Basically, what you record intracellularly is the change of the membrane battery voltage due to changed permeabilities for differently charged ions. This is the voltage difference between cell's interior and the extracellular space. What you record extracellularly is the voltage drop produced by the current flowing trough the extracellular fluid.
What are intracellular recordings?
Intracellular recordings form a group of techniques used to measure with precision the voltage across, or electrical currents passing through, neuronal or other cellular membranes by inserting an electrode inside the neuron.
What is extracellular recording in electrophoresis?
A far less demanding technique, extracellular recording, involves placing one electrode in close proximity to the excitable cell and the reference electrode at some location in the extracellular fluid. This arrangement records potential changes at the membrane surface rather than across the membrane.
How accurate is intracellular recording of electrical activity?
The intracellular recording technique does allow for very accurate assessment of the electrical activity of a single cell, but it is very difficult to do in vertebrate nerve fibres and can involve considerable damage to the membrane around the electrode tip.
Can extracellular recordings be used with microelectrodes?
However, extracellular recordings can normally only pick up fast electrical events, like action potentials, but fail in case of slower, graded voltages, such as receptor potentials or synaptic potentials. Intracellular recordings can be done only with glass micropipettes (or microelectrodes) at present.
What are extracellular recordings?
Extracellular recording is an electrophysiology technique that uses an electrode inserted into living tissue to measure electrical activity coming from adjacent cells, usually neurons.
What is intracellular recording?
Intracellular recording is an electrophysiology technique that uses a microelectrode inserted into a single cell, usually a neuron, to measure its electrical activity.
What do intracellular recordings measure?
Intracellular recordings form a group of techniques used to measure with precision the voltage across, or electrical currents passing through, neuronal or other cellular membranes by inserting an electrode inside the neuron.
Why is the maximum voltage value not the same for intracellular and extracellular recordings?
Since the resistance of the membrane is much higher than the resistance of the extracellular liquid, the voltage drop on the membrane is much higher than the extracellular voltage (Same Ohm's law V = I x R).
What is biphasic recording?
The BIPHASIC action potential results from the recording system which uses two surface electrodes of opposite polarity. Electrical stimulation of the nerve gives rise to a compound nerve action potential (CNAP). The resulting wave of depolarisation is conducted towards the two recording electrodes.
What is electrophysiological recording?
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.
What is sharp electrode recording?
Intracellular (sharp electrode) recording. This approach uses a fine-tipped (~100 nm) glass micropipette inserted into the neuron, allowing direct recording of electrical events generated by the neuron (membrane potential, resistance, time constant, synaptic potentials and action potentials).
What is multi unit recording?
The phrase "multiunit recording" has been used for the measurement of neuronal activity at a variety of scales, encompassing both averaged measurements of the activity of many thousands (sometimes millions) of neurons, as well as measurement of the individual action potentials from a handful, perhaps a hundred, of ...
What causes the negative phase of an extracellular recording of a cap?
The negative phase of the extracellular recording is due to the different voltages recorded by two wire recording electrodes, as ions pass through the two electrodes at different time.
How is action potential recorded?
There are two major requirements for accurate recording of action potentials: (I) ensuring a tight seal between the cell membrane and the electrode so as to minimize signal loss to the bath medium, and (II) achieving low impedance across the cell-electrode interface so as to increase the signal collection efficiency.
What is Electrophysiology in nervous system?
Electrophysiology comprises investigation of the electrical response characteristics of nerve and muscle. The synonymous term “nerve conduction studies” (NCS) encompasses properties of transmission of electrical current along nerve and muscle fiber membranes. Motor and sensory nerve fibers have different properties.
What is compound action potential amplitude?
The amplitude of the recorded compound action potential is a summation of the individual action potentials from the different axons. When the waves pass the recording site in phase they add constructively and display a higher peak. On the other hand, when they are out of phase, they add destructively.
What is the difference between intracellular and extracellular fluid?
The main difference between intercellular and extracellular fluid is that intracellular fluid is the liquid found inside the cell whereas extracellular fluid refers to all the body fluids outside the cell. The intracellular fluid is also known as the cytosol of the cell, comprising a complex mixture of organelles, proteins, and ions.
Where does the exchange of materials between intracellular fluid and extracellular fluid occur?
The exchange of materials between intracellular fluid and extracellular fluid occurs between the cell membrane.
What is intracellular fluid?
Intracellular fluid (ICF) refers to the fluid found inside the cell, which is separated into a compartment by the cell membrane. The cell membrane forms separate compartments inside the cell as well and these compartments are known as organelles. The content inside the cell, which is encircled by the cell membrane is also called the cytosol. The cytosol mainly comprises water. 70% of the total volume of the cytosol is made up of water. Therefore, the pH of the cytosol is 7.0-7.4. The concentration of sodium, calcium, and chloride ions in the cytosol is lower than that of the external environment of the cytosol. However, potassium and magnesium ion concentration in the cytosol is higher than that of the external environment of the cell. The low concentration of calcium ions in the cytosol allows the signal transduction inside the cell. A lot of proteins are found dissolved in the cytosol. This includes proteins such as microtubules, microfilaments, and intermediate filaments, which make up the cytoskeleton. The cytosol is not considered as an ideal solution due to its highly concentrated nature. The intracellular fluid along with the other fluids are shown in figure 1.
What is the difference between cytosol and tissue fluid?
Cell membrane act as the margin of each fluid. Cytosol is the component of intracellular fluid whereas tissue fluid, blood plasma, and transcellular fluid are the components of the extracellular fluid. The concentration of potassium and magnesium ions in the intracellular fluid is high while the concentration of sodium and calcium ions are high in ...
How much of the body is made up of extracellular fluid?
Extracellular Fluid: The extracellular fluid comprises about 45% of body water.
Which ions are high in extracellular fluid?
Extracellular Fluid: The concentration of sodium ions is high in extracellular fluid and the concentration of potassium ions is low.
Where is extracellular fluid found?
Extracellular Fluid: The extracellular fluid is found outside the cell.
What is intracellular recording?
Intracellular recordings form a group of techniques used to measure with precision the voltage across, or electrical currents passing through, neuronal or other cellular membranes by inserting an electrode inside the neuron.
What are intracellular electrodes made of?
Intracellular electrodes are made of thin glass pipettes that are pulled to a very fine and sharp ending or tip. Although historically this was also done manually, special devices, microelectrode pullers, have been used since 1950s, and microprocessor-controlled pullers since the end of 1980s. In all pullers the glass is heated to a melting point, subsequently pulled and cooled quickly, either passively or with the help of additional air flow. In this process the electrode tip is formed when the two halves are separated. The sharpness of the resulting electrodes depends on the glass type (borosilicate, aluminosilicate or quartz), the manner of pulling, and the puller device technology, but the outer diameter of the tip is typically of the order of 50-500 nanometers. The fabrication method crucially defines the usefulness and the properties of the microelectrode, and special attention has to be paid to the selection of the puller. Some pullers (because of the technological method used) may be more suitable for some specific purpose than another.
How to manipulate a cell?
A straight-forward manipulation of the recorded cell could be done by injecting an electrical current through the recording electrode. This is normally done to probe the passive or active properties of the cell membrane. The current injection causes a displacement of the cell’s membrane voltage, but also a voltage change in the electrode resistance. Various techniques exist to avoid this electrode artifact. The oldest is realized by a bridge-balance circuit in the amplifier, which can only compensate for the resistive artifact, not the effects of the capacitance. The latter can be compensated with newer methods requiring the use of time-sharing (switched) techniques.
What is the tip potential of a glass microelectrode?
The tip potential may be up to nearly -100 mV, and it is the larger, the sharper is the electrode.
Is glass a capacitance?
The glass electrode has also a (distributed) capacitance, which is high enough (in the range of picoFarads) to define, with the electrode resistance, a large time constant for the electrode (the time constant ).
Can you record intracellular recordings with glass?
Intracellular recordings can be done only with glass micropipettes (or microelectrodes) at present. The basic idea is to insert a conductive medium (the electrolyte filling the pipette, e.g. 1-3 M KCl) through the cell membrane with minimal damage to the cell.
Can extracellular recordings be done with glass?
Intracellular recordings can be done only with glass micropipettes (or microelectrodes) at present.
Membrane Potential and Action Potential
Intracellular recordings from neurons in the mammalian central nervous system (CNS) reveal that different types of neurons exhibit different resting membrane potentials.
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Vision I
Intracellular recordings of photoreceptors in the intact animal are demanding, and values for resting potential, and input resistance may often be underestimated due to the shunt resistance introduced by electrode penetration. The best recordings report resistances of up to ∼200–500 MΩ, and resting potentials of ∼−70 mV ( Juusola, M. and Hardie, R.
Electrogenesis of the Electroretinogram
In retinal intracellular recordings from many different species, high-frequency oscillations have rarely been observed in responses of photoreceptors, horizontal, or bipolar cells. In contrast, membrane oscillations have been observed in recordings from amacrine cells, especially in turtle and fish retina.
Where is the electrode placed in extracellular recording?
A far less demanding technique, extracellular recording, involves placing one electrode in close proximity to the excitable cell and the reference electrode at some location in the extracellular fluid. This arrangement records potential changes at the membrane surface rather than across the membrane.
What happens to the potential of a CAP as it progresses between two recording electrodes?
As the CAP progresses between both recording electrodes, the recorded potential returns to the base line (no voltage difference between the two recording electrodes).
What happens if two electrodes are not separated by a large distance?
If the electrodes are not separated by such a large distance, the two phases will not be of equal amplitude. The CAP will not have completely passed the first electrode before reaching the second. Adding the two opposite signed deflections will reduce the amplitude of the negative phase and decrease the apparent width of both.
Why is there no deflection recorded in an amplifier?
There will be no deflection recorded because the amplifier takes the difference of the two inputs before passing the signal on to the A/D converter.
How to measure trans-membrane potential?
One can measure a single trans-membrane potential by inserting a glass pipette into one cell and recording the potential changes with respect to an extracellular reference electrode. This intracellular technique is used, for example, to record the resting membrane potential of a muscle in the Resting Membrane Potential Lab.
How many electrodes are there in a differential amplifier?
There are two wire recording electrodes (R1 and R2) touching the nerve, each connected to one input of the differential amplifier. The animation below illustrates how the shape of the CAP depends on the position of the two electrodes with respect to the travelling CAP. For an in-depth explanation, please read on below.
Is an action potential intracellular or extracellular?
Action potentials recorded extracellularly differ from those recorded intracellularly in several important respects. The size of any one action potential will be obviously reduced. The shape of the waveform for any one action potential will depend on the exact geometry of its contact with the electrode. Extracellular techniques are therefore better suited where one only wants to know that an action potential has occurred or to record the activity of an entire population of cells.
History
Basic Principles of Intracellular Recording
- When the investigator desires to record neuronal membrane signals reliably with high signal-to-noise ratio in situ, that is, in tissue, the intracellular recording technique has to be employed. Although in some cases the use of other methods, like whole-cell patch clamp, would be possible, the intracellular recording technique remains the method of choice for this purpose. Certainly, ex…
Fabrication and Properties of Glass Microelectrodes
- Fabrication
Intracellular electrodes are made of thin glass pipettes that are pulled to a very fine and sharp ending or tip. Although historically this was also done manually, special devices, microelectrode pullers, have been used since 1950s, and microprocessor-controlled pullers since the end of 198… - Electrical properties
The electrolyte inside creates a (distributed) resistor, but normally most (probably more than half) of the resistance resides in the tip. Typical resistances of intracellular electrodes to DC-current are 10-500 Megaohms. The resistance depends not only on the length of the electrode shank and th…
Electrode in The Cell - Voltage Recording
- When the electrode is advanced through the cell membrane in a measurement set-up, a recording circuit is formed. A voltage-follower based amplifier (an “Intracellular amplifier”) is normally used with glass microelectrodes. It is a DC-amplifier with a large input resistance (of the order of ohms). How fast signals can be recorded (how reliable is t...
Advanced Techniques
- Current injection
A straight-forward manipulation of the recorded cell could be done by injecting an electrical current through the recording electrode. This is normally done to probe the passive or active properties of the cell membrane. The current injection causes a displacement of the cell’s memb… - Voltage clamp
Classical voltage clamp with two or more electrodes (TEVC) requires the use of intracellular techniques, whereby one or two electrodes record intracellular voltage and an additional electrode injects current. A voltage-clamp amplifier forms a feedback circuit between the recorded voltag…
References
- Hodgkin A.L., Huxley A.F., and Katz B. (1952) Measurement of current-voltage relations in the membrane of the giant axon of Loligo. J. Physiol. 115(4):424-48.
- Hodgkin A.L. and Huxley A.F. (1952) A quantitative description of membrane current and its application to conduction and excitation in nerve. J. Physiol. 117(4):500-44
- Ling, G. and Gerard, R.W. (1949). The normal potential of frog sartorius fibres.
- Hodgkin A.L., Huxley A.F., and Katz B. (1952) Measurement of current-voltage relations in the membrane of the giant axon of Loligo. J. Physiol. 115(4):424-48.
- Hodgkin A.L. and Huxley A.F. (1952) A quantitative description of membrane current and its application to conduction and excitation in nerve. J. Physiol. 117(4):500-44
- Ling, G. and Gerard, R.W. (1949). The normal potential of frog sartorius fibres.
- Marmont G. (1949) Studies on the axon Membrane; a new method. J Cell Physiol. 34:351-82.
