The Essay On Melatonin's Importance For Body Homeostasis.

The human body’s physiological systems rely on control at both a local level and by neural and hormonal reflexes for homeostasis and normal functioning of the body. One of the major controls is through hormonal regulation, which offers sustained regulation.

This learning and assessment task is designed to help you explore a specific hormone and how it is important for homeostasis. You will gain skills in searching for literature and increase your knowledge base and understanding of a physiological control system, whilst producing an assignment that is informative, interesting and creative.

• Students must produce an informative, interesting and creative assignment that describes the physiology of one hormone in depth and how that hormone is important to physiological functioning.
• Students may elect to complete the assignment as an individual or as a self-nominated group, with a maximum of 4 students per group.
• A list of suitable hormones is published to Blackboard and a maximum of 4 students/groups may complete the assignment on a given hormone.
• Individual students/groups must nominate their chosen hormone to the Course Coordinator by email, no later than Friday Week 5.

What to include

• You must address the following points systematically:

Structure of the hormone, including chemical characteristics

The hormone’s production

Mechanism(s) for the release of the hormone – including any feedback mechanisms

Mode of action of the hormone at the target cells (i.e. receptors and cell response)

Big-picture physiological action of the hormone on the target cells/tissue(s) and or/organ(s)

Keep in mind that the text should be able to be read easily and that the formatting suits your media style

• Depending on the format chosen you may need to complete a separate but related component to satisfy the Creative criterion.

o For example, if you chose a Narrated Powerpoint presentation you would also produce a narration script for the slides which would be academically written – this could be saved as a video MP4;

o If you chose a game or puzzle you must link a written academic component to the object

o A poster with text, images and referencing, however, could satisfy both components.

o If you are not sure please check with the Course Coordinator

Preferred reference material

• It is best to use relevant and recent journal articles – either quality review articles or research articles.
• Use specialised text books (secondary references).
• Your text book is not a primary source, so should be used minimally.
• Don’t use multiple copies of similar textbooks (e.g. three general Physiology and Anatomy texts or, even worse, three editions of the same text).
• Avoid the use of unsubstantiated websites as most them are not peer-reviewed.

Overview of Hormonal Regulation in the Body

Hormones are part of the body’s communication pathways. They are chemical messengers of the endocrine framework. Endocrine organs make hormones, which are transported throughout the body by the circulatory system to tissues and organs, and control the more significant part of the body's systems. The endocrine system regulates our pulse, digestion – how the body gets energy from the nourishment we eat – hunger, state of mind, reproductive capacity, reproduction, development and growth, rest cycles among many other functions.

Melatonin is a chemical substance secreted by the pineal organ, a small pinecone-shaped organ of the endocrine framework. The gland is located at the midline of the right and left hemisphere of the brain, which is at the diencephalon. The gland is composed of both the pinealocyte cells and cells of the sensory framework referred to as glial cells. The pineal organ joins the hormonal systems with the nervous framework in that it translates impulses from the sympathetic structure of the peripheral nervous framework into hormone messages. Melatonin is likewise secreted from other somatic cells and tissues including retinal cells, white blood cells, gonads, and the skin.

The hormone was first isolated in 1958 by an American doctor Aaron B. Lerner and his associates at Yale University School of Medicine. They named the hormone based on its capacity to enhance skin lightening in frogs by turning around the skin-obscuring impacts of the melanocyte-stimulating hormone. Melatonin is subordinate to an amino acid tryptophan. The production of the hormone occurs in humans, different warm-blooded animals, winged creatures, reptiles, and the amphibians.

Melatonin is the primary recognized chemical produced by the pineal organ and is discharged in relation to varying intensity of dimness thus the name, "hormone of darkness" (Srinuvasan et al., 2009, pp.779-785). Melatonin is delivered from serotonin which is produced using tryptophan, through a course of enzymatic reactions. The biosynthesis of melatonin through the traditional pathway includes four remarkable advances incorporating hydroxylation, decarboxylation, acetylation, and methylation (Johnston and Skene, 2015, p.15).

An antecedent atom, L-tryptophan is created because of protein catabolism or from chorismate through the shikimate pathway. Then a catalase called tryptophan hydrolase hydroxylates the L-tryptophan to an indole ring shaping a side-effect alluded to as 5-hydroxytryptophan (5-HTP). This is followed by decarboxylation reaction on 5-HTP when it reacts with pyridoxal phosphate in the presence of a catalyst of 5-hydroxytryptophan decarboxylase forming a synapse compound called serotonin. The last final stages in the series of reaction incorporate the transformation of serotonin into N-acetylserotonin (NAS) enhanced by the compound arylalkylamine N-acetyltransferase (AANAT) and then by the converting of N-acetylserotonin into melatonin in the presence of hydroxyl-indole-O-methyltransferase catalyst (Roberts and Fitzpatrick, 2013, pp.350-357).

Structure and Production of Melatonin Hormone

The pineal organ receives impulses from postganglionic strands, prompting the arrival of noradrenaline and high-level generation of the cyclic AMP, in this way initiating the chemical AANAT that is fundamental for the synthesis of melatonin. However, the storage of this hormone does not occur in the pineal organ but instead is discharged into the circulatory system and then enters all body parts (Master et al., 2014, p.4). It is worth noting that dimness invigorates the pineal organ to secret melatonin while the introduction to light restrains this system (Hardeland, 2013, pp.5817-5841).

Strangely, the pineal organ, although embryologically a component of the brain, is situated beyond the blood (BBB)-brain barrier and connects with the central nervous system (CNS), through the sympathetic nerves as its primary connection. This maybe represents the capacity of the pineal organ to carry out significant absorption of tryptophan prompting a high melatonin creation and emission because of darkness. This process likewise provides relative security from untimely enzymatic debasement which prompts a 10-20 overlap increment in plasma melatonin concentrations that effectively move through cell films and diffuses past the BBB.

Melatonin generation is fundamental in controlling the sleep-wake cycles referred to as circadian rhythm, and its generation is dictated by the recognition of light and darkness. The retina relays impulses concerning the recognition of both light and darkness to a zone of the mind known as the hypothalamus. The impulses are at the end transmitted to the pineal organ. The more light recognized, the little the amount of melatonin delivered and discharged into the body’s circulatory system. Melatonin concentrations are at their most elevated amid darkness, and this advances alterations in the body that bring about sleep. Low concentration of melatonin during sunshine hours initiate and maintain wakefulness. The hormone has been utilized in remedying rest related issues such as jet lag and shift-work rest issues. In these two situations, the human’s circadian cycle is altered either because of movement over numerous time zones or because of working night shifts or rotational shifts. Melatonin has additionally been utilized in the correcting of a sleeping disorder (insomnia) and the depression issue.

Melatonin’s rest advancing activities are for the most part as a result of its feedback to the suprachiasmatic core (SCN) which is referred to them as the ‘master clock.’ The feedback pathways are mainly on the melatonin receptors (MT1 and MT2) (Srinuvasan et al., 2009, pp.779-785). By taking a shot at the SCN, melatonin synchronizes the circadian rhythm by influencing both the stage and abundance of the mood (Hardeland et al., 2008, pp.1-10). It is believed that neuronal activation is reversed through MT1 receptors though MT2 receptors are in charge of changing phases.

Mechanism of the Release of Melatonin Hormone

Melatonin affects the development of the reproductive system as well as its structures. It represses the secretion of some reproductive chemicals from the pituitary organ that impact on the male and female reproductive structures. These hormones, referred to as gonadotropins, trigger reproductive organs to discharge sex hormones such as the luteinizing hormone and the follicle stimulating hormones. The bonding of melatonin to the receptors on the pituitary organ as well as the ovaries is believed to perform a function in controlling the production of reproductive hormones in females. For example, the planning, length, and recurrence of menstrual cycles in females are affected by melatonin. Therefore, this hormone is vital in regulating sexual development in both female and male reproductive systems.

Melatonin has antiaging properties. The hormone is an antioxidant whereby it neutralizes toxic oxidative radicals, and it is fit for actuating certain cancer prevention agent compounds. The melatonin hormone can prevent Radiation-induced cell infections in humans. Studies have depicted that the metabolites of this hormone rummage the free oxygen radicals that often result from the exposure to radiations. This shields humans from oxidative pressure (Tan et al., 2007, pp.28-42). The supporting principle is the counteractive action for the formation of hydroxyl during ionization which destroys DNA, proteins and the cell membrane. Melatonin generation gradually decreases with age, and its misfortune is related with a few age-related maladies.

Melatonin additionally plays a role in adjusting some aspects of the immunity structure. Melatonin associate with the immunity framework. The impacts might be initiated by the high-affinity melatonin receptors (MT1 and MT2) which are represented in immunocompetent cells. The hormone facilitates the generation of cytokine and might be helpful in battling infectious maladies. The endogenous melatonin in human lymphocytes has been associated with the release of interleukin-2 (IL-2) as well as the expression of the IL-2 receptor.

There are varieties of studies continuing concerning the melatonin hormone. Primarily, the interest in this hormone is because of its valuable application and other possible uses.

Among them are various researches to assess whether melatonin advances rest among grown-ups in intensive care units (ICU) (Lewis et al., 2018). The ICUs are occupied continuously for 24 hours a day. Patients in the ICU face rest depriving experiences due to the great commotion, expanded patient exercises, and obtrusive monitoring which is a piece of their care program. The absence of rest has consequences for the physical and mental wellbeing of the ICU patients amid their stay in the healthcare facility. During the night melatonin levels are expected to build; however, their discharge is hampered because of the artificial lighting. Since melatonin emphatically influences the circadian rhythm the illumination and activities in the ICU may reset the natural rhythm disturbing regular rest. The findings from this study will illuminate clinic organization about the impact of these melatonin medicines in improving rest which is crucial in enhancing the recuperation of ICU patients.

In conclusion, melatonin hormone is vital for all organisms for its benefits cannot be overestimated. More research on the hormone will elucidate on other applications of this hormone, especially in medicine.

References

Hardeland, R., 2013. Chronobiology of melatonin beyond the feedback to the suprachiasmatic nucleus—Consequences to melatonin dysfunction. International Journal of Molecular Sciences, 14(3), pp.5817-5841.

Hardeland, R., Poeggeler, B., Srinivasan, V., Trakht, I., Pandi-Perumal, S.R. and Cardinali, D.P., 2008. Melatonergic drugs in clinical practice. Arzneimittelforschung, 58(01), pp.1-10.

Johnston, J.D. and Skene, D.J., 2015. Regulation of mammalian neuroendocrine physiology and rhythms by melatonin. Journal of Endocrinology, pp.JOE-15.

Lewis, S.R., Pritchard, M.W., Schofield?Robinson, O.J., Alderson, P. and Smith, A.F., 2018. Melatonin for the promotion of sleep in adults in the intensive care unit. Cochrane Database of Systematic Reviews, (5).

Masters, A., Pandi-Perumal, S.R., Seixas, A., Girardin, J.L. and McFarlane, S.I., 2014. Melatonin, the hormone of darkness: From sleep promotion to ebola treatment. Brain disorders & therapy, 4(1).

Roberts, K.M. and Fitzpatrick, P.F., 2013. Mechanisms of tryptophan and tyrosine hydroxylase. IUBMB life, 65(4), pp.350-357

Srinivasan, V., Spence, W.D., Pandi-Perumal, S.R., Zakharia, R., Bhatnagar, K.P. and Brzezinski, A., 2009. Melatonin and human reproduction: shedding light on the darkness hormone. Gynecological Endocrinology, 25(12), pp.779-785.

Tan, D.X., Manchester, L.C., Terron, M.P., Flores, L.J. and Reiter, R.J., 2007. One molecule, many derivatives: a never?ending interaction of melatonin with reactive oxygen and nitrogen species?. Journal of pineal research, 42(1), pp.28-42.