Science. The Alberts text discusses how the "cellular building blocks" move to shape developing s. It is also common to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrochemistry
Electrochemistry is the branch of physical chemistry concerned with the relationship between electrical potential difference, as a measurable and quantitative phenomenon, and identifiable chemical change, with the potential difference as an outcome of a particular chemical change, or vice versa. These reactions involve electrons moving via an electronically-conducting phase (typically an external electrical circuit, but not necessarily, as in electroless plating) between electrodes separated by an ionically conducting and electronically insulating electrolyte (or ionic species in a solution). When a chemical reaction is driven by an electrical potential difference, as in electrolysis, or if a potential difference results from a chemical reaction as in an electric battery or fuel cell, it is called an ''electrochemical'' reaction. Unlike in other chemical reactions, in electrochemical reactions electrons are not transferred directly between atoms, ions, or molecules, but via ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrophysiology
Electrophysiology (from Greek , ''ēlektron'', "amber" Electron#Etymology">etymology of "electron" , ''physis'', "nature, origin"; and , ''-logia'') is the branch of physiology that studies the electrical properties of biological cells and tissues. It involves measurements of voltage changes or electric current or manipulations on a wide variety of scales from single ion channel proteins to whole organs like the heart. In neuroscience, it includes measurements of the electrical activity of neurons, and, in particular, action potential activity. Recordings of large-scale electric signals from the nervous system, such as electroencephalography, may also be referred to as electrophysiological recordings. They are useful for electrodiagnosis and monitoring. Definition and scope Classical electrophysiological techniques Principle and mechanisms Electrophysiology is the branch of physiology that pertains broadly to the flow of ions ( ion current) in biological tissues and, in pa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Medial Temporal Lobe
The temporal lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The temporal lobe is located beneath the lateral fissure on both cerebral hemispheres of the mammalian brain. The temporal lobe is involved in processing sensory input into derived meanings for the appropriate retention of visual memory, language comprehension, and emotion association. ''Temporal'' refers to the head's temples. Structure The temporal lobe consists of structures that are vital for declarative or long-term memory. Declarative (denotative) or explicit memory is conscious memory divided into semantic memory (facts) and episodic memory (events). Medial temporal lobe structures that are critical for long-term memory include the hippocampus, along with the surrounding hippocampal region consisting of the perirhinal, parahippocampal, and entorhinal neocortical regions. The hippocampus is critical for memory formation, and the surrounding medial temporal cortex is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Entorhinal Cortex
The entorhinal cortex (EC) is an area of the brain's allocortex, located in the medial temporal lobe, whose functions include being a widespread network hub for memory, navigation, and the perception of time.Integrating time from experience in the lateral entorhinal cortex Albert Tsao, Jørgen Sugar, Li Lu, Cheng Wang, James J. Knierim, May-Britt Moser & Edvard I. Moser Naturevolume 561, pages57–62 (2018) The EC is the main interface between the hippocampus and neocortex. The EC-hippocampus system plays an important role in declarative (autobiographical/episodic/semantic) memories and in particular spatial memories including memory formation, memory consolidation, and memory optimization in sleep. The EC is also responsible for the pre-processing (familiarity) of the input signals in the reflex nictitating membrane response of classical trace conditioning; the association of impulses from the eye and the ear occurs in the entorhinal cortex. Structure In rodents, th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ion Transporter
In biology, a transporter is a transmembrane protein that moves ions (or other small molecules) across a biological membrane to accomplish many different biological functions including, cellular communication, maintaining homeostasis, energy production, etc. There are different types of transporters including, pumps, uniporters, antiporters, and symporters. Active transporters or ion pumps are transporters that convert energy from various sources—including adenosine triphosphate (ATP), sunlight, and other redox reactions—to potential energy by pumping an ion up its concentration gradient. This potential energy could then be used by secondary transporters, including ion carriers and ion channels, to drive vital cellular processes, such as ATP synthesis. This page is focused mainly on ion transporters acting as pumps, but transporters can also function to move molecules through facilitated diffusion. Facilitated diffusion does not require ATP and allows molecules, that are unabl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
M Current
M current is a type of noninactivating potassium current first discovered in bullfrog sympathetic ganglion cells. The ''M-channel'' is a voltage-gated K+ channel ( Kv7/KCNQ family) that is named after the receptor it is influenced by. The M-channel is important in raising the threshold for firing an action potential. It is unique because it is open at rest and even more likely to be open during depolarization. Furthermore, when the muscarinic acetylcholine receptor ( MAChR) is activated, the channel closes. The M-channel is a PIP2-regulated ion channel. Kv7 channels have a prominent expression throughout the brain. Function Actions of M-currents: "phasic-firing" M-channels are the reason for slow depolarizations produced by ACh and LHRH in the autonomic ganglia and other specified areas. 1. Initial depolarization of a neuron increases likelihood that M-channels will open. 2. M-channels generate an outward potassium current (IK). 3. Potassium efflux counteracts sodium influx in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
