Out messengers. The reason I believe that the

Out of all the physiological system I learned this semester the one I feel is the most important system of them all would be the endocrine system system in chapter five that focus on the chemical messengers. The reason I believe that the endocrine system is the most important is because it allows communication between the other system in the body and helps maintain homeostasis of the body. In most of cases, intercellular communication is performed by using chemical messengers such as hormones, neurotransmitters, and paracrine to bring about cell responses through signal transduction by binding of extracellular messenger to matching receptor. Hormones are long range messengers that are secreted into the bloodstream by the endocrine gland in response to appropriate signal which exert effects on target cells some distance away from their release site. On the other hand, neurotransmitters are short range chemical messengers that diffuse across narrow space to act locally on adjoining target cells such as a neuron or muscle. The third chemical messenger paracrine only acts locally on neighboring cells in immediate environment of their secretion site. When the endocrine gland secretes these chemical messengers, many of the body function are being regulated such as metabolism and the body’s growth. Usually disease in the body occur when the endocrine glands either produce too much or too little of a certain hormone. Throughout the semester I learned how certain chemical messengers produce by the endocrine gland affects other body system, such as the reproductive, skeletal and urinary system.

One of the body system that is affected by the endocrine system producing hormones would be the reproductive system. During a woman’s pregnancy a lot of hormone are produce by the endocrine gland and in response the body react to those hormones to aid in childbirth. One of hormone that the posterior pituitary gland, an endocrine gland, secrete would be oxytocin. This hormone is used in the uterus to help with contraction during childbirth and the breast also response to this hormone to help produce milk for the infant. Though secreted by the posterior pituitary gland, oxytocin is produce in the hypothalamus and stimulates the uterine muscle to contract and increases production of prostaglandins, which increase the contractions further. After birth, oxytocin then help promotes the movement of milk into the breast, allowing the mother to breastfeed her child. Oxytocin can also play a role in the male reproductive system as well because this hormone release from the endocrine system can promote sperm movement and production of testosterone by the testes. The way that oxytocin is controlled in the body and help regulate the reproductive system is through a positive feedback. When oxytocin is released from the posterior pituitary gland it causes an action that stimulates more oxytocin to be released such contractions as well in the uterus cause the release of oxytocin which in turn increase the rate and strength of the contraction in the uterus causing more oxytocin to be released. This positive feedback mechanism also works when a mother is breastfeeding her child. The sucking on the nipple by the infant stimulates the release of oxytocin into the bloodstream and causes mile to excrete from the mother’s breast. With the posterior gland producing oxytocin, the endocrine system can help and affect the reproduce system in the body.

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Another body system that is affected by the endocrine system would be the skeletal system. The parathyroid essentially helps the muscular systems function properly and is the primary element that causes muscles to contract. PTH is a hormone secreted by parathyroid gland cell and is an important endocrine regulator of calcium concentration in the extracellular fluid, which in turn affect a person’s bones. The control mechanism for parathyroid secretion is monitor by the amount of calcium that is in the body. If there is a low amount of calcium in the body, calcium receptors will sense this and in response to low extracellular concentrations of calcium, PTH will be released from the parathyroid.  PTH indirectly stimulates osteoclast activity within the bone marrow, in an effort to release more ionic calcium into the blood to elevate serum calcium levels. The bone is stored with a lot of calcium, and when the body needs calcium it is taken from the bone and with high levels of PTH the bones to release their calcium into the blood. Unfortunately, if the parathyroid releases too much or not enough PTH, then it can have a negative effect on the body in a variety of ways. One disease caused by an unnormal amount of PTH is hyperparathyroidism, which is an excess amount of PTH being secreted by the parathyroid. Another disease that results from too much PTH could be osteoporosis which is the deterioration of bone in the body. When too much PTH is released from an overactive thyroid gland this can cause the bones to release calcium constantly into the bloodstream. Bones start to lose their density and hardness when there is not enough calcium stored in them. Having the endocrine system secreting the hormone PTH helps regulate the amount of calcium in the bone and prevent a person from developing these diseases which can affect the skeletal system.

Finally, the digestive system is another body system that is affected by the hormones produced by the endocrine glands. One of the hormones produces by the endocrine gland that help that controls parts of the digestive system and maintains water balance in the body would be secretin. Secretin is responsible for controlling the pH in a person’s stomach and duodenum, and when the pH gets to be too high secretin is secreted from the pancreas to help get the pH level back to normal. Some problems that could arise if the pH gets high enough is that the food in the stomach would not be able to be broken down, or if the pH level gets too low then it could cause damage to the organs. Secretin is released from the pancreas when food enters the small intestines, causing other organs to release digestive fluids into the small intestines and stomach to help break down the food. If too much acid is released into the stomach, then the secretin stimulates cells in the pancreas to release bicarbonate. Bicarbonate is the substance that is used to neutralize an acid, thereby lowering the pH and protecting the organs from being damaged by being an extreme acidic environment. Secretin also plays a role in stimulating the liver to release bile, which contains bile acids, which are critical for digestion and absorption of fats and fat-soluble vitamins in the small intestine. Bile is also used to eliminate the waste product from the body by secretion into bile and elimination in feces. This hormone is secreted in response to acid in the duodenum and stimulates biliary duct cells to secrete bicarbonate and water, which expands the volume of bile and increases its flow out into the intestine. Having this hormone secreted by an endocrine gland help regulate and maintain homeostasis of the digestive system.

In conclusion, I learned a lot about the physiology of the body, but out of all the chapters that were discussed this semester the endocrine system was the one that stuck out the most to me and had the most importance. With the endocrine system, the body systems can communicate with each other and help keep the homeostasis in balance. Using hormones, and other chemical messengers, are useful ways to allow communication with the body and bring forth a beneficial response.