The complex structure of the human brain reveals the secrets of our behavior, explains the laws of mental activity, the flow of emotions and feelings. Each hemisphere of the brain is responsible for its specific functions and tasks (for example, it is known that the right one is responsible for logic, and the left - for imagination and fantasy), but there are also structures that provide a single and coordinated work of the entire central nervous systems. One of these structures is the reticular formation.
General information
The reticular formation is a section of the brainstem, represented by an extensive network of nerve cells and nuclei that connect different parts of the brain. Unlike other structures - for example, the thalamus, hypothalamus, cerebellum - which have a certain integral shape (nuclei, glands), reticular the formation is not represented by a single morphological formation, but is a "network" (from the Latin reticulum - network) of dendrites and axons, which with with varying degrees of density, they penetrate between the departments and structures of the brain, combining them with each other and ensuring their joint activity.
Metaphorically speaking: if our brain is presented in the form of some kind of product, say, a shirt, then the reticular formation is the threads with which the shirt is sewn. The reticular formation penetrates the structures of the medulla oblongata, midbrain and pons, has direct connections with cerebellum, spinal cord, thalamus and mediated - with the overlying sections: hypothalamus, visual nuclei and bark.
How it works
The reticular formation includes a huge number of neurons with branched dendrites and long axons, due to which it becomes possible to transmit nerve impulses to various parts of the head and spinal brain. In this case, two largest groups of neural clusters can be distinguished:
- Reticulotegmental nucleus, whose neurons receive signals from the overlying parts of the GM (quadruple, thalamus) and transmit them further into the structures of the cerebellum, thereby regulating some vital motor functions: coordination of gaze, movement eye.
- The lateral nucleus, whose neurons ascend from the structures of the spinal cord and vestibular nuclei and provide informing the cortex of GM about the position of the body in space, are involved in the regulation of respiration and vascular innervation.
- In addition, the reticular formation includes neurons that take an important part in the work of the centers of thermoregulation, satiety and hunger.
Main functions
The main purpose of the reticular formation is sensory analysis of numerous signals coming from different parts of the GM.
Due to close connections with the spinal cord, it also takes an active part in motor regulation, from the swallowing reflex to complex motor operations. In addition, the reticular formation carries out an activating effect on the entire GM as a whole, participating in the regulation of the sleep and wakefulness cycles.
In general, the functions of the reticular formation are as follows:
- Regulation of skeletal muscles (involved in controlling body movements) and autonomic functions (breathing, sneezing, blood circulation, etc.).
- Control of the processes of sleep and wakefulness (due to the provision of an activating and inhibitory effect on the cerebral cortex).
- Activating function (manifested in the fact that the reticular formation provides a constant tonic stimulation of the GM cortex, due to which it becomes possible to maintain attention, consciousness and the flow of mental processes.)
- Processing signals from the external and internal environment.
Properties of the reticular formation
Distinctive features of the work of the reticular formation are associated, first of all, with certain properties of its neurons:
The nerve cells that make up the reticular formation have an increased capacity for tonic stimulation. This means that most of the neurons are in constant excitement and generate nerve impulses that are transmitted to the overlying parts of the GM. This tonic activity is due to a number of factors:
- The permeability of a large number of signals through the structures of the reticular formation. Here's a simple analogy: Imagine a grand piano or some other stringed instrument. It is clear that when we directly touch the strings, they begin to vibrate and make a sound. The same thing happens with nerve cells when signals from other neurons arrive at them. However, let us further imagine that we do not directly touch the strings of the instrument, but, say, jump next to it, knocking our feet strongly on the floor. We may not hear the sound of the instrument, but a barely noticeable vibration of the strings will still take place. The same thing happens with the neurons of the reticular formation. Since some signals (both afferent and efferent) from various structures of the central nervous system constantly pass through it, this creates constant tonic excitation of neurons of the reticular formation, due to the fact that it is located in the epicenter of a constant neuro-impulse exchange.
- Increased sensitivity of neurons to chemicals (hormones, medications, psychotropic substances). A cup of coffee drunk in the morning “turns on” the structures of the reticular formation and, due to the long-term preservation of excitation in its neurons, keeps us active.
Downward and upward influence of the RF
As already noted, the reticular formation has an exciting and inhibitory effect on various parts of the GM. In this case, two departments can be distinguished that specialize in the transfer of excitation to certain structures of the brain.
Descending division: represented by autonomic and motor centers and exerts a descending influence on the spinal cord divisions. The corresponding neural clusters regulate the activity of the respiratory, vasomotor, salivary centers, as well as centers responsible for the construction of simple and complex motor reactions. This indicates the decisive role of the central nervous system in the regulation of even elementary unconditioned reflexes. Stimulation of the descending section leads to inhibition of the spinal centers and induces in the natural environment a state of deep sleep (sleep "without hind legs"). The same effect can be induced artificially, for example, by introducing a person into a state of trance or anesthesia.
Ascending section: represented by nerve fibers connecting the structures of the reticular formation with the overlying sections: thalamus, hypothalamus, cerebellum and cortex. The upward effect has a stimulating effect on the cortical structures and provides an active state of consciousness. The upward influence does not stop even when we sleep. If our brain could completely "shut down", then every awakening would be akin to a birth: who am I? Where I am? How did I get here? However, due to the work of the reticular structures, we still have the opportunity to always return to that initial state of consciousness in which we were before the moment of sleep. In addition, even during a night's rest, we still have the ability to respond to some vital stimuli, i.e. we, as a rule, do not sleep "dead sleep" and we can wake up if a child moved and cried nearby, something fell loudly and etc.
Manifestation of damage to structures
The reticular formation plays a significant role in the integrative activity of the entire brain. Due to the performance of the function of the leading conductor of all types of nerve impulses to all parts of the central nervous system, the reticular formation is in constant operation. Excessive mental and emotional overload is harmful to the brain in general and to the reticular formation in particular. Fortunately, timely administration of sedatives can (due to the increased susceptibility of neurons to chemical effects) quickly correct the situation and normalize the condition.
However, less favorable outcomes are also possible. Damage is possible as a result of craniocerebral trauma, oncological diseases of the brain, infectious lesions.
The main manifestation of unhappiness is loss of consciousness.
Violation of ascending connections reveals itself in a state of apathy, weakness, increased sleepiness, motor disintegration, disturbed night sleep. Concomitant autonomic disorders are common.
