Key Hormonal Pathways Controlling Major Organ Functions
Hormones are generally secreted by the endocrine glands. They function as chemical messengers which signal and regulate the body’s metabolism. However, there are other tissues in the human body which are not a part of the endocrine system by secreting important hormones that play a major role in various bodily activities. Some of these tissues are tissues of the heart, kidney and the gastrointestinal tract. They have active sites of release for hormones and then these hormones travel to the target sites and are used in various functions. The following is a summary of the different types of hormones produced by non-endocrine tissues. These are:
Kidney hormones
Heart hormones
Git hormones
The kidneys produce two major types of hormones and some hormones like substance:
Hormones Secreted by Kidney
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Hormones Secreted by Heart
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Hormones of Gastrointestinal Tract (GIT)
The gastrointestinal tract is one of the non-endocrine tissues that secretes several hormones which help in the digestion process by acting as stimulants for different enzymes and gastric juices.
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Hormones Secreted by the Liver
FAQs on Hormones and Their Roles in the Heart, Kidney, and GIT
1. What primary hormone is secreted by the heart and what is its main function according to the Class 11 syllabus?
The heart's atrial walls secrete a peptide hormone called Atrial Natriuretic Factor (ANF). Its primary function is to decrease blood pressure. When blood pressure increases, ANF is released, causing the dilation of blood vessels (vasodilation), which in turn reduces the overall blood pressure.
2. What is the main hormone produced by the kidneys and what is its function?
The juxtaglomerular cells of the kidney produce a peptide hormone called erythropoietin. The primary function of this hormone is to stimulate erythropoiesis, which is the process of forming new red blood cells (RBCs) in the bone marrow.
3. How does the kidney's hormonal function help the body adapt to high altitudes?
At high altitudes, the oxygen levels are lower, leading to hypoxia. In response, the kidneys increase the secretion of erythropoietin. This hormone stimulates the bone marrow to produce more red blood cells. An increased number of RBCs enhances the oxygen-carrying capacity of the blood, helping the body compensate for the lower oxygen availability in the environment.
4. What are the four major peptide hormones secreted by the gastrointestinal tract?
The gastrointestinal (GIT) tract secretes four major peptide hormones that regulate digestion. These are:
- Gastrin: Stimulates the secretion of hydrochloric acid (HCl) and pepsinogen.
- Secretin: Acts on the exocrine pancreas to stimulate the secretion of water and bicarbonate ions.
- Cholecystokinin (CCK): Stimulates the pancreas to release enzymes and the gallbladder to release bile juice.
- Gastric Inhibitory Peptide (GIP): Inhibits gastric secretion and motility.
5. How does the Atrial Natriuretic Factor (ANF) from the heart act as a check on the renin-angiotensin mechanism?
The renin-angiotensin mechanism typically functions to increase blood pressure. ANF opposes this action. When blood pressure is high, ANF is released and causes vasodilation. It also inhibits the release of renin from the kidneys, thereby suppressing the entire renin-angiotensin pathway. This provides a crucial negative feedback loop to maintain blood pressure within a normal range.
6. What is the difference in the primary stimulus for the release of Secretin versus Cholecystokinin (CCK)?
The primary stimulus for the release of Secretin is the presence of acidic chyme entering the duodenum from the stomach. In contrast, the primary stimulus for the release of Cholecystokinin (CCK) is the presence of fats and proteins in the chyme within the duodenum. This ensures that the correct digestive juices are released in response to the specific composition of food.
7. Why are the heart, kidneys, and gastrointestinal tract considered endocrine organs despite their primary functions?
Although the heart, kidneys, and GIT have primary roles in circulation, excretion, and digestion respectively, they are also considered endocrine organs because they contain specialised cells that produce and secrete hormones. These hormones enter the bloodstream and act on distant target tissues to regulate various physiological processes, which is the defining characteristic of an endocrine function.
8. What would be the immediate physiological consequence if the stomach stopped producing gastrin?
If the stomach stopped producing gastrin, the secretion of hydrochloric acid (HCl) and pepsinogen from the gastric glands would be significantly reduced. This would severely impair protein digestion in the stomach, as pepsinogen requires an acidic environment (provided by HCl) to be converted into its active form, pepsin. It would also reduce the stomach's ability to kill ingested pathogens.
