The nervous and endocrine system Essay

The human body consists of cells, which form different systems, and they all in turn are united into a single system of the organism. Myriad of cellular elements could not operate as a unit, if the body did not have a complex mechanism of regulation, and special role in the regulation play the nervous system and endocrine systems. Those systems are interconnect ted, and the nature of the processes occurring in the central nervous system is largely determined by the state of the endocrine regulation.
In this paper it is necessary to consider nervous and endocrine systems and their interaction. Also it is needed to consider in detail the mechanism of transmission of nerve impulses in the nervous system, both through the synapses and through the nerve membrane. At the end will be studied synapses and their role in the mechanism of transmission of nerve impulses.

Interaction of nervous and endocrine systems
Human body consists of cells that are connected into systems and form a single body system. Functioning of the whole organism as a unified system exists because of mechanism of regulation processes. According to scientific representations, each genetic process in the body occurs not in isolation, but in close dependence on other associated processes. In other words, it is always under the control of a number of systems, ranging from the genetic system of cells in which this process occurs, and then in systems of tissues, organs, and finally the whole organism. (Sherwood, 2006, p.5)
Leading role in establishing the relationship of genetic processes at the level of the whole organism has the interaction of the nervous and endocrine systems. These two regulatory systems complement each other, form a functionally single mechanism, which ensures high efficiency of neuro-humoral regulation, puts it at the head of systems, connecting all the vital processes in multicellular organism. This interaction is so consistent that it is sometimes spoken of a single neuro-endocrine system, meaning the union of the nervous and endocrine systems in the process of regulation of vital activity. (Sherwood, 2008, p.128-129)
Neuroendocrine regulation is the result of the interaction of the nervous and endocrine systems. It is implemented through the influence of higher autonomic centers of the brain – the hypothalamus on the brain. (Rushton, 2009, p.34)
The autonomic nervous system permeates the entire body and has two branches: the excitation and inhibition. The nerve endings secrete mediators that stimulate the adrenal glands to release powerful hormones – adrenaline and noradrenaline. They, in turn, increase heart rate and respiratory rate, and act on the digestive process by providing acid in the stomach. (Sherwood, 2008, p.133)
The endocrine system of the human body combines small and different in structure and functions endocrine glands that make up the endocrine system. Sphere of influence of hormones is extremely high, as they have a direct impact on the growth and development of the organism, for all types of metabolism in puberty. There is no direct anatomical connections between the endocrine glands, but there is interdependence of functions of one gland from another. The basis of all regulation is the main supreme endocrine gland – the pituitary gland. (Sherwood 2008, p.128)
The pituitary gland receive signals indicating about what happens in the body, but it has no direct relationship with the environment. As the supreme gland of the endocrine system, the pituitary itself is subject of control of the central nervous system, and in particular of the hypothalamus. This higher vegetative center continually coordinates and regulates the activities of different parts of the brain, all internal organs. Heart rate, tone of blood vessels, body temperature, the amount of water in blood and tissues, the accumulation or consumption of proteins, fats, carbohydrates, mineral salts – in other words, the existence of the whole body is controlled by the hypothalamus. (Sherwood 2008, pp. 661-665)
Most of the neural and humoral regulation goes at the level of the hypothalamus, and thus is formed a single neuroendocrine regulatory system in the organism. To the cells of the hypothalamus fit the axons of neurons, located in the cerebral cortex and subcortical structures. These axons secrete a variety of neurotransmitters, which have on the secretory activity of the hypothalamus activating and inhibitory effect. Coming from the hypothalamus of the brain nerve impulses “turns” in the endocrine stimuli, that can be strengthened or weakened depending on the humoral signals, coming to the hypothalamus from the glands and tissues under it. (Sherwood, 2006, pp.540-542)
Transmission of nerve impulses
Nerve impulse is a wave of excitation propagating through the nerve fiber in response to stimulation of neurons, and ensures the transfer of information from receptors in the central nervous system and from it to the executive organs (muscles, glands). Transmission of nerve impulses goes due to the ability of membranes of neurons to change their electrochemical potential. Interneuronal transmission of nerve impulses occurs at synapses, and the speed of nerve impulses is about 3 to 120 m / sec. (Campbell, 2007, Ch.48)

Despite the different signal values, their nature in all cases is identical, and consists in changing the electrical potential on the plasma membrane of the neuron. Transmission of signals is based on the fact that the electric disturbance, which arose in one area of cells, is spreading to other areas. If there is no additional gain, these perturbations are attenuated with distance from their sources. At short distances the attenuation is insignificant, and many neurons carry signals passively, without amplification. However, for long-distance communication of such a passive signal propagation is not enough, so neurons with long processes have an active developed signaling mechanism. Electrical stimulus, which strength exceeds a certain threshold, causes an explosion of electrical activity that spreads with great speed along the plasma membrane of the neuron. This wave of excitation is called nerve impulse. (Campbell, 2007, Ch.48)
Transmission of nerve impulses along the synapse comes through the ends of axons – the nerve endings, through which electrical impulses are transmitted from one neuron to another. Transmission of nerve impulses is an electrochemical process. The mechanism of chemical transmission of nerve impulses across the synapse: the contents of synaptic vesicles (mediator) comes in small portions (quanta) in the synaptic cleft and interacts with receptor proteins of postsynaptic membrane. This causes membrane depolarization and excitation of the next neuron. Ultrastructural features of the synapse and the mechanism of transmission of impulses determine the strict unidirectional transmission of impulses that underlies the transmit of impulses in the reflex arcs. (Sherwood, 2006, p.82-87)
Specific characteristics and advantages of synaptic transmission of nervous impulses.

Synapses are special intercellular connections that are used for signal transfer from one cell to another (Pic 1).
Synapses also act as amplifiers of nerve signals on their way. The effect is achieved by a relatively low-powered electrical impulse which frees hundreds of thousands of molecules of neurotransmitter from set of synaptic vesicles. The flow of neurotransmitter molecules simultaneously influence on a small part of the neuron, where are focused postsynaptic receptors – specialized proteins that convert the signal from the chemical form to electric. (Sherwood, 2006, p.82-87)
It is important to point out the so-called synaptic delay, which is defined as the interval between the arrival of a nerve impulse in the presynaptic fiber end and the beginning of post-synaptic potential. At synapses with a chemical mechanism of transferring the synaptic delay is from 0,3-0,5 to a few milliseconds. Most of this time goes to the process of releasing of neurotransmitter presynaptic terminal under the influence of nerve impulse. At synapses with electrotonic transmission (Pic.2) the synaptic delay is virtually absent, which is considered an advantage. (Corn 2008, p. 99)