Applications of electrophysiology Introduction Electrophysiology is the study of electrical

Pinnington, N., Elliott, A., Sciences, F. of L., Manchester and Kingdom, U. (2007) Proceedings of the physiological society. Available at: http://www.physoc.org/proceedings/abstract/Proc%20Physiol%20Soc%208PC39 (Accessed: 3 March 2016).

Extracellular recording electrodes were used to measure the compound action potentials (CAPs) in a cockroach leg nerve. CAPs are the summations of all present action potentials (APs) in the individual axons of the nerve. When an AP is conducted along an axon, sodium channels open and positively charged sodium ions enter the axon. Therefore the inside and the outside voltage changes. The voltage changes in the extracellular fluid were measured. A depolarisation of the axonal membrane causes a local negative charge in the extracellular fluid. The summation of all the voltage changes in the extracellular fluid at a specific position is measured by the recording electrodes.

DROGMAN G, RAEMAEKERS L & CASTEELS R 1977, ‘Electro- and pharmomechanical coupling in the smooth muscle cells of the rabbit ear artery’, Journal of General Physiology, vol. 70, no. 2, pp. 129-148

An electrical stimulus was applied to the heart; the following graph shows the refractory period of the frog’s heart when an extra-systole was induced. It can be seen that right after the recording was marked “Refractory 3,” an extra-systole was detected.

Have you ever been shocked or electrocuted back to life? In December 1818, Andrew Ure claimed, “by stimulating the phrenic nerve with electric charges life could be restored in cases of suffocation, drowning, or hanging”. The medical advances accomplished throughout all the years has been truly amazing, from discovering blood cells, using human skin cells to create embryonic stem cells and many more.

As an action potential travels down the axon of the presynaptic neuron, the action potential reaches the axon terminal synaptic vesicles which migrate toward the synapse. They then release neurotransmitters into the synaptic cleft. The neurotransmitters travel through the synaptic cleft and bind to ligand-gated ion channels on the postsynaptic neuron membrane. The channels open and allow chemicals to enter the cell (i.e. sodium). Then positively charged sodium enters the cell and causes the cell to depolarize. The depolarization spreads down the axon and an action potential is generated. The process then starts over at the axon terminals.

Both electrical and chemical forces combine to determine the resting membrane potential of the cell. Although the resting membrane potential of most cells is normally negative, the selective permeability of the membrane allows certain ions in and out, causing the neuronal membrane voltage to become depolarized (more positive), or hyperpolarized (more negative). Key ions involved in muscle membrane potential are sodium, potassium, and chloride, which move via passive or active diffusion through ion channels and transporter pumps (Baierlein et al. 2011). The Nernst equation predicts the membrane voltage based on the assumption that the membrane is only permeable to one type of ion. In this investigation, we are seeking to understand the basis for how different ions interact to produce the membrane potential of DEM, DEL1, and DEL2 crayfish muscle

When a membrane is excited depolarization begins. When the membrane depolarizes the resting membrane potential of -70 mV becomes less negative. When the membrane potential reaches 0 mV, indicating there is no charge difference across the membrane. the sodium ion channels start to close and potassium ion channels open. By the time the sodium ion channels finally close. The membrane potential has reached +35 mV. The opening of the potassium channels allows K+ to flow out of the cell down its electrochemical gradient ( ion of like charge are repelled from each other). The flow of K+ out of the cell causes the membrane potential to move in a negative direction. This is referred to as repolarization. ( Marieb & Mitchell, 2009). As the transmembrane potential comes back down towards its resting potential level and the potassium channels begins to close, the trasmembrane potential level goes just below -90mV, causing a brief period of hyperpolarization (Martini, Nath & Bartholomew, 2012). Finally, as the potassium channels close, the membrane turns back to its resting potential until it is excited or inhibited again.

The findings of this experiment reinforced the hypothesis that the resting membrane potential is most influenced by the ion potassium. We were able to deduce this through the collection of a multitude of intracellular and extracellular recordings, such as the one shown below in Figure 1. This shows how this experiment was able to record every single resting membrane potential in all three different muscle groups under all six solutions.

In the first part of the practical, we will dissect the heart of a sheep and observe its anatomical structure. We will also examine the structure of blood vessels at a microscopic level. My hypothesis is that by examining the anatomy of the cardiovascular system, we will be able to detect differences in both vessels and the chambers of the heart. In the second part of the practical we will examine the electrical activity of the heart. In doing so my aim will be to produce a familiar ECG reading containing a P wave, QRS complex and T wave. Futhermore, we will take blood pressure readings by listening to the korotkoff sounds of the heart using a sphygmomanometer and stethoscope. We hypothesis that the higher the arm position is from the ground, the smaller the blood pressure reading will

Whenever the balance is altered, the process of transmitting electrical signals, which is called action potential initiates by carrying information across a neuron’s axon; which is called resting membrane potential. This process occurs as uneven ions distribution flow across cell membrane, creating electrical potential. As a result, the duration of active potential can be as fast as 1 ms. Similarly, the average resting membrane is between -40 mV and -80 mV. Since the membrane from inside is more negatively charged than the outside, it reflected on the negative average voltage readings of the resting membrane.

The ECT was being administered in theatre in the general hospital. In advance of the treatment the clients vital signs were checked and it was confirmed that consent was given. The client was then transferred to theatre. Present in the room was the anaesthesiology team, ECT nurse, surgical nurse, psychiatric consultant, registrar, psychiatric nurse and student nurse. Initially the client was hooked up to a machine to record her vital signs, anaesthetic and muscle relaxants were administered and the client was ventilated with 100% oxygen. Under anaesthetic the client has reduced capacity to breathe hence oxygen is administered, pure oxygen also reduces the deleterious effects on memory. Anaesthesia and muscle relaxants reduce the seizure threshold and the risk of injuries from motor activity during the seizure (Fink 2009). The client remained in the supine position, conductive jelly was applied bilaterally to the temples and the psychiatrist administered the electrical stimulus. The choice between unilateral and bilateral electrode placement remains

Biphasic CAP. For the recording of a biphasic compound action potential, both the positive and negative recording electrodes were used, with the negative recording electrode at position ‘D’ and the positive recording electrode at position ‘E’ (refer to Figure 1). The extracellular bipolar recording takes the difference between what the negative electrode picked up and what the positive electrode picked up. The first, positive deflection of the CAP was caused by the extracellular negative charge of the action potential recorded by the negative electrode subtracted from the positive resting charge at the positive electrode—a positive value minus a negative value yields a positive value, hence the positive, upward deflection of the

The purpose of these lab exercises is to understand the function and importance of an electrocardiogram. This lab will demonstrate how stress levels or different elevations can affect human heart rate. Furthermore, the equipment used in the experiment will show the functions in the right and left arm; as well as, in the right and left ankles. Finally, the lab will serve a purpose as a way to know how to read an electrocardiogram and calculate the heart rate.

The neurons in the brain tissue communicate with each other via electrical signals, generating measurable action potential activity. Electrophysiological techniques have been developed to measure this electrical activity. Electrophysiological techniques are some of the classic methods of brain research, partly because they are very sensitive and accurate. They provide quite a number of insights into the subject’s mind as well as allow for study of how the brain works. They can be used during brain surgery as well as when the patient is awake and conscious, as the brain itself does not sense pain during the measurements. Although electrophysiology has been around for close to half a century, it has attained appreciable advances only in the last two decades. These advances have revolutionized the study of brain structure and functions, allowing neurophysiologists to monitor the brain’s activities directly during experiments (Sutler et al., 1999). Even with its significant impact in neurology, however, its presence has been so commonplace that many people no longer realize its ubiquity. This essay explores three electrophysiological techniques namely patch clamp, sharp electrodes, and brain slice recording. It describes how each of these techniques works as well as how advances in the techniques have