Neuronal cable theory is a set of assumptions and results relating to the propagation and interaction of electrical signals in spatially extended nerve cells.
What is cable theory of nerve conduction?
On the basis of this equivalent circuit model, the conduction of the nerve is often described by using a theory in which the conduction is regarded as an electric current on imaginary electric longitudinal leads running inside and outside the axon membrane, known as a cable theory (Koch, 1984).
What is cable model?
Classical cable theory uses mathematical models to calculate the electric current (and accompanying voltage) along passive neurites, particularly the dendrites that receive synaptic inputs at different sites and times.
Are dendrites passive cables?
Information flows in the nervous system from the soma to the axon and then to the dendrites. In most models, the dendrites are regarded as being passive electrical cables.
What are cable properties?
– properties of the nerve; axon, cell body and dendrite that affect distance and speed of a membrane potential. – passive conduction properties are called cable because they are analogous to properties of long copper telecommunication cables (before satellites)
What is the function of axoplasm?
Axoplasm is integral to the overall function of neurons in propagating action potential through the axon. The amount of axoplasm in the axon is important to the cable like properties of the axon in cable theory.
What is cable constant?
Impedance – Cable constants calculation is an easy-to-use tool for positive and zero sequence impedance calculations. It uses the user-friendly graphical interface of the cable editor and the complete ETAP cable library.
Who Discovered cable theory?
William Thompson (Lord Kelvin) developed cable theory in the 1850s as a way to model the decay of signals along underwater telegraph cables. Hodgkin and Rushton applied it to passive conduction along axons (Hodgkin and Rushton, 1946).
How do you solve cable equations?
λ = r m r e + r i and τ = r m c m , where ri and re are the intracellular resistance (in Ω/cm) and extracellular resistance (in Ω/cm). The values rm and cm are the membrane resistance (in Ω/cm) and membrane capacitance (in F/cm), respectively.
What is a time constant neuron?
The index is denoted by the symbol τ and called the time constant. It is defined as the amount of time it takes for the change in potential to reach 63% of its final value. … Therefore, if this neuron had a time constant of 5 msec, then in 5 msec the membrane potential would reach -53.7 mV.
What is a cable modem do?
A cable modem delivers high-speed Internet to your devices by using coaxial cables that connect to the back of the modem and the bolt-like outlet in your wall or on your cable box. DSL and dial-up modems use a cable that connects to your phone line. … You do not need a modem for fiber-optic technology Internet service.
What is the membrane resistance?
The membrane resistance is a function of the number of open ion channels, and the axial resistance is generally a function of the diameter of the axon. The greater the number of open channels, the lower the rm. … where rm is the resistance across the membrane and I is the current flow.
What is the relationship between the cable radius and length constant?
The larger rm (less leaky) is, the larger the length constant will be. ri is the resistance of the intracellular fluid (called axoplasm) inside the axon. Conversely, the lower ri is, the larger the length constant will be.
What is membrane capacitance?
Membrane capacitance is the electrical capacitance associated with a biological membrane, expressed in units of Farads (F). … Because membrane capacitance determines the time constant of a neuron (τm ¼ rmcm), it plays an important role in the integration of the electrical inputs a neuron receives.
Why the upper part of brain is white?
It contains nerve fibers (axons), which are extensions of nerve cells (neurons). Many of these nerve fibers are surrounded by a type of sheath or covering called myelin. Myelin gives the white matter its color.
How does myelination affect time constant?
In textbooks, it says that myelination doesn’t really affect the time constant as tau=RC where R is the membrane resistance and C is the membrane capacitance. Myelin increases membrane resistance while decreasing membrane capacitance so there isn’t really an overall effect on the time constant.
What are the two types of graded potentials?
Graded potentials can be of two sorts, either they are depolarizing or hyperpolarizing (Figure 1).
How does myelin increase conduction velocity as explained by cable theory?
By acting as an electrical insulator, myelin greatly speeds up action potential conduction (Figure 3.14). … For example, whereas unmyelinated axon conduction velocities range from about 0.5 to 10 m/s, myelinated axons can conduct at velocities up to 150 m/s.
What is Axolemma and axoplasm?
The axolemma is the cell membrane of an axon. The similar term axoplasm refers to the cytoplasm of an axon. The axolemma is responsible for maintaining the membrane potential of the axon, and contains ion channels through which ions can flow rapidly.
What are Schwann cells?
Schwann cells serve as the myelinating cell of the PNS and support cells of peripheral neurons. A Schwann cell forms a myelin sheath by wrapping its plasma membrane concentrically around the inner axon.
What is the function of Neurofibrils?
Neurofibrils are bundles of neurofilaments that extend into the dendrites and axon, and provide internal support to them. … The cell body.
| Structures | Functions |
|---|---|
| Neurofibrils | Determine shape of neuron |
| Microfilaments | Help to form and retract cell processes; assist in cellular transport |
What is the range of super tension cable?
Super-tension cables — the operating voltage of super tension cable is from 22 kV to 33 kV. Extra high-tension cables — from 33 kV to 66 kV. Extra super voltage cables — beyond 132 kV.
Which of the following faults is most likely to occur in cables 1 point?
Detailed Solution. Open circuit fault, short circuit fault and breakdown of cable insulation, all these faults are frequently occurs on cables.
What should be the desirable characteristics of insulating materials used in cables?
The insulating materials used in cables should have the following properties : (i) High insulation resistance to avoid leakage current. (ii) High dielectric strength to avoid electrical breakdown of the cable. (iii) High mechanical strength to withstand the mechanical handling of cables.
What is an action potential?
The action potential is an explosion of electrical activity that is created by a depolarizing current. This means that some event (a stimulus) causes the resting potential to move toward 0 mV. When the depolarization reaches about -55 mV a neuron will fire an action potential. This is the threshold.
What is sodium conductance?
A rapidly inactivating inward sodium conductance underlies the depolarizing phase of the action potential. Each sodium channel is composed of a complex of three polypeptide subunits: a major α subunit and two smaller β subunits that influence the kinetic properties of the α subunit.
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