PHYSIOLOGY OF EXCITABLE TISSUES

STATE GOVERNMENT-FUNDED EDUCATIONAL INSTITUTION OF HIGHER PROFESSIONAL TRAINING UNDER THE MINISTRY OF HEALTH OF THE RUSSIAN FEDERATION VOLGOGRAD STATE MEDICAL UNIVERSITY DEPARTMENT OF NORMAL PHYSIOLOGY GUIDE BOOK PRACTICAL MANUAL IN NORMAL PHYSIOLOGY PHYSIOLOGY OF EXCITABLE TISSUES For 2 nd year students of MD-programme Name: Group: Volgograd, 2012

УДК Physiology of excitable tissues. Guide book. Practical manual in normal physiology. Volgograd: VolgSMU, 2012. 13 p. Compiled by: Klauchek S. V., Lifanova E. V., Khvastunova I. V., Kudrin R. A., Akhundova R. E., Doletsky A. N., Schmidt S. A. Approved by the Central Methodology Board of the Volgograd State Medical University. This manual summarizes the practical tasks of human physiology of excitable tissues. It caters for teachers and students in the English-speaking medium of higher medical educational institutions. Volgograd State Medical University, 2012. 2

CONTENT Practical class 1. Introduction to the physiology 4 Practical class 2. Excitable tissues: nerve tissue 7 Practical class 3. Excitable tissues: muscle tissue 9 Practical class 4. Synaptic transmission 11 Practical class 5. Concluding class devoted to the themes Introduction to the physiology, Excitable tissues: nerve tissue, Excitable tissues: muscle tissue, Synaptic transmission (intermediate oral examination). 13 3

Practical class 1. Introduction to the physiology. Questions for discussion 1. Biomembranes, their structure and functions. 2. Ionic channels, their classification and role. 3. Types of transport through biomembranes. 4. The concept of excitability. Properties of excitable tissues. 5. Basic laws of stimulation. «All-or-none» law. Threshold of stimulation. 6. Strength-duration curve. 7. Accommodation. 8. Basic laws of stimulation. Electrotonic potentials. 9. Resting membrane potential. Its ionic basis. Practical works 1. Making of nerve-muscular preparation. 2. First and second experiments of Galvani. 3. Secondary tetanus. Books recommended 1. Ganong W. F. Review of Medical Physiology. 20th ed; McGraw-Hill Companies, Inc., 2001. P. 1-17, 27-35. 2. Guyton A. C., Hall J. E. Textbook of Medical Physiology, 12th ed; WB Saunders, 2005. P. 43-59. Practical work 1. Making of nerve-muscular preparation. Objective: studying how to make a nerve-muscular preparation. Technique. Making a nerve-muscular preparation includes 3 stages. They are the following: I. Making a preparation of hind legs. 1. Wrap up a frog into a gauze napkin. 2. Insert the scissors into the oral cavity and cut off the frog s maxilla behind the eyes. 3. Put a probe into the cerebrospinal canal and destroy the spinal cord. 4. The spine, internal organs, skin and muscles of the abdominal wall should be cut off. 6. Holding the backbone with one hand, take the skin edge with the other hand with the help of a napkin and peel it off. 7. The preparation of the frog s hind legs is ready. II. Preparation of a rheoscopic leg. 1. The preparation of the frog s hind legs should be taken by the backbone and bent so that the coccyx should protrude. 2. Cut out the coccyx with a pair of scissors. 3. Put the preparation with the abdomen upwards. 4. Try not to touch the nerve trunks of the sacral plexus; the backbone and other tissues should be cut along the middle line in order to separate the legs from each other. Holding the remainder of the backbone, find the ischiadic nerve; remove the pelvic bone cutting it near the backbone and the hip. III. Making a nerve-muscular preparation. The next stage is the preparation of the ischiadic nerve and the calf muscle. 1. To prepare the nerve, the femur has to be located with it`s back surface up; the muscles have to be put apart and the sciatic nerve is prepared lengthwise. 4

2. Raise the nerve by the remainder of the backbone and cut carefully the adjacent tissues with the help of a pair of scissors. 3. Cut off the leg above the knee-joint. 4. The remainder of the femur muscles should be also removed. 5. After that place the scissors under the Achilles tendon, separate it lengthwise and cut below the sesamoid bone. 6. Cut off the leg below the knee-joint. 7. The nerve-muscular preparation of the gastrocnemius muscle and the sciatic nerve is ready. 8. Wrap the preparation into the napkin moistened with Ringer solution and put it into Petri dish. Result: 5

Practical work 2. The first and second experiments of Galvani. Objective: familiarizing with the 1st and 2nd experiments of Galvani. Technique. I) The first experiment of Galvani (contraction stimulated by metal exposure). 1. Make a preparation of a frog s hind legs. 2. Holding the preparation by the remainder of the spine, place one of the branches of galvanic pincers under the nerve roots of the sacral part of the spinal cord. 3. Touch the femur muscles of a frog with the second branch of galvanic pincers. 3. Observe muscle contraction of the preparation. The muscles will contract as long as they are exposed to metal galvanic pincers. Draw a scheme of the experiment and make a conclusion. Result: Technique. II) The second experiment of Galvani (contraction which is not stimulated by metal exposure). 1. Make a preparation of a frog s rheoscopic leg and a damaged muscle of a nerve-muscluar preparation. 2. Apply the nerve of the rheoscopic leg quickly to the damaged area of the muscle so that it could touch simultaneously the damaged and the intact surface of the muscle. 3. Observe the contraction of leg muscles. 4. The experiment is successful, if the nerve is highly excitable and the femur muscle has just been incised. Draw a scheme of the experiment and make a conclusion. What are the differences between the 1st and 2nd experiments of Galvani? Result: 6

Practical work 3. Secondary tetanus. Objective: observing the arising currents of action in excited tissues and their possible transmission to other tissues. Technique. 1. Make a preparation of a frog s rheoscopic hind legs and fix it in a support. 2. Place the nerve of the second preparation along the gastrocnemius muscle of the first hind leg. 3. Using electrodes of a stimulator, send rhythmic stimuli to the nerve of the first preparation to cause tetanic muscle contraction. 4.Observe muscle contraction of the second rheoscopic leg. Draw a scheme of the experiment and make a conclusion. Result: Practical class 2. Excitable tissues: nerve tissue. Questions for discussion 1. Action potential. Electrogenesis and ionic basis of action potential. 2. General characteristics of a single excitation cycle. 3. Local response and propagation of excitation on biomembrane, their comparative characteristics. The firing level. 4. Changes in excitability during action potential (compare phases of action potential with the phases of excitability changes). 5. Mechanism of excitation conduction in nerve fibers (in myelinated and unmyelinated nerve fibers). 6. Laws of conduction in nerve fibers. 7. Types of nerve fibers and their functions. 7

Practical works 1. Importance of physiological integrity of the nerve for conducting excitation. 2. Isolated conduction of excitation along the nerve fiber. 3. Bilateral conduction of excitation. Books recommended 1. Ganong W. F. Review of Medical Physiology. 20th ed; McGraw-Hill Companies, Inc., 2001. P. 49-61. 2. Guyton, A. C., Hall, J. E. Textbook of Medical Physiology, 12th ed; WB Saunders, 2005. P. 60-70. Practical work 1. Importance of physiological integrity of the nerve for conducting excitation. Objective: proving the importance of physiological integrity of the nerve for conducting excitation in the course of the experiment. Technique. A frog`s rheoscopic leg should be used for the experiment (see practical work1). 1. Fix the bone of a frog s rheoscopic leg in a support. 2. Apply the sciatic nerve onto the electrodes. 3. After that you should apply the ligature (or ammonium chloride, novocaine) onto the nerve between the muscle and the electrodes. 4. Stimulate the nerve: between the ligature and the end of the nerve; between the muscle and the applied ligature. Draw a scheme of the experiment and make a conclusion. Results: Practical work 2. Isolated conduction of excitation along the nerve fiber. Objective: proving experimentally that excitation is conducted isolatedly within one fiber. Technique. A frog s hind leg preparation should be used for the experiment. 1. Place a thread under each nerve root. 2. Stimulate each root which spreads from the spinal cord by means of sending weak rhythmic impulses (using an electrostimulator). Mind that when different roots are stimulated, different groups of muscular fibers contract, despite the fact, that the nerve fibers of these roots pass through the trunk of the sciatic nerve. Write down your observations. 8

Explain under what conditions isolation of excitation conduction along the nerve fiber occurs? Results: Practical work 3. Bilateral conduction of excitation. Objective: proving experimentally that excitation is conducted along the nerve fiber in both directions from the stimulated area. Technique. 1. Cut off gracilis muscle paying special attention to the branches of the nerve on the inner surface of the muscle. 2. Disintegrate the muscle carefully into two parts so that the halves should be connected with each other by means of nerve branches. 3. Stimulate one half of the muscle by means of sending rhythmic impulses with the help of a stimulator. 4. Note that when stimulated, both halves of the muscle preparation should contract. 5. If you apply the electrodes onto the second half of the muscle, you ll observe contraction of both parts. Draw a scheme of the experiment. In conclusion work out the law of bilateral conduction of excitation. Results: Practical class 3. Excitable tissues: muscle tissue. Questions for discussion 1. Structure of skeletal muscles. 2. The motor unit. Fast and slow motor units. 3. General characteristics of smooth muscles. 4. Types of muscle contraction. Isotonic and isometric contractions. 5. Summation of contractions. Types of tetanus. 6. Mechanism of muscle contraction (sliding filament theory). 9

7. Types of muscular fibers (red muscles and white muscles). Relation of muscle length and tension to the velocity of muscle contraction. 8. Work and strength of skeletal muscles. Body mechanics. 9. Muscular fatigue. Muscular fatigue theory. Practical works 1. Recording different types of skeletal muscle contraction. Books recommended 1. Ganong W. F. Review of Medical Physiology. 20th ed; McGraw-Hill Companies, Inc., 2001. P. 62-80. 2. Guyton, A. C., Hall, J. E. Textbook of Medical Physiology, 12th ed; WB Saunders, 2005. P. 71-90. Practical work 1. Recording different types of skeletal muscle contraction. Objective: recording different types of muscle contraction (complete and incomplete tetanus. Technique. A neuro-muscular preparation should be fixed in a myograph. 1. Apply the nerve of the preparation onto the electrodes of an electrostimulator. 2. Set the frequency of stimulation of 1 Hz and establish the threshold of excitability caused by single impulses (by means of turning the handle of frequency). 3. After that you should make the power of the current get closer to the threshold and record single muscle contractions. 4. The frequency of stimulation should be increased: by means of turning the handle of frequency one division further, and making a record every time. Before increasing the frequency of stimulation, you should turn off the stimulator every time. 5. Record complete and incomplete tetanus. Record the curves of single muscle contraction, incomplete and complete tetanus in the protocol. Explain the mechanisms of the development of different types of skeletal muscle contraction. Results: 10

Practical class 4. Synaptic transmission. Questions for discussion 1. Structure of synapse. 2. Types of synapses. 3. Electrical events in pre- and postsynaptic structures. Excitatory and inhibitory postsynaptic potential. 4. Electrical and chemical transmission. Neurotransmitters. 5. General properties of chemical synapses. 6. Neuromuscular synapse. Blockers of neuromuscular synapse. Practical works 1. Work of the muscle. Dependence of work value on load. 2. Dynamometry. Books recommended 1. Ganong W. F. Review of Medical Physiology. 20th ed; McGraw-Hill Companies, Inc., 2001. P. 81-114. 2. Guyton, A. C., Hall, J. E. Textbook of Medical Physiology, 12th ed; WB Saunders, 2005. P. 546-558. Practical work 1. Work of the muscle. Dependence of work value on load. Objective: establishing dependence of work value on load. Technique. The muscle performs a certain amount of work when it contracts or something is lifted. This work is calculated according to the following formula: A = P x h, where P is weight of load, h is height at which something is lifted. 1. Set a unit for recording muscle contraction. A neuro-muscular preparation is required for the experiment. Fix the muscle in a myograph so that the forceps should be located above the recorder. Connect the lower end of the muscle with the Achilles tendon at Engelman's level with the help of a hook. 2. Apply various loads onto the same shoulder of the preparation (10, 20, 50, and 100 g), stimulating the muscle by using an electrostimulator every time. 3. Record the frequency of muscle contractions on the drum of the kymograph every time it has been stopped. Calculate the work performed by the muscle and draw a curve of dependence of work value on load values; mark load values on the axis of abscises and on the axis of ordinates (g/cm). In conclusion formulate the rule of average loads. Results: 11

Practical work 2. Dynamometry. Objective: measuring the maximal value of muscular effort and muscle endurance of the hand. Technique. 1. A student should stand up and draw aside one of his (her) arm with a dynamometer in his (her) hand so that there is a direct angle between the arm and the trunk. The second free arm is down and relaxed. 2. The student should press the dynamometer with maximum strength twice after a signal. The best result is obtained to estimate muscle strength. 3. Then the student should press the dynamometer 10 times with the frequency of 1 time per 5 seconds consecutively. 4. Record the results and determine muscle efficiency according to the following formula: P = (F1 + F2 + F3 + Fb) / b, where P level of muscle efficiency, F1-Fb readings of the dynamometer for single muscular efforts, b number of attempts. 5. These results are used for determining the index of decreased muscle efficiency according to the following formula: S = [(F1 Fmin)/Fmax] x 100, where S index of decreased muscle efficiency, F1 value of the initial muscular effort, Fmin minimal value of muscular effort, F max maximal value of muscular effort. Calculate and record the power and the level of muscle efficiency in the protocol. Draw a curve of decreased muscle efficiency. Results: 12

Practical class 5. Concluding class devoted to the themes Introduction to the physiology, Excitable tissues: nerve tissue, Excitable tissues: muscle tissue, Synaptic transmission (intermediate oral examination). Questions for discussion 1. Biomembranes, their structure and functions. 2. Ionic channels, their classification and role. 3. Types of transport through biomembranes. 4. The concept of excitability. Properties of excitable tissues. 5. Basic laws of stimulation. «All-or-none» law. Threshold of stimulation. 6. Strength-duration curve. 7. Accommodation. 8. Basic laws of stimulation. Electrotonic potentials. 9. Resting membrane potential. Its ionic basis. 10. Action potential. Electrogenesis and ionic basis of action potential. 11. General characteristics of a single excitation cycle. 12. Local response and propagation of excitation on biomembrane, their comparative characteristics. The firing level. 13. Changes in excitability during action potential (compare phases of action potential with the phases of excitability changes). 14. Mechanism of excitation conduction in nerve fibers (in myelinated and unmyelinated nerve fibers). 15. Laws of conduction in nerve fibers. 16. Types of nerve fibers and their functions. 17. Structure of skeletal muscles. 18. The motor unit. Fast and slow motor units. 19. General characteristics of smooth muscles. 20. Types of muscle contraction. Isotonic and isometric contractions. 21. Summation of contractions. Types of tetanus. 22. Mechanism of muscle contraction (sliding filament theory). 23. Types of muscular fibers (red muscles and white muscles). Relation of muscle length and tension to the velocity of muscle contraction. 24. Work and strength of skeletal muscles. Body mechanics. 25. Muscular fatigue. Muscular fatigue theory. 26. Structure of synapse. 27. Types of synapses. 28. Electrical events in pre- and postsynaptic structures. Excitatory and inhibitory postsynaptic potential. 29. Electrical and chemical transmission. Neurotransmitters. 30. General properties of chemical synapses. 31. Neuromuscular synapse. Blockers of neuromuscular synapse. 13