Thyrotropin-releasing hormone (TRH) targets the pituitary gland which produces a stimulating hormone (TSH) that targets the thyroid gland. The thyroid gland releases thyroxine that is involved in the regulation of the bodys metabolism and general physiological processes. Thyroxine levels and the bodys physiological state exert a negative feedback effect on the hypothalamus, which thereby, regulates its blood levels.
Gonadotropin-releasing hormone (GnRH) is a hormone produced by the hypothalamus whose effect is directed to the anterior pituitary gland. The anterior pituitary gland then produces luteinizing hormone (LH) and follicle stimulating hormone directed to the testes and ovaries. The proper and controlled functioning of the internal sex is therefore kept in check by the hypothalamus.
Finally, the hypothalamus produces the prolactin-releasing hormone (PRH) and prolactin-inhibiting (PIH) that act on the anterior pituitary to regulate the production of prolactin that is involved with milk production.
1. Functions of the pituitary gland
a) Storage of hormones;
b) Regulation of the production of hormones by other glands in the body;
c) Production of hormones which are involved with:
- regulation of metabolism in the body;
- regulation of growth and development in the body;
- regulation of milk production;
- regulation of blood pressures through its influence on the kidneys;
- maintenance of the bodys homeostasis.
2. Neural control leads to faster body response as compared to hormonal control. This is because neural control involves direct chemical communication yet in hormonal, the response is slower since it may require the synthesis of the hormone, transportation through blood to the target organ and transcription to form the proteins needed for the physiological process or adaptation triggered by the hormone.
Hormonal systems involve the use of organic compounds as messengers. The blood transports these compounds to their target organs. On the other hand, in the neural system, neurotransmitters act as chemical messengers to the target cells. The chemical agents depend on action potentials generated in the neurons in response to stimuli.
The nervous system is mainly mediates the bodys response to the external environment, but, it also works synergistically with the hormonal system to in helping the body respond to change in internal body milieu. On the contrary, the hormonal system is mainly involved with the internal body milieu changes. The hormones work to maintain homeostasis.
The effects of the hormonal response are long lasting. This is because in some, proteins are synthesized which thus, lead to structural change. On the other hand, in the neural system, the effects are short-lived since they do not result in any structural change in the body.
Finally, in the neural system, the message is directed specifically to the target organ. On the other hand, in the hormonal system, the hormone is deposited in blood where it is transported around the body but will only have a direct effect on the organ that has the specific receptors.
3. Glucose serves as an indispensable source of energy for all body cells for the maintenance of their structure integrity and the fulfillment of their physiological roles. Therefore, due to this requirement, the body keeps the levels of glucose in constant check. The gland involved in the regulation of the levels of glucose is the pancreas. Hypoglycemia, low blood glucose levels lead to increased production of glucagon which acts on the adipose tissue leading to a generation of glucose from the stored lipids in a process called gluconeogenesis.
Therefore, from the above example, we have seen that since the body detected a change from the normal homeostatic levels of glucose in the blood, it triggered the production of a messenger molecule, insulin, (hormone) to act on a target site, adipose tissue. The resultant gluconeogenesis, therefore, restores the blood glucose levels to homeostatic levels.
4. Stress is any disturbance of the human environment from its normal equilibrium. These disturbances, therefore, trigger the body to adapt to the changes by releasing different hormones that may alter the normal physiologic pattern to suit the changes. During any stressful situation, the body prepares for fight or flight. The neural system comes into play by the recruitment of the sympathetic system whereas the hormonal system joins with the release of catecholamines and cortisol through the activation of the pituitary-adrenal axis. The pituitary-adrenal axis and sympathetic nervous system activation leads to vasoconstriction, increased cardiac output and respiratory rate, bronchial dilatation, increased glucose production and closure of sphincters. The increase in respiration and cardiac output is to produce enough oxygen and supply of adequate energy to the organs, like muscles, which are required for the response to the stress.
5. The parasympathetic and the sympathetic system constitute the Autonomic nervous system. Their actions oppose each other. The main reason for this feature is to enable moderation of the changes that are effected by either system. This regulation is required since the body requires a certain homeostatic range to work optimally relative to the envir...
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