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[image] RCSI. RCSI Royal College of Surgeons in Ireland Coláiste Ríoga na Máinleá in Éirinn.

[Audio] Today, we will be discussing the second slide of our presentation on GIT hormones. The topic for today is "Learning Outcomes." Our first learning outcome is to be able to describe the main factors, including hormones, that inhibit gastric acid secretion. This is important in understanding how our gastrointestinal system functions. We will also be learning about two specific hormones - secretin and cholecystokinin (CCK). It's important to know their origin, function, and the factors that influence their secretion. This will help us understand how our body responds to different stimuli. Next, we will look at the main hormonal and neuronal control mechanisms that regulate exocrine pancreatic and biliary secretions, as well as the secretions of Brunner's glands. These are crucial for maintaining a balanced digestive system. We will also outline the role of additional gastrointestinal hormones such as motilin, serotonin, GIP, VIP, and somatostatin in gastrointestinal function. This will give us a comprehensive understanding of the various hormones involved in our digestive process. Lastly, we will discuss how GIT hormones are involved in the control of food intake. This is an interesting aspect to explore as it will help us understand our body's regulatory mechanisms for food consumption. Let's strive to achieve these learning outcomes and gain a deeper understanding of GIT hormones..

[Audio] Today, we will be discussing the major hormones involved in our digestive process and how they are regulated. This lecture was previously taught to first year students in the GIHEP module at RCSI by Professor Christopher Torrens on 18/09/25. We will be revisiting some of the major hormones and their actions in the digestive system, such as gastrin, cholecystokinin, and secretin. These hormones also have non-gastric effects on other parts of the digestive system, including the pancreas and the production of bile. Additionally, we will discuss the role of neurohumoral signals in regulating food intake. This is an important aspect of digestion that is often overlooked. Our presentation will examine the vital role that gastrointestinal hormones play in our digestive system and overall health. Let's continue to explore this fascinating topic..

[Audio] Today, we will discuss hormones and communication in the human body. Hormones are crucial for regulating bodily functions and maintaining homeostasis. We have previously learned about the different types and functions of hormones. Now, we will focus on their mode of communication: autocrine, paracrine, and endocrine. Autocrine communication occurs between the same cell, while paracrine communication involves neighboring cells. Endocrine communication takes place between distant cells. It's important to note that hormones can refer to all three forms of communication as they can act on the same cell, nearby cells, and cells in distant parts of the body. This highlights their complexity and importance in our body. As first year students in the GIHEP module at RCSI, understanding hormone communication is vital for our academic and future healthcare careers. I hope this overview has sparked your interest and I look forward to further discussion on this topic. See you in our next lesson.".

[Audio] In our last slide, we learned about the various types of hormones in the gastrointestinal tract and their functions. Now, let's focus on the five main hormones in this system. First, there is gastrin, which is produced in the antrum of the stomach and stimulates gastric acid secretion and smooth muscle contractions. Next, we have cholecystokinin (CCK), which is produced in the duodenum and jejunum and triggers the release of digestive enzymes from the pancreas and the contraction of the gallbladder. Secretin, also produced in the duodenum, helps regulate stomach acidity and pancreatic bicarbonate production. Moving on, we have GIP (Glucose-dependent Insulinotropic Peptide), which is produced in the duodenum and jejunum and plays a crucial role in regulating insulin release in response to glucose levels in the blood. Lastly, we have motilin, which is produced in the duodenum and jejunum and helps control the movement of food through the digestive tract. These hormones are released from enteroendocrine cells in the mucosa, rather than from glands, and act through different pathways. The primary sites for these hormones are the duodenum and jejunum, with some contribution from the antrum (gastrin) and ileum (motilin and GIP). This can be seen in the accompanying diagram. That concludes our discussion on the five main GIT hormones. In the next slide, we will examine the specific functions of each hormone and how they interact within the gastrointestinal system..

[Audio] Today, we will focus on the cephalic, gastric, and intestinal phases of digestion. The cephalic phase is triggered by sensory cues and stimulates the release of the hormone gastrin, which prepares the stomach for food by initiating the production of mucous, hydrochloric acid, and pepsinogen. In the gastric phase, the stretching of the stomach activates stretch receptors, leading to peristalsis and the mixing of food and gastric juices, ultimately breaking down the food into chyme. The intestinal phase is initiated by the presence of nutrients in the small intestine, which triggers the release of the hormones CCK and secretin. These hormones slow down gastric emptying and inhibit gastric secretions to allow for proper digestion and absorption of nutrients, highlighting the importance of a healthy diet. By understanding the role of hormones and the different phases of digestion, we can better comprehend the complex process of nutrient absorption. Our discussion will continue in our next lesson..

[Audio] We will now focus on the structural homology of two important GIT hormones - Gastrin and Cholecystokinin (CCK). Both hormones share a structural similarity due to the same C-terminal 5 amino acids - Glycine, Tryptophan, Methionine, Aspartic Acid, and Phenylalanine. This allows for cross-reactivity at receptors, meaning they can bind to the same receptors and produce a similar effect. The CCK-1 receptor, found in the gallbladder and pancreas, is mainly activated by CCK, while the CCK-2 receptor (also known as the gastrin receptor) is primarily located in the stomach and responds to gastrin. It is important to note that although these hormones have some overlapping functions, their receptors are specific to their respective hormones. In future lessons, we will explore their functions and the effects of their activation. Understanding the structural homology and receptor specificity of these hormones is crucial in comprehending their roles in digestion and overall body functioning. Take a moment to reflect on the important role these hormones play in our bodies and how their structural similarities allow for cross-reactivity at receptors..

[Audio] During this presentation, we will discuss the site of gastrin release and the stimuli for its release. Gastrin is a hormone that regulates digestion and acid secretion in the stomach. It is primarily released from G cells in the antrum of the stomach, with some also present in the proximal duodenum. The release of gastrin can be triggered by three phases - the cephalic phase, the gastric phase, and the intestinal phase. The cephalic phase, also known as the "vagal phase", is triggered by conditioned reflexes such as sight, smell, chewing, and swallowing, which stimulate the vagus nerve to release GRP, a peptide that stimulates G cells to release gastrin. The gastric phase is triggered by stomach distension and the presence of peptides and amino acids from protein digestion. The intestinal phase plays a minor role, with amino acids and peptides in the duodenum stimulating G cells to release gastrin. Overall, gastrin release is mainly triggered by stimuli in the cephalic and gastric phases, with the intestinal phase having a minor role. Thank you for your attention and for attending this class on GIHEP at RCSI. I hope this presentation has provided a better understanding of the site and stimuli for gastrin release and I look forward to seeing you in our next session..

[Audio] Today, we will be discussing the actions of gastrin, a hormone involved in the digestive system. Hormones are vital in maintaining homeostasis and regulating bodily functions. In this class, we will focus on gastrin's main actions and its effects on the gastrointestinal system. Gastrin acts on the stomach, specifically on gastric acid secretion. When released, it binds to CCK-2 receptors on parietal or oxyntic cells, triggering a cascade of events involving IP₃ and calcium ions, leading to an increase in gastric acid secretion. This is important for breaking down food and aiding digestion. Gastrin also binds to ECL cells, which release histamine, further increasing gastric acid secretion through the cAMP pathway. This maintains optimal pH levels in the stomach for proper digestion. In addition to these actions, gastrin also stimulates the growth of the gastric mucosa, preventing gastric issues and maintaining a healthy stomach. Its long-term effects are believed to be partly mediated by histamine. Furthermore, gastrin weakly activates CCK-1 receptors, leading to an increase in splanchnic blood flow. This aids in digestion and overall gastrointestinal health. In conclusion, gastrin is crucial in maintaining a healthy digestive system. Its actions on gastric acid secretion, trophic effects, and other functions make it an important hormone for our overall well-being. As we continue in the GIHEP module, it is essential to understand the role of gastrin and its significance in the gastrointestinal system..

[Audio] We will discuss cholecystokinin, or CCK, which is a hormone that aids in digestion. CCK is mainly released by I cells in the duodenum and to a lesser extent, the jejunum. There are few I cells in the ileum. CCK is released when nutrients are present in the lumen, or cavity, of the small intestine. This includes peptides and amino acids from protein digestion, as well as fatty acids and monoglycerides from fat digestion. CCK is released through sensing by I cells and also through the vago-vagal reflex involving the vagus nerve. After the nutrients are absorbed in the mucosa, or inner lining, of the intestine, CCK triggers the gallbladder to contract and release bile and the pancreas to release digestive enzymes. This results in increased absorption of nutrients into the bloodstream. In summary, CCK is released by I cells in the duodenum and jejunum in response to nutrients in the lumen. Its role is to stimulate the release of bile and pancreatic enzymes for proper digestion and absorption of nutrients. We look forward to discussing more about GIHEP in the future..

[Audio] Today, we will discuss the important topic of gastrointestinal hormones. This is slide number 11 out of 40 in our presentation on GIT hormones, taught by Prof. Christopher Torrens on 18/09/25 to the first year class in the GIHEP module at RCSI. On this slide, we will focus on the main actions of these hormones, including gallbladder contraction which leads to the release of bile and the stimulation of pancreatic acinar cells resulting in enzyme secretion. These hormones also have some effects on the stomach, stimulating acid secretion through CCK-2 receptors and inhibiting acid production through CCK-1 receptors, ultimately leading to a decrease in gastric emptying and acid levels. In addition to these effects, these hormones also increase blood flow to the splanchnic area and can promote a feeling of fullness or satiety by slowing down gastric emptying. Overall, gastrointestinal hormones play a crucial role in regulating various functions in our digestive system. Let's move on to the next slide to learn about the other hormones involved in digestion..

[Audio] We will be discussing gastrointestinal hormones and their site of release in this class. This is slide 12 out of 40 in our presentation on GIT hormones in the GIHEP module at RCSI, taught by Professor Christopher Torrens on 18/09/25. The main site of release is from S cells in the duodenum and a few in the jejunum. The main trigger for secretion is a decrease in pH levels below 4.5 in the duodenal lumen. Other weak stimuli include fatty acids. There are a few possible mechanisms for the release of these hormones, such as secretin-releasing peptide activating sensory afferents or direct sensing of pH by the S cells. These hormones increase bicarbonate-rich secretions from pancreatic and biliary duct cells and also increase insulin secretion from the pancreas. They also decrease gastric acid secretion through somatostatin released by D cells and slow down gastric motility through vagal inhibition. In addition, they increase splanchnic blood flow. Understanding the site of release and stimuli for these hormones is important in comprehending the complex regulation of the digestive system. Let's move on to our next slide..

[Audio] Today, we will be discussing additional regulatory hormones that are important for the gastrointestinal system. These hormones include somatostatin, produced by D cells in the stomach and pancreas, and GIP, produced by K cells in the duodenum and jejunum. These hormones have various functions, such as decreasing gastric acid secretion, controlling motility, and regulating glucose levels. In addition, we will also be discussing the incretin hormone and its role in the development of new medications like tirzepatide and Mounjaro. These hormones are essential for maintaining the proper functioning of the GI system. Let's continue our exploration of GIT hormones on the next slide..

[Audio] Today we will be discussing two hormones related to the motor and reflex functions of the gastrointestinal tract: Motilin and Serotonin. Motilin is released by Mo cells in the upper small intestine during periods of fasting, approximately every 90 minutes. Its main role is to initiate the migrating motor complex which helps clear debris and foreign bodies in the gut, causing the familiar rumbling sound in our stomach. Next, we have Serotonin, also known as 5-HT, which is released in response to gut irritation and can trigger the vomiting reflex. This is why it is often targeted by antiemetic medications. Thank you for joining us for this presentation on GIHEP and stay tuned for more on the world of GIT hormones..

[Audio] Today, we will be discussing the major gastrointestinal hormones, including gastrin, cholecystokinin (CCK), and secretin. These hormones play important roles in regulating our digestive system. Gastrin and CCK, produced by the stomach, stimulate the release of gastric acid and enzymes to aid in digestion. Secretin, released by the small intestine, stimulates the pancreas to release digestive enzymes. It's worth noting that there are various other hormones that also contribute to the proper functioning of our digestive system. These hormones not only have an effect on the stomach, but they also have non-gastric actions. For example, CCK can also cause the release of pancreatic enzymes and stimulate bile production in the liver. Secretin also plays a role in the production of a mucus-rich fluid in the duodenal Brunner's glands, which helps neutralize stomach acid. Additionally, these hormones play a crucial role in regulating our food intake and appetite, making them an important area of research in understanding and treating conditions such as obesity and eating disorders. It is essential for us to have a thorough understanding of these hormones in our medical education as they have a significant impact on our digestive system. As we conclude slide number 15, we are reminded of the importance of highlighting the various functions and regulation of these hormones..

[Audio] Today, we will discuss the overview and structure of pancreatic secretions. The pancreas is a dual gland with both endocrine and exocrine functions. The endocrine function releases hormones into the bloodstream, while the exocrine function releases secretions into the digestive system. We will focus on the exocrine function, particularly the release of aqueous and enzymatic secretions. Aqueous secretions contain sodium and bicarbonate ions, which help neutralize the acidic stomach environment. Enzymatic secretions, released from the cells of the pancreas, include proteases, amylase, and lipase, which aid in the digestion of proteins, carbohydrates, and fats. Pancreatic secretions are vital for proper digestion and nutrient absorption in the GIHEP module. This lecture was delivered by Professor Christopher Torrens on 18/09/25 to a first-year class at RCSI. I hope this has provided a better understanding of pancreatic secretions. Thank you for joining, and I will see you in the next lecture. Have a great day!.

[Audio] This presentation will cover slide number 17 on GIHEP module at RCSI. Today, we will be discussing GIT hormones and their significance in gastrointestinal health. The diagram on the slide shows the different hormones in the human body and their functions. These hormones play a crucial role in regulating various digestive processes. Poon, pou, and npupuds are the key hormones responsible for stimulating stomach acid production, slowing down food movement in the intestines, and regulating hunger and fullness sensations. The hormone pnp, produced by the pancreas, aids in nutrient absorption in the small intestine. The last hormone, epq, helps maintain a healthy balance of bacteria in the colon. It is important to understand the individual functions of each hormone and how they work together for a healthy digestive system. As future healthcare professionals, understanding these hormones is essential for your studies and future career. Abbreviations for each hormone will be used throughout the presentation. Please review the material covered today and come prepared with any questions in our next session on GIT hormones. Thank you for your attention..

[Audio] Slide number 18 out of 40 in our presentation on GIT hormones discusses pancreatic secretions and their important role in digestion. The exocrine secretory units of the pancreas, which are like lobules supplied by branches of the pancreatic duct, are the focus of this conversation. These units secrete a small volume of protein-rich "juice" into the ducts, containing inactive precursors of digestive enzymes. Before reaching the small intestine, the "juice" is diluted by a larger volume of aqueous solution from the ductal epithelial cells, which helps to neutralize the acidic environment of the stomach. This process is crucial for efficient digestion and absorption of nutrients in our body. It is just one of the many amazing processes that our bodies undergo every day. That concludes our discussion on pancreatic secretions..

[Audio] Today, we will be discussing the control of pancreatic secretion. This process is essential for digestion and involves the release of enzymes and hormones. During the interdigestive phase, the basal secretion of pancreatic enzymes increases up to 20 times during meals. This is due to the activation of different mechanisms. The first mechanism is parasympathetic vagal stimulation, triggered by the release of acetylcholine. This stimulation prepares our digestive system for food by increasing enzyme production. Another mechanism is the release of CCK from the duodenum, which is stimulated by the presence of food in the small intestine and further enhances enzyme release. The third mechanism is the release of secretin, triggered by a drop in pH levels in the duodenum. This signals for the pancreas to release its enzymes. The control of pancreatic secretion occurs in three phases: the cephalic, gastric, and intestinal phases. The cephalic phase is stimulated by thoughts, smells, or sights of food. The gastric phase occurs when food enters the stomach, and the intestinal phase takes place in the small intestine. Overall, the control of pancreatic secretion involves multiple mechanisms and hormones, and understanding this process is crucial for comprehending the digestive system..

[Audio] Today, we will be discussing the control of pancreatic secretion, specifically the cephalic and gastric phases. The cephalic phase is triggered by conditioned reflexes such as smell, taste, chewing, and swallowing. These stimuli activate the vagal efferents which release the neurotransmitter acetylcholine. This acetylcholine then stimulates the secretion of digestive enzymes and bicarbonate from the pancreas. In addition, gastrin can also stimulate the acinar cells in the pancreas, although its direct effect on pancreatic secretion in humans is still unclear. Moving on to the gastric phase, this is triggered by the presence of food in the stomach. Similar to the cephalic phase, the neural pathways involved in this phase are also initiated by the vagus nerve. Gastric distension, which is the stretching of the stomach due to food, stimulates the release of pancreatic secretions through the vagovagal reflex. Gastrin is also released during this phase, stimulated by the breakdown of proteins and gastric distension. However, it has little to no direct effect on the secretion of pancreatic enzymes in humans. The control of pancreatic secretion is a complex process involving both neural pathways and hormonal stimuli. Understanding these mechanisms is important for understanding how our digestive system functions..

[Audio] Today, we will be discussing the role of the intestinal phase in the secretion of pancreatic enzymes. This phase accounts for 70-80% of the total pancreatic secretion and is primarily triggered by digestion products and H⁺ in the small intestine. Hormonal regulation is a major factor in this phase, with the release of two key hormones, secretin and CCK. Secretin is released from S cells in response to the presence of acid and fatty acids, stimulating ductal cells and increasing bicarbonate-rich aqueous secretion and the volume and pH of pancreatic secretion. In contrast, CCK is released from I cells in response to fats and proteins, indirectly stimulating acinar cells and increasing enzyme secretion through vagal afferents and vagovagal reflexes. It is important to note that hormonal regulation plays a larger role in the intestinal phase compared to the cephalic and gastric phases. Therefore, a good understanding of this phase is crucial in understanding the impact on pancreatic secretion. I hope this has given you a better understanding of the intestinal phase and its hormonal regulation in the secretion of pancreatic enzymes..

[Audio] Today, we will be discussing the topic of gastrointestinal hormones. Our focus will be on the different phases and their main stimuli, mediators, primary targets, and secretory effects. Before we begin, let's take a moment to review the basics of the GIHEP module at RCSI, which provides a strong foundation in the study of the gastrointestinal system. Now, let's move on to slide number 22 which contains important data on the three phases of GIT hormone secretion. The first phase, known as the cephalic phase, is triggered by sensory stimuli and is primarily mediated by acetylcholine with a minor role played by gastrin. The targets of this phase are acinar and ductal cells, which secrete enzymes and HCO₃⁻. The gastric phase is initiated by gastric distension and the presence of peptides and amino acids. It is mainly mediated by the vagal reflex and has a moderate secretion of enzymes. The intestinal phase is triggered by certain substances in the duodenum and is mediated by secretin and cholecystokinin. The primary targets are ductal and acinar cells, with a major secretion of HCO₃⁻ and enzymes. As we wrap up, I hope you have gained a deeper understanding of the different phases and their effects. Thank you for your attention and I look forward to exploring more fascinating topics with you in the future..

[Audio] Today's lesson will focus on bile, a crucial fluid produced by the liver and stored in the gallbladder. It is released into the small intestine and made up of various components including water, bile salts, cholesterol, bilirubin, phospholipids, and electrolytes. Bile salts, specifically made up of bile acids, are necessary for breaking down and absorbing fats in the small intestine. Figure 10.1 shows the active transport of bile salts and how they contribute to the overall biliary system and enterohepatic circulation. Along with other factors like acetylcholine, cholecystokinin, and bicarbonate, bile secretion is regulated. The enterohepatic circulation conserves bile acids for efficient usage and recycling in the body, making it a complex and important process involving multiple organs and hormones. In conclusion, bile is essential for fat digestion and absorption, and we will continue to explore its role in our gastrointestinal system in our next lesson. Thank you for your attention and we will see you in the next slide..

[Audio] Today's topic for discussion is the GIHEP module and specifically the role of GIT hormones. The three important hormones we will be talking about on slide number 24 are secretin, cholecystokinin (CCK), and the vagus nerve. These hormones are crucial for the proper secretion of bile and maintaining pH balance in the small intestine. Secretin stimulates the production of watery and bicarbonate-rich fluids, which helps neutralize acidic contents from the stomach. CCK has two functions: contracting the gallbladder and relaxing the sphincter of Oddi, resulting in the release of bile into the small intestine for fat digestion. The vagus nerve, responsible for parasympathetic stimulation, also aids in gallbladder contraction. Moving onto the key concept of enterohepatic circulation, bile salts are actively reabsorbed in the ileum and returned to the liver for future use. Overall, understanding these hormones is crucial for comprehending the digestive process and maintaining balance in the body..

[Audio] We will now discuss the function and regulation of secretion of Brunner’s glands. These glands, located in the submucosa of the proximal duodenum, are important for maintaining the health of our intestinal lining. Their main function is to secrete alkaline mucus, containing HCO₃⁻, which protects the duodenal mucosa from acidic gastric chyme and acts as a lubricant for smooth food passage. The secretion of Brunner’s glands is stimulated by the presence of food in the duodenum, through mechanical distension or irritation, as well as through vagal stimulation and the presence of secretin and CCK. On the other hand, sympathetic stimulation, such as the stress response, can inhibit the secretion of these glands. It is important to note that Brunner’s gland secretion is crucial for the protection of the small intestine. Understanding their function and regulation is essential for a better understanding of our digestive system. As we continue, we will explore more about GI hormones and their impact on our overall health..

[Audio] Today, we will be discussing two major gastrointestinal hormones, gastrin and cholecystokinin (CCK), as well as the hormone secretin and its various counterparts. We will also be going over the non-gastric actions of these hormones, specifically in pancreatic acinar cells and bile duodenal Brunner's glands. These hormones play a crucial role in the regulation of food intake and are controlled by a complex interplay of neurohumoral signals. We will delve deeper into the functions of gastrin, which is responsible for stimulating the secretion of gastric acid and pepsin in the stomach and is involved in the growth and maintenance of the gastric mucosa. Cholecystokinin, also known as CCK, is released by the small intestine in response to the presence of fat and protein in the gastrointestinal tract. It has several functions, including stimulating the release of digestive enzymes from the pancreas and triggering the contraction of the gallbladder to release bile. Secretin, a hormone released by the small intestine in response to acidic chyme, stimulates the pancreas to secrete bicarbonate to neutralize the acidic chyme. These hormones also have non-gastric actions in the body, such as stimulating the secretion of enzymes in the pancreas and playing a role in the release of bile from the liver. The regulation of food intake is a complex process involving the interaction of various neurohumoral signals, such as hormones and neurotransmitters, to control appetite and satiety. This overview of gastrointestinal hormones will help to deepen your understanding and prepare you for our upcoming exam..

[Audio] In our study of GIT hormones, we are exploring the mechanisms of food intake regulation. Today, we will be focusing on the central regulation of food intake, which is controlled by the hypothalamus. This area acts as the command center, receiving signals from digestion and from emotional, behavioral, and reward circuits. It also receives signals from various sources such as sensory and hormonal signals about nutrient levels, gut stretch and digestion, and emotional and reward states. After receiving these signals, the hypothalamus sends out efferent pathways to carry out necessary actions. These pathways can be divided into two categories: the anorexigenic pathway, which suppresses appetite and increases metabolism, and the orexigenic pathway, which stimulates appetite and decreases metabolism. The hypothalamus plays a crucial role in balancing energy intake and expenditure by coordinating afferent inputs and effector outputs. This is why it is often referred to as the "hunger and satiety center" of the brain. Now that we have a better understanding of how the hypothalamus regulates food intake, let's move on to our next topic..

[Audio] Slide number 28 of our presentation on the GIHEP module at RCSI discusses the anorexigenic pathway of the melanocortin system. This pathway, also known as the inhibitory pathway, regulates our appetite and energy expenditure. It is activated by signals from the hormones leptin and insulin, produced in our fat stores and pancreas. These signals travel to the arcuate nucleus of the hypothalamus, where they stimulate POMC neurons. These neurons release α-MSH, which binds to the MC4R receptor in the paraventricular nucleus of the hypothalamus. This triggers inhibitory signals to areas involved in regulating appetite and metabolism. The overall result is a decrease in appetite and an increase in energy expenditure, earning the pathway the nickname "stop eating" pathway. In summary, the anorexigenic pathway plays a significant role in regulating our food intake and energy balance. Thank you for your attention and I look forward to discussing the rest of the module in our next class..

[Audio] We will now proceed to slide number 29, where we will discuss the orexigenic pathway. This pathway, also known as the stimulatory pathway, is controlled by the neuropeptide Y system. The primary components of this pathway are the hunger signals, which are typically activated by low energy levels or a lack of food, and ghrelin, a hormone produced by the stomach. These signals and ghrelin reach the hypothalamus and stimulate NPY/AgRP neurons in the arcuate nucleus. This results in two main effects: firstly, NPY binds to Y1 receptors on neurons in the lateral hypothalamus, promoting an increase in food intake and making us feel hungrier. However, this also leads to a decrease in energy expenditure and metabolism. The second key player in this pathway is AgRP, which stands for Agouti-related protein. We will further explore AgRP on the next slide. Please take note of the key players and their effects in the orexigenic pathway, as this knowledge will be crucial for the remainder of our presentation. Next, we will delve deeper into the role of AgRP on the upcoming slide..

[Audio] Slide number 30 of our presentation will focus on the central regulation of GIT hormones in the GIHEP module. The activation of these hormones is important in controlling our feeding behavior and maintaining energy homeostasis. There are two main pathways involved in this central regulation: the inhibitory pathway, known as POMC, and the stimulatory pathway, known as NPY/AgRP. These pathways are mutually exclusive, meaning that when one is activated, the other is inhibited. AgRP, as an endogenous antagonist, competes with α-MSH for the same MC4R receptors, which can lead to different eating patterns and potential health complications if the balance between these pathways is disrupted. Ultimately, the intricate and delicate relationship between the inhibitory and stimulatory pathways is crucial for maintaining a healthy balance in our bodies..

[Audio] Today, we will be discussing two important concepts related to the gastrointestinal system: Vagal Afferent Signals and Hormonal Satiety Signals. These concepts are crucial for understanding gut function and the regulation of food intake. Vagal Afferent Signals are carried by the vagus nerve from the gut to the brainstem, where they can trigger vago-vagal reflexes that impact gut function and satiety. In other words, the vagus nerve plays a vital role in regulating both aspects. On the other hand, Hormonal Satiety Signals, specifically insulin and leptin, also play a role in promoting satiety. Insulin, produced by the pancreas after a meal, activates the hypothalamus to promote fullness, while leptin, produced by adipocytes, activates the POMC pathway to suppress appetite and inhibit the NPY pathway to stimulate appetite. Overall, the release of these hormones leads to a decrease in food intake and an increase in energy expenditure. In summary, understanding and considering both Vagal Afferent Signals and Hormonal Satiety Signals is essential for maintaining a healthy gut function and managing food intake. Thank you for your attention and we will continue our discussion in the next lesson..

[Audio] Today, we will discuss two important hormones involved in regulating hunger and satiety. These hormones are CCK and PYY. CCK is released when food enters the small intestine and works by activating vagal afferents and stimulating insulin release. PYY is secreted from cells in the ileum and colon in response to fat digestion products and works by inhibiting NPY orexigenic neurons in the hypothalamus. Both CCK and PYY play crucial roles in regulating appetite and promoting meal termination, along with other factors such as gastric distension. This combination of gastric distension and gut peptides helps to reduce our food intake. In summary, it is important to remember that CCK and PYY work together to keep our food intake in check and promote meal termination. I encourage you to continue learning about the complex mechanisms of our hormonal signaling in relation to satiety and feeding..

[Audio] Today, we will be discussing the hormone ghrelin and its role in regulating our appetite and food intake. Ghrelin is secreted by the P/D1 cells in the stomach and potentially from other sites in the body. It stimulates the release of growth hormone and activates orexigenic neurons in the arcuate nucleus, leading to an increase in food intake. Ghrelin is not suppressed by protein intake or gastric distension, meaning it can drive our appetite even when we have recently eaten or our stomach is full. However, ghrelin is not the only factor in appetite regulation. Dopaminergic reward pathways, involving dopamine-producing neurons in the midbrain, also play a crucial role. These neurons are activated by the sight, smell, and taste of food, and influence the hypothalamus to enhance our motivation to eat. It's important to note that ghrelin and dopamine work in different ways. While ghrelin drives our homeostatic hunger, dopamine reinforces our hedonic or reward-based eating. Additionally, both ghrelin and dopamine are influenced by other metabolic signals, like leptin. This complex interplay between hormones and neural pathways ultimately regulates our appetite and food intake..

[Audio] In our next topic, we will explore the control of food intake and its connection to the hormones in our body. The hypothalamus, a small yet powerful structure in our brains, plays a crucial role in regulating our food intake. When we are in a fasted state, the hypothalamus sends signals to increase our food intake. This is where the hormones POMC and NPY come into play - POMC promotes satiety while NPY stimulates our appetite. Insulin is released in response to food intake and helps regulate our blood sugar levels. Notably, insulin also suppresses NPY, further promoting satiety. Ghrelin is the hormone responsible for making us feel hungry, and its levels decrease after eating. Interestingly, insulin also has an inhibitory effect on ghrelin, reducing our appetite. Overall, POMC and insulin work to promote satiety, while NPY and ghrelin stimulate our appetite, and maintaining this balance is crucial for a healthy diet. That concludes our discussion on the control of food intake and the role of hormones in our body. I hope this has given you a better understanding of this intricate system. See you in our next class..

[Audio] In our presentation on GIT hormones, we have reached slide number 35 out of 40. In our last class, we learned about various hormones and peptides involved in regulating gastrointestinal function. Today, we will explore the sources, stimuli, target organs, and actions of each hormone in more detail. We will begin with gastrin, which is produced by G cells in the antrum of the stomach and duodenum. It is stimulated by peptides, amino acids, stomach distension, and vagal GRP, and its target organs are the parietal cells and ECL cells in the stomach. Gastrin aids in increasing gastric acid secretion and promoting mucosal growth. Moving on, we have CCK, produced by I cells in the duodenum and jejunum. This hormone is stimulated by peptides, amino acids, fatty acids, and monoglycerides, and its target organs are the gallbladder, pancreas, and stomach. CCK triggers gallbladder contraction, pancreatic enzyme secretion, and decreases gastric emptying. We will then discuss secretin, produced by S cells in the duodenum. It is stimulated by a decrease in pH and fatty acids, and its target organs are the pancreas, liver, and stomach. Secretin helps to increase HCO₃⁻ secretion, bile secretion, and decrease gastric acid secretion and motility. Another hormone, somatostatin, is produced by D cells in the pancreas and stomach. It is stimulated by an increase in blood glucose and amino acids and decreases gastric acid and GI secretions, motility, and blood flow. We will also cover motilin, produced by enteroendocrine cells in the upper GI tract. This hormone is released cyclically during fasting and is inhibited by meals. Its target organ is the GI smooth muscle, and it helps to initiate contractions of the migrating motor complex. Additionally, we will discuss GIP, which is produced by K cells in the duodenum and jejunum. This hormone is stimulated by glucose, fatty acids, and amino acids, and its target organs are the pancreatic beta cells and stomach. GIP aids in increasing insulin secretion and decreasing gastric secretion and motility. Lastly, we will talk about serotonin, which is produced by enterochromaffin cells in the GI tract. It is stimulated by mechanical or other factors and plays a role in various physiological processes..

[Audio] Today's class is focused on GIT hormones and their role in the gastrointestinal tract. The GI tract is responsible for digesting and absorbing nutrients from the food we eat. The table on slide 36 summarizes the different hormones triggered in the GI tract and their functions. These hormones are necessary for proper digestion and a healthy gut. The first hormone on the list is gastrin, which stimulates the release of stomach acid for breaking down food. CCK aids in the digestion of fats and proteins, while secretin triggers the release of an alkaline substance to neutralize stomach acid. GIP regulates insulin secretion and aids in glucose metabolism. Motilin controls intestinal muscle movement and helps food move through the GI tract. These hormones are triggered by factors such as acid, carbohydrates, fats, proteins, distension, and nervous signals, all essential for a smooth digestive process. Understanding the functions of GIT hormones is vital for a healthy gut and proper digestion. The table has hopefully provided a better understanding of the role of hormones in the GI tract. See you in our next class..

[Audio] Today's lesson will focus on GI hormones and their role in bodily functions. The table on slide 37 shows how different hormones affect acid secretion in the stomach and gastric emptying. It's important to note that these hormones can impact digestion and nutrient absorption. Moving on to pancreatic secretion, all four hormones play a crucial role in stimulating the pancreas to release enzymes for proper digestion in the small intestine. Additionally, these hormones have both positive and negative effects on gastric and intestinal motility, which is necessary for food movement in the digestive tract. Lastly, insulin release, controlled by gastrin, CCK, and GIP, is crucial for regulating blood sugar levels and is a fundamental part of the digestive process. Understanding the actions of these hormones is essential for diagnosing and treating digestive disorders and maintaining overall digestive health..

[Audio] Today, we will be discussing key hormones related to gastrointestinal functions. These hormones play a crucial role in maintaining a healthy digestive system and ensuring proper digestion and absorption of nutrients. The first hormone we will discuss is gastrin, which is responsible for increasing acid secretion and promoting mucosal growth in the G cells located in the antrum. It also helps to regulate acid levels in the stomach. Another important hormone is CCK, which causes gallbladder contractions and stimulates the release of pancreatic enzymes. It also slows down gastric emptying to allow for thorough digestion. Secretin is responsible for promoting the production of bicarbonate and decreasing acid levels and motility in the duodenum. GIP, or glucose-dependent insulinotropic polypeptide, regulates insulin production and decreases gastric activity. It is produced by the K cells in the duodenum and jejunum. Motilin initiates the migrating motor complex (MMC) during fasting and is produced by the Mo cells in the upper GI. The inhibition of gastric secretion is controlled by hormones such as CCK, secretin, somatostatin, and GIP, which work to decrease acid levels in the stomach. CCK and secretin also stimulate the release of enzymes and bicarbonate in the pancreas and biliary system. The vagus nerve and its neurotransmitter acetylcholine play a role in neural stimulation. Additionally, the Brunner's glands, which produce alkaline mucus, are stimulated by the vagus nerve, as well as CCK and secretin. The central nervous system, specifically the hypothalamus, plays a crucial role in the regulation of food intake. Hormones such as POMC decrease appetite, while NPY/AgRP increases appetite..

[Audio] Slide number 39 discusses various hormones involved in the gastrointestinal system. Today's focus is on determining whether these hormones are considered GI hormones. This involves asking if a meal or physiological event can stimulate one part of the GI tract to affect another, if the effect persists without nervous communication, and if a substance can be isolated and synthesized to mimic the effect. Currently, only gastrin, CCK, secretin, GIP, and motilin meet all four criteria and are classified as GI hormones. However, there are many other potential candidates that have not met these four requirements. It is important to continue questioning and researching to expand our knowledge of GI hormones..

[Audio] This marks the final slide of our presentation, ladies and gentlemen. To summarize, we have covered a significant amount of material in this module and I trust that you now have a deeper comprehension of gastrointestinal hormones. During this session, we examined the function and regulation of these hormones in the alimentary system. As we have discovered, they hold an essential role in the breakdown and absorption of food, as well as the overall well-being of our digestive system. For additional information, I suggest referring to Chapter 15 in your textbook and pages 812 to 816 for more details on the alimentary system. These resources will provide a more thorough understanding of the subject. I would like to express my gratitude for your attention and participation in today's session. As we conclude this presentation, I encourage you to continue exploring and learning about the intriguing world of gastrointestinal hormones. Thank you and have a wonderful day..