The organism as a transmission system of biosignals

To understand the following lines, we will understand the human organism as a set of different biosignals operating on different physical principles.

Biosignal

The received signal can be mechanical, chemical, acoustic, optical, thermal, electrical, electromagnetic, magnetic and other stimuli that change in the organism. When passing through the nervous system , the stimulus is conducted using synapses . The excitation on the membranes of neurons is transmitted using a change in electrical potential , i.e. as an electrical impulse. This change in electrical potential is transmitted chemically across the synaptic cleft by synaptic vesicles. The output reaction to the received stimulus can again be mechanical, chemical, thermal.

A stimulus to which the body can react must meet certain parameters. In order, for example, for an optical stimulus to evoke the desired response of the organism, it must first act on a relevant, functional organ with a functional sensory and motor pathway and a functional brain center. In addition, its wavelength must be in the interval that is defined for visible light , namely approx. 400-750 nm. This corresponds to a wave frequency of approx. 3.9×10 ¹⁴ –7.9×10¹⁴ Hz. The intensity of the stimulus must also be sufficient to elicit a response from the organism. Although electromagnetic radiation in other wavelengths and frequencies does not cause visual perception in the organism, it nevertheless affects it. Parts of the spectrum with λ ≤ 400 nm are divided into γ radiation from the smallest λ,x-rays and UV rays; radiation with λ ≥ 750 nm is again divided into infrared radiation and radio waves from the smallest λ. All these radiations are biosignals acting on the organism: γ radiation affects genetic information, UV radiation is responsible for tanning the skin, infrared radiation partly causes the body to heat up, etc.

Biosignal division

According to the course in time, biosignals can be divided into deterministic and stochastic , whereby deterministic are those that are determined (determined) by the exact time of origin, (disappearance) and their course in time. A certain randomness and unpredictability play a role in the principle of stochastic biosignals, but we can still predict the outcome of the process based on physical laws. An example of a stochastic process is, for example, diffusion - we cannot accurately predict the development of the movement of an individual particle, but we can predict the development of the entire system over time.

According to the principle of biosignal formation, active and passive signals are distinguished - active is one that arises in the organism (e.g. changes in electrical voltage, on the basis of which an EKG can be read, for example), passive signal is the reaction of the organism to an external factor. The properties of such a signal can be evaluated according to the decay of the external factor. Ultrasonography, for example, is based on this principle.

Biosignal model

To clarify various processes in the organism, we can use the so-called model. It means a certain form of abstraction from the complex, interwoven functioning of the organism. Depending on the type of abstraction, we can talk about several types of models. Let's see some models in more detail:

• If we understand the human body as a physical model, it is an abstraction (simplification) of the entire organism, when we focus on only one specific event, therefore we can ignore other structures of the organism that are not related to this event. We are looking for a different – ​​analogous – system in which the selected plot takes place as similarly as possible. On the basis of such a physical model, we can clarify more complex processes. If we find a sufficiently accurate model (this process is called model identification), we can predict behavior well – behavior is predicted.
• The structural model involves a closer examination of individual structures and their interconnection.
• The functional model is free from the processes taking place in the system, only the input and output values ​​are essential here - a very similar concept of the course of a certain event also exists, for example, in chemistry in the form of Hess's law , where the course of a chemical reaction does not matter, we only evaluate the state at the beginning and at the end of the process.
• The mathematical model sees all movements in the human body as a set of mathematical functions.
• A computer model is a simplification of a mathematical model because it solves complicated mathematical problems from a mathematical model of an organism instead of a human. Currently, computer programs simulate body movements to clearly represent and understand their nature.

Use

Understanding biosignals has versatile uses in medicine, zoology, ethology. The study of biosignals now makes it possible to check, for example, the functionality and readiness of the hearing organ of newborns thanks to otoacoustic emissions. It was found that a healthy, functional ear responds to sound stimuli by creating harmonic oscillations of hair cells (otoacoustic emissions), which can be sensed quite easily. A favorable result indicates the proper development of the ear itself, thereby increasing the probability of normal sound perception, but this examination cannot reveal possible disorders in the transmission system, so it cannot disprove deafness by itself.

Links

References

• Heřman, P.:Biosignály z pohledu biofyziky; https://cs.wikisource.org/wiki/Biosignály_z_pohledu_biofyziky#Model_syst.C3.A9mu
• NAVRÁTIL, Leoš – ROSINA, Jozef. Medicínská biofyzika. 1 (dotisk 2013) edition. 2005. 524 pp. ISBN 978-80-247-1152-2.

• KONRÁDOVÁ, Václava – UHLÍK, Jiří – VAJNER, Luděk. Funkční histologie. 2. edition. 2000. 291 pp. ISBN 80-86022-80-3.