Electrophysiology (from Greek. Planar patch clamp is a novel method developed for high throughput electrophysiology. [6] Instead of positioning a pipette on an. The patch clamp technique is a laboratory technique in electrophysiology that allows the study of single or multiple ion channels in cells. The technique can be. 全部 DOC PPT TXT PDF XLS 百度文库 专业资料 医药卫生 膜片钳1_医药卫生_专业资料 暂无评价 0人阅读 0次下载 举报文档 膜片钳1_医药卫生_专业资料。膜片钳先关国外. Patch Clamp Electrophysiology for the Study of Bacterial Ion Channels in Giant Spheroplasts of E. coli 关键词: patch clamp electrophysiology 2014-03-17 11:22. Patch clamp recording is an extremely useful technique for investigating the biophysical properties of the ion channels that control. Patch Clamp Electrophysiology. ELECTROPHYSIOLOGY Single Neuron Recording Patch Clamp Recording ECG EEG- Brain activity Recording PET, MRI, fMRI,CAT Single-unit recording It is the use of an. Cardiac Cel lu lar Electrophysiology, Volt age Clamp, PatchClamp Yi-Jen Chen, Yao-ChangChen. Ad di tion ally, quitedif fi cult perform patch clamp longer du ra exper. . Taipei, Taiwan Recent Advances in Basic EP Molecularcloning of ion channels Intracellularrecordings Voltageclamp and patch clamp What is an ion channel? PPT – ELECTROPHYSIOLOGY Power. Point presentation free to download. Power. Show. com is a leading presentation/slideshow sharing website. Whether your application is business, how- to, education, medicine, school, church, sales, marketing, online training or just for fun, Power. Show. com is a great resource. And, best of all, most of its cool features are free and easy to use. You can use Power. Show. com to find and download example online Power. Point ppt presentations on just about any topic you can imagine so you can learn how to improve your own slides and. Or use it to find and download high- quality how- to Power. Point ppt presentations with illustrated or animated slides that will teach you how to do something new, also for free. Or use it to upload your own Power. Point slides so you can share them with your teachers, class, students, bosses, employees, customers, potential investors or the world. Or use it to create really cool photo slideshows - with 2. D and 3. D transitions, animation, and your choice of music - that you can share with your Facebook friends or Google+ circles. That's all free as well! For a small fee you can get the industry's best online privacy or publicly promote your presentations and slide shows with top rankings. But aside from that it's free. We'll even convert your presentations and slide shows into the universal Flash format with all their original multimedia glory, including animation, 2. D and 3. D transition effects, embedded music or other audio, or even video embedded in slides. All for free. Most of the presentations and slideshows on Power. Show. com are free to view, many are even free to download. You can choose whether to allow people to download your original Power. Point presentations and photo slideshows for a fee or free or not at all.) Check out Power. Show. com today - for FREE. There is truly something for everyone! Or use it to find and download high- quality how- to Power. Point ppt presentations with illustrated or animated slides that will teach you how to do something new, also for free. Or use it to upload your own Power. Point slides so you can share them with your teachers, class, students, bosses, employees, customers, potential investors or the world. Or use it to create really cool photo slideshows - with 2. D and 3. D transitions, animation, and your choice of music - that you can share with your Facebook friends or Google+ circles. That's all free as well! For a small fee you can get the industry's best online privacy or publicly promote your presentations and slide shows with top rankings. But aside from that it's free. We'll even convert your presentations and slide shows into the universal Flash format with all their original multimedia glory, including animation, 2. D and 3. D transition effects, embedded music or other audio, or even video embedded in slides. All for free. Most of the presentations and slideshows on Power. Show. com are free to view, many are even free to download. You can choose whether to allow people to download your original Power. Point presentations and photo slideshows for a fee or free or not at all.) Check out Power. Show. com today - for FREE. There is truly something for everyone! Electrophysiology - Wikipedia, the free encyclopedia. Electrophysiology (from Greekἥλεκτρον, Д“lektron, "amber" [see the etymology of "electron"]; П†ПЌПѓО№П‚, physis, "nature, origin"; and - О»ОїОіОЇО±, - logia) is the study of the electrical properties of biological cells and tissues. It involves measurements of voltage change or electric current on a wide variety of scales from single ion channelproteins to whole organs like the heart. In neuroscience, it includes measurements of the electrical activity of neurons, and particularly action potential activity. Recordings of large- scale electric signals from the nervous system, such as electroencephalography, may also be referred to as electrophysiological recordings.[1]. Current Clamp" is a common technique in electrophysiology. This is a whole- cell current clamp recording of a neuron firing due to it being depolarized by current injection. Definition and scope[edit]Classical electrophysiological techniques[edit]Principles and mechanisms[edit]Electrophysiology is the science and branch of physiology that pertains to the flow of ions (ion current) in biological tissues and, in particular, to the electrical recording techniques that enable the measurement of this flow. Classical electrophysiology techniques involve placing electrodes into various preparations of biological tissue. The principal types of electrodes are: simple solid conductors, such as discs and needles (singles or arrays, often insulated except for the tip),tracings on printed circuit boards, also insulated except for the tip, andhollow tubes filled with an electrolyte, such as glass pipettes filled with potassium chloride solution or another electrolyte solution. The principal preparations include: living organisms,excised tissue (acute or cultured),dissociated cells from excised tissue (acute or cultured),artificially grown cells or tissues, orhybrids of the above. If an electrode is small enough (micrometers) in diameter, then the electrophysiologist may choose to insert the tip into a single cell. Such a configuration allows direct observation and recording of the intracellular electrical activity of a single cell. However, at the same time such invasive setup reduces the life of the cell and causes a leak of substances across the cell membrane. Intracellular activity may also be observed using a specially formed (hollow) glass pipette containing an electrolyte. In this technique, the microscopic pipette tip is pressed against the cell membrane, to which it tightly adheres by an interaction between glass and lipids of the cell membrane. The electrolyte within the pipette may be brought into fluid continuity with the cytoplasm by delivering a pulse of negative pressure to the pipette in order to rupture the small patch of membrane encircled by the pipette rim (whole- cell recording). Alternatively, ionic continuity may be established by "perforating" the patch by allowing exogenous pore- forming agent within the electrolyte to insert themselves into the membrane patch (perforated patch recording). Finally, the patch may be left intact (patch recording). The electrophysiologist may choose not to insert the tip into a single cell. Instead, the electrode tip may be left in continuity with the extracellular space. If the tip is small enough, such a configuration may allow indirect observation and recording of action potentials from a single cell, and is termed single- unit recording. Depending on the preparation and precise placement, an extracellular configuration may pick up the activity of several nearby cells simultaneously, and this is termed multi- unit recording. As electrode size increases, the resolving power decreases. Larger electrodes are sensitive only to the net activity of many cells, termed local field potentials. Still larger electrodes, such as uninsulated needles and surface electrodes used by clinical and surgical neurophysiologists, are sensitive only to certain types of synchronous activity within populations of cells numbering in the millions. Other classical electrophysiological techniques include single channel recording and amperometry. Electrographic modalities by body part[edit]Electrophysiological recording in general is sometimes called electrography (from electro- + - graphy, "electrical recording"), with the record thus produced being an electrogram. However, the word electrography has other senses (including electrophotography), and the specific types of electrophysiological recording are usually called by specific names, constructed on the pattern of electro- + [body part combining form] + - graphy (abbreviation Ex. G). Relatedly, the word electrogram (not being needed for those other senses) often carries the specific meaning of intracardiac electrogram, which is like an electrocardiogram but with some invasive leads (inside the heart) rather than only noninvasive leads (on the skin). The various "Ex. G" modes are as follows: Optical electrophysiological techniques[edit]Optical electrophysiological techniques were created by scientists and engineers to overcome one of the main limitations of classical techniques. Classical techniques allow observation of electrical activity at approximately a single point within a volume of tissue. Essentially, classical techniques singularize a distributed phenomenon. Interest in the spatial distribution of bioelectric activity prompted development of molecules capable of emitting light in response to their electrical or chemical environment. Examples are voltage sensitive dyes and fluorescing proteins. After introducing one or more such compounds into tissue via perfusion, injection or gene expression, the 1 or 2- dimensional distribution of electrical activity may be observed and recorded. Intracellular recording[edit]Intracellular recording involves measuring voltage and/or current across the membrane of a cell. To make an intracellular recording, the tip of a fine (sharp) microelectrode must be inserted inside the cell, so that the membrane potential can be measured. Typically, the resting membrane potential of a healthy cell will be - 6. V, and during an action potential the membrane potential might reach +4. V. In 1. 96. 3, Alan Lloyd Hodgkin and Andrew Fielding Huxley won the Nobel Prize in Physiology or Medicine for their contribution to understanding the mechanisms underlying the generation of action potentials in neurons. Their experiments involved intracellular recordings from the giant axon of Atlantic squid (Loligo pealei), and were among the first applications of the "voltage clamp" technique. Today, most microelectrodes used for intracellular recording are glass micropipettes, with a tip diameter of < 1 micrometre, and a resistance of several megohms. The micropipettes are filled with a solution that has a similar ionic composition to the intracellular fluid of the cell. A chlorided silver wire inserted in to the pipet connects the electrolyte electrically to the amplifier and signal processing circuit. The voltage measured by the electrode is compared to the voltage of a reference electrode, usually a silver chloride- coated silver wire in contact with the extracellular fluid around the cell. In general, the smaller the electrode tip, the higher its electrical resistance, so an electrode is a compromise between size (small enough to penetrate a single cell with minimum damage to the cell) and resistance (low enough so that small neuronal signals can be discerned from thermal noise in the electrode tip). Voltage clamp[edit]Main article: Voltage clamp. The voltage clamp uses a negative feedback mechanism. The membrane potential amplifier measures membrane voltage and sends output to the feedback amplifier. The feedback amplifier subtracts the membrane voltage from the command voltage, which it receives from the signal generator. This signal is amplified and returned into the cell via the recording electrode. The voltage clamp technique allows an experimenter to "clamp" the cell potential at a chosen value. This makes it possible to measure how much ionic current crosses a cell's membrane at any given voltage. This is important because many of the ion channels in the membrane of a neuron are voltage- gated ion channels, which open only when the membrane voltage is within a certain range. Voltage clamp measurements of current are made possible by the near- simultaneous digital subtraction of transient capacitive currents that pass as the recording electrode and cell membrane are charged to alter the cell's potential. Current clamp[edit]The current clamp technique records the membrane potential by injecting current into a cell through the recording electrode. Unlike in the voltage clamp mode, where the membrane potential is held at a level determined by the experimenter, in "current clamp" mode the membrane potential is free to vary, and the amplifier records whatever voltage the cell generates on its own or as a result of stimulation. This technique is used to study how a cell responds when electric current enters a cell; this is important for instance for understanding how neurons respond to neurotransmitters that act by opening membrane ion channels. Most current- clamp amplifiers provide little or no amplification of the voltage changes recorded from the cell. The "amplifier" is actually an electrometer, sometimes referred to as a "unity gain amplifier"; its main job is to change the nature of small signals (in the m. V range) produced by cells so that they can be accurately recorded by low- impedance electronics. The amplifier increases the current behind the signal while decreasing the resistance over which that current passes. Consider this example based on Ohm's law: A voltage of 1. V is generated by passing 1. MО© of resistance. The electrometer changes this "high impedance signal" to a "low impedance signal" by using a voltage follower circuit. A voltage follower reads the voltage on the input (caused by a small current through a big resistor).
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