Question

Describe how ventilation is regulated by six different neural (sensory and autorhythmic), chemical, and higher brain (conscious/emotional) inputs. Explain the responses to and the results of each of these regulatory signals.

Answer 1

Ventilation, the movement of air in and out of the lungs, respiratory muscles must contract and relax rhythmically to alternatively fill the lungs with air in inspiration, and then empty them in expiration. the muscles of inspiration, unlike the cardiac cells  require nervous stimulation to trigger muscle contraction .Neurons, located in the pons and medulla are responsible for generating the rhythmic pattern of breathing. The cells bodies of these neurons form the respiratory control centre in the medulla, which sends impulses to stimulate the contraction of the diaphragm and intercostal muscles through the phrenic nerve and intercostal nerves respectively. Once the neurons stop firing, then the inspiratory muscles relax and expiration occurs.

Chemoreceptor mechanism

Central Chemoreceptor : They are sensitive to the pH of their environment. The rate of ventilation is tightly controlled by the level of carbon dioxide in the blood, these levels are sensed by the chemoreceptors, which are found both centrally and peripherally. Chemoreceptors detect the levels of carbon dioxide in the blood by monitoring the concentrations of hydrogen ions in the blood, when there is increase in CO2 levels in the body, the pH reduces, in response to this the lungs starts to increase the rate and depth of breathing, when the CO2 levels are low the reverse happens the lungs start to decrease the rate of breathing.

Peripheral chemoreceptors : Consists of the aortic body, which mainly detects changes in blood oxygen and carbon dioxide, but not pH, and have less of an impact on the respiratory rate compared to the central chemoreceptors.

Voluntary control : Voluntary respiration is important for the higher functions that involve air supply, such as voice control. Conscious control of respiration through the motor cortex in the cerebrum, which receives inputs from the limbic system and hypothalamus.