Applications of electrophysiology
Introduction
Electrophysiology is the study of electrical properties of tissues and cells. It is said to be the “gold standard”, when investigating neuronal signalling (Massimo Scanziani et Michael Häusser, 2009). Measurements are taken of the voltage change or the electrical current on an extensive variety of scales from a single ion channel protein (e.g. potassium channels) to large organs (e.g. the heart). There are many areas in which electrophysiology can be applied to.
Applications of electrophysiology
Electrophysiology can be applied to many aspects within the scientific field. It can be used during carotid endarterectomy, during cardiac surgery, during neurosurgical procedures, during endovascular procedures, Arteriovenous malformation resections, electrocorticography, intraoperative stimulation studies, and intracellular recordings involved in the electrical properties of biological cells (Delores Quinonez, 1998). A variety of techniques are needed to analyse these areas involved in electrophysiology.
Electrophysiology techniques
Electrophysiology can be measured intracellular (inside the cell) or extracellular (outside the cell). Depending on what electrical activity is being measured.
Intracellular recordings
Intracellular recordings take place when a measurement of voltage or current is taken across the membrane of a cell. It generally involves inserting an electrode into the cell and another electrode outside of the cell. To measure the membrane potential the electrodes are then connected to an amplifier either in response to a current injected through the intracellular electrode (current clamp) or this current is injected through the intracellular electrode; when the membrane po...
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...rophysiological characterization. Journal of the American Heart Association. 68 (1), 114-130.
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...ending on the size and tolerances of the patients, the voltages could have ranged anywhere form 70 to 130 volts. As a direct effect from the large amounts of electricity being imposed into the patient’s body they will lose consciousness almost immediately. The shocks sent them in to convulsions or seizures and therefore increased their insulin levels. After a patient regains consciousness, he or she will not remember any of the events of being shocked. (Noyes and Kolb).
Therefore any changes in the cell are ascribable to the working electrode. The control of potential of working electrode with respect to reference electrode is equivalent of the controlling of energy of electrons within the working electrode. As shown in Fig. 1.3, scanning the potential in the negative direction makes the electrode a stronger reductant, whereas scanning the potential in the positive direction makes it a better
The purpose of this paper is to inform the reader about Wilder Penfield and his research over electric brain stimulation. This essay will give a brief biography of Wilder Penfield, a description of his research, and finally discuss the insight his experiments provided and the influence they had on our body and behavior in general.
amygdala and the hippocampus. Those parts of the brain link fear and memory together. With
Shining blue light (473 nm wavelength photons) on these cells, in vitro, would cause them to send a nerve impulse 1-2 milliseconds later. Once the light was turned back off, the cells returned to normalcy. In their resting state, a electrical potential exists between the interior of the cell and outside. When ChR2 was activated, its channel would open and cause an influx of positive ions to increase the internal negative charge. This is a similar process to what is occurring all over the brain during every emotion, action, and sensory input we
The second part of this lab was a computer simulation program to illustrate a frog’s electrocardiogram using various drugs in an isolated setting. The computer program entitled “Effects of Drugs on the Frog Heart” allowed experimental conditions to be set for specific drugs. The different drugs used were calcium, digitalis, pilocarpine, atropine, potassium, epinephrine, caffeine, and nicotine. Each of these drugs caused a different electrocardiogram and beats per minute reading. The calcium-magnesium ration affects “the permeability of the cell membrane”(Fox). When calcium is placed directly on the heart it results in three physiological functions. The force of the heart increases while the cardiac rate decreases. It also causes the appearance of “ectopic pacemakers in the ventricles, producing abnormal rhythms” (Fox). Digitalis’ affect on the heart is very similar to that of calcium. It inhibits the sodium-potassium pump activated by ATP that promotes the uptake of extracellular calcium by the heart. This in return strengthens myocardial contraction (Springhouse). Pilocarpine on the other hand
Before ECT begins, patients are given a short-acting anaesthetic and a nerve-blocking agent, paralysing the muscles of the body to prevent them from contracting during the treatment and causing fractures. Oxygen is also given to patients to compensate for their inability to breathe. Then they receive either unilateral ECT or bilateral ECT. In unilateral ECT, an electrode is placed above the temple of the non-dominant side of the brain, and a second in the middle of the forehead. Alternatively in bilateral ECT, one electrode is placed above each temple. After this, a small amount of electrical current (approximately 0.6 amps) is passed through the brain, lasting about half a second. This produces a seizure that lasts up to one minute which affects the entire brain. ECT is usually give...
The brain is part of the central nervous system, which consists of neurons and glia. Neurons which are the excitable nerve cells of the nervous system that conduct electrical impulses, or signals, that serve as communication between the brain, sensory receptors, muscles, and spinal cord. In order to achieve rapid communication over a long distance, neurons have developed a special ability for sending electrical signals, called action potentials, along axons. The way in which the cell body of a neuron communicates with its own terminals via the axon is called conduction. In order for conduction to occur, an action potential which is an electrical signal that occurs in a neuron due to ions moving across the neuronal membrane which results in depolarization of a neuron, is to be generated near the cell body area of the axon. Wh...
In time domain analysis, SDNN, (standard deviation of all normal sinus RR ) an index of overall Heart Rate Variability, RMSSD (root-mean-square of the successive normal sinus RR interval) and percentage of differences between adjacent normal RR intervals exceeding 50 milliseconds (pNN50%) are studied. RMSSD and pNN50 shows greater correlation with parasympathetic nervous activity. In frequency domain analysis, spectral estimates of RR intervals is done by integrating the power as Total Power ( TP) from 0.04 to 0.40 Hz, Low frequency power(LF) from 0.04 to 0.15 Hz, HF (high frequency) power from 0.15 to 0.40 Hz .Power contained in VLF band is not calculated because of its dubious physiologic significance.
The neuron has two important structures called the dendrite and axon, also called nerve fibers. The dendrites are like tentacles that sprout from the cell and the axon is one long extension of the cell. The dendrites receive signals from other neurons, while the axon sends impulses to other neurons. Axons can extend to more than a meter long. Average sized neurons have hundreds of dendrites; therefore it can receive thousands of signals simultaneously from other neurons. The neuron sends impulses by connection the axon to the dendrites of another nerve cell. The synapse is a gap between the axon and the adjacent neuron, which is where data is transmitted from one neuron to another. The neuron is negatively charged and it bathes in fluids that contain positively charged potassium and sodium ions. The membrane of the neuron holds negatively charged protein molecules. The neuron has pores called ion channels to allow sodium ions to pass into the membrane, but prevent the protein molecules from escaping (potassium ions can freely pass through the membrane since the ion channels mostly restrict sodium ions). When a neuron is stimulated (not at rest), the pores open and the sodium ions rush in because of its attraction to the negatively charged protein molecules, which makes the cell positively charged. As a result, potential energy is released and the neurons send electrical impulses through the axon until the impulse reaches the synapse of any neurons near it.
In their inactive state neurons have a negative potential, called the resting membrane potential. Action potentials changes the transmembrane potential from negative to positive. Action potentials are carried along axons, and are the basis for "information transportation" from one cell in the nervous system to another. Other types of electrical signals are possible, but we'll focus on action potentials. These electrical signals arise from ion fluxes produced by nerve cell membranes that are selectively permeable to different ions.
Electroencephalography is a cheap non-invasive technique which has become widely used in studying brain activity to measure the electric potential differences on the scalp produced by the active cortical neurons (5).
...regions of the fish, there are electroreceivers that detect distortions in the electric field (1993). The arrangements of the electrocytes are important because it allows the gymnotid to detect what’s ahead and then use its tail to produce a charge. If electroreceivers were in the tail region, the mammal would detect electric signals a lot slower. In ion-poor waters, like freshwater, allows the gymnotid to generate electric signals because little current is needed to sustain a detectable voltage (Stoddard, 2009).
Scientific interest in the heart goes back centuries. Some of the most basic understandings about the operation and specifically the electrical currents of the heart were discussed during the May 17, 1888 Proceedings of the Royal Society of London by Professor J.A. McWilliam of the University of Aberdeen. The following conclusions were based on his studies of mammalian hearts in cats, dogs, rabbits, rats, hedgehogs, and guinea-pigs.
Electrical Engineers research, develop, design, and test electronic components, products, and systems for commercial, industrial, medical, military, and scientific applications (Cosgrove 749). They are concerned with devices that use small amounts of electricity that make up electronic components such as integrated circuits and microprocessors. By applying principles and techniques of electronic engineering they design, develop, and manufacture products such as computers, telephones, radios, and stereo systems (EGOE, 121). Electrical engineers touch everyone lives through the things they have designed or created. Electrical engineers have invented the lights in your house, the television, the stereo, the telephone, computers, and even your doctor’s blood pressure gauge (Stine 300).