Now that we’ve practiced building a homeostatic path model, I need your help to identify a homeostatic path model of blood sugar regulation in megaraffes.

Now that we’ve practiced building a homeostatic path model, I need your help to identify a homeostatic path model of blood sugar regulation in megaraffes. With this model, we can predict the impact of dysregulation of blood glucose in megaraffes – and hopefully get a better sense as to why Xor is ill. Before we get started, it is important to note how organisms use sugars. Your bodies – like megaraffes – are in constant need of energy in order to perform the key cellular processes that keep them alive. These processes range from building new molecules/cells and repairing damaged cells, maintaining key cellular structures, all the way to breaking down molecules and removing waste. Everything you and a megaraffe do – moving, breathing, eating…everything – relies on energy to perform these functions.

Where does this energy come from? Like you, megaraffes eat food. That food contains important macronutrients, such as fats, proteins, and carbohydrates (i.e., sugars). Organisms are capable of breaking each of these macronutrients down to produce energy; however, sugars are one of the principle macronutrients cells use to produce energy via metabolism. Some cells – like brain cells – primarily use sugars to produce energy. You may notice when your blood sugar gets too low – you may feel irritable, anxious, hungry – these are all signs that your body needs food to produce energy. When food isn’t available or in between feedings, your body’s internal systems work to keep blood sugar within acceptable ranges. These internal systems are especially important when one is not eating – as the cells throughout your body – like a megaraffe – need a constant supply of fuels such as sugars to continue producing energy. Failure to do so could eventually lead to very severe symptoms and even death. Hence why it is important for human bodies, like megaraffes, to maintain blood sugar homeostasis.

The Intergalactic Wildlife Sanctuary archives have given us a starting point for constructing a model of blood sugar regulation in megaraffes. I was able to compile a description of cells, tissue, and organs that play a key role in blood sugar regulation in megaraffes, described below.

• Alpha cells: These cells do not have receptors for carbohydrates or insulin. An alpha cell receives signals indicating the current concentration of carbohydrates. As an alpha cell receives fewer signals, the cell secretes more of a hormone called glucagon. Conversely, as an alpha cell receives more signals, the cell secretes less glucagon.
• Beta cells: These cells do not have receptors for glucagon or insulin. A beta cell receives signals indicating the current concentration of carbohydrates. As a beta cell receives fewer signals, the cell secretes more of a hormone called insulin. Conversely, as a beta cell receives more signals, the cell secretes less insulin.
• Body cells: Cells other than alpha or beta cells have receptors for insulin. When insulin binds to a receptor, the cell produces additional proteins called membrane-bound channels. These channels become part of the cell’s membrane, enabling carbohydrates to diffuse into the cell. As carbohydrates enter cells, the concentration in the blood decreases.
• Liver: This organ consists of cells that have receptors for glucagon and insulin. When glucagon binds to a receptor on a liver cell, this cell produces additional proteins called enzymes. These enzymes convert large carbohydrates stored in the cell into a smaller form that can leave the cell. These smaller carbohydrates enter the bloodstream, increasing the concentration in the blood. When insulin binds to a receptor on a liver cell, this cell produces additional enzymes that convert small carbohydrates into larger one stored in the cell. This conversion of carbohydrates causes a net flux of small carbohydrates into the cell, decreasing the concentration in the blood.
• • Sensors: These cells do not have receptors for glucagon or insulin. The sensors communicate with other cells in the body. As the concentration of carbohydrate blood sugar increases, the sensors send signals less frequently. Conversely, as concentration of carbohydrates in the blood decreases, the sensors send signals more frequently.

  Let’s start by first identifying what the control center(s), effector(s), and sensor(s) are in this system.

  Use the information above to answer questions 15-17. 

   

  15.  Which of the following structure(s) is/are the control center(s) in this system? Select ALL that apply.

  Group of answer choices

  Alpha cells

   

  Beta cells

   

  Body cells

   

  Liver

• Sensors

   

  None of these

   

  16.  Which of the following structure(s) is/are the effector(s) in this system? Select ALL that apply.

  Group of answer choices

  Alpha cells

   

  Beta cells

   

  Body cells

   

  Liver

   

  Sensors

   

  None of these

• 17.  Which of the following structure(s) is/are the sensor(s) in this system? Select ALL that apply.

  Group of answer choices

  Alpha cells

   

  Beta cells

   

  Body cells

   

  Liver

   

  Sensors

   

  None of these