No. 1. The concept of excitable tissues. St-va excitable tissue. Irritability and irritability.

The general physiological properties of tissues include:

1) excitability - the ability of living tissue to respond to the action of a sufficiently strong, fast and long-acting stimulus by a change in physiological properties and the occurrence of an excitation process. 

A measure of excitability is the threshold of irritation. The threshold of irritation is the minimal strength of the stimulus that first causes visible responses;

2) conductivity - the ability of a tissue to transmit the resulting excitation due to an electrical signal from the site of irritation along the length of the excitable tissue; 

3) refractoriness - a temporary decrease in excitability simultaneously with the excitation that has arisen in the tissue. Refractoriness is absolute; 

4) lability - the ability of an excitable tissue to respond to irritation at a certain rate. 

The main property of any tissue is irritability , i.e. , the ability of a tissue to change its physiological properties and exhibit functional functions in response to the action of stimuli. 

 

No. 2. Irritants, their classification. The concept of irritation.

Irritants are external or internal environmental factors that act on excitable structures. There are two groups of irritants:

1) natural; 

2) artificial: physical. Biological classification of stimuli: 

1) adequate, which, with minimal energy costs, cause tissue excitation in the natural environment of the organism; 

2) inadequate , which cause excitation in the tissues with sufficient strength and prolonged exposure. 

 

Number 3. Laws of irritation. The role of the steepness factor of the increase in the strength of the stimulus . The phenomenon of accommodation.

There are three laws of irritation of excitable tissues:

1) the law of force of irritation; 

2) the law of the duration of irritation; 

3) the law of the gradient of irritation. 

The law of the force of irritation establishes the dependence of the response on the strength of the stimulus. This relationship is not the same for individual cells and for whole tissue. For single cells, addiction is called "all or nothing." The nature of the response depends on a sufficient threshold value of the stimulus.

The law of duration of irritation. The response of the tissue depends on the duration of irritation, but is carried out within certain limits and is directly proportional.

The law of the gradient of irritation. A gradient is the steepness of an increase in irritation. The response of tissue depends to a certain extent on the gradient of irritation.

 

•                                                      Accommodation is the adaptation (of the membrane) to the current with a slow slope, while the slope decreases to a certain minimum level ("minimum gradient" or "critical slope"), the action potential does not arise. 

Number 4. Methods for quantifying the degree of excitability. The concept of the threshold of irritation and good time.

 

A measure of excitability is the threshold of irritation. The threshold of irritation is the minimum stimulus strength that first causes visible responses.

 

ALL THOSE FOUND ON THIS QUESTION. IF THERE IS MORE, SHARE !!!

 

No. 5. The concept of functional rest and functional activity.

 

No. 6. Excitation, specific and non-specific manifestations.

Excitation is an active physiological process that occurs in a tissue under the influence of an irritant, while the physiological properties of the tissue change. Excitation is characterized by a number of signs:

1) specific signs characteristic of a certain type of tissue (excitation by nerve tissue, muscle contraction, secretion of glands) ; 

2) nonspecific signs characteristic of all types of tissues (permeability of cell membranes, the ratio of ion fluxes, charge of the cell membrane change, an action potential arises that changes the level of metabolism, oxygen consumption increases and carbon dioxide emission increases). 

 

Number 7. Membrane theory of excitation.

 

According to the membrane theory, electrical phenomena in the nerve fiber are determined by the selective permeability of the nerve cell membrane for sodium and potassium ions, and this permeability is in turn regulated by the potential difference on both sides of the membrane.

 

Number 8. The ratio between the strength of the stimulus and the time it acts on the tissue. The force-time curve.

 

 The stronger the stimulus used, the less time it took to get the minimum effect, and vice versa, the weaker the stimulus, the longer it should take. For the first time, this pattern was received by the scientists Gorweg and Weiss and presented in the form of a graph.

 As the curve shows, if the stimulus is applied for more than 1 ms, then a line parallel to the ordinate axis is observed, indicating independence of the duration of the stimulus action from its strength ( useless time ). If the stimulus is used for less than 1 ms, then the inverse dependence of the strength of the stimulus on the time of its exposure is observed ( good time ).

 

No. 9. The concept of good time of action of the stimulus, reobase and chronaxy. The magnitude of chronaxy of muscles and nerves.

 

Reobase (threshold of irritation) - the minimum amount of current that causes excitation.

 

To characterize the excitability of tissue over time, the concept of a threshold of time has been introduced - the minimum (useful) time during which the stimulus of a threshold force must act in order to cause excitation.

Chronaxia is the time during which a double rheobase stimulus must act to cause arousal. Chronaximetry is used in assessing the functional state of the neuromuscular system in humans.

 

No. 10. Chronaximetry and its importance for assessing the functional state of excitable tissues.

 

Chronaximetry is a method that determines the magnitude of chronaxy.

Chronaximetry is used in assessing the functional state of the neuromuscular system in humans. With its organic lesions, the magnitude of chronaxy and rheobase of nerves and muscles increases significantly. Chronaximetry is used to determine nerve degeneration in injuries of various nerve centers. Chronaxy studies help to establish shifts of excitability under the influence of various factors: work, heat, cold, atmospheric pressure, etc.

 

No. 11. The optimum and pessimum of the frequency of irritation according to N. E. Pozdensky .

 

About ptimum y Level of force or frequency of stimulation, at which the organ or tissue maximum activity. 

 

P e maximum is the inhibition of the activity of an organ or tissue caused by the excessive frequency or strength of the applied irritations; described in 1886 by N.E. Vvedensky . Studying the features of the conduction of a nerve impulse in the frog's neuromuscular preparation, he found that the strengthening of the fused muscle contraction - the so-called tetanus , caused by a gradual increase in the frequency or strength of irritations, with their further increase or intensification, is suddenly replaced by muscle relaxation and complete inhibition of its activity.    

 

No. 12. The concept of lability and its measure. The role of the absolute refractory phase.

 

Lability is the functional mobility of excitable tissues. A measure of lability is the number of action potentials that a tissue can generate per unit time.

During active depolarization and the initial stage of repolarization, the cell is absolutely unexcited ( absolute refractoriness ).

 

No. 13. A measure of the lability of nerves, muscles and neuromuscular synapses. Lability of the heterogeneous excitability of the system (neuromuscular preparation).

 

The lability of excitable tissue is primarily determined by the length of the refractory period. The most labile are the auditory nerve fibers, in which the frequency of PD generation reaches 1000 Hz. Most somatic lability have myelinated nerves (500 pulses / s), for autonomic fibers - 200 pulses / s. For skeletal muscles - 200 imp / s, for smooth - 10-20 imp / s. The motor nerve ending can transmit to the skeletal muscle no more than 100-150 excitations in 1 s .  

 

No. 14. The main stages in the development of ideas about the nature of electrical phenomena in excitable tissues.

 

In 1791, in the Treatise on the Forces of Electricity in Muscular Movement, the famous discovery made by Galvani was described . The first to investigate electrical phenomena during muscle contraction (“animal electricity”). I discovered the occurrence of a potential difference upon the contact of different types of metal and electrolyte .    

Heinrich Emil Du Bois-Reymond on snovopolozhnik electrophysiology - set a number of rules that characterize the electrical phenomena in the muscles and nerves. The author of the molecular theory of biopotentials .   

Alan Lloyd Hodgkin and Andrew Fielding Huxley winner 's Nobel Prize in Physiology and Medicine "for discoveries concerning the ionic mechanisms of excitation and inhibition in the peripheral and central portions of the nerve cells ."       

Bernard Katz is a Nobel laureate in physiology and medicine ( 1970 , together with Julius Axelrod and Ulf von Oiler ) for his "discoveries in the study of mediators of nerve fibers and the mechanisms of their conservation, excretion and inactivation ."       

 

No. 15. Methods for the study of electrophysiological phenomena in excitable tissues.

Any physiological setup designed to study excitable cells and tissues should contain the following basic elements: 1) electrodes for registration and stimulation; 2) amplifiers of bioelectric signals; 3) regi istrator; 4) a stimulant; 5) a system for processing physiological information. Depending on the objectives of the study, additional equipment is usually required. Since in modern medicine widely used methods elektrofiziolo cal research and electric shock exposure, it is necessary to meet briefly with the basic methodological techniques.   

When working on isolated organs, tissues and individual cells using special cameras and solutions of certain composition, for example Ringer-Locke , Tyrode's , Hank's , allowing to maintain for a long time nor mal vital functions of the biological object. During the experiment, the solution should be saturated with oxygen and have the appropriate temperature (for cold-blooded animals +20 ° C , for warm-blooded + 37 ° C). During the experiment, it is necessary to use flow chambers for continuous updating of the solution in which the biological object is located.

In electrophysiological studies using different types of electro rows, a detailed description can be found in relevant manuals. If the electrophysiological experiment examined actual driving process, it is necessary to use two electrodes with different values of the contact surface area (preferably in a ratio of at least 1: 100), the electrode at the area called the active or the reference , more PLO show mercy - passive or indifferent .

To avoid possible distortion electrophysicists ziologicheskih experiments tend to use special Weekly polarized electrodes, for example silver-silver chloride or calomel having little polarization potential. In the study of single cell electrophysiological characteristics uc polzujut glass microelectrodes . They are a micropipette with a tip diameter of less than 0.5 μm, filled with 3M potassium chloride solution. In electrophysiological experiments used a variety of forces Teli biological signals to measure current minimum change (10 A) and voltage (up to 10 -7) Due to the fact that the recorded signals may have a high rate of rise of the leading edge, the amplifiers should have a sufficiently broad bandwidth (hundreds of kHz).

 

No. 16. The structure and functions of cell membranes.

 

In 1972, Singer and Nicholson proposed a liquid-mosaic model of KM . According to this model, the membrane is represented by a bilayer of phospholipid proteins, oriented in such a way that hydrophobic tails inside the bilayer , and hydrophilic ones on the outside. Globular B. are integrated in the phospholipid layer . These integrated B. perform various functions , including receptor, enzymatic, and form ion channels.

KM functions : Barrier, transport, energy.

 

Number 17. Types of ion channels, their functional significance.

 

1.                           Potassium-sodium leak: responsible for the leak of potassium at rest. F- ii : the creation of PP.

2.                           Sodium channel: quickly activated during depolarization, then voltage- dependent inactivation follows . F-ii : generation of the front front of the PD.

3.                           Calcium channel: slow activation in d e polyariatsii ; inactivation depends on the membrane potential. F-ii : the generation of slow depolarizing potentials.

 

№18. The concept of conductivity and selectivity of ion channels.

Selectivity is the selectively increased permeability of the ion channel for certain ions and reduced for others. Such selectivity is determined by a selective filter - the narrowest point of the channel pore. The filter, in addition to narrow sizes, can also have a local electric charge.  

The conductivity of the various channels is not the same. The conductivity of the ion channel depends on two factors: firstly, on the ease with which the ions pass through the open channel. This intrinsic property of the channel is known as channel permeability. Secondly, the conductivity depends on the concentration of ions near the channel mouths.

 

No. 19. The concept of ion asymmetry , the concentration of ions of sodium, potassium, chlorine - outside and inside the cell on the example of a frog.

 

Ionic asymmetry - a different concentration of the cytoplasm of the cell and the ions of the environment.

Intracellular conc : sodium - 10 mm , potassium - 140 mm .

Extracellular conc : sodium - 120 mM , potassium - 2.5 mm.

 

We can do without chlorine, maybe Yandex sent me to hell with this request.

 

No. 20. PP formation mechanism. The role of individual ions. The value of the equilibrium potassium potential.

 

PP is the difference in charges between the inner and outer surfaces of the membrane. Conditions for formation: gradient of ion concentration on both sides of the membrane, selective membrane permeability. At rest, the KM sodium and potassium channels are closed. And potassium ions exit the cell through potassium-sodium leakage channels . As the negative charge inside the cells formed a membrane potential value , at which potassium output power is balanced by the concentration gradient of the electric power output to the gradient - the equilibrium potential of potassium.

 

No. 21. The concept of passive and active changes in the membrane under the action of the stimulus. Local response and critical level of depolarization.

 

Under the action of an irritant ( mechanical, chemical or electrical), the membrane potential changes downward.

The local response is the threshold changes in membrane potential.

The threshold current is the current required to reach a critical potential.

The critical level of depolarization is the value of the membrane potential, upon reaching which an action potential arises. 

 

Number 22. PD, its phases, mechanism of their origin.

 

By the action potential is understood the rapid fluctuation of the resting potential, accompanied, as a rule, by recharging the membrane.  

PD phases:

1.                                                    Prespike is the process of slow depolarization of the membrane to a critical level of depolarization (local excitation, local response).   

2.                                                    Peak potential, consisting of the ascending part (membrane depolarization) and the descending part ( membrane repolarization ). 

3.                                                    Negative trace potential - from the critical level of depolarization to the initial level of polarization of the membrane ( cell excitability is increased ). 

4.                                                    A positive trace potential is an increase in the membrane potential and its gradual return to its original value ( cell excitability is reduced ). 

MORE ANYTHING GOOD ABOUT THE PHASES WERE NOT FOUND ...

Number 23. Sodium-potassium pump and its meaning.

 

The major mechanism for maintaining low intracellular accurate ion concentration of Na ⁺ and high ion concentration of K ⁺ is the sodium-potassium pump (Fig. 2.9). It is known that there is in the cell membrane transporter system, each to toryh located 3 binds to intracellular ions Na ⁺ , and outputs them to the outside. On the outer side carrier associated with the cell 2 located outside the ions K ⁺ , which are transferred to the cytoplasm . energy monitoring of vector systems is provided by ATP. The operation of the pump according to this scheme leads to the following results. 1. Supported by the high concentration of ion K ⁺ within the roll stands ki that provides a constant value of the resting potential. Due to the fact that for one cycle of exchange ions from the cells is shown on one positive ion is larger than the injected active transport plays a role in establishing the resting potential. In this case, they talk about an electrogenic pump. However, the magnitude of electrogenic pumps contribution to the total value of the resting potential is typically not large, and is several millivolts.      

2. Supported by the low concentration of sodium ions inside the cell, on the one hand, it ensures operation of the mechanism re neratsii action potential, on the other - normally maintains the osmolality and cell volume.

3.         Maintaining a stable concentration gradient of Na ⁺ , sodium-potassium pump conjugate promotes transport amino acids of sugars and through the cell membrane.

Number 24. Dynamics of changes in cell excitability in various phases of PD.

 

REWIND ALL CHAPTER 2.1.5 DOES NOT HAVE SENSE, READ FOR YOURSELF!

 

Number 25. The nature of the effect of depolarizing and hyperpolarizing current on the membrane of excitable tissues.

 

With a short-term transmission of a threshold constant electric current, the excitability of the tissue under the stimulating electrodes changes. KM depolarization occurs under the cathode, hyperpolarization under the anode . In the first case, the difference between the critical potential and the membrane potential decreases, i.e., the excitability of the tissue under the cathode increases. Excitability decreases under the anode.

No. 26. Nerve fibers, their classification and structural features.

Classification:

1) Type A fibers are thick, myelin, with far extending nodal intercepts, conduct pulses up to 120m / s      

2) Type B fibers of medium thickness, myelin, smaller diameter, with a thinner myelin sheath, 3-14 m / s      

3) C- type fibers are thin, myelin- free, 0.5-2m / s      

 

A single myelin fiber consists of an axial cylinder, which has a membrane and axoplasam. The median membrane, a product of vital activity and Schwann cells, consists of: 8 0 % lipids, 20% protein. There are nodal intercepts-open horns of the axial cylinder.

Bezmyelinovye nerve fibers are covered only with Schwann cells.

 

No. 27. Physiological properties of nerve cells.

1) Excitability-the ability to come into a state of excitement in response to a spewing agent .      

2) Conductivity-the ability to transmit nervous excitation in the form of PD from the site of irritation along the entire length      

3) Refractoriness-property for a time to sharply reduce the excitability in the process of excitation        

4) labile i- ability to respond to a certain stimulus speeds      

 

No. 28. The mechanism and speed of excitation in myelinated nerve fibers

In myelin fibers, excitation covers only the zones of nodal intercepts, i.e., bypassing the zones covered by myelin ( Saltation excitation), the speed is 15-20 m / s

 

No. 29. The role of the functional features of the fiber membrane in the field of interception of Ranvier .

The nodal interceptions Quantity sodium channel dostiget 12 000 per 1 mm² , which is significantly more than in the other portion of the fiber. As a result, nodal hooks are the most excitable and provide a high rate of excitation. The time of excitation along the myelin fiber is inversely proportional to the length between intercepts. 

 

No. 30. The dependence of the speed of passage of excitation on the diameter of the fiber.

The larger the diameter of the fiber, the higher the rate of excitation.

The length of the sections between the nodal interceptions depends on the thickness of the nerve fiber: the thicker it is, the longer the distance between the intercepts.

 

No. 31. The mechanism and speed of excitation in myelin-free nerve fibers.

In non-myelin fibers, the excitation gradually covers adjacent sections of the axial cylinder membrane and so extends to the end of the axon. The spread of excitement comes with a gradual weakening, with decrement.

 

Number 32. The nature and speed of axonal transport. Transported islands and their importance.

Axonal transport is moving ve stances from the body of a neuron processes in ( anterograde axo current ) and reverse (retrograde axo- flow ). There are slow axonal flow of substances (1-5 mm per day) and fast (up to 1-5 m per day). Both vehicles ICU threads are present in axons and dendrites in. Axonal transport ensures the unity of the neuron. It creates a permanent connection between the body of the neuron (trofiche University Center) and processes. Main synthetic about the processes going in perikaryon. Here are concentrated The necessity mye for this organelle. The synthetic processes of pro processes occur weakly. Anterograde fast system conveys to the nerve endings proteins and organelles necessary for synaptic functions (mitochondria membrane fragments, vesicles, enzymes are proteins involved in the exchange neuromas diatorov , as well as precursors of neurotransmitters ). Ret rogradnaya system returns perikaryonic used nye and damaged membranes and proteins for degradation whether zosomah and updates, brings about the periphery of the state, nerve growth factors. Slow transport - is anterograde system, conductive proteins and other substances to update axon plasma of mature neurons and processes to ensure growth in their development and regeneration. Retrograde transport can play a role in pathogenesis ogy. Due to his neurotropic viruses (herpes, Raging CTBA, polio) can be moved from the periphery to the central nervous system.

 

 No. 33. Nerves and their fiber composition. The concept of innervation.

 

No. 34. The laws of the excitation of the nerve .

1) The law of functional continuity of the nerve      

2) The law of bilateral conduct      

3) Law of isolated conduct      

 

No. 35. Methods for determining the speed of propagation of excitation along the nerves.

The original method consisted in irritating the thick motor fibers of mixed nerve trunks of a person at two points and recording evoked responses in the innervated muscle, followed by calculating the difference in their latent periods and calculating the speed of the pulse in meters per second ( m / s). 

 

Number 36. Types of muscle fibers.

1) Slow phase fibers of the oxidizing type, a high content of myoglobin . Maintain a person’s posture.      

2) Fast phase oxidative fibers, many mitochondria, performing fast energetic movements      

3) Fast phase fibers with glycolytic type, ATP due to glycolysis, myoglobin is absent      

4) Tonic fibers.      

 

 

Number 37. Structural and functional organization of skeletal muscle (s. Fiber , myofibril, sarcomere , myofilament ) pp. 77-78

 No. 38. microstructure of actin and myosin filaments . Page 77-78

 

Number 39. Physiological and physical properties of mice. T ani , their character .

Muscles convert the chemical energy of nutrients into mechanical energy. Moving the body in space, maintaining a certain posture, heart, blood vessels, pishch .T rakta a person osuzhestvlyaetsya muscles 2 types: smooth and striated (skeletal)

Functions:

1) Provide a pose of the human body      

2) Move the body in space      

3) Heat source, thermoregulation function      

Skeletal muscle properties:

1) Excitability      

2) Conductivity      

3) Contractility      

4) Elasticity      

5) Tonus      

 

Number 40. Muscle contractility. Mechanism of muscle contraction and eo steps ... ..

Pages 78-86 Tutorial

 

No. 41. The mechanism of muscle relaxation.

The Ca concentration decreases and the myosin heads are disconnected from the actin filaments .

 

Number 42. Chemical and thermal processes in the muscle during contraction .

Page 85-86.

 

No. 43. Isotonic, isometric and auxotonic reduction modes.

1) Isotopically d- voltage practically unchanged, while changing only the length of the muscle vookna      

2) Isometric-muscle fiber is fixed on both sides and cannot be freely shortened, the length does not change      

3) Auxotonic - the development of tension is accompanied by a shortening of the length of the muscle.      

 

44. Single muscle contraction and its periods.

Contractility - the ability of the skeletal muscle to be characterized by the force of contraction that the muscle develops: strength (total, which the muscle contracts and the absolute self ( per 1 cm ² cross section)); shortening length; degree of stress; shortening speed; relaxation rate. Irritation of muscle fiber by a threshold stimulus leads to the appearance of a single muscle contraction, which consists of several periods: 1 - latent (a latent period from the moment of application of irritation to the appearance of muscle contraction of 0.01 s); 2- shortening (stress development: the voltage does not change, and the length is shortened); 3- relaxation (detachment of actin and myosin). The magnitude of a single contraction is determined by the number of motor units involved in the contraction.

 

 

45. Neuromotor unit. The number of muscle fibers in a neuromotor unit depending on muscle function .

A neuromotor unit or motor unit is a functional unit of skeletal muscle. It includes a motor neuron and a group of muscle fibers innervated by axon branches of this motor neuron located in the central nervous system. The number of muscle fibers that make up the motor unit is different and depends on the function that the muscle as a whole performs.

Eyes - Less than 10                                                       

Fingers - 10-25                                         

Biceps - About 750                           

Soleus muscle - "2000             

The muscles that provide the exact movement of the DE are composed of several muscle fibers, and the muscles that support the posture, up to several hundred and even thousands of muscle fibers.

 

 

46. ​​Dependence of the amplitude of contraction on the strength of the stimulus in the initial muscle length ( sarcomere length )

The strength of contraction of an isolated skeletal muscle, ceteris paribus, depends on the initial muscle length. Moderate stretching of the muscle leads to the fact that the force developed by it increases compared to the force developed by the unstretched muscle. There is a summation of passive stress due to the presence of elastic components of the muscle, and active contraction. The maximum contraction force is achieved with a sarcomere size of 2-2.2 microns. An increase in the length of the sarcomere leads to a decrease in the force of contraction, since the area of ​​mutual overlap of actin and myosin filaments decreases . With a sarcomere length of 2.9 μm, the muscle can develop a strength equal to only 50% of the maximum possible.

Under natural conditions, the force of contraction of skeletal muscles during their stretching, for example during massage, increases due to the work of gamma-efferents .

 

 

47. Summation of muscle contraction and its types

Summation - an increase in the amplitude of contraction when 2 or more stimuli act on the muscle, if the interval is longer than the latent period, but less than a single muscle contraction.

2 types:

Full - during the shortening period; underlies the smooth tetanus.

Incomplete - during the period of relaxation; underlies the toothed tetanus.

Thetanus is a strong and lasting muscle contraction. It is believed that the basis of this phenomenon lies upconcentration ii io calcium newly in the cell, allowing the reaction carried interaction of actin and myosin in muscle force generation and transverse bridges for quite a long time. With tetanus, the summation of muscle contractions occurs, while the PC of muscle fibers does not stack.

 

48. Changes in the excitability of muscle fibers during excitation

Excitation is the response of the tissue to the action of the stimulus.

The greater the strength of the stimulus, the higher the response from the excitable tissue.

It is known that under the influence of an irritant, living cells and tissues from a state of physiological rest go into a state of activity. The greatest response among tissues to irritation is observed from the nervous and muscle tissue. The main properties of nervous and muscle tissue are excitability, arousal, conduction, refractoriness and contractility.

 

 

49. The mechanism of summation of muscle contractions

The summation of muscle contractions occurs with tetanus. Thetanus is a strong and lasting muscle contraction. It is believed that the basis of this phenomenon lies upconcentration ii io calcium newly in the cell, allowing the reaction carried interaction of actin and myosin in muscle force generation and transverse bridges for quite a long time. With a decrease in the frequency of stimulation, an option is possible when a second stimulus is applied during the relaxation period. In this case, there is a summation of muscle contractions, but it will be observed characteristic retraction of the curve of muscle contraction - incomplete summation or jagged tetanus.

In vivo, single skeletal muscle contractions do not occur. There is an addition, or superposition , of contractions of individual neuromotor units. In this case, the contraction force can increase both due to a change in the number of motor units participating in the contraction, and due to a change in the frequency of impulse motoneurons . In the case of an increase in the impulse frequency , a summation of the contractions of individual motor units will be observed.

1 reason - the frequency of pulses generated by motor neurons .

2 reason - an increase in the number of excited motor neurons and synchronization of the frequency of their excitation.