Why Is Homeostasis Important

Homeostasis-Blood Glucose Regulation

Definition of Homeostasis

Homeostasis is the maintenance of a constant internal environment of an organism despite external fluctuations. All complex multi-cellular organisms maintain this internal environment at it’s optimal point by using their organs system. An example of this is the blood glucose regulation within humans.

Purpose of Homeostasis

The purpose of the homeostatic system is to keep the internal factors of the human body within the range at which it can function normally; and therefore allow the body to perform at it’s optimal level to survive and cope with the body’s external and internal activities. For example, a few internal factors homeostasis works to keep within the maintainable range

are salt levels in the body, temperature, water and energy levels. This allows the organism to move freely about and have a wide range of different environments it can survive in, as the body does not rely on its external environmental factors (e.g weather, climate, temperature etc) to keep the body stable and alive. Organisms that can move about within a wider range of different environments, are able to cover a wider area of them influencing the gene pool and pass on their successful genes, ensuring the survival of their species. Those who have struggles maintaining a homeostasis, find it more difficult to move about to fluctuating environments, and thus cannot widespread their genes around the world as much.

Purpose of Homeostasis with blood glucose Regulation
Glucose is essential to our bodies as it is the main organic molecule which the body uses to obtain energy in the form of ATP. This process is called respiration, which takes place within both the body and gamete cells. Without enough energy doing daily activities which involve any need of energy cannot happen (basically keeps the body alive and moving), thus it is important to have enough glucose in our bloodstream for our cells to use. But it is also important that the blood glucose levels are not too high, otherwise it means that the cells are not taking in the glucose flowing in the bloodstream and using it to undergo respiration. The demand for ATP varies widely depending on the activities we do in our day to day lives; thus the body is constantly working to change the level of blood glucose to maximize the availability of glucose the cells require. Most tissues in the body require a constant supply of glucose to function normally such as red blood cells, immune cells, brain cells, and the nervous system. There are two hormones responsible for controlling the blood glucose levels; insulin and glucagon. Both of these hormones are made in the pancreas.

Blood glucose regulation is a homeostatic example of using the negative feedback mechanism to re-establish homeostasis. Negative feedback is a regulatory mechanism within organisms, in which a stimulus causes a reaction in the body to oppose the stimulus and minimise the stress to bring the body back to a homeostasis. Once the body reaches homeostasis again, the sensor/detector senses this, and tells the control mechanism to stop producing the opposing output, ending the negative feedback cycle to ensure it does not create the opposite extreme of the stimulus within the body.

Glucose-What is it and why do we need it?
Glucose is the main organic molecule which our body uses to obtain energy in the form of ATP.

When we eat, the body works to break down our food to this simplest form of organic molecule. Once the glucose is obtained, it is released into the bloodstream to be delivered to the cells, which is then absorbed into the cell and undergoes the process of respiration to get ATP. Most excess glucose is then stored as glycogen, mostly in the liver, so that the body tissues which need a constant glucose supply are able to get it without us having to be constantly eating.

How the Components work to regulate Blood Glucose

There are 3 main components of the negative feedback system that works to keep the internal body at a set point; the sensor/receptor: which senses the stress and sends signals either through the nervous system or hormones to the control centre; the control centre: which receives the sensors message and sends an appropriate signal related to the stress, to the effector; and the effector which, once receiving the signal from the control centre, produces a response to the stress to reestablish the body back to the set point. 7. Once homeostasis is reached, the system shuts off (negative feedback)

Diagram for High Blood Glucose Levels 23

Stimulus:
When the glucose level in the bloodstream gets too high (hyperglycemia).

Receptor/Control:
When the blood glucose levels increase, homeostasis responds to bring the glucose level back to the set point (roughly between 4.0-6.0mmol/L). The stress here is the change in blood glucose levels.
For blood glucose regulation, the pancreas acts as both the sensor and control centre. Located in an area of the pancreas (known as the Islet of Langerhans) are found what are called the Beta cells which are responsible for the excretion and production of the hormone insulin. The time it take to make insulin is about 30-60 minutes, but when our blood glucose level rises, we need insulin very quickly thus, beta cells make insulin in advance and package them in vesicles so that insulin is instantly available when needed. The beta cells then proceeds to produce more insulin to replace the ones that are used.

Effector:
Once insulin enters the bloodstream, insulin binds with an insulin sensor called the glycoprotein which is embedded into the membranes of liver, fat and muscle cells. This sends a signal within the cell that there is glucose in the bloodstream. When the insulin binds to the insulin receptor, the protein end within the cell changes shape, which activates an enzymatic activity (the catalytic effect of a chemical reaction caused by enzymes 26) signalling the cell to send GLUT proteins (glucose transporters) to the cell’s membrane surface, allowing glucose to pass through the cellular membrane and enter the cell, where it will undergo the respiration process. Excess glucose is then stored mostly in the liver as glycogen through the process of glucose synthesis, so that the body may constantly have a supply of glucose during starvation and when glucose levels get too low. This in turn lowers the blood glucose levels, bringing it back to the normal set point. The more glucose in the bloodstream, the more insulin is released sending more signals to the cell, which will increase the number of GLUTs embedded into the membrane, and thus help re-establishing homeostasis. 9. When the glucose levels are decreased in the bloodstream and has reached homeostasis, the pancreas detects this change again and shuts off the negative feedback cycle, stopping the secretion of insulin so that the blood glucose levels are not too dangerously low (hypoglycemia). To stop the insulin's’ signal that are already bonded to the cells, the section of the cell membrane with the insulin is absorbed into the cell via endocytosis, creating a vesicle within the cell carrying the insulin. The vesicle is then acidified within, changing the shape of the insulin sensor (the protein denatures) making the insulin no longer able to bond with the glycoprotein and shutting off it’s signal, thus stopping the glucose synthesis reaction.

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Why High levels of Glucose is Dangerous
Glucose molecules are constantly trying to bind with proteins found the in bloodstream.

This process is called glycation, which is the bonding of glucose and amino acids without the presence of enzymes. This chemical reaction eventually produces an end product of what are known as AGEs (advanced glycation end products). AGEs are known for its ability for covalent crosslink between the AGE molecule itself and other proteins in the body, subsequently altering the shape and form of the protein itself and creating a domino effect (AGE is mostly known as an “aging product” as it deforms the amino acids of the body, aging the body faster in the process of breaking down). The more glucose there is in the body, and if left untreated for a period of time, the more AGEs molecules that will be produced due to the high glucose molecules available for this reaction to occur. As such, having a high blood glucose level often (both in a diabetic and non-diabetic) can speed up the body's aging process as it breaks down the body’s organic molecules. Thus, the body uses insulin to counteract this stimulus. For the diabetics, where insulin is difficult to manage, the glucose molecules are constantly attacking the body’s proteins, which is why most diabetics have a shorter lifespan than a normal person. Another reason high glucose levels are dangerous is because it can increase other health problems such as kidney and heart disease, liver disease and affect the nervous

system.