Contraction in the Vessels and Nerves - Assignment Example

The change in the tone of the vessel is a very important physiologic process because it leads to either vasodilatation or vasoconstriction of the vessel. According to Ganong, vasoconstriction or dilation is important in that it is able to control the flow of blood (2005: 595). It can be useful in the determination of the pressure of blood. This is the case when there is low blood pressure in which the vessels constrict and therefore increasing the resistance of blood. Since the blood pressure is directly proportional to the resistance of blood flow in the vessel, vasoconstriction leads to an increase in the blood pressure.

The vessel size is also useful in the control of the temperature of the body. During cold, the blood vessels of the skin constrict due to the increase in the tone of the blood vessels and therefore reducing the flow of blood to the skin (Ganong, 2005: 252). This minimizes the amount of blood that comes in contact with the skin and therefore reduces the chances of the blood losing heat. During the hot times, blood needs to be brought near the skin surface and therefore lose more heat. This is achieved by the dilatation of the vessels of the skin due to the decrease in the muscular tone of the vascular smooth muscles. As a result, there is more blood in contact with the skin and therefore more evaporation and sweating the individual which will reduce the temperature of the individual.

Another important physiologic function is the regulation of the blood flow to the brain and the regulation of intracranial pressure. According to Ganong, when there is an increase in the pressure of the cerebrospinal fluid in the skull, the arteries are stimulated to increase the vascular tone which will lead to vasoconstriction (2005: 609). The vasoconstriction will then reduce the amount of blood reaching the brain and therefore reduce the pressure of blood. Through the nerve stimulation, the veins of the brain will also undergo vasodilatation leading to increased flow of blood from the brain back to the heart and therefore helping in the reduction in the pressure within the cranial cavity.

As seen from these responses and other more physiologic responses, the vessel tone and hence the vessel constriction is an important component of the normal physiologic responses. The vessel tone is regulated by the nervous system, the endocrine system, the immune system, and drugs. Therefore neurovascular transmission is a very important part of the control of the tone of the blood vessels and therefore the dilatation or vasoconstriction of the blood vessels. There has to be communication between the vessels and the neurons which are in the form of neurotransmitters and other components of nerve transmission. These neurotransmitters include epinephrine, nor-epinephrine, and neuropeptide Y among others (Ganong, 2005: 95). They are released by the nerve endings innervating the blood vessels and their release leads to a change in the tone of the smooth muscles supplying the blood vessels.

There has been a lot of research which have been done in the past regarding the conversion of the action potentials of the nerves to become a contraction in the vessels. These researches have focused on the way the action potential which is present within the nerve cell membrane innervating the blood vessel brings about the change in the tone of the vascular smooth muscles. These researchers have come up with some ideas for the vascular transmission of nerve impulses.