Researchers set out to conduct a series of separate experiments to explore how the mammalian respiratory system functions. Using rats as a model for exploring respiration (assume the mechanics for breathing and maintaining homeostatic regulation of Pco2, Po2, and pH are the same for humans and rats), the researchers performed several separate experiments on these otherwise healthy rats. The rats were allowed to fully recover after the conclusion of each experiment, thus ensuring no carry over effects from one experiment to the next. Throughout the baseline observations and experiments, the researchers closely monitored the rats ventilation; Pco2, Po2, and pH levels in the systemic arteries and systemic veins; and the Pco2 and Po2 in the alveoli. The experiments are described below:
Baseline observations: They don’t do anything to the rats…the rats are just at rest. Baseline is basically what the body is doing before any manipulations or experiments.
Experiment 1: They experimentally removed chemosensors for CO2, O2, and pH in the rats.
Experiment 2: They artificially lowered the Pco2 levels in the systemic arteries well below the set point for Pco2.
Experiment 3: They artificially altered the thickness of the alveoli, making the alveolar membranes thicker than normal.
Experiment 4: They administer a neurotoxin that causes the rat’s diaphragm to stay in a contracted state indefinitely.
Experiment 5: They artificially alter the conducting pathways in the lungs of the rat, making them more narrow than normal, thus increasing resistance to airflow.
1. In the homeostatic regulation of breathing, what is/are the control center(s)?
|
a |
the contraction of the respiratory muscles |
| b | Structures in the body that monitor changes in PCO2, PO2, and pH |
| c | Regions of the brainstem that compare compare sensory information with the set point range |
| d | the respiratory muscles like the diaphragm |
| e | the neurons that cause respiratory muscles to contract |
2. What would be the direct impact of experiment 1 on the homeostatic regulation of Pco2, Po2, and/or pH?
| (a) | The rats would become hypersensitive to changes in CO2, O2, and/or pH. |
| (b) | The rats would become unresponsive to changes in CO2, O2, and/or pH. |
| (c) | None of these is correct. |
|
(d) The rats would respond to changes in CO2, O2, and/or pH in the same way as they would in baseline conditions. |
(3) In the baseline condition, the Po2 and Pco2 in the alveoli should likely be similar to the Po2 and Pco2 values observed in the: (select all that apply)
| (a) | pulmonary arteries |
| (b) | right ventricle |
| (c) | pulmonary veins |
| (d) | systemic arteries |
| (e) | systemic veins |
| (f) |
left ventricle |
(4) During experiment 5, in order for the rat to maintain the same flow rate of air into the lungs relative to a rat at rest in the baseline conditions, the rats in experiment 5 would have to
| (a) | Cause their lungs to expand to volumes that are greater than those observed for a rat at rest in baseline conditions (take deeper breaths) |
| (b) | Cause their lungs to expand to volumes that are less than those observed for a rat at rest in baseline conditions (take shallower breaths) |
| (c) | There would be no change in their breathing patterns |
1) Control centres are those areas that control the rate of respiration based on the concentration of CO2, O2 and H+. These are located in yhe brainstem. Thus, option C is correct.
Option a, contraction of respiratory muscle is a motor response due to signals from control centres.
Option B, these are the sensors which tell the control centres about the pCO2, pO2, pH.
Option d, diaphragm or other respiratory muscles Contract because of signals from control centres.
Option e, the neurons which are responsible for contraction consists the motor pathway. They bring the signal of contraction from the control centres.
Researchers set out to conduct a series of separate experiments to explore how the mammalian respiratory...