We planet Earth

The ability segmental redistribution of blood flow, so necessary for the terrestrial life, time of occurrence coincides with the appearance of a new system of encoding information in the autonomic nerves. If the fish of all the nerve fibres are thick myelin sheath and thanks to conduct agitation fast (at 40-80 m per second, sometimes faster), then in amphibians can be found thin demielinizirutaya nerve fibers that carry out agitation slowly (about 1 m per second). In the further evolution applies these "slow" fiber all the more willingly and always for the implementation of the autonomic reflexes. It would seem, cardiovascular reflexes because it must be very late, but it's not that: the speed is required mainly from neurons of the somatic nervous system. But the benefits of a new invention that through thick and thin fibers excitement reaches the goal of multi-temporal - creates a temporary variance pulses (in addition to spatial). In addition, fiber compact. More importantly, the sheath of thin fibers does not prevent the transfer of proceedings from one fiber to the adjacent parallel, and thin fiber is Packed into a common shell on neskolku pieces. This enables animation - multiply pulses and reliability of the whole system. Mathematically proved that the system of the many unreliable, overlapping elements stronger system of the few reliable and laminated, especially as our live elements to some extent able to heal itself.
Modernization of the autonomic system allowed to apply a new method of encoding information using thick and thin fiber in different proportions. The frog, despite the presence of both types of neurons, vascular reactions still going on in the old way, on the principle of "all at once". The warm-blooded reptiles and already possible cardiovascular reflexes, redistributing the flow, and probably only with the introduction of this principle of regulation is possible to finally break with water habitats, to achieve decent for terrestrial animals size, and hence to develop the brain, powerful muscles, and thermoregulation.
Segmentation vascular reactions can be seen in those experiments, which we put on crampons, irritating their receptors of the heart. We made sure that in response to such stimuli changes in blood pressure, i.e., if we neglect the small changes in cardiac output, total changes resistance of vessels. The vessels of different areas answer impact differently, and if the impact is not too much, then the total effect of all changes in the flow resistance is zero: blood pressure remains the same. This creates a false impression that the reception frog's heart more sensitive than the cat. However, this was not in the sensitivity of receptors, and in the perfection of the entire regulatory apparatus. Maybe, just so you can smoke a cigarette and stay alive. More severe irritation of receptors of the heart (or other body) already exceeds the possibilities of segmental redistribution of blood flow is changed overall blood pressure. Now the algebraic sum of the changes in resistance of all vascular regions already deviates from zero and in accordance with arousal (or off) receptors of the studied body issues a characteristic two-humped curve.

Pages: 1 2 3 4 5 6 7