Info

Treadlift Workout

Treadmill Cardio Workouts

Get Instant Access

of the treadmill increased, the respiratory gas exchange rate of the dogs increased but the Pco2 of the dogs' blood remained constant. Before concluding that blood Pco2 is not the metabolic feedback information for breathing rate, however, the researchers changed their experiment. Instead of increasing the speed of the treadmill, they gradually increased its slope so that the dogs were running at the same speed, but were working harder because they were running uphill.

In this experiment, the Pco2 of the blood increased as the slope of the treadmill increased and as the respiratory gas exchange rate increased. The researchers concluded that the Pco2 of the blood is the primary metabolic feedback information for breathing. However, when an animal starts to run or changes its running speed, additional feedback information from receptors in muscles and joints changes the sensitivity of the CO2 sensors—an example of feedforward information.

Where are partial pressures of gases in the blood sensed? The major site of CO2 sensitivity is an area on the ventral surface of the medulla, not far from the groups of neurons that generate the breathing rhythm. Primary sensitivity to Po2 in the blood resides in nodes of tissue on the large blood vessels

Neural input from higher brain centers-

Chemoreceptors on the surface of the medulla are sensitive to the partial pressure of carbon dioxide and the pH of the cerebral spinal fluid.

Chemoreceptors on large blood vessels leaving the heart are sensitive to the oxygen in the blood.

Carotid body Carotid artery Aorta Aortic body

Neural input from higher brain centers-

Chemoreceptors on the surface of the medulla are sensitive to the partial pressure of carbon dioxide and the pH of the cerebral spinal fluid.

Chemoreceptors on large blood vessels leaving the heart are sensitive to the oxygen in the blood.

Carotid body Carotid artery Aorta Aortic body

Medulla Carotid Body Aortic Body

Neurons that excite breathing neurons in medulla

Medulla

Breathing control area

-Spinal cord

Gutput to respiratory muscles

Heart

Neurons that excite breathing neurons in medulla

Medulla

Breathing control area

-Spinal cord

Gutput to respiratory muscles

Heart

48.17 Feedback Information Controls Breathing The body uses feedback information from chemosensors in the heart and the brain to match breathing rate to metabolic demand.

leaving the heart: the aorta and the carotid arteries (Figure 48.17). These carotid and aortic bodies receive enormous supplies of blood relative to their small size, and they contain chemoreceptors. If the blood supply to these structures decreases, or if the Po2 of the blood falls dramatically, the chemoreceptors are activated and send nerve impulses to the breathing control center. Although we are not very sensitive to changes in blood Po2, the carotid and aortic bodies can stimulate increases in breathing during exposure to very high altitudes or when blood volume or blood pressure is very low.

Was this article helpful?

0 0
The Donts of Treadmill Buying

The Donts of Treadmill Buying

Though competitive runners are advised to run on the road, there are several reasons why you should buy treadmills anyway. You might have a family which means that your schedule does not have the flexibility it once had.

Get My Free Ebook


Post a comment