Materials for auditory self-work. 4.1. List of study practical tasks necessary to perform at the practical class.
4.1. List of study practical tasks necessary to perform at the practical class.
Materials and methods: electromyography, ready electromyograms.
Investigation object: person.
Task 1.
Acquaintance with EMG qualitative analysis
Qualitative EMG analysis –EMG character describing:
– saturated;
– non-saturated;
– EMG rounding curve character – activity slow or sharp increasing and decreasing;
– activity phases number.
Task 2
Acquaintance with EMG quantitative analysis
This analysis includes:
– activity and rest phases duration;
– temporary intervals between activity beginning in different muscles;
– common electrical muscular activity level (the most important parameter) – is determined by EMG oscillations altitudes measurement and by means of special devices. Moda (the most common oscillations numeral, number that are repeated the most often in variation row) is usually taken as the level of summary EMG oscillations altitude. It’s necessary to measure all main oscillations during definite time period (for example, for 0,5 sec) and to determine the altitude meaning the most often meets from peak to peak. Second way of summary oscillations altitude assessment is to measure 10 most expressed oscillations at definite time period with farther estimation of their middle meaning. Then the altitude of this section must be compared with proper meaning of calibrating signal and EMG altitude received must be expressed in mcV. Received EMG summary altitude is a conditional quantity but very important because it’s a proportional to (it’s correlated to) isometric muscular contraction intensivity at any assessment way.
– Oscillations frequency – under norma is great (100 oscillations per second) and isn’t connected with muscular contraction force. Thus, EMG looks like saturated one. In such cases EMG is not analysed.
Fig. 5. Masticatory muscles EMG (usual one-sided mastication).
Fig.6. Scheme of EMG summary amplitude estimation. Horizontal lines run on peaks of most frequent amplitudes; vertical line is summary amplitude.
Fig. 7. Non-saturated EMG (it is possible to estimate frequency and altitude on it).
5. Literature recommended:
1. Methodical instructions on Normal Physiology on practical classes for dental and medical students.-P.9-12.
2. Guyton A.C. Textbook of Medical Physiology.-NY, 1992.-P.134-135.
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6. Materials for self-control:
A. Control questions.
1. Electromyogram as diagnostic method.
2. Principles of EMG qualitative and quantitative analysis.
3. EMG clinical application (in neurology, traumatology, surgery, pediatry, surgical, therapeutical, children and orthopedical dentistry particularly).
LESSON 4
Skeletal muscles contraction mechanisms investigation
The topic studied actuality.
Doctors meet patients with skeletal muscles disorders at different pathological conditions. Myopathies (both innate and acquired) are widely-spread nowadays. Gnatodynamometry, myoartrography belong to widely-spread diagnostic methods in dentistry.
Nearly 40% of the body is skeletal muscles. One can differentiate the following types of muscular contraction according to the shortness size:
§ isotonic is the muscular contraction, at which its fibers are shortened at a constant external load (under real conditions such type is practically absent);
§ isometric is a muscular activation type, at which it develops a strain (tension) without the length change, it underlies the static work;
§ auxotonic is a regimen, in which the muscles develop a tension and are shortened, such reductions are the characteristic of walking, run, sailing, tongue contractions. This regimen is the mostly widely-spread in human organism.
1. Study aims:
To know: skeletal muscle excitement changings during its contraction; contractive regimes and types; contraction and relaxation molecular mechanisms.
To be able to: draw singular and tetanic (grouped) contractions.
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