Why did Xor collapse after we administered a drug to dilate her blood vessels?
attached are data sets and lab instructions, along with questions on my assignment. I need someone to help answer and explain, most questions don’t need explanation and are multiple-choice. an excel sheet needs to be presented.
Requirements: not too long
Lab Instructions: Physiology Act II Mission Memo
Greetings Fellow Explorer:
Thanks to your efforts, we were able to rule out two of the possible causes of Xor’s symptoms. Xor’s blood oxygen concentration and blood glucose concentrations are within the typical ranges. It seemed that Xor’s blood pressure was too high – so I decided to administer Xor a drug that would dilate her blood vessels. Unfortunately, I only made matters worse. On top of that – the gravity in the megaraffe enclosure seems to be too high. I’m really in a bind now and I need your help yet again. The fate of Xor and the megaraffe population rests in your hands.
Xor’s symptoms, her response to the vasodilators, and the seemingly elevated gravity in the megaraffe enclosure must be connected. We must determine if an increase in the gravity was the cause of Xor’s symptoms and, if so, by how much I need to correct the gravity before it’s too late. If the gravity needs to be reset, we’ll need to make sure we have the proper treatments on hand to keep Xor stabilized while I reset the gravity in the enclosure.
Use the following questions to guide your work.
Why did Xor collapse after we administered a drug to dilate her blood vessels? (Appendix 1)
How much should we reduce the gravitational force in Xor’s environment? (Appendix 2)
How should we treat Xor to stabilize her cranial blood pressure? (Appendix 3)
The appendices to this mission memo will guide you in answering these questions.
Once you have completed your analyses, report your conclusions via Canvas before returning to the Sanctuary.
Do not underestimate the urgency of your work.
Universally in your debt,
The AI
Appendix 1
Why did Xor collapse after we administered a drug to dilate her blood vessels?
Thanks to GUS, we might have discovered the cause of Xor’s illness—an increase in the gravitational force of her environment. In other words, the current gravitational force exceeds the set point of the Sanctuary’s gravitational control system, a homeostatic system designed to regulate gravity. If GUS is correct, the problem likely resulted from damage to the system, caused when the Sanctuary collided with space debris.
Still, we must be sure that all of our observations support GUS’s hypothesis. We already administered an incorrect treatment, making Xor’s condition worse. We don’t want to administer another incorrect treatment!
Complete the following steps to determine whether an increase in gravitational force can explain why Xor fainted after we dilated her blood vessels.
Step 1: Model the effect of gravity on the distribution of blood. Construct a model illustrating how a change in gravitational force would affect the distribution of blood in a megaraffe. This step will enable us to construct an argument in Step 3.
Step 2: Model how a change in the distribution of blood would affect the cranial blood pressure. Using the model constructed in Step 1, explain how the blood pressure in each part of the circulatory system would change as the gravitational force increased. This step will enable us to construct an argument in Step 3.
Step 3: Determine why Xor fainted after we dilated her blood vessels. Construct an argument to answer the question “Could an increase in gravitational force explain why Xor fainted after we dilated her blood vessels?” Your argument should draw on your answers in Steps 1 and 2.
Step 1: Model the effect of gravity on the distribution of blood
The challenge here is that because the gravitational fields in the Sanctuary were pre-programmed by my creators, I don’t have any data that would explain how a change in gravitational force would impact blood pressure or the distribution of blood in megaraffes, let alone other species. However, humans have been a spacefaring species for more than 60 years and, based on your archives, it appears that the effects of microgravity have been well documented in humans. Perhaps this could lend some insight as to what was happening to Xor? Let’s work together to find out.
Effects of microgravity on blood distribution in humans
Organisms on Earth, like in the megaraffe enclosure, are subjected to a constant force of gravity. On Earth, the gravitational force equals 9.8 N kg-1. How does Earth’s gravity affect the distribution of blood in your body?
A typical adult human has about 5 liters of blood. But how is that blood distributed throughout the body? Is it evenly distributed, or does one part of the body have more blood than other parts?
The answer choices below show three distributions of blood in the body of an adult human. This person is standing but not performing any other physical activity. The darker the shading of an area, the greater the amount of blood in that area. Select the figure that best represents the distribution of blood in the body of a human on Earth.
Answer choice 1
Answer choice 2
Answer choice 3
Through careful research, scientists on Earth discovered that more blood lies in the lower half of the body when a person stands (Figure 1). At first, this might seem counterintuitive. Important organs, such as the brain, reside in the upper half of the body. So why would more blood occur in the lower half? The answer is gravity.
As blood flows through arteries, delivering oxygen and vital nutrients to cells, it eventually must travel back to the heart through veins (Figure 7, Mission Memo 1, Appendix 1, Step 1 of the Physiology module). Traveling back to the heart is a straightforward task for blood returning from the head, because gravity pulls it downward. However, blood returning from the legs must move against the force of gravity. As a consequence, more blood remains in the lower half of the body than in the upper half.
In space, one lies so far from Earth that the force of gravity drops to a very small value, which we call microgravity. The lack of gravity in space is why the Sanctuary has mechanical systems to create artificial gravity. Life on Earth has evolved under the same gravitational conditions for several billions years. Thus, when human astronauts leave Earth and transition to microgravity, they experience a novel condition. How does this sudden decrease in gravitational force affect the distribution of blood in the body?
2. The answer choices below show three possible distributions of blood in the body of a typical adult human in space, where the gravitational force is effectively zero. This person is standing but not performing any other physical activity. The darker the shading of an area, the greater the amount of blood that occurs in that area. Select the figure that best represents the distribution of blood in the body of a human in space.
Answer choice 1
Answer choice 2
Answer choice 3
Scientists on Earth discovered that the shift from Earth’s gravitational force to space’s microgravitational force redistributes the blood in an astronaut’s body. Specifically, blood becomes more evenly distributed.
Why does this redistribution occur? Blood shifts upward when traveling to space, because little gravitational force pulls the blood toward the feet. As a consequence, astronauts experience swelling and puffiness of the face. Figure 2 (below) contrasts the distributions of blood in the body of a typical human on Earth and in space.
Effects of changes in gravity on blood distribution in megaraffes
Now that we understand how gravitational force affects the distribution of blood, let’s consider how the increase in gravitational force in the Sanctuary might have affected Xor. To help us, I modeled the expected distribution of blood in a typical megaraffe at rest, not performing any physical activity, and exposed to the typical gravitational force of Phygaris (7 N kg-1). Figure 3 shows this distribution.
As in humans, more blood resides in the lower half of the body of a megaraffe when it’s standing. This uneven distribution makes sense given what we know about humans. But how would an increase in gravity affect the distribution of blood?
Directions: To answer questions 3-4, use the modeled distribution of blood in a typical megaraffe under normal gravity (Figure 3) and your answers to questions 1-2.
3. The answer choices below show three possible distributions of blood in the body of Xor under increased gravitational conditions. Xor is standing but not performing any other physical activity. The darker the shading of an area, the greater the amount of blood that occurs in that area. Select the figure that best represents the distribution of blood in Xor’s body under this elevated force of gravity. To help you answer this question, a reference image is provided to show the expected distribution of Xor’s blood when exposed to the typical gravitational force of Phygaris.
Answer choice 1
Answer choice 2
Answer choice 3
4. Justify your answer to the previous question. Your justification should minimally discuss why the answer choice you selected is the best answer choice as compared to the other answer choices.
Step 2: Model how a change in the distribution of blood would affect the cranial blood pressure
Now that we know how an increase in gravity could have redistributed Xor’s blood, we can think about how this redistribution of blood would affect Xor’s cranial blood pressure.
Why think about blood pressure? Blood pressure is an important variable regulated by many organisms, including humans and megaraffes. Failure to regulate blood pressure can be fatal. For example, low blood pressure can cause dizziness, weakness, confusion, or fainting. High blood pressure can cause headaches, chest pain, difficulty breathing, and nosebleeds.
I accessed a scientific database on Earth, in hopes that research by human scientists will enable us to infer how an increase in gravitational force would affect blood pressure. As before, we will draw on studies of astronauts traveling to space.
Effects of microgravity on blood pressure in humans
Recall that, for a human on Earth, gravity causes the more blood to occupy the lower half of the body (Figure 1). How does this uneven distribution of blood affect the blood pressure? Figure 4 shows the typical blood pressures in different regions of a human body.
What pattern(s) do you notice in Figure 4?
5. Examine Figure 4. Which statement best describes the relationship between the amount of blood in a region of the body and the blood pressure in that region?
The more blood in a region of the body, the higher the blood pressure.
The more blood in a region of the body, the lower the blood pressure.
There is no relationship between the amount of blood in a region of the body and blood pressure.
Recall that blood pressure is the force that blood exerts against the walls of a blood vessel (Mission Memo 1, Figure 15). When the amount of blood in a vessel increases, the force exerted against the walls also increases. In other words, blood pressure increases as more blood flows through a vessel, assuming that the diameter of the vessel remains the same. This principle explains why the blood pressure in arteries of the legs greatly exceeds the blood pressure in arteries of the head (Figure 4).
Let’s determine how a change in gravitational force would affect the blood pressure in different regions of the body. In space, the gravitational force is effectively zero, causing blood to redistribute from the legs to the head. Consequently, blood pressure in these regions of the body will change (Figure 5). An increase in the amount of blood in the upper half of the body causes an increase in blood pressures in this region. Conversely, a decrease in the amount of blood in the lower half of the body causes a decrease in blood pressures in that region.
Effects of changes in gravity on blood pressure in megaraffes
Inspired by the work of human scientists, I modeled the blood pressure of a megaraffe exposed to the typical gravitational force on Phygaris. The results for a megaraffe, standing but performing no other activity, are shown in Figure 6.
As with humans, the blood pressure of a megaraffe is positively related to the amount of blood distributed to the arteries in a region of the body. The blood pressure is lowest in arteries serving the head and highest in those serving the legs. If the gravitational force in the Sanctuary rose above the typical value, how would blood pressure change throughout a megaraffe’s body?
Directions: Use Figure 6 to help you answer questions 6-7. For questions 6-7, assume that Xor is standing but not performing any other physical activity. Remember that a megaraffe typically experiences a gravitational force of 7.0 N kg-1 on Phygaris.
6. If the gravity in the Sanctuary rose above the typical gravitational force on Phygaris, Xor’s cranial blood pressure would be ____ her cranial blood pressure under the typical gravitational force on Phygaris.
Less than
Greater than
Similar to
7. If the gravity in the Sanctuary rose above the typical gravitational force on Phygaris, Xor’s femoral blood pressure would be ____ her femoral blood pressure under the typical gravitational force on Phygaris.
Less than
Greater than
Similar to
Recall that Xor was disorientated, sluggish, and uncoordinated even before I administered the vasodilators. The question is – why was she exhibiting these symptoms?
Directions: Use your answers to the previous questions to answer question 8. For question 8, assume that vasodilators have not been administered to Xor.
8. Put it all together: Why did Xor only begin exhibiting disorientation, sluggishness, and lack of coordination after space debris struck the Sanctuary and the gravitational force in the Sanctuary increased? Your answer should minimally include a discussion of how an increase in the gravitational force in the Sanctuary may have changed the distribution of blood in Xor’s body and the subsequent impact on Xor’s cranial blood pressure.
Step 3: Determine why Xor fainted after we dilated her blood vessels
Why did Xor faint after we dilated her blood vessels?
Now that we know how gravity affects the blood pressure of a megaraffe, we need to determine why Xor collapsed after we administered a drug to dilate her blood vessels.
Let’s review what we know. When we examined Xor, she was disoriented, confused, and weak. The concentrations of O2 and carbohydrates in Xor’s blood were within the expected ranges; however, her blood pressure—measured while lying down—was greater than expected. We administered a drug to dilate Xor’s blood vessels, which quickly brought her blood pressure back within a healthy range. However, as Xor stood up, she fainted.
Xor’s symptoms—disorientation, confusion, and weakness—suggested that she might suffer from high blood pressure. Indeed, we did observe a high blood pressure in the femoral artery of Xor’s leg. However, disorientation, confusion, and weakness can stem from low blood pressure as well as high blood pressure. When blood pressure in the head drops to a very low value, the brain receives insufficient nutrients to perform its functions. In Appendix 1, Step 2 of this mission memo, you considered how an increase in the gravity in the Sanctuary would impact Xor’s femoral and cranial blood pressure and ultimately if an increase in gravity could have caused Xor’s symptoms. The question remains, why would dilating Xor’s blood vessels make her condition worse?
Xor’s blood pressure, her symptoms, her response to the drug, and her fainting upon standing must be connected. Let’s explore what we know about the factors that regulate blood pressure; perhaps this information will enable us to infer what happened to Xor.
Factors that regulate blood pressure
Blood pressure depends primarily on the volume of blood in a vessel. When blood enters a vessel, the pressure increases. Conversely, when blood leaves a vessel, the pressure decreases.
The heart raises the blood pressures of arteries by pumping blood into these vessels. Because the flow of blood changes as the heart contracts and relaxes, blood pressure also changes over time (Figure 7). We will focus on the maximal blood pressure during contraction, called the systolic blood pressure.
Blood flows along a gradient of pressure, from a point of high pressure to a point of low pressure. For example, Figure 8 shows a gradient in which the pressure at point A exceeds the pressure at point B, such that blood would flow from point A to point B.
Therefore, the rate of blood flow depends on the difference in pressure between two regions of the circulatory system. We can model this relationship with the following formula:
F = (P1 – P2) / R
where:
F = rate of flow (ml min-1)
P1 = pressure at point 1 (mmHg)
P2 = pressure at point 2 (mmHg)
R = resistance to flow (mmHg min ml-1)
This formula accounts for the effect of resistance (R), as well as the gradient of pressure (P1 – P2). Resistance is the force that opposes the movement of blood through a vessel.
Let’s pause for a moment to make sure we fully understand the relationship between the resistance to blood flow, the gradient of pressure, and the rate of flow of blood.
Directions: Use the formula for estimating blood flow (above) to help you answer questions 9-11. Set R to 1 mmHg min ml-1 for questions 9-11. Round all calculated values to the nearest one’s place. For example, if you calculate the value as 3.821853, round to 4.
9. If the difference between P1 – P2 was 40 mmHg, what would the rate of blood flow (F) equal in ml min-1?
Rate of blood flow (ml min-1) =
10. If the difference between P1 – P2 was 10 mmHg, what would the rate of blood flow (F) equal in ml min-1?
Rate of blood flow (ml min-1) =
11. Based on your answers to the two previous questions, what is the relationship between the difference in pressure (P1 – P2) and the rate of blood flow (F)? As the difference in pressure ____, the rate of blood flow ____.
increases, increases
increases, decreases
There is no relationship between the difference in pressure and the rate of blood flow
Directions: Use the formula for estimating blood flow (above) to help you answer questions 12-14. Set the difference between P1 – P2 to 40 mmHg for questions 12-14. Round all calculated values to the nearest one’s place. For example, if you calculate the value as 3.821853, round to 4.
12. If R is 1 mmHg min ml-1, what would the rate of blood flow (F) equal in ml min-1?
Rate of blood flow (ml min-1) =
13. If R is 4 mmHg min ml-1, what would the rate of blood flow (F) equal in ml min-1?
Rate of blood flow (ml min-1) =
14. Based on your answers to the two previous questions, what is the relationship between the resistance to blood flow (R) and the rate of blood flow (F)? As the resistance to blood flow ____, the rate of blood flow ____.
increases, increases
increases, decreases
There is no relationship between the resistance to blood flow and the rate of blood flow
Excellent work! Now that we have a better understanding of the relationship between the resistance to blood flow, the gradient of pressure, and the rate of flow of blood, we’re ready to explore why Xor fainted after we dilated her blood vessels. We’ll focus specifically on the role that resistance to blood flow played in causing Xor to faint.
Although several factors affect resistance, only one of these factors was affected by the drug that we gave Xor: the diameter of blood vessels.
Certain blood vessels have muscle tissue that affects their diameter. When this muscle tissue contracts, the diameter of a blood vessel decreases. This decreasing diameter causes more molecules in the blood to collide with the walls of the vessel, increasing resistance and ultimately increasing the blood pressure upstream. The process by which a blood vessel narrows through muscular contraction is called vasoconstriction.
Conversely, when the muscle tissue relaxes, the diameter of a blood vessel increases. This increasing diameter causes fewer molecules in the blood to collide with the walls of the vessel, reducing resistance and ultimately reducing the blood pressure upstream. The process by which a blood vessel widens through muscular relaxation is called vasodilation.
15. What is the relationship between vasoconstriction and blood flow? When blood vessels constrict, blood flow to adjacent regions ____.
Increases
Decreases
16. What is the relationship between vasodilation and blood flow? When blood vessels dilate, blood flow to adjacent regions ____.
Increases
Decreases
Directions: For questions 17-18, assume the following: (a) Xor is standing up and not performing any other physical activity and (b) the gravity in the Sanctuary is higher than the typical gravitational force on Phygaris.
17. Compare the flow of blood to Xor’s legs prior to and after the administration of vasodilators to Xor. After the administration of vasodilators, would the flow of blood to Xor’s legs likely increase, decrease or stay the same?
Increases
Decreases
Stay the same
18. Compare the flow of blood to Xor’s head prior to and after the administration of vasodilators to Xor. After the administration of vasodilators, would the flow of blood to Xor’s head likely increase, decrease or stay the same?
Increases
Decreases
Stay the same
We’re finally ready to explain why Xor fainted after we administered a drug to dilate her blood vessels. Answer the question, “Why did Xor faint after we dilated her blood vessels?”
As you answer this central question, assume the following:
Xor is standing up and not performing any other physical activity
The gravity in the Sanctuary is higher than the typical gravitational force on Phygaris.
As you answer this central question, consider the following sequence of related questions:
What impact would an increase in the gravity in the Sanctuary have on the distribution of blood in Xor’s body?
What impact would any change in the distribution of blood have on the blood pressure in Xor’s head and legs?
What impact would vasodilation have on the flow of blood to Xor’s head and legs? The blood pressure in Xor’s head and legs?
19. Put it all together: Why, from a biological perspective, did Xor pass out after she was given vasodilators? Your answer should minimally address the following: What role, if any, did an increase in the Sanctuary’s gravity have on Xor’s cranial blood pressure prior to administering vasodilators? What role, if any, did the vasodilators have in altering Xor’s cranial blood pressure?
Appendix 2
How much should we reduce the gravitational force in Xor’s environment?
Excellent work! We now know if our data support GUS’s hypothesis; an increase in gravitational force could explain Xor’s illness. To correct any problem with the gravitational control system, we must quantify the current gravitational force of Xor’s environment.
Fortunately, we can use our knowledge of Xor’s blood pressure to estimate the gravitational force. The pressure of blood entering the arteries in the head (cranial blood pressure, P), depends directly on the height of the head above the heart (h):
P = (-1∙c∙g∙d)∙h + b
where:
P = cranial blood pressure (mmHg)
c = a constant that converts the unit of pressure from Newtons per square meter (N m-2) to millimeters of mercury (mmHg)
g = force of gravity (N kg-1)
d = density of blood (kg m-3)
h = height of the head relative to the heart (m); a positive value indicates a height above the heart
b = a constant representing the expected value of P when h equals zero
This function is a linear relationship between h and P, in which the slope equals -1∙c∙g∙d.
You might recognize the linear relationship more easily if we condense some of the terms into a single parameter. Let’s define a parameter a as follows:
a = -1∙c∙g∙d.
In this case, the relationship between the relative height of the head and the cranial blood pressure becomes
P = ah + b
We can use this relationship to estimate the force of gravity. This process will require two steps. In the first step, we will use your observations of Xor’s cranial blood pressure to estimate the slope of the relationship (a). In the second step, we will use the estimated slope to calculate the force of gravity.
Step 1: Estimate the slope of the relationship, a. Model the relationship between the position of Xor’s head and her cranial blood pressure. This step will provide us with the information needed to determine if gravity in the megaraffe enclosure is off and by how much.
Step 2: Calculate the force of gravity in Xor’s environment and recommend whether this force should be corrected. Use the slope estimated in Step 1 to calculate the force of gravity. This step will enable us to determine whether this force exceeds the set point of the homeostatic system that regulates gravity in the Intergalactic Wildlife Sanctuary.
Step 1: Estimate the slope of the relationship, a
During your last visit to the Sanctuary, you monitored Xor’s blood pressure continuously as she moved from a sitting position to a standing position. During this movement, the height of Xor’s head rose from being level with her heart to being 10 m above her heart. We can use your data to estimate the slope of the relationship between the relative height of Xor’s head and her cranial blood pressure.
Directions: For questions 20-21, download the Excel file, “Data: Effect of Head Height on Head Blood Pressure,” containing the data for the relative height of Xor’s head and her cranial blood pressure (N = 13). Use Excel for calculations, modeling, and graphing. Round all calculated values to the nearest one’s place. For example, if you calculate the value as 3.8218, round to 4.
20. Plot the linear relationship between the relative height of Xor’s head and her cranial blood pressure. This plot should follow the formatting guidelines listed below.
Formatting Instructions
General
Chart type: X Y (Scatter)
Quick layout: Layout 1 – Scatter
Y-axes title: “Xor’s cranial blood pressure (mmHg)”; Font size = 18
Y-axis numbers: Font size = 14
X-axis title: “Relative height of Xor’s head (m)”; Font size 18
X-axis numbers: Font size = 14
Y-axis
Bounds: minimum at 0, maximum at 1200
X-axis
Bounds: minimum at -10.0, maximum at 15.0
Trendline (linear model)
Line: Solid line
21. Estimate the slope (mmHg m-1) of the linear relationship between the relative height of Xor’s head and her cranial blood pressure.
Slope =
Step 2: Determine if the gravity exceeds the set point in the megaraffe enclosure and, if so, by how much
Now that you know the relationship between the relative height of Xor’s head and her cranial blood pressure, you can use the slope of this relationship to calculate gravity.
Recall that the slope (a, mmHg/m) depends on the density of blood (d) and the force of gravity (g):
a = -1∙c∙d∙g.
where c is a constant that converts the unit of pressure from N m-2 to mmHg; the value of this constant equals 0.0075 mmHg m2 N-1.
By inserting the value of c, we can simplify the function:
a = -1 ∙ 0.0075 mmHg m2 N-1 ∙ d ∙ g.
The density of blood (d) for a megaraffe equals 1025 kg m-3.
By inserting the value of d, we can simplify the function even further:
a = -1 ∙ 0.0075 mmHg m2 N-1 ∙ 1025 kg m-3 ∙ g,
Finally, we can rearrange the equation to solve for the force of gravity:
g = a / (-1 ∙ 0.0075 mmHg m2 N-1 ∙ 1025 kg m-3),
Multiplying the terms in the denominator yields
g = a / -7.6875 mmHg kg N-1 m-1,
To put this in words, the force of gravity equals the slope (a) that you calculated in Step 1, divided by -7.6875 mmHg kg N-1 m-1.
An example of how to calculate gravity
Before using your data to calculate the force of gravity in the Sanctuary, let’s consider an example.
Figure 9 shows a relationship between the relative height of the head and cranial blood pressure. The slope of this relationship (a) equals -80.8 mmHg m-1.
To calculate the force of gravity, we insert the slope into the equation above:
g = -80.8 mmHg m-1 / -7.6875 mmHg kg N-1 m-1.
To simplify the quotient on the right-hand side of this equation, be sure to remember two rules of algebra.
We can cancel any unit that occurs on the top and on the bottom of a quotient.
We can flip any unit with a negative exponent from the top of the quotient to the bottom (or vice versa) and the exponent becomes positive.
Try simplifying the equation above using these rules. You should obtain a force of gravity (g) equal to 10.5 N kg-1. Interestingly, this value lies very close to the gravitational force on Earth, which equals 9.8 N kg-1.
Now you’re ready to estimate the gravity in the megaraffe enclosure.
Directions: Use the model of the linear relationship between the relative height of Xor’s head and her cranial blood pressure that you constructed in Appendix 2, Step 1 of this mission memo to answer questions 22-23. Round all calculated values to the nearest tenths of a decimal place. For example, if you calculate the value as 3.8218, round to 3.8.
22. Calculate the gravity in the megaraffe enclosure. The units of your calculation should be in N kg-1.
Gravity =
23. Typically the gravity in the megaraffe enclosure and on Phygaris is 7.0 N kg-1. Is the current gravity you calculated in the previous question greater than, less than, or equal to the typical gravity in the megaraffes’ enclosure?
Greater than
Less than
Equal to
Appendix 3
How should we treat Xor to stabilize her cranial blood pressure?
Excellent work! Now that we know the current gravitational force in Xor’s environment, I can reprogram the gravitational control system to lower the gravitational force to the appropriate value.
Unfortunately, I will have to reboot the system during this process. Upon startup, the system will cause the gravitational force in Xor’s environment to fluctuate rapidly before settling down to an equilibrium (Figure 10).
As we already know from your work in Appendix 1, fluctuations in gravitational force can affect the distribution of blood and thus blood pressure. For a megaraffe, the typical set point for cranial blood pressure is 105 mm Hg. We need to help Xor maintain this blood pressure as the gravitational force fluctuates.
Complete the following steps to determine how we should treat Xor to stabilize her cranial blood pressure while I attempt to fix the gravity in the Sanctuary.
Step 1: Determine how the effectors in Xor’s homeostatic system could stabilize her cranial blood pressure. Use a model of a homeostatic system to determine how each effector could stabilize Xor’s cranial blood pressure as the gravitational force fluctuates. This step will help us to determine how to treat Xor in Step 2.
Step 2: Determine how to treat Xor when the gravitational force increases or decreases: Use a model of a homeostatic system to determine the best way to treat Xor when the gravitational force of her environment increases or decreases.
Step 1: Determine how the effectors in Xor’s homeostatic system could stabilize her cranial blood pressure
To decide how to treat Xor as gravity fluctuates, we need to know how the effectors in her homeostatic system should respond to regulate the cranial blood pressure.
Figure 11 shows a path model of the homeostatic system that regulates blood pressure in a megaraffe. You analyzed this path model previously, when we thought that Xor was possibly suffering from high blood pressure.
Recall from Appendix 1 of this mission memo that the gravitational force of a megaraffe’s environment affects the distribution of its blood, and thus blood pressure in the head and legs. Your understanding of how gravity affects blood pressure will help us to develop a treatment for Xor.
Directions: Use Figure 11 to answer questions 24-25. Assume that Xor is standing but not performing any other physical activity, that the effect of the vasodilators has completely worn off, and that the AI is resetting the gravity in the Sanctuary, such that gravity may increase or decrease as indicated by questions 24-25.
24. How should the rate of blood flow from Xor’s heart change to maintain a healthy cranial blood pressure when the gravitational force of the environment increases? The rate of blood flow from the heart should ___.
Increase
Decrease
25. How should the rate of blood flow from Xor’s heart change to maintain a healthy cranial blood pressure when the gravitational force of the environment decreases? The rate of blood flow from the heart should ___.
Increase
Decrease
Step 2: Determine how to treat Xor when the gravitational force increases or decreases
Now that we know how Xor’s heart should respond to an increase or decrease in gravitational force, we can choose a treatment to help Xor regulate her blood pressure as the gravitational force fluctuates.
Since we already treated Xor with a vasodilating drug, which decreased the resistance of blood vessels, we will focus our treatment on the second effector: the rate of blood flow from the heart.
We have two drugs in the Sanctuary that affect the rate of blood flow from a megaraffe’s heart. One drug, called an agonist, activates receptors in the membranes of cardiac muscle cells, causing the heart to beat faster and stronger. Administering the agonist to Xor would increase the flow of blood from her heart. Another drug, called an antagonist, deactivates receptors in the membranes of cardiac muscle cells, causing the heart to beat slower and weaker. Administering the antagonist to Xor would decrease the flow of blood from her heart.
Use this information to determine how to treat Xor as the AI resets the gravitational force in the Sanctuary.
Directions: Use Figure 11 and your answers to questions 24-25 to answer questions 26-27. Assume that Xor is standing but not performing any other physical activity, that the effect of the vasodilators has completely worn off, and that the AI is resetting the gravity in the Sanctuary, such that gravity may increase or decrease as indicated by questions 26-27.
26. Which drug should we administer to regulate Xor’s blood pressure as the gravitational force of the environment increases?
administer the agonist, which will cause Xor’s heart to beat faster and stronger
administer the antagonist, which will cause Xor’s heart to beat slower and weaker
27. Which drug should we administer to regulate Xor’s blood pressure as the gravitational force of the environment decreases?
administer the agonist, which will cause Xor’s heart to beat faster and stronger
administer the antagonist, which will cause Xor’s heart to beat slower and weaker
What dosage of drug should we use to increase Xor’s cranial blood pressure?
The typical cranial blood pressure in a healthy megaraffe is 105 mmHg. As the gravitational force fluctuates, her blood pressure will likely oscillate between 70 mm Hg and 150 mm Hg. During this oscillation, you will need to administer a certain dosage of each drug at the appropriate times.
Figure 12 (below) shows the completed path model for the homeostatic system that regulates the blood pressure of a megaraffe with the addition of a box representing the dosage of a drug that increases the flow of blood from the heart. For simplicity, this figure highlights only those components needed to calculate the correct dosage of the drug. These components include the relationships among the dosage of the drug, the rate of blood flow from the heart, and blood pressure. The slopes for these relationships have been provided.
In the absence of the drug, Xor’s blood pressure would drop as low as 70 mmHg. As the blood pressure falls to 70 mm Hg, how much drug should we administer to restore the blood pressure to 105 mmH?
To answer this question, assume the following conditions:
the drug directly affects the rate of blood flow from the heart (L min-1),
the drug has no effect at dosages below 41 g and has a linear effect on the rate of blood flow at dosages above 41 g. The slope of this linear effect is 2.91 L min-1 / g of drug, and
the drug must increase the rate of blood flow enough to increase the blood pressure from 70 mm Hg to 105 mmHg, and
the slope of the linear relationship between the rate of blood flow from the heart and the blood pressure in megaraffes is 0.225 mmHg/(L min-1).
Our goal is to determine the dosage of the drug needed to increase the blood pressure by 35 mmHg. We’ll work backwards from this goal to determine the correct dose.
Directions: Use the path model and slopes in Figure 12 to answer questions 28-29. Round all calculated values to the nearest one’s place. For example, if you calculate the value as 3.821853, round to 4.
28. How much does the rate of blood flow from the heart (L min-1) need to increase to cause the blood pressure to increase by 35 mmHg?
Amount to increase the rate of blood flow from the heart (L min-1) =
29. What dosage of the drug (g) must we administer to change the rate of blood flow from the heart (L min-1) by the amount that you indicated in your answer to the previous question? Remember that the drug has no effect on the rate of blood flow at dosages of 41 g or less, so be sure to add 41 g to your final answer.
Dosage of drug (g) =
What dosage of drug should we use to decrease Xor’s cranial blood pressure?
Now that we know the appropriate dosage for increasing the flow of blood from Xor’s heart, we need to calculate the dosage needed to decrease the flow of blood.
Figure 13 (below) shows the completed path model for the homeostatic system that regulates the blood pressure of a megaraffe with the addition of a box representing the dosage of a drug that decreases the flow of blood from the heart. For simplicity, this figure highlights only those components needed to calculate the correct dosage of the drug. These components include the relationships among the dosage of the drug, the rate of blood flow from the heart, and blood pressure. The slopes for these relationships have been provided.
In the absence of the drug, Xor’s blood pressure would rise as high as 150 mmHg. As the blood pressure rises to 150 mm Hg, how much drug should we administer to restore the blood pressure to 105 mmH?
To answer this question, assume the following conditions:
the drug directly affects the rate of blood flow from the heart (L min-1),
the drug has no effect at dosages below 322 g and has a linear effect on the rate of blood flow at dosages above 322 g. The slope of this linear effect is -0.34 L min-1 / g of drug,
the drug must decrease the rate of blood flow enough to reduce the blood pressure from 150 mm Hg to 105 mmHg, and
the slope of the linear relationship between the rate of blood flow from the heart and the blood pressure in megaraffes is 0.225 mmHg/(L min-1).
Our goal is to determine the dosage of the drug needed to decrease the blood pressure by -45 mmHg. We’ll work backwards from this goal to determine the correct dose.
Directions: Use the path model and slopes in Figure 13 to answer questions 30-31. Round all calculated values to the nearest one’s place. For example, if you calculate the value as 3.821853, round to 4.
30. How much does the rate of blood flow from the heart (L min-1) need to decrease to cause the blood pressure to decrease by -45 mmHg? Hint – your answer should be a negative number because you are decreasing the rate of blood flow from the heart by that amount.
Amount to decrease the rate of blood flow from the heart (L min-1) =
31. What dosage of the drug (g) must we administer to change the rate of blood flow from the heart (L min-1) by the amount that you indicated in your answer to the previous question? Remember that the drug has no effect on the rate of blood flow at dosages of 322 g or less, so be sure to add 322 g to your final answer.
Dosage of drug (g) =
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