Glucose Blood Regulation Processes

The process behind the regulation of blood glucose levels:

Introduction

The endocrine system is made up of many different organs that secrete different hormones into the blood stream. The endocrine system works as a chemical messenger system within the human body, made up of all the glands that make hormones. These hormones are chemical messages that travel through your blood system to target the cells or organs to produce a prolonged effect. The purpose of the endocrine, is to keep the body in a homeostatic state constantly maintaining the internal conditions of the body. There are many glands which make up the endocrine as illustrated in the diagram below (figure 1). (Prime Health Channel, 2010)

              Figure 1 (Bodytomy, 2018)

Each of these glands have a very special role within the endocrine system and all help the body to function at its optimum level and to keep the body’s internal environment stable and constant. The Hypothalamus functions as the control centre as it controls the release of major hormones through the pituitary gland as well as linking the nervous system to the endocrine.

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This unit will focus on the pancreas and liver and how they work together to regulate the blood glucose levels of the body. This unit will also cover topics such as glucose regulation, how it is kept at a homeostatic level, negative feedback, how it works within the body when the blood glucose level needs to be maintained at a particular level as well as how the pancreas works in coordination with the other organs to achieve this.

Glucose Regulation

Glucose is a monosaccharide sugar and the regulation of glucose is incredibly important as it is essential in preventing diseases like diabetes however the most important reason that glucose is essential to the survival of cells is that it is the key to cellular respiration. Cellular respiration is when glucose is converted into adenosine triphosphate which is also known as ATP this is a form of chemical energy which cells can then use, ATP is able to store and transport energy within a cell. (Grogan & Suter, 2011)  If glucose levels are low, this prevents the cells from having enough for cellular respiration. Glucose is needed by all cells and organs within the body. Some cells, such as red blood cells and brain cells rely solely on glucose for energy. Although, glucose becomes an energy source for all cells. (Grogan & Suter, 2011)

We obtain glucose through everything we eat especially starch rich foods as seen in the diagram below (figure2).

                                        Figure 2 (Nutrients Review, 2014)

The Pancreas

The main endocrine organ responsible for the control of glucose levels in the blood is called the pancreas. The pancreas, which is a flat, long, endocrine gland is located in the abdomen and rests behind the stomach.

 Diagram showing the position of the pancreas

(Bodytomy, 2018) 

The pancreas secretes a number of different hormones involved in the regulation of blood glucose levels. These are listed below:

-Insulin

-Glucagon

-Somatostatin (Scienceisntfiction, 2011)

 The pancreas is made up of endocrine tissue known as islets of Langerhans which are made up of 4 different types of cells and these cells produce the hormones required to regulate the blood glucose levels. The main cells within the islets of Langerhans are the alpha, beta and delta cells. Each of these cells have different functions. These functions are summarized in the table below (Walsh, 2017):

 The Alpha cells secrete glucagon, which elevates sugar levels when the blood sugar levels become low this often happens after several hours of not eating when the body is said to be in its post-absorptive state insulin levels along with glucose levels drop and so glucagon is released by the alpha cells, when glucagon is released, it binds to receptors on liver cells. (Walsh, 2017) The liver also plays an important role in the regulation of glucose levels as it stores glucose so that it can be used when your body requires it. Alpha cells make up 20% of the islet’s cells.

If your glucose levels are high, the liver responds by absorbing glucose and storing it in bundles known as glycogen.

Beta cells have a function of storing and releasing insulin. Insulin is a hormone that lowers the glucose level of blood. Beta cells have the ability to react very quickly to spikes in the blood glucose level as they are able to release the stored insulin while at the same time, making more. Insulin and glucose have an opposite effect on each other, which is what allows the blood glucose level to be regulated. (Grogan & Suter, 2011)

The regulation of blood sugar is what is referred to as glucose homeostasis.

 Below is a diagram of an islet cell within the pancreas (figure 3):

                                              Figure 3 (Cram, 2017)

The role of the Liver explained:

The liver is made up of cells called hepatocytes. One of the liver’s purposes is to produce, release and store glucose depending on if the body’s blood sugar levels are low or high and it’s need for glucose these hepatocytes are responsible for the storage and release of glucose. The liver is often referred to as the body’s reservoir for glucose (Weber, 2017). An example of how the liver regulates blood glucose is when you consume food, the food is digested and absorbed into your body. During this absorption, the body breaks down the food to its simplest form, glucose. The liver plays a very important role in the process of keeping blood sugar levels regulated by balancing the uptake and storage of glucose via glycogenesis which is when extra glucose is removed from the blood by being turned into glycogen which is the storage form of glucose in the liver and occurs via the liver’s hepatic cells other processes in the liver that balance glucose levels are the release of glucose via glycogenolysis and gluconeogenesis (Weber, 2017).

   Figure 4  (Prime Health Channel, 2010)                                                                                                                     This diagram shows the location of the liver it is located in the pelvic region of the abdomen below the diaphragm and the ribs.

Negative feedback

Blood sugar levels are regulated by a process called negative feedback, otherwise known as balancing feedback (Grogan & Suter, 2011). Negative feedback is operated in a loop system so that the body is able to function at its optimal state and if there are any irregularities within the body they are able to be controlled and the bodies internal environment returned to normal via negative feedback. In a negative feedback loop there needs to be a:

Stimulus– This is what produces a change to a variable which is the factor that is being regulated or kept constant.

Receptor– This is what actually detects the change. The receptor constantly monitors the environment and responds to any change if there is an imbalance.

Input– information travels along the (afferent) pathway to the control centre. The control centre is what determines what the best response and course of action is to return the internal environment back to its balanced state.

Output– information sent from the control centre and travels down the (efferent) pathway to the effector which is what makes the actual change.

Response– a response from the effector balances the internal environment and returns it to its homeostatic state (Science Aid, 2016).

How do they work together?

 The receptor senses change which could be one of a number of things throughout the body and passes the message on through to the control center which then decides what should be done and causes an effector to react in a way that deduces the change that is taking place so the body is able to return to its homeostatic state, the receptor(sensor) will be able to detect if the effector has done its job and if the change that has occurred has been returned to normal if the body is still not at its homeostatic state then the receptor will send a message back to the control center and it will just send the message back to the effector once again and so a loop is created until the body’s internal environment is returned to its constant homeostatic state. Negative feedback decreases the reaction that is causing an imbalance in the system, the negative feedback reaction always has an opposite effect to the initial reaction (Cram, 2017). Below there are two diagrams displayed the first diagram (figure 5) is a general negative feedback loop and (figure 6) that of a negative feedback loop that illustrates how the blood glucose levels are controlled within the human body when sugar levels are too high or too low.

Figure 5 (Scienceisntfiction, 2011)                                                       Figure 6 (Lumen, 2012)

Diagrams explained

When there is an increase in your blood glucose level (e.g. after eating a something sweet like a chocolate) the insulin secreting cells within the pancreas i.e., the beta cells are activated and secrete insulin into your blood, the insulin then stimulates the liver to take in(absorb) glucose but store it as glycogen at the same time the uptake of glucose from the blood is enhanced in the body’s cells before the blood glucose level then returns to a homeostatic level, if the glucose levels are still high then the negative feedback loop will just repeat itself. Once the homeostatic level is reached the stimulus for the release of insulin then stops (Lumen, 2012).

The second half of the negative feedback loop shows how negative feedback works when blood sugar levels are low (e.g. after not eating for a while a meal) the glucagon releasing cells of the pancreas i.e. the Alpha cells, are stimulated and release glucagon into the blood which then stimulates the liver and the liver then breaks down it’s glycogen storage and releases glucose that the cells are able to absorb which then raises the glucose levels back to a homeostatic level the same applies to this example as the previous that if the homeostatic level is not reached then the process will repeat itself until it is (Scienceisntfiction, 2011).

Positive Feedback

There is another type of feedback system known as positive feedback. Positive feedback loops have an opposite effect to a negative feedback loop negative feedback loops take away whatever is causing the imbalance and restore the body to a homeostatic level but positive feedback amplifies changes and move the body away from its homeostatic state (Keywords king, 2017). There are good positive feedback loops which we need however, most often there are positive feedback loops can actually harm us. An example of a positive feedback loop would be when a mother is giving birth as seen in the diagram provided. (figure 7) (Keywords king, 2017)

When a mother goes into labor the baby moves down deeper into the birth canal and the baby’s head pushes against the cervix and stretches it which then stimulates nerve impulses to the brain causing the pituitary gland that releases a hormone called oxytocin into the bloodstream to be stimulated. Oxytocin, which is a very important hormone during child birth and breast feeding is produced by the hypothalamus and stored in the pituitary as well as secreted by the pituitary (Anatomy and Physiology, 2017). Oxytocin is then carried through the bloodstream to the uterus and causes extreme contractions that push the baby towards the cervix which results in more pressure on the wall of the cervix and so an even greater amount of oxytocin is released. This loop will continue until the mother gives birth to the baby, once the baby is born the cervix does not get pushed against and so the stimulus stops and so the positive feedback loop is broken and the body returns to its homeostatic levels (Anatomy and Physiology, 2017).

2003 Words

Bibliography

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