What is chronaxie and its significance?
Chronaxie is the minimum time required for an electric current double the strength of the rheobase to stimulate a muscle or a neuron. Rheobase is the lowest intensity with indefinite pulse duration which just stimulated muscles or nerves.
What are rheobase and chronaxie?
Rheobase—The minimum current required to depolarize a nerve given an infinite duration of stimulation. Chronaxie—The duration of current required to depolarize a nerve to threshold when the current is two times the rheobase.
What is the significance of rheobase?
Mathematically, rheobase is equivalent to half the current that needs to be applied for the duration of chronaxie, which is a strength-duration time constant that corresponds to the duration of time that elicits a response when the nerve is stimulated at twice rheobasic strength.
What is the difference between rheobase and threshold potential?
The threshold , or minimal stimulus , is defined as “the electrical stimulus whose strength (or voltage) is sufficient to excite the tissue. Rheobase is defined as “the minimum strength (voltage) of stimulus which can excite the tissue”.
What muscle has highest chronaxie?
Among the different types of muscle tissue, skeletal striated muscles have the briefest chronaxie. The chronaxie of the heart muscle is more prolonged, and that of the smooth muscles is the most prolonged.
How do you calculate rheobase and chronaxie?
The Chronaxie is a duration measurement, corresponding to twice the Rheobase. From the graph above, the Rheobase is approximately 0.64 volts, and the Chronaxie is about 0.16 ms….
| Strength (V) | Duration (ms) |
|---|---|
| 0.64 | 1.0 |
| 0.8 | 0.42 |
| 1.0 | 0.25 |
| 1.2 | 0.18 |
How do you find rheobase?
Step 1 – determine the rheobase, which is the minimum Stimulus Strength that will produce a response. This is the voltage to which the Strength-Duration curve asymptotes. In the example above, this value is 0.35 V. Step 2 – calculate 2´rheobase ( = 0.7 V in the above example).
How can you get the rheobase and chronaxie using strength duration curve?
A: Given that two nerves have the same Rheobase, the Chronaxie (the stimulus duration corresponding to twice the rheobase) can give an indication of their relative excitabilities. In the strength-duration curve to the right, nerve B is the more excitable….
| Strength (V) | Duration (ms) |
|---|---|
| 0.8 | 0.42 |
| 1.0 | 0.25 |
| 1.2 | 0.18 |
| 1.42 | 0.134 |
Why is chronaxie shorter in red muscles?
Chronaxie is defined as the shortest duration of stimulus required to excite a tissue by a current strength equal to twice of Rheobase voltage. Chronaxie of a tissue is a definite measure of its excitability. A less excitable tissue has a longer chronaxie, whereas a more excitable tissue has a shorter one.
What is innervated and denervated muscles?
Innervated muscles refer to the muscles that have a good supply of nerves, while denervated muscles refer to muscles that do not have a good supply of nerves.
What is rheobase physiology?
Medical Definition of rheobase : the minimal electric current required to excite a tissue (as nerve or muscle) given an indefinitely long time during which the current is applied — compare chronaxie.
How do you determine chronaxie and rheobase?
What is SD curve?
Strength duration curve is a graph between electrical stimuli of different intensities and recording the time needed by each stimulus to start the response. S-D curve should be plotted after 20th day of injury/lesion. S-D curve should be plotted after 20th day of injury/lesion.
How do you calculate chronaxie and rheobase?
The Chronaxie is a duration measurement, corresponding to twice the Rheobase. From the graph above, the Rheobase is approximately 0.64 volts, and the Chronaxie is about 0.16 ms….
| Strength (V) | Duration (ms) |
|---|---|
| 0.8 | 0.42 |
| 1.0 | 0.25 |
| 1.2 | 0.18 |
| 1.42 | 0.134 |
Why is chronaxie more in infants?
The tissues of the new-born child possess chronaxies which are ten times longer than those of adults. This explains the slower movements of infants. ii. Tissue of cold-blooded animals generally possesses longer chronaxies (i.e., they are more sluggish) than those of warm-blooded types.
What is denervation and reinnervation?
If a substantial number of motor axons within a nerve trunk have deteriorated (i.e., denervation has occurred), increasing voluntary effort will result in overly rapid firing of a reduced number of motor unit potentials (a reduced recruitment pattern). Denervated muscle fibers can often be reinnervated.
What is a denervation potential?
There are certain classic findings on needle EMG that strongly indicate muscle denervation due to a neurogenic (i.e., lower motor neuron) disorder. The hallmark of denervation is fibrillation potentials; these are spontaneous repetitive action potentials of single denervated muscle fibers.