Biology Assignment (Essay Sample)

Biology Assignment
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Modes of action of nerves and hormones
The nervous system and the endocrine system function independently to effect unique functions. They do so by employing different methods. However, it is also common to realize that both systems use similar, but not same, elements to effect certain body functions. These systems function in concert with each other to coordinate and control the internal environment of an organism. This process of maintaining a stable internal environment of an organism is termed homeostasis (Tortora & Derrickson, 2009).
Comparison
With the above knowledge of homeostasis, it is possible to develop a comparison of the mode of action of the nerves and hormones. First, the nerves act as an interconnected system that has highly specific structural organization or arrangement. This arrangement is present between neurons and the site of action; the target cells. In this arrangement, the interconnection ensures structural continuity in the nervous system and the action is thus uniform and smooth. The hormones, on the other hand, function independently since the endocrine glands are dispersed widely throughout the body. The hormones, thus, have no structural relationship to one another; neither do they have a structural relationship with each other’s target cells.
A major difference in the mode of action comes with the chemical messenger employed. The functioning of nerves is such that they release neurotransmitters at the synaptic junctions. The release of neurotransmitters, into the synaptic cleft, serves a vital role in the speed of effecting function of the nerves (Sherwood, 2010). On the other hand, hormones are secreted from the endocrine glands and released into the blood. Further, another difference in the mode of action with regards to the chemical messenger employed is the distance of action. This is because neurotransmitters, which the nerves employ, act through extremely short distances, and this is the diffusion across the synaptic cleft while the hormones cover a longer distance to effect their action and this are evident from the fact that they get carried in the blood.
The nerves and hormones differ in the mode of action with regard to the specificity of action relevant on the target cell. This is because nerve action depends on a close anatomic relationship between the nerve supply and the target cells. Nerves that supply a given region must be in proximity to that region of the body. However, the specificity of action depends on the target cell binding specificity. Further, the latter also depends on the type or level of responsiveness of the target cell to a given hormone. Each hormone is, therefore, particular to a given receptor that allows it to effect its action (Tortora & Derrickson, 2009).
Another comparison between the two systems of coordination and homeostasis is the speed of response elicited by the mode of action. This is because the action of nerves is rapid and takes only a few milliseconds. The hormones, on the other hand, are rather slow with their speed of response ranging from minutes to hours.
The duration of action is also a competent aspect of comparison between nerves and hormones’ mode of actions. This is because the duration of action of nerves is remarkably brief and, just as the speed of response, lasts only a few milliseconds. In contrast to this, the duration of action of hormones is long. This ranges from minutes to days or longer.
The last key point of comparison in the mode of action of nerves and hormones is the effect of the systems or their principal functions. The nerves act to coordinate the rapid responses of the body. These responses are precise and effective unless abnormalities are present from lesions or disease conditions. Hormones, in contrast, control those activities in the body that need long duration instead of speed of action.
Homeostatic Regulation of Blood Glucose
The homeostatic regulation of the level of glucose in blood is the function of two critical hormones; insulin and glucagon.
Insulin
The role of insulin in regulation of blood glucose gets summarized in three activities mediated by this hormone. These include liver uptake, the storage and usage of glucose in the body. The most significant effect of insulin is evident after the absorption of a meal.
Insulin has potent effects on the metabolism of glucose, promotes its uptake by the hepatic cells and promotes the use of glucose as a fuel source for the body’s energy needs. All these actions of insulin occur in several steps that take place almost simultaneously. Insulin inactivates an enzyme referred to as liver phosphorylase (Tortora & Derrickson, 2009). This enzyme is responsible for the breakdown of glycogen to glucose in the liver and by inactivating it, insulin serves to prevent the addition of glucose to the body system to allow absorption of glucose after a meal.
Further, the insulin produced by the beta cells of the pancreas increases the activity of the enzyme, glucokinase that phosphorylates the blood glucose priming it for uptake by liver cells for different metabolic pathways.
Insulin promotes activity of glycogen synthase, an enzyme that is responsible for glycogen synthesis from glucose. Further, insulin acts to suppress the postprandial secretion of glucagon. By promoting the synthesis of other essential macromolecules, such as proteins and fats, insulin indirectly promotes the breakdown of the extra blood glucose in the metabolic pathways that lead to energy production. The net effect of these actions an increase in the amount of glycogen stored in the liver by about five to six percent.
However, when blood glucose level drops below normal the beta cells of the pancreas decrease the secretion of glucose. This stops the synthesis of glycogen and also allows the ...