Question

Read the given statements and select the correct option. Statement \(1:\) Rate of breathing is regulated by respiratory centres present in the medulla oblongata. Statement 2 : Changes in the \(\mathrm{CO}_{2}\) level of the arterial blood control the rate of breathing. (a) Both statements 1 and 2 are correct and statement 2 is the correct explanation of statement 1 . (b) Both statements 1 and 2 are correct but statement 2 is not the correct explanation of statement 1 . c) Statement 1 is correct and statement 2 is incorrect. d) Both statements 1 and 2 are incorrect.

Short answer

Both statements are correct and statement 2 is the correct explanation of statement 1, so the answer is (a).

Step-by-step solution

Understand the role of the medulla oblongata

The medulla oblongata is a portion of the brainstem that controls several vital functions, including respiration. Respiratory centres located here help regulate the rate of breathing by responding to various physiological cues.

Assess the impact of \(\mathrm{CO}_2\) levels on breathing

Changes in the carbon dioxide (\(\mathrm{CO}_2\)) levels in the blood can signal the respiratory centres to adjust breathing. An increase in \(\mathrm{CO}_2\) levels can speed up breathing, whereas a decrease can slow it down. This is part of the body's way of maintaining homeostasis.

Evaluate the relationship between the statements

Since statement 1 addresses where breathing is regulated and statement 2 describes a mechanism through which it is regulated, if both statements are correct, it must be determined whether statement 2 is the underlying reason for the fact stated in statement 1.

Select the correct option

Both statements are correct. Statement 1 is a fact about the location of respiratory control and statement 2 describes a feedback mechanism influencing the regulation mentioned in statement 1. Thus, statement 2 is a correct explanation of statement 1.

Key concepts

Medulla Oblongata

The medulla oblongata is an essential part of the human brain located at the brainstem's lower end, continuing downward from the spinal cord. It plays a critical role in maintaining our body's vital functions such as heart rate, blood pressure, and importantly, breathing.

The medulla contains specialized areas known as the respiratory centers: the dorsal respiratory group (DRG) and the ventral respiratory group (VRG). These groups are responsible for the basic rhythm and depth of breathing and can adjust the respiratory rate to meet the body's needs at any time.

For students striving to grasp the significance, imagine the medulla oblongata as the conductor of an orchestra where each musician represents different reflexes and bodily functions. It integrates both voluntary and involuntary inputs to ensure that breathing proceeds rhythmically and adjusts as per changes in the body's status, ensuring that we can focus on our daily tasks without needing to consciously manage every breath.

Carbon Dioxide (CO2) Level

Carbon dioxide (CO2) levels in the bloodstream act as a fundamental signal in regulating the respiratory process. When CO2 concentration rises, it lowers blood pH by forming carbonic acid, which signals the respiratory centers that the blood is becoming more acidic.

This change is detected by chemoreceptors located in the medulla and in the arteries. They are like chemical detectives, on the lookout for any imbalance. When they sense an increase in CO2 and consequently a decrease in pH, these receptors send urgent messages to the respiratory centers to increase the rate and depth of breathing, often referred to as hyperventilation, to expel more CO2 and restore balance.

Similarly, when CO2 levels are low, which causes blood pH to rise, signaling a more alkaline state, the chemoreceptors inform the respiratory centers to slow down the breathing rate, termed hypoventilation. Understanding this concept can help students recognize the delicate balance the body always tries to maintain.

Respiratory Centres

The respiratory centers are control hubs located within the medulla oblongata, acting as master regulators of breathing. There are two main centers to be familiar with: the dorsal respiratory group (DRG) and the ventral respiratory group (VRG). The DRG principally controls the rhythm of quiet breathing, while the VRG becomes active when more forceful breathing is necessary, such as during exercise or in response to stress.

Integration with Other Systems

The respiratory centers do not work in isolation; they interact with other parts of the brain and body. Signals from the limbic system and the hypothalamus, which reflect emotional and thermal stimuli, respectively, as well as voluntary control from the cerebral cortex, can modify the activity of the respiratory centers.

Importance in Homeostasis

The responsiveness of the respiratory centers to CO2 levels makes them key players in maintaining homeostasis—the body's stable internal environment. A deeper understanding of these centers provides students with insights into how the body automatically adjusts breathing patterns to suit different situations, an activity so fundamental to life yet often taken for granted.