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Endocrine & Reproductive System

EPO testing in sports EPO testing in sports Erythropoietin (EPO) is a naturally occurring glycoprotein hormone that controls red blood cell (rbc) production (erythropoiesis) and also said to be performance‐enhancing hormone. It can be used (illegally) by athletes to increase the level of rbcs in their blood, allowing them to transport more oxygen around their body. This test looks for raised levels of rbcs in a sample. The blood has been spun at very high speeds in a centrifuge, causing the blood to separate into three layers: red blood cells, white blood cells and plasma. If the red blood cells constitute more than 50% of the volume of the blood it is presumed that the athlete took EPO. In this chapter, we will examine the major types of hormones in humans, including where they are formed in the body and their major effects on reproductive system.

Learning Objectives

After completing the topic, the student will be able to:

  • Appreciate the importance of hormones in our life right from our birth.
  • Deduce the integration between nervous system and endocrine system and list the differences between hormonal control and nervous control.
  • Understand and explore the mechanism of hormonal signaling and explain how local regulators enhance this phenomenon.
  • List the different types of hormones produced by endocrine glands and review their functions.
  • State the major difference between positive and negative feedback systems and illustrate different types of endocrine disorders.
  • Describe the anatomy and functions of both male and female reproductive system of humans.
  • Explore the details of embryonic development and birth.
  • Summarize how modern reproductive technology helps to solve infertility problems.
Hormones Hormones Hormones play a very important role in our life right from our birth by regulating reproduction, growth and development in many ways and help maintain homeostasis.
Hormones and Endocrine System

Hormones {horma: to stir up/to excite/to put into action} play a very important role in our life right from our birth by regulating reproduction, growth and development in many ways and help maintain homeostasis. The moodiness of teenagers, obesity of humans and even the transformation of caterpillar into a butterfly are regulated by hormones.

Millions of people with diabetes all over the world take the hormone insulin. Hormones are also used in cosmetics to keep the skin smooth and in livestock feed to fatten cattle. So our life style, moods and emotions are also influenced by the hormones. The activities in our body are highly complex and they need to be so regulated that every activity takes place at a proper time and in a correct sequence. For example, the gastric juice, bile and pancreatic juice should be poured into the food canal only when there is food in it. Though this kind of regulation is done to some extent by the nervous system but it also brought about by hormones.

Insulin Insulin Showing a part of the molecule of human insulin. A single insulin molecule is made up of two chains of amino acids, the A and B chains, which are held together by di‐ sulphide bridges. Insulin is a hormone which is produced in the pancreas by cells of the Islets of Langerhans. Its function is to regulate blood sugar levels. Insufficient production of insulin leads to an accumulation of glucose in the blood, causing diabetes mellitus.
How hormones work?

These are the steps below, how hormones come into play

  1. Biosynthesis of a particular hormone in a particular tissue
  2. Storage and secretion of the hormone
  3. Transport of the hormone to the target cells
  4. Recognition of the hormone by an associated cell membrane or intracellular receptor protein
  5. Relay and amplification of the received hormonal signal via a signal transduction process: This then leads to a cellular response. The reaction of the target cells may then be recognized by the original hormone‐producing cells, leading to a down‐regulation in hormone production. This is an example of a homeostatic negative feedback loop.
  6. Degradation of the hormone.

Hormone cells are typically of a specialized cell type, residing within a particular endocrine gland, such as thyroid gland, ovaries, and testes. Hormones exit their cell of origin via exocytosis or another means of membrane transport.

The hierarchical model is an oversimplification of the hormonal signaling process. Cellular recipients of a particular hormonal signal may be one of several cell types that reside within a number of different tissues, as is the case for insulin, which triggers a diverse range of systemic physiological effects. Different tissue types may also respond differently to the same hormonal signal.

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