BIO 181 - General Biology I M3A1_Student Version Lab Instructions: Physiology Act I
Mission Memo 2025-2026 Arizona State University
Greetings Fellow Explorer:
Despite your efforts to treat Xor, she remains weak and disoriented. To make matters
worse, the herd will not leave Xor to continue on its journey. If we cannot help Xor
recover quickly, the other megaraffes will soon be in danger.
Having ruled out dehydration as a cause of Xor's symptoms, three potential causes
remain: (1) a low concentration of oxygen in the blood, (2) a low concentration of
carbohydrates in the blood, and (3) a high blood pressure in the arteries.
You must investigate the homeostatic systems that regulate these three variables in a
megaraffe. Use the following questions to guide your work.
● How does a megaraffe regulate variables in the body that affect the reactions
needed to survive? (Appendix 1)
● How should we treat Xor if one of her homeostatic systems has failed? (Appendix
2)
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
How does a megaraffe regulate variables in the body that affect the
reactions needed to survive?
To survive, an organism must regulate many variables in the body that affect the chemical
reactions of life. For example, a megaraffe must ensure that its blood carries sufficient
resources to all cells of the body. These resources include carbohydrates and oxygen
(O2), which are needed to fuel critical reactions in cells. If an organism cannot deliver
enough of these resources, illness, or even death could occur.
Xor's disorientation might have resulted from a failure to regulate the concentration of O2
[O2], or carbohydrates in her blood, or a failure to maintain a blood pressure needed for
the blood to carry these resources to cells.
The regulation of blood O2 concentration, blood carbohydrate concentration, and blood
pressure is critical to the survival of a megaraffe. On earth, systems of cells, tissues, and
organs in every large, multicellular organism collaborate to maintain these variables
within a narrow range needed to sustain life. The process of regulation, called
homeostasis, is how organisms such as megaraffes keep their internal conditions within
limits necessary for survival.
To diagnose whether Xor's symptoms stem from a failure to regulate the concentration of
[O2], concentration of carbohydrates, or blood pressure, we must use a path model of a
homeostatic system. Let's start by making sure that we’re interpreting a path model
correctly. We’ll practice interpreting a path model of a homeostatic system that regulates
the concentration of O2 in the blood of megaraffes.
We need to complete the following step to understand how megaraffes regulate the O2
concentration in their blood.
Step 1: Interpret a path model: Interpret a path model of a homeostatic system that
regulates O2 concentration in the blood of megaraffes. This step will prepare us to
diagnose potential causes of Xor's condition and determine the appropriate treatment.
, Step 1: Interpret a path model
All organisms, from the smallest bacteria to the largest species in the universe, need to
maintain a relatively constant internal environment despite a changing external
environment. The process by which organisms maintain a consistent internal
environment is called homeostasis.
What is homeostasis?
Homeostasis is the process by which organisms maintain a relatively stable internal
environment in an ever-changing external environment. Like any system, homeostatic
systems involve a set of components that interact to achieve a desired outcome. In this
case, the outcome is the regulation of a variable within a range required to sustain life;
the mean value of a regulated variable is called a set point, reflecting the idea that the
organism attempts to set the value of the variable at that point. Examples of regulated
variables in humans include blood O2 concentration, blood glucose concentration, blood
pressure, and body temperature.
How does an organism detect when the value of a variable deviates from the set point
and return the variable to the set point? First, the system must have a component called
a sensor, which measures the magnitude of the regulated variable.
A sensor relays information about the magnitude of a variable to a component called the
integrator. The integrator sums the information from all sensors and responds by
activating a component that can return the regulated variable to the set point.
How does the integrator cause the variable to return to the set point? Depending on the
information that the integrator receives from the sensors, it sends its own signals to cells
called effectors. These signals cause the effectors to function in a way that returns the
variable to the set point.
To summarize, a homeostatic system with a sensor, integrator, and effector detects a
change in the value of a variable and counteracts that change, restoring the initial value.
Because the change caused by a homeostatic system opposes the direction of the initial
change, a homeostatic system is also called a negative feedback loop.
Figure 1 shows a generic path model of a homeostatic system as a set of boxes and
arrows. The regulated variable is represented with a dashed black box containing black
, text. Each component of the system is represented by a black box containing black text.
These boxes state the action of the component and include the name of the component
within the box - e.g., sensor, integrator, effector 1 and effector 2. In practice, the activity of
each component would be measured by a specific variable; for example, a sensor's
activity might be measured by the rate of electrical impulses fired by a nerve cell.
Additionally, that sensor would not be labeled as a “sensor” but rather would be labeled
as the name of the cell or tissues. In this example, we would call the sensor a nerve cell.
An arrow connecting one box to another indicates a relationship between two
components. The direction of the arrow tells us about cause and effect; for example, the
arrow pointing from the sensor's box to the integrator's box tells us that the activity of the
sensor directly affects the activity of the integrator. When modeling this relationship, we
can think of the activity of the sensor as an independent variable and the activity of the
integrator as a dependent variable.
Mission Memo 2025-2026 Arizona State University
Greetings Fellow Explorer:
Despite your efforts to treat Xor, she remains weak and disoriented. To make matters
worse, the herd will not leave Xor to continue on its journey. If we cannot help Xor
recover quickly, the other megaraffes will soon be in danger.
Having ruled out dehydration as a cause of Xor's symptoms, three potential causes
remain: (1) a low concentration of oxygen in the blood, (2) a low concentration of
carbohydrates in the blood, and (3) a high blood pressure in the arteries.
You must investigate the homeostatic systems that regulate these three variables in a
megaraffe. Use the following questions to guide your work.
● How does a megaraffe regulate variables in the body that affect the reactions
needed to survive? (Appendix 1)
● How should we treat Xor if one of her homeostatic systems has failed? (Appendix
2)
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
How does a megaraffe regulate variables in the body that affect the
reactions needed to survive?
To survive, an organism must regulate many variables in the body that affect the chemical
reactions of life. For example, a megaraffe must ensure that its blood carries sufficient
resources to all cells of the body. These resources include carbohydrates and oxygen
(O2), which are needed to fuel critical reactions in cells. If an organism cannot deliver
enough of these resources, illness, or even death could occur.
Xor's disorientation might have resulted from a failure to regulate the concentration of O2
[O2], or carbohydrates in her blood, or a failure to maintain a blood pressure needed for
the blood to carry these resources to cells.
The regulation of blood O2 concentration, blood carbohydrate concentration, and blood
pressure is critical to the survival of a megaraffe. On earth, systems of cells, tissues, and
organs in every large, multicellular organism collaborate to maintain these variables
within a narrow range needed to sustain life. The process of regulation, called
homeostasis, is how organisms such as megaraffes keep their internal conditions within
limits necessary for survival.
To diagnose whether Xor's symptoms stem from a failure to regulate the concentration of
[O2], concentration of carbohydrates, or blood pressure, we must use a path model of a
homeostatic system. Let's start by making sure that we’re interpreting a path model
correctly. We’ll practice interpreting a path model of a homeostatic system that regulates
the concentration of O2 in the blood of megaraffes.
We need to complete the following step to understand how megaraffes regulate the O2
concentration in their blood.
Step 1: Interpret a path model: Interpret a path model of a homeostatic system that
regulates O2 concentration in the blood of megaraffes. This step will prepare us to
diagnose potential causes of Xor's condition and determine the appropriate treatment.
, Step 1: Interpret a path model
All organisms, from the smallest bacteria to the largest species in the universe, need to
maintain a relatively constant internal environment despite a changing external
environment. The process by which organisms maintain a consistent internal
environment is called homeostasis.
What is homeostasis?
Homeostasis is the process by which organisms maintain a relatively stable internal
environment in an ever-changing external environment. Like any system, homeostatic
systems involve a set of components that interact to achieve a desired outcome. In this
case, the outcome is the regulation of a variable within a range required to sustain life;
the mean value of a regulated variable is called a set point, reflecting the idea that the
organism attempts to set the value of the variable at that point. Examples of regulated
variables in humans include blood O2 concentration, blood glucose concentration, blood
pressure, and body temperature.
How does an organism detect when the value of a variable deviates from the set point
and return the variable to the set point? First, the system must have a component called
a sensor, which measures the magnitude of the regulated variable.
A sensor relays information about the magnitude of a variable to a component called the
integrator. The integrator sums the information from all sensors and responds by
activating a component that can return the regulated variable to the set point.
How does the integrator cause the variable to return to the set point? Depending on the
information that the integrator receives from the sensors, it sends its own signals to cells
called effectors. These signals cause the effectors to function in a way that returns the
variable to the set point.
To summarize, a homeostatic system with a sensor, integrator, and effector detects a
change in the value of a variable and counteracts that change, restoring the initial value.
Because the change caused by a homeostatic system opposes the direction of the initial
change, a homeostatic system is also called a negative feedback loop.
Figure 1 shows a generic path model of a homeostatic system as a set of boxes and
arrows. The regulated variable is represented with a dashed black box containing black
, text. Each component of the system is represented by a black box containing black text.
These boxes state the action of the component and include the name of the component
within the box - e.g., sensor, integrator, effector 1 and effector 2. In practice, the activity of
each component would be measured by a specific variable; for example, a sensor's
activity might be measured by the rate of electrical impulses fired by a nerve cell.
Additionally, that sensor would not be labeled as a “sensor” but rather would be labeled
as the name of the cell or tissues. In this example, we would call the sensor a nerve cell.
An arrow connecting one box to another indicates a relationship between two
components. The direction of the arrow tells us about cause and effect; for example, the
arrow pointing from the sensor's box to the integrator's box tells us that the activity of the
sensor directly affects the activity of the integrator. When modeling this relationship, we
can think of the activity of the sensor as an independent variable and the activity of the
integrator as a dependent variable.
