Talk:Electrophysiology Information & Talk:Electrophysiology Links at HealthHaven.com

WikiProject Molecular and Cellular Biology

(Rated Start-Class, Mid-importance)

MCB portal

This article is within the scope of the Molecular and Cellular Biology WikiProject. To participate, visit the WikiProject for more information. The WikiProject's current monthly collaboration is focused on improving Gene expression.

Start

This article has been rated as Start-Class on the project's quality scale.

Mid

This article has been rated as Mid-importance on the project's importance scale.

WikiProject Medicine

(Rated Start-Class, Low-importance)

Medicine portal

This article is within the scope of WikiProject Medicine. Please visit the project page for details or ask questions at Wikipedia talk:WikiProject Medicine.

Start

This article has been rated as Start-Class on the project's quality scale.

Low

This article has been rated as Low-importance on the project's importance scale.

[edit] I

I agree with Dan. The current definition of electrophysiology at the top of the article excludes all extracellular techniques. I would reccommend adding mention of single-channel recordings. This is, after all, the reason why patch-clamping was developed, and it would permit lots of nice cross-indexing with the ion-channel article. -- Mattv May 6, 2006

I find the definition of electrophysiology in this article to be a little restrictive. How about broadening the definition to include the "studing electrical properties of biological systems" be they cells, tissues, and even organs. Some people may consider methods such as EKG and EOG to be electrophysiology as well. What do you guys think? -- Dan

I know that this is getting too long. I think the next big task is to break it up onto sub-pages. I need to put more topic headings in first. Synaptidude

That's exactly what I was going to suggest, rather than delete the old, incorporate it into your text. -Purkinje 23:36, 23 Jun 2005 (UTC)

Hey Purkinje,

ITA. I'm basically rewriting the whole thing (I'm an electrophysiologist), but there are good things in the old article, and I'm incorperating them as I go. So I've not deleted them. Things will get more organized as I work on the article, but, as I ssid, I want to respect the work of the original authors, so I'm leaving it for now, but will incorperate it into the overall structure before I'm done.

-Synaptidude

P.S. Do you exist mostly in a 2-dimentional plane? ;-)

I really like the major edits added recently by Synaptitude and the anonymous user, however the article now has a large amount of redundancy regarding techniques. It might be helpful to re-organize the entire thing so that it has a more logical integration of the old article and the new editsPurkinje 02:09, 23 Jun 2005 (UTC)

[edit] Re: request for cleanup

I'm working on this when I can. I have a lot of content to add, but I'll try to clean it up a bigt

Well, I think you should know that cardiologist who study and treat arrhythmias by radiofrequency ablation call our field Electrophysiology and ourselves Electrophysiologists. Silvia

[edit] Separate pages

I agree with Purkinje and Synaptitude above that the page should be broken into more pages. What about separate pages for voltage and current clamp? delldot | talk 16:25, 23 November 2005 (UTC)

I'm going to go ahead and move the voltage clamp material to a new page. If you have concerns about this, you can move it back or discuss it with me here or on my talk page. delldot | talk 02:55, 25 November 2005 (UTC)

[edit] Old text (to be incorporated)

I'm moving this text here from the article itself so the article will look more professional. delldot | talk 16:58, 23 November 2005 (UTC)

_____________________________ Text below here is "old" and has not yet been incorperated into the new structure. Feel free to do so, I will get to it soon if someone else doesn't Synaptidude 23:02, 15 August 2005 (UTC) _____________________________

[edit] Current clamp

At the cellular level, these techniques include so-called passive recordings, sometimes referred to as "current clamp". Current clamp is used to record a cell's membrane potential. "Current clamp" is something of a misnomer, because nothing is "clamped" while using this technique. Unlike voltage clamp recording where the cell's membrane voltage is held, or "clamped", at a particular value, in current clamp recording, the current flow across the cell's membrane is not controlled. The misnaming derives from two sources. First current clamp is perceived as the "opposite" of voltage clamp, and second, when using current clamp, the experimenter has the opportunity to inject specificed current offsets into a cell. However, even with such offsets, the cell is still free to vary its membrane current in response to other stimuli. The experimenter has no direct control over the current flow across the cell's membrane. Current clamp is nothing more than a method of passively recording a cell's trans-membrane voltage with the added ability to produce voltage offsets by injecting current into the cell through the recording electrode. Current clamp is useful anytime the experimenter needs to record the voltage across a cell's membrane such as during studies of cell excitability by analyzing the action potentials under conditions more consistent with the cell's natural environment. Though most scientists understand that "current clamp" involves no clamping of anything, they still use the term as it has become the vernacular to describe voltametry.

The most common electrophysiological recording techniques establish electrical contact with the inside of a cell or tissue with a "glass electrode." Such an electrode is fashioned by the experimenter from a fine capillary glass tube, which is then pulled to an even finer (but still hollow of about 1 micrometer diameter for patch-clamp, 0.1 micrometer for intracellular "sharp electrode" recording) tip under heat and allowed to cool. This glass "micropipette" is then filled with a salt solution, and a silver chloride-coated silver wire is inserted to establish an electrochemical junction with the pipet fluid and the tissue or cell into which the pipet is inserted (typically with the aid of a microscope and finely adjustable pipet holders, known as micromanipulators). This salt electrode filling solution varies widely depending on the planned experiment. For sharp microelectrode intracellular recording, high concentration (2-3 molar) salt is used. Potassium chloride, potassium acetate, potassium methylsulfate are salts commonly used to fill shart microelectrode. Note that all contain potassium to match the predominant intracellular ion (although in special circumstance, cesium salts may be used instead of potassium). While a filling solution of potassium chloride gives the smallest and most stable electrochemical "junction potential" when in contact with silver chloride, care must be taken when using chloride as the counter ion to potassium. Injection of chloride ions into the cell will raise the chloride concentration and thus reverse the direction of the cell's choride currents (this characteristic is often used as an easy way to identify chloride currents). The chloride-coated silver wire connects back to the amplifier. Classically, electrophysiologists watched biological currents/voltages on an oscilloscope and recorded them onto chart paper/screen, but now the vast majority use computers. Other requirements are an air or sand table to reduce vibration, and a Faraday cage to eliminate outside interference from the tiny measured currents.

Where experiments require low impedance measurements and no ionic contribution from the microelectrode, the chloride solution is replaced with cerralow, a low melting temperature alloy. The tip is electroplated with soft gold and platinum black, from chloroplatinic acid. Electrodes of this type are used to measure electrical pulses in unmyelinated axons down to 100 nm.

There are four main types of cellular electrophysiological recordings:

1. Intracellular recording. This technique entails impaling a cell, usually a neuron, with a sharp glass electrode and recording either the voltage (current-clamp) or the current (voltage-clamp) across the membrane. This technique is widely used when recording from brain slices or when performing "in-vivo" recording from live animals. While sharp electrode recordings are typically used for recording voltage, voltage-clamp recordings can be performed by impaling larger cells with two sharp electrodes. This is the original voltage-clamp method, which has been superceeded by the superior patch-clamp recording (see below). The two-electrode voltage clamp was used by Alan Lloyd Hodgkin and Andrew Fielding Huxley to describe the ionic-basis of the action potential. This work won them the Nobel Prize in 1963.

2. Extracellular recording. In this technique an electrode is placed on the extracellular medium and field-potentials contributed by the action potentials of many neurons are recorded. Some popular clinical applications of extracellular recording are the electrocardiogram (ECG) and the electroencephalogram (EEG).

3. The patch-clamp technique. With this technique it is possible to clamp the cell potential (voltage-clamp) or the cell current (current-clamp) using a glass micropipette as explained previously. Current-clamp recordings allow the detection and measurement of action potentials in excitable cells such as neurons and the beta cells of the pancreas. Voltage-clamp recordings are very popular for measuring macroscopic currents in which the activity of many ion channels is occurring at the same time. However with this powerful technique it is also possible to measure the current flowing through a single ion channel and study its behavior. There are different modalities of the patch-clamp technique. This technique was developed by Erwin Neher and Bert Sakmann who received the Nobel Prize in 1991.

Cell attached mode.

Advantages: Single channels can be recorded and channel properties are not changed.

Disadvantages: Poor pharmacology.

Whole cell mode.

Advantages: Good pharmacology, large current is recorded because it is the whole cell.

Disadvantages: The cell is perforated so some cell contents are diluted.

Excised patch (inside-out or outside-out patch).

Advantages: Recordings can be taken from individual channels, good pharmacology and the inside/outside solutions can be changed.

Disadvantages: Risk that channel properties are changed.

Perforated patch.

Advantages: It is possible to obtain large, whole cell currents without washing out the intracellular medium.

Disadvantages: Impossible to record from single channels.

4. Axon recording.

Advantages: Chemistry of cell is unchanged, axon pulses are discriminated from the less frequent retrograde cell action potentials.

Disadvantages: Experimental protocol requirements are strict.

OK I should have looked at the talk page first before trying to salvage the present article; the above is great. There should probably be a section on contemporary multi-unit recording techniques (tetrodes etc) if anyone has the energy, and optical recording techniques Gleng 23:22, 23 February 2006 (UTC)

Having (now) looked at the structure of related articles, it seems perhaps sensible to leave details of the techniques to their respective specialised articles, while leaving this page as an overview of the different approaches, mentioning some highlights of their application. I have deleted the technical account of extracellular recording theory though not for this reason alone, but because I do not think that it is correct as far as single unit recording is concerned (though I think it is correct for field potential recording); most obviously, the action potentials recorded extracellularly from cell bodies are not generally inverted w.r.t. intracellular recordings, and there is no reversal when moving from extrcellular recording activity just outside a cell and penetrating that cell. Gleng 23:20, 25 February 2006 (UTC)

[edit] missing links, explanations

relation to photobiomodulation and photobiology?

[edit] Electrotridoshagram/Graph

Last Ten years, I am using a machine for electrical scanning of Human body. Earlier when I recorded the tracings that was taken from the different parts of the human body, I could not well interpreted the tracings which I collected. After continuous efforts, This came in my knowledge that it can quantify the status of AYURVED, which is known INDIAN SYSTEM OF MEDICINE, FUNDAMENTAL'S, which are Vata, Pitta, Kappha. Later after practising I got success to identify the TRIDOSHA BHED [Kinds], which are 15 in numbers. Later I got also success to identify SAPTA DHATU, MAL, OAJ, AGNI, which are basic of AYURVED PHILOSOPHY. Since five thousand years, only Radial Pulse examination was the only source for quantification of these fundamentals.

I am a 62 years old Medical Practitoner, practicing in Modern Western Medicine, Ayurved, the Indian System of Medicine and Homoeopathy including Naturecure etc etc. With this technology, I have also tried to quantify the status of HOMOEOPATHIC FUNDAMENTALS PSORA, SYCOSIS, SYPHILIS laid down by the Father of Homoeopathy, DR SAMUEL HAHNEMANN.

I have tried to diagnose the diseases by this technology. I have found that it capture the electrical behavoiur of the Viscera and body organs. I am capable now to dignose the several disese conditions very earlier because it indicate the worst part of the body, which is a center for trouble. It is a tool for comprehensive treatment of the human body, instead of the partial treatment.

I have named it ELECTRO-TRIDOSHA-GRAM/GRAPH Technology.

User:Dbbajpai1945@sify.com

[edit] Electrotridoshagraphy ETG practiced in CRIA Hospital

Electrotridoshagraphy technology is being practiced in the Central Research Institute of Ayurveda Hospital, Road no. 66, Punjabi bagh, New Delhi, India. ETG technique quantifies the status of the basic fundamentals of Ayurveda in evidence based forms. The technique scans the whole body parts and thus also diagnose the diseases of human body. This a very cheap scanner. user:debbe, 22 March 2007, 06:20 PM IST

Contents