Ministry of education and science of ukraine sumy State University medical institute department of Physiology and Pathophysiology icon

Ministry of education and science of ukraine sumy State University medical institute department of Physiology and Pathophysiology




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PRACTICAL CLASS #3 Date: ____________

^ THEME: “RESEARCH OF MECHANISMS OF ELECTRIC IRRITATION OF EXCITABLE STRUCTURES AND MECHANISMS OF CONDUCTING OF EXCITATION IS ON NERVOUS AND MUSCULAR FIBRES”


Questions for discussion:

  1. Propagation of the action potential. Mechanism of distribution of action potential for nervous and muscles fibres.

  2. Laws of conducting of excitation for nervous and muscles fibres. The safety factor for propagation.

  3. Special characteristics of signal transmission in nerve trunks.

  4. Excitation of a nerve fiber by a negatively charded metal electrode.

  5. Threshold for excitation and “acute local potentials”.

  6. Factors which determine speed of conducting of action potential for nervous and muscles fibres.

  7. Physiological anatomy of the neuromuscular junction.

  8. Secretion of acetylcholine by nerve terminals. Effect of Ach on the postsynaptic muscle membrane. Destruction of the released Ach.

  9. Molecular biology of the acetylcholine formation and release.

  10. End plate potential and axitation of the sckeletal muscle fiber.

  11. The structural and functional organization of nerve-muscle synapses (chemical and electric synapses). Axonal transport.

  12. Characteristics of the basic stages of nerve-muscles transmission


Literature:

Guyton, Arthur C. Textbook of medical physiology – Ch. 5,7.


Practical work #1 “A study of the bioelectric phenomena in living tissues. The 1st Galvani’s experiment.”

In excitable tissues, the bioelectric phenomena can be observed by both biological and physical methods. Although the biological method in our time lost the value as a research method, for a physiologist it will always be interesting due to a prominent role which it played in history of opening of the bioelectric phenomena. At the biological method by Galvani was the first to lead to the existence of «animal electricity» and the same time begin a new direction in physiology – studies about electric processes in an organism. Essence of the first experience of Galvani shows that when touched with bimetallic pincers a preparation of gastrocnemius muscle, there is reduction of muscles. The current which arises between two heterogeneous metals, copper and iron, is the reason of irritation of the muscle.


Materials and equipments: set of preparing tools (anatomic pincers, small scissors, large scissors, scalpel, probe), physiological solution, preparing small planks, serviettes, cotton wool, tray, electrostimulator, with electrodes, bimetal pincers with copper and zinc ends, a research object is a frog.


Procedure:

  1. Prepare the spinal frog.

  2. Cut the column in the middle of the body

  3. Remove the skin from preparation

  4. Place the preparation on the gum carpet

  5. Place one tip of the bimetallic pincers under the root of the sacrum’s part of the frog’s spinal cord (fig.1)

  6. During the experiment one should wet the nerve-muscular preparation using a physiological solution.

  7. Observe the contraction of the muscles when we touch the nerve-muscular preparation with the bimetallic pincers and write your observations and conclusions.




Fig.1


Results: 1 What’s observed when you touch the nerve-muscular preparation with metallic pincers?

2 To draw the scheme of the experiment.


1_________________________________________________________________________________________________________________________________________________________


2 The scheme of experiment:


Conclusion: 1 How was the proved existence of the bioelectric phenomena proved in excitable structures?

2 What is the reason of irritation of a muscle?

_________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________


^ Practical work #2: The 2nd Galvani’s experiment


This experiment of Galvani consisted of the reduction of muscles of frogs foot was reproduced without participation of a metal, by throwing of preparation of sciatic nerve on the damaged area of thigh. Difference of potentials between an external surface of a muscle and the inside surface, which exists at rest, expressly shows up when a muscle is damaged. Potential which arises up between unharmed and damaged areas is called «potential of damage». When a nerve gets on the damaged electronegative area of muscle, there is shorting of chain, in which positive pole (the unharmed surface of muscle) and the area of nerve which compresses with it take part. Thus in the second experiment of Galvani reason of excitation of nerve is an irritating action of current which arises directly in tissues.

Between an external surface of a muscle and the inside surface in a state of rest, is a difference potential, which brightly shows up at a damage. Potential which arises between the damaged and unharmed areas of a muscle, «potential of damage» can be reason of excitation a nerve.


Procedure:

  1. Cut the frog along on the middle line of spine (fig. 2).

  2. Prepare the rheoscopical paw (pad) on one leg of the frog.

  3. Cut across the hip muscle of the other leg of the frog (fig. 3).

  4. Place the buttock’s nerve of the rheoscopical paw in the cross-section on the leg muscle and observe the reaction (fig. 4).

  5. During experiment it is necessary to moisten nerve-muscular preparation by physiological solution.




Fig. 2 Fig. 3 Fig. 4


Results: 1 What was observed after the contact of the sciatic nerve of rheoscopic

paw with the damaged area of muscle of the second half of frog?

2 To draw the scheme of experiment.


1______________________________________________________________________________________________________________________________________________________________________________________________________________________________________


2 The scheme of experiment:


Conclusion: What arises up between the damaged and unharmed areas of a muscle, how does it influence on a rheoscopic paw experiment?

_______________________________________________________________________________________________________________________________________________________________________________________________________________________________________

^ Practical work #3: “An exposure of electric current in experiment with the second reduction (Experiment of Matteuchi).”


Matteuchi showed that it is possible to cause reduction of muscles of nerve-muscular preparation, by putting a nerve to the muscles of the second preparation, which grow short. This experiment demonstrates that in a muscle which grows short there are considerable currents, which can be utilized in the quality of an irritant for the nerve of the second preparation. These currents are called «currents of action».


Procedure:

  1. To prepare a rheoscopic paw from the second half of frog.

  2. Place the buttock’s nerve of the 1st part on the electrodes.

  3. Place the buttock’s nerve of the 2nd part along the shin muscle of the 1st part.

  4. Give the electric current of 2V for 0,5 ms (fig. 5). Observe the twitching of the two legs.

  5. During the experiment it is necessary to moisten nerve-muscular preparation by physiological solution.




Fig. 5


Results: 1) How does excitation of muscle of the first preparation affect the state of the second

preparation?

2) Draw the location of rheoscopic quotation marks in experience of Matteuchi.


1______________________________________________________________________________________________________________________________________________________________________________________________________________________________________


2 The scheme of experiment:


Conclusion: Why is there reduction of muscles of the second preparation at reduction of muscles of the first preparation?

____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________


Teacher’s signature ___________________


Work for the independent exercise:

1. Draw graphically law of force-time. Mark needed points.








  1. Calculate the safety factor for propagations when the resting potential nerve fiber is-80mV, the critical level of depolarization is - 60 mV, overshoot is +20 mV. What this demonstrates the value of reliability factor? Draw Active Potential that applies.

_____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________









  1. Draw neuromuscular synapse, sign its parts.




  1. Draw the acetylcholine channel. Release of Ach from synaptic vesicles.




  1. Draw the acute local potentials.








  1. Two people accidentally hit by a uniform alternating current high voltage, but different frequencies. In the first case the frequency is 50 Hz, and second - 500 000 Hz. One man was injured and another suffered electrical injury. Which? Why?

____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________


  1. Irritate the nerve fiber impulses constant electric current through microelectrodes. Anode is on the outer surface of the membrane, cathode - inside. Voltage and pulse duration - threshold. What is the process occur at the membrane? Why?

____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________


PRACTICAL CLASS #4 Date:____________

^ THEME: “THE INVESTIGATION OF THE MAIN CHARACTERISTICS OF MUSCULAR CONTRACTION”


Questions for discussion:

1. Structural organization of the skeletal muscle.

2. The theory “sliding myofilaments” of the muscle contraction.

3. The structure of actin and myosin filaments.

4. The “walk-along” theory “of the muscle contraction. Fenn effect (ATP)

5. Stages of muscle contraction.

6. The concept of the motor unit. Classification of motor units. Fast fibers, slow fibers.

7. Physiological characteristics of muscle contraction: length of the sarcomer, isometric – isotonic, multiple fiber, summation – frequency summation (tetanization), muscle hypertrophy - muscle atrophy, muscle tone – muscle fatigue.

8. Types of the smooth muscle. Physical basis for smooth muscle contraction.


Literature:

Guyton, Arthur C. Textbook of medical physiology – Ch. 6,7.


Practical work #1: The determination of the absolute muscular strength of a hand.

Materials and equipments: dynamometers.


Procedure:

  1. To demonstrate the method of determination of absolute force of muscles of hand;

  2. To demonstrate the method of determination of level of capacity of muscles of hand;

  3. To demonstrate the method of determination of index of decline of capacity of muscles of hand.

A tester in the standing position takes his hand with a dynamometer aside on the right angle of 90° in relationship to the body. Another hand is let down and relaxed. On a signal the tester makes the maximum efforts on the dynamometer 5 times with an interval in 5 seconds. One should hold the dynamometer by fingers without jerks but with all his strength. Every result should be fixed down. The muscular strength is estimated on the best result.


Results:

f1=________

f2=________

f3=________

f4=________

f5=________


Conclusion: The absolute muscular strength of the hand is _______________ H/cm2


Practical work #2: The determination of the level of the ability to work of a hand.

Materials and equipments: dynamometers.


Procedure:


  1. A tester measures an absolute muscular strength of the hand 10 times with an interval in 5 seconds.

  2. The results should be fixed down.

  3. The levels of the muscular ability to work are set with the help of the formula:


P = (f1 + f2 + f3 + f4 + f5 + f6 + f7 + f8 + f9 + f10):10


P- is the ability to work level,

f – the dynamometer index.


Results: f1 =______ f6 =_______

f2 =______ f7 =_______

f3 =______ f8 =_______

f4 =______ f9 =_______

f5 =______ f10 =_______


P = (_____+ _____+ ______+ ____ + _____ + _____ + _____+ _____ + ____ + ____) : 10 =


P = _________


Conclusion: The levels of the muscular ability to work is ___________________ H/cm2


^ Practical work #3: “The determination of the reduction of the muscular ability to work level of the hand.”


Materials and equipments: dynamometers.


Procedure:

Using the results that had been received in the experiment 2, one should calculate the reduction of the ability to work index with the help of the formula:


S = ((f1 - fmin) : fmax) x 100%


S – is the reduction of the ability to work index;

f1 - the rate of the primary dynamometry =_________________________

fmax - the maximum rate of efforts =______________________________

fmin - the minimum rate of efforts=________________________________


Results: 1. S = ((______ - ______) : ______ ) x 100% S = ____________%


2. Draw the graph that will make clear the character of ability to work reduction:
On the abscissa axis you should put down the numbers of efforts, on the coordinate axis you should put down of the dynamometer on every effort.


Score
dynamometer


Number efforts

1 2 3 4 5 6 7 8 9 10


Conclusion: the reduction of the ability to work index is ___________________ %


Teacher’s signature ___________________


Work for the independent exercise:

  1. Draw the sarcomere. Designate its component parts.




  1. Draw the molecule of myosin. Mark its components.




  1. Draw the molecule of actin. Mark its components.




  1. Draw the scheme of the excitation-contraction coupling.




  1. Draw physical structure of smooth muscle.




  1. What length sarcomere force reductions greatest? Why? _________________________________________________________________________________________________________________________________________________________________________________________________________________________________




  1. On muscle inflict frequent rhythmic irritations. On myogram register smooth tetanus. how to find out, does a muscle answer to every irritation?

_______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________



  1. The period reduction in single muscle irritation is 0.04 sec., relaxation time - 0.05 sec. Find the type of contraction in frequency of muscle irritation 5 imp / sec.

__________________________________________________________________________________________________________________________________________________________________________

6. Calculate, which must irritate the minimum frequency of muscle to get: a) incomplete tetanus, b) complete tetanus. If irritation single length of the muscle contraction - 0.02 sec, relaxation time - 0.03 sec (latent period lasts 0.002 sec, it can be neglected). __________________________________________________________________________________________________________________________________________________________________________


PRACTICAL CLASS #5 Data:_______________

THEME: "^ PRACTICAL SKILLS IN PHYSIOLOGY EXCITABLE STRUCTURES".

Questions for discussion:

  1. The structure features of cellular membrane, functions of it, basic components.

  2. Differences of chemical composition of extracellular liquid and intracellular environment.

  3. The passive transport of components, its types and mechanisms (diffusion, osmosis).

  4. Protein channels: selective permeability, gating.

  5. Factors that affect net rate of diffusion.

  6. The active transport of components, its types and mechanisms. Co- transport, counte- transport.

  7. Pinocytosis, phagocytosis.

  8. Intercommunication of organism with an environment. A concept is about irritants, irritations, biological reaction, excitation, excitability, excitative structures.

  9. Methods of physiological investigations.

  1. A concept of the membrane potential and resting potential. Methods of registration of resting potential, and its physical characteristics.

  2. The ionic mechanisms of origin of the normal resting membrane potential (diffusion potential, Nernst potential).

  3. Resting membrane potential of nerves and skeletal muscles fibers. Main and complimentary factors which influence on a value of the resting membrane potential.

  4. Action potential: the structure, physical and physiological characteristics.

  5. Structure and basic properties of ionic protein channels, which take part in development of active potential. Voltage-gated sodium and potassium channels.

  6. Ionic mechanisms of development of basic phases of active potential.

  7. Initiation of the action potential: a positive-feedback mechanism, threshold for initiation of the AP.

  1. Excitability, its changes during development of active potential, refractory period.

  2. Propagation of the action potential. Mechanism of distribution of action potential for nervous and muscles fibres.

  3. Laws of conducting of excitation for nervous and muscles fibres. The safety factor for propagation.

  4. Special characteristics of signal transmission in nerve trunks.

  5. Excitation of a nerve fiber by a negatively charded metal electrode.

  6. Threshold for excitation and “acute local potentials”.

  7. Factors which determine speed of conducting of action potential for nervous and muscles fibres.

  8. Physiological anatomy of the neuromuscular junction.

  9. Secretion of acetylcholine by nerve terminals. Effect of Ach on the postsynaptic muscle membrane. Destruction of the released Ach.

  10. Molecular biology of the acetylcholine formation and release.

  11. End plate potential and excitation of the skeletal muscle fiber.

  12. The structural and functional organization of nerve-muscle synapses (chemical and electric synapses). Axonal transport.

  13. Characteristics of the basic stages of nerve-muscles transmission

  14. Structural organization of the skeletal muscle

  15. The theory “sliding myofilaments” of the muscle contraction.

  16. The structure of actin and myosin filaments.

  17. The “walk-along” theory “of the muscle contraction. Fenn effect (ATP). Stages of muscle contraction.

  18. The concept of the motor unit. Classification of motor units. Fast fibers, slow fibers.

  19. Physiological characteristics of muscle contraction: length of the sarcomer, isometric – isotonic, multiple fiber, summation – frequency summation (tetanization), muscle hypertrophy - muscle atrophy, muscle tone – muscle fatigue.

  20. Types of the smooth muscle. Physical basis for smooth muscle contraction.

Literature:

Guyton, Arthur C. Textbook of medical physiology – Ch. 2,4,5,6,7.

PRACTICAL CLASS #6 Date:____________

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