Neural impulses and RNA

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Neural impulses and RNAThe structural element of nervous activity in the brain is a nerve cell (neuron). Its functional activity is investigated by many methods - histological, histochemical, electron microscopic, radiographic and others. A large number of works on the nerve cell have been published, but the functional significance of its individual constituent parts remains unknown.

Nerve cells are formed from mother cells in the early stages of the body's development. Initially, a nerve cell is a nucleus surrounded by a small amount of cytoplasm. Then in the cytoplasm there are thin threads surrounding the nucleus - neurofibrils; simultaneously with this, the development of the axial process of the nerve cell begins - the axon, which grows towards the periphery up to the final organ. Much later than the axon, other processes appear, which are called dendrites. During development, dendrites branch out. The nerve cell and its axon are covered with a membrane that separates the contents of the cell from the environment.

The nerve cell is excited as a result of stimuli coming to it along the axons of other nerve cells. The endings of axons on the cell body and dendrites are called synapses. It was not noticed that excitement coming through one synapse caused an impulse in any neuron; a neuron can be fired by pulses arriving through a sufficient number of neighboring synapses for a period that lasts less than a quarter of a millisecond.

Neurons differ significantly in the shape of the cell body, in length, number and degree of branching of axons and dendrites. Neurons are classified into sensory (sensory), motor (motor), and intercalary. In sensory neurons, dendrites are connected to receptors, and axons to other neurons; in motor neurons, dendrites are connected to other neurons, and axons are connected to some effector; in interneurons, both dendrites and axons are connected to other neurons. The function of a huge number of intercalary neurons, which are the main structure of the central and peripheral nervous system, is to transfer information from one part of the body to another.

In humans and other mammals, nerve fibers that quickly conduct impulses from receptors to the brain and from the brain to muscles and thereby provide a quick adaptive response of the body are dressed like a sheath with a fatty sheath. Hence, these nerves are called myelinated. The myelin sheath gives the axons a white color, while the cell bodies and dendrites that do not have a myelin sheath are gray.

Nerve fibers coming from the cells of the cortex or to them are divided into three main groups: projection - connecting the subcortex with the cortex, associative - connecting the cortical zones of the same hemisphere, commissures - connecting the two hemispheres and going in the transverse direction. The bundle of these fibers is called the corpus callosum.

Nerve impulses are transmitted along the nerve fibers, which are of a rhythmic nature. The nerve impulse is not an electric current, but an electrochemical disturbance in the nerve fiber. Caused by an irritant in one part of the nerve fiber, it causes the same disturbance in the neighboring one, etc., until the impulse reaches the end of the fiber.

Neural impulses and RNAThe nerve begins to react when a certain stimulus of minimal strength is applied to it. Nerve impulses are transmitted to fibers periodically. After one pulse has been transmitted, a certain amount of time (0.001 to 0.005 seconds) elapses before the fiber can transmit the second pulse.

The period of time during which chemical and physical changes occur, as a result of which the fiber returns to its original state, is called the refractory period.

There is an opinion that the impulses transmitted by neurons of all types - sensory, motor and intercalary, are basically similar to each other. The fact that different impulses cause different phenomena - from mental states to secretory reactions - depends entirely on the nature of the structures to which the impulses come.

Each nerve impulse, propagating, say, along the afferent nerve, reaches the body of the nerve cell. It can pass through the cell further, to its other processes and move through synapses to one of the fibers of the next cell along the chain or several cells at once. So the nerve impulse makes its way, say, from the nasal mucosa through the central cerebral nuclei to the executive organ (muscle fiber or gland), which comes into an active state.

Not every impulse that reaches a synapse is transmitted to the next neuron. Synaptic connections offer a certain resistance to the flow of impulses. This feature of the work of synapses is, one must think, adaptive. It promotes a selective response of the body to a certain irritation.

Thus, studies of the microstructure of the brain indicate the interconnected work of nerve cells. We can talk about a system of neurons. But its function as a whole is not the sum of the activity of individual neurons. One neuron does not generate mental phenomena. Only the aggregate work of the neurons that make up a certain system can give a mental phenomenon. It is based on specific material processes occurring in neurons.

And yet, the study of the processes occurring in individual neurons contains certain perspectives in relation to the disclosure of the mechanisms of behavior and psyche. In this case, we mean studies of the molecular level of neurons, which have outlined the connection between the physiology of higher nervous activity and molecular biology.

The first who penetrated into the molecular depths of the nerve cells of the brain was the Swedish neurohistologist and cytologist H. Hiden. The beginning of his work dates back to 1957. Hiden developed a special set of microinstruments with which he was then able to perform operations with a nerve cell.

The experiments were carried out on rabbits, rats and other animals. The experiment was as follows. At first, the animals were aroused, forced to do something, for example, to climb on the wire for food. The experimental animals were then immediately sacrificed to analyze their brain nerve cells.

Two important facts have been established. Firstly, any excitement significantly increases the production of so-called ribonucleic acid (RNA) in the neurons of the brain. Second, a small fraction of this RNA differs in base sequence, or chemical composition, from any RNA found in the neurons of untrained, control animals.

Since the RNA molecule, as one of the main biological macromolecules (along with the molecule of deoxyribonucleic acid - DNA), has a huge information capacity, on the basis of the above experiments it was suggested that the acquired knowledge is encoded in the above differing RNA molecules. This laid the foundation for the molecular hypothesis of long-term memory.

In the development of Hyden's experiments, attempts were made to transfer RNA molecules from the brain of trained animals to the brain of untrained ones. The most sensational experiments were the American psychologists McConnell and Jacobson.

Neural impulses and RNAIn 1962, McConnell experimented with planaria - flat, transparent worms that are so highly voracious that they eat each other. These worms developed a conditioned motor reflex under the influence of light.The worms trained in this way were chopped up and fed to untrained worms. It turned out that the latter developed a conditioned reflex to light twice as fast as those who did not feed on trained planarians.

Jacobson and his co-workers conducted experiments on the "transfer" of behavior on rats and hamsters. Rats, for example, were trained to run to the feeder after a sharp click was heard. At the same time, a portion of food fell into the trough. After the end of training, the animals were killed and the RNA isolated from their brains was injected into untrained animals. A control group of rats received RNA injections from the brains of untrained animals. The experimental and control rats were then tested to see if the click would have any effect (25 clicks were given for each animal, but no food reward). It turned out that the experimental animals approached the feeder much more often than the control ones.

These and other, more complex experiments led Jacobson to conclude that RNA carries information and the transfer phenomenon refers to memorization.

Until recently, psychology only mentioned the mechanism of formation and strengthening of neural connections as the physiological basis of memorization. The basis of reproduction is the revitalization of the nervous connections - associations, established in the process of memorizing or memorizing. And now the molecular hypothesis of memory is being advanced. The future should show how the molecular mechanisms of memory are connected with reflex mechanisms.

The results of the experiments of McConnell and Jacobson cause a lot of controversy and objections among scientists. The fact is that the same experiments were carried out in other scientific laboratories, but similar results were not obtained. In addition, certain theoretical premises of this hypothesis meet with objection. Scientists argue for the truth. At the same time, the very idea of ​​RNA participation in the phenomena of long-term memory does not raise objections. The subsequent development of scientific research will undoubtedly lead to a fundamental solution to the problem of this important mental process associated with thinking and cognition of the surrounding reality.

V. Kovalgin - Revealing the secrets of the psyche


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