RAT: Oxygen Consumption Using an Open System

Question 1

In an open system, how do you calculate the O2 consumption rate? (to get the % O2 used in an open chamber)

Answer 1

(pO2 (initial)-pO2(final))/750mmHG

or any barometric pressure.

Question 2

From the graph of the rat data for ml O2/hr/g at the varying temperatures, is that trend seen in the mouse data? Differences in slope?

Answer 2

mlO2/hr/g is SPECIFIC METABOLIC RATE.

Both rat and mouse are endotherms, so they should exhibit the same trend: slowing of metabolism as temp increases because less energy is needed to maintain an internal temperature. However, the mouse should have a faster metabolism in general and be expending more energy and thus needing MORE O2 than the rat.

The rat may have a smaller slope, meaning it is less affected by temperature change than mouse. this is because
1) lower SA/vol ratio–> metabolism is slower in general and thus less oxygen consumption per gram. (lower specific metabolic rate)

2) more heat loss mechanisms (ex/ more fat)

Question 3

Why doesn’t tidal volume equal the amout of oxygen that reaches the tissue?

Answer 3

because some O2 is still left in the lungs, it is part of the dead space. 350/500ml of air truly reaches the tissues (in a human)

Question 4

What are some advantages of an open system? (where fresh air is continuously drawn through the chamber) disadvantages?

Answer 4

• can evaluate a wide range of animals (you aren’t limited by size of animal you can fit in a box, like in a closed system)
• don’t need to worry about accidently creating a hypoxic environment
• allows for comparing CO2 and O2 levels. Can give you more info about what kind of fuel you’re burning depending on the ratio.
• don’t need chemicalss like carbsor or a dessecant to absorb water moisture, unlike in a closed system.
• disadvantages: cannot measure anaerobic metabolism (metabolism that doesn’t require O2)

Question 5

Why do we use a log graph when measuring metabolic rate and mass?

Answer 5

allows for us to see a linear relationship

Question 6

From the graphs of the data values for oxygen consumption at room temperature for the rat, mouse and human - log ml O2/animal and log ml O2/h/g vs log mass of the animal, explain the difference between the 2 plots.

Answer 6

Relationship/slope between log mlO2/hr/animal vs log mass should be around +0.7.
- the human will generally consume more O2 than the mouse for example, because they are heavier.(more O2/hr per ANIMAL)

Relationship between log mlO2/hr/g (SPECIFIC MR) vs log mass should be around -0.25 or -0.33
- the human expends LESS ENERGY heating each gram of tissue compared to a mouse. The mouse expents more energy to heat each gram of its tissue because it it has the highest surface area to volume ratio. The house is more metabolically active.

Question 7

Basal metabolic rate vs resting metabolic rate

Answer 7

resting: metabolic rate of an animal at REST. will be higher than basal
basal: metabolic rate of an inactive, quiet, stress free animal with NO DIGESTION occurring.

Question 8

T/F in endotherms, metabolism increases when trying to dissipate heat

Answer 8

FALSE. In hot environments when trying to get rid of heat, the body does not need to use as much energy to maintain the high internal temperature because it is already hot.

Question 9

endotherms experience greater activity in ____ temperatures

Answer 9

cold