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.
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 .
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.
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.
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.
Change in contraction force is observed with high-frequency rhythmic stimulation of skeletal muscles. The strong and lasting contraction that arises in this case is called the tetanus.
If the skeletal muscle is irritated with such a frequency of rhythmic impulses at which each subsequent irritation will fall into the muscle relaxation period from the previous irritation, then the so-called incomplete summation of single muscle contractions occurs and a jagged tetanus is formed . At the same time, the force of contraction gradually increases, and characteristic teeth and depressions are recorded on the contraction curve.
If the frequency of irritation is increased to such an extent that each subsequent irritation will fall into the period of shortening or development of muscle tension from the previous irritation, then the so-called total summation of single contractions occurs . In this case, a smooth tetanus arises, in which the contraction force increases faster, smoothly and to more significant values.
When a second stimulus is applied during a period of shortening or development of muscle tension, the summation of two successive contractions occurs and the resulting response in amplitude becomes much higher than with a single stimulus; if the muscle fiber or muscle is stimulated with such a frequency that repeated stimuli will fall on the period of shortening, or the development of tension, then the total summation of single contractions occurs and a smooth tetanus develops. Thetanus is a strong and lasting muscle contraction. It is believed that the basis for this phenomenon is an increase in the concentration of calcium inside the cell, which allows the reaction of actin and myosin to interact and the generation of muscle strength by the transverse bridges for a fairly 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, the summation of muscle contractions will also occur, however, a characteristic retraction on the muscle contraction curve will be observed - incomplete summation, or dentate tetanus.
With tetanus, the summation of muscle contractions occurs, while PD of muscle fibers do not stack
With contractions of the skeletal muscles in vivo, mainly in the isometric contraction mode, for example, with a fixed pose, they talk about static work, and when making movements - about dynamic work.
The contraction force and the work performed by the muscle per unit time (power) do not remain constant during static and dynamic work. As a result of prolonged activity, the performance of skeletal muscles decreases. This phenomenon is called fatigue contraction and a period of relaxation.
Static operation is more tedious than dynamic. Fatigue of an isolated sk . muscle is due primarily to the fact that in the process of doing work in the muscle fibers accumulate oxidation products - lactic and pyruvic acid.
According to the laws of physics, work is the energy expended on the displacement of the body with a certain strength to a certain distance: A = the F * the S . If muscle contraction occurs without load (in isotonic mode), then mechanical work is zero. If, at maximum load, muscle shortening does not occur (isometric mode), then the work is also zero. In this case, the energy of the working muscle is completely converted into thermal energy.
According to the law of medium loads, the muscle can perform maximum work with medium loads.
The contractile ability of the skeletal muscle is characterized by the contraction force that muscle a develops ( evaluate the Total Strength - develops the muscle, and the Absolute Strength - coming 1 cm square cross section), the length of the shortening, the degree of muscle fiber tension, the speed of shortening and development of tension, the speed relaxation.
Annoyed mouse . Fibers with a single threshold or superthreshold stimulus lead to the appearance of a single contraction, which consists of several periods. The first is latent , which is the sum of time delays due to excitation of the mouse membrane . fiber, the spread of PD through the T-system into the fiber, the formation of inositol triphosphate , an increase in the concentration of intracellular calcium and the activation of transverse bridges. Vtoroe d- period shortening, or the development of stress. In the case of free shortening of the mouse . the fibers speak of an isotonic contraction mode, in which the voltage remains practically unchanged , and only the length of the mouse changes . fiber. If a mouse . the fiber is fixed on both sides and cannot be freely shortened, it is said that the contraction mode is isometric. In this mode, abbr. mouse length . fiber does not change, while the size of sarcomeres change due to the sliding of actin and myosin filaments relative to each other. Third perio railway relaxation when concentration decreases Ca 2+ and disconnected from the myosin head actin filaments . (further pages 83-84 smooth and serrated titanus )
.№56. Parameters characterizing muscle contractility.
Skeletal muscle contractility characterized ized power reduction that develops muscle (usually estimated total power that can develop the muscle, and absolute, t. E. Power per 1 cm2 cross-section) .d Lina shortening of, degree of muscle fiber stress rate shortening of time and voltage Vitia, According Since these parameters are largely determined by the initial length of the muscle fibers and the strain on the muscles, the study of the contractile ability of muscles to produce various Regis max.
Strength and muscle work. Distinguish between absolute and absolute power . The total strength is determined by that maximum load, the muscle is still able to lift. This value depends on the structure of the muscle, its functional state, the influence of the central nervous system and other factors. Strength is greater, the larger the diameter and the “physiological” muscle cross section. The strength of muscles with an oblique arrangement of fibers is greater than with a longitudinal one. Absolute strength is the ratio of maximum strength to the cross-sectional area of the muscle. This value allows you to compare the strength of the various muscles of one organism and the strength of the muscles of various animals. For example, the absolute strength of the human gastrocnemius muscle is 5.9 kg / cm 2 , chewing 10 kg / cm2, triceps brachii - 16.8 kg / cm2. When training muscles, accompanied by their working hypertrophy, muscle strength increases significantly.
Measurement of strength of individual human muscle groups by means of special devices - Dynamometer s health. Using hand dynamometers measure the strength of the muscles that bend your fingers, using a deadweight dynamometer - the strength of the muscles that straighten the body (“dead” force), etc. Dynamometric indicators can be expressed in absolute terms ( kgf ) and in relative values , for example, in relation to the mass (weight) of a person’s body. D.'s data are taken into account in anthropometry, professional selection, in physiology and occupational and sports hygiene, medicine, and are used as an additional sign for assessing the degree of a person’s physical development.
Synapses are contacts that establish neurons as independent entities. They are a complex structure and consist of a presynaptic part (axon end, transmitting a signal), a synaptic cleft and a postsynaptic part (structure of a receptive cell).
Classification:
1) by location - neuromuscular and neuronuronal (axosomatic, axoaxonal , axodendritic, dendrosomatic );
2) by the nature of the action - exciting and inhibitory;
3) by the method of signal transmission - electrical, chemical, mixed.
- and the neuron xon is in contact with another neuron. Subdivided into:
a) axosomatic - with the body of another neuron;
b) axoaxonal - with the axon of another neuron;
c) axodendritic - with the dendrite of another neuron.
The transmission of a nerve impulse through the synapse occurs with the help of mediators. Among the most important include: acetylcholine, norepinephrine, serotonin , dopamine, glutamate , GABA, endorphins and ecnephalins .
Synthesis of a mediator: the enzymes necessary for the formation of a neurotransmitter are synthesized in the pericarion and transported to the synaptic terminal along the axon, where they interact with molecules of neuronal precursors.
Storage: accumulates in the nerve terminal , being inside synoptic vesicles along with ATP and some cations. There are several thousand molecules in a bubble, which makes up a quantum.
Any chem. the synapse is activated by PD, which extends to the presynaptic membrane from the body of the neuron. Under the action of its PD depolarization occurs that increases the permeability of Ca 2 + channels and leads to an increased entry into presinaps Ca . Calcium is needed for the interaction of membrane proteins of synoptic vesicles - synaptotagmine and synaptobrevin with plasma membrane proteins - syntaxin and SNAP- 25. As a result of their interaction, synoptic vesicles move to the active zones and adhere to the plasma . m embrane. After this, exocytosis begins . 100-200 quanta are being released. Having left in syn . Spruce , the mediator interacts with special. postsynaptic membrane receptors. They regulate the permeability of ion channels. There is an increase in permeability to sodium and calcium ions, which causes depolarization of the postsynaptic membrane.
Noticed a joke with confused numbers? :)