Humans need both the Nervous and the Endocrine systems basically because they do different things in different ways. They both have a co-ordination role and send instructions to other parts of the body. The nervous system does this by way of chemical messengers), which are able to get messages through at very high speeds, and the endocrine system by way of hormones,( also chemical messengers), which are released from glands and travel slowly as they can only move at the speed of the blood flow into which they have been released.

In those areas where there is most co-operation of the two systems, there is a third entity referred to as the Neuroscience system. The nervous system is a communication network for the body and it receives and passes on messages to the endocrine system in order that specific areas may make or Increase production of specific hormones which are then sent to the target area in order to begin or inhibit a process taking place at that site, I. E. A target cell. The specific hormone has a unique ‘entry code’ that enables it to attest the target cell.

The nervous system works by the rain receiving signals from the sensory neurons and then messages are sent back again via the connecting neurons in order to target the area required. Things happen fast and the reactions are communicated over short distances with a short lived response. The endocrine system gets messages from the brain and then releases hormones from the relevant gland into the blood stream. Distances are longer and the transmission can take minutes or days, the response also being longer lived: the one exception to the latter being the hormones Adrenaline and Noradrenalin.

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The est. example of the speed available to the nervous system is evidenced by the Reflex Arc, Figure 1 below, Figure 1. The Reflex Arc. Http://www. Google. Co. UK/search? Q=diagram+of+the+reflex Reflex Arc Is a series of neural connections that travel through a pathway that does not necessarily go via the brain. For example, it a harmful/acute stimulus is picked up by the sensory areas of the fingers, I. E. A hot roasting tin from the oven, then the bodily reflex is to drop that stimulus before damage has occurred. In the specific example. He impulses travel to the Sacral Plexus of nerves at the base of the spine, Sears and Window 1983), are interpreted and then responded to before the stimulus has registered at the brain. Other reflexes do go through the brain but are not registered consciously, Like the Impulses that result In the pupil of the eye opening wider or closing In swift response to changing levels of light entering the eye. In the normal firing of a nerve impulse, the sensory neurons would pick up the sensation and pass it on to the connecting neurons which would take the message all the way to the brain, (Hanson, M. 004), before initiating any action to be taken ND passing that message back down the neural pathway, down the spinal cord and activating specific muscles by way of the motor neurons. The Neurological and balance or, Homeostasis. One of the best examples of how this works is in the way that blood glucose levels are maintained in the body. Glucose is defined as a simple sugar which is necessary to the energy regulation of living organisms, (Houdini et al, 1980) The level of glucose in the blood directly controls Clangor, (a hormone produced in the pancreas which helps to breakdown Glycogen and change it to Glucose in the liver).

When the blood glucose levels fall below a homeostasis level, this is picked up by the nervous system and instructions go out to the alpha cells of the Pancreas to make more Clangor to help raise levels again. As the process continues, at some point the balance is reached and the message- negative feedback- goes back to the alpha cells that this has happened and therefore production levels may revert to normal. If this message does not get through and supplies of Glycogen were to continue at a raised level, then the blood sugar would continue to fall causing Hypoglycemia and eventually, Diabetic coma, see figure 2.

Figure 2. How homeostasis is maintained in Blood Glucose Levels. Http://www. Biology-online. Org/4/3_blood_sugar. HTML There are hormones with very specific roles, known as steroid hormones. These substances are fat soluble which other hormones are not and it is this characteristic which enables them to bring about changes within a cell by passing through the phosphoric bilateral cell membrane of that particular target cell. Fat insoluble molecules are not able to diffuse into the cell in this way. Strongest, Androgen’s and Protesting are three of the groups coming under the heading of natural steroid- hormones.

Strongest and Androgen’s affect sexual development and function. Strongest, ( Stetsons and Steroidal), are manufactured in the Adrenal Cortex, – above the kidneys- and in the gonads of the female. They are primarily concerned with maturation [puberty , secondary female sex organs, and sexual behavior patterns. They are forms of testosterone made in the ovaries. During puberty estrogen is responsible for the changes taking place in the breasts, vagina, uterus ND fallopian tubes as well as the distribution of fat deposits in the typically female’ areas of the body, ( Wright. 007). Protesting, (Progesterone), help to mediate the ovarian cycle and maintain pregnancy. They originate from the ovaries and the placenta, making sure that that the best conditions exist for the implantation of the egg in the uterus and for keeping a pregnancy from coming to term before the fetus is ready. One of the most important of Progesterone’s functions is to enable the endometrial in the uterus to secrete special proteins during the second half of the menstrual cycle to promote the easy implantation of ova.

In the case where this does not happen, then negative feedback ensures that the levels of Estrogen and Progesterone drop with the resultant menstruation each month when the lining of the uterus breaks down and is expelled. During pregnancy, progesterone is produced by the placenta and is in evidence until shortly after birth at higher levels than normal. This elevation means that further eggs are not produced during the pregnancy and also that the breasts and milk production are ready for birth. Androgen’s too, (Testosterone and Undertones), originate in the Adrenal Cortex and organs.

Testosterone is needed for the manufacture of sperm, the development of the male reproductive organs and such things that differentiate the male from the female, e. G. Facial hair, deep voice and male musculature. It is produced in the testes and the adrenals. To a lesser extent, testosterone is made by females too and its role is connected to bone density, sex drive and the development of muscles. Synthesized steroids are used in medicine to rectify ailments such as respiratory disorders and inflammation disorders- corticosteroids.

Another group of manufactured steroids, anabolic steroids, are known for their misuse in sports and body building where they are used to promote extra muscle mass. They have severe side effects however, such as mood changes, raised blood pressure and fluid retention, peptic ulcers, reduced effects of insulin, osteoporosis and bruising. REFERENCES. Fulfill, A. (1998). Advanced Biology. Henchman, I-J. Hanson, M. ( 2004). Perspectives in Advanced Biology. Hooded and Sought, I-J. Houdini, M. Et al (1980). A Guidebook to Biochemistry. 4th Edition. Cambridge University Press.


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