Respiration. Part 4

Summary

This script delves into the regulation of respiration, highlighting both humoral and neural mechanisms. It details the pivotal role of carbon dioxide in stimulating the respiratory center and the influence of peripheral chemoreceptors. The script also discusses the respiratory center's location in the medulla oblongata and its broader neural network. It touches on the first breath of a newborn, the effects of high and low pressure on respiration, and the dangers of decompression sickness during diving, emphasizing the importance of gradual ascent.

Takeaways

• 🫁 The regulation of respiration involves both humoral and neural mechanisms.
• 🐕 The Frederick experiment on two dogs demonstrated humoral regulation through carbon dioxide's effect on respiration.
• 🔄 When CO2 levels rise, it stimulates the respiration center in the brain, increasing the frequency and depth of breathing.
• 🧠 The respiration center, located in the medulla oblongata, has separate inspiration and expiration centers, which work reciprocally.
• 💡 High CO2 concentrations activate the inspiration center through peripheral chemoreceptors, increasing respiratory activity.
• 😤 Voluntary hyperventilation leads to temporary apnoea as CO2 is washed out of the blood, causing reduced respiratory drive.
• 🧠 In a broader sense, respiration is controlled by multiple parts of the CNS, including the medulla, pons, limbic system, neocortex, and spinal cord.
• 🫨 Nervous regulation of respiration involves the vagus nerve, which transmits signals from stretch receptors in the lungs to the expiration center.
• 👶 A newborn's first breath is triggered by elevated CO2 levels, which stimulate the respiratory center and lead to the first inspiration.
• 🏔 High altitude induces hypoxia, increasing heart rate and respiration frequency, while chronic adaptation involves higher hemoglobin levels.

Q & A

What is the Frederick experiment and what does it prove?

The Frederick experiment involved two dogs with cross-circulation of blood between their brains. It demonstrated that carbon dioxide (CO2) levels in the blood regulate respiration. When CO2 levels increased, it stimulated respiration in the second dog, proving the importance of humoral regulation in respiration.

How does the humoral regulation of respiration work?

Humoral regulation of respiration is influenced by the levels of carbon dioxide (CO2), oxygen (O2), and blood pH. Increased CO2 levels stimulate the respiratory center in the brain, increasing the frequency and depth of breathing to expel excess CO2.

What are the inspiration and expiration centers in the brain, and how do they interact?

The inspiration and expiration centers are located in the medulla oblongata. When the neurons in the inspiration center are activated, they inhibit the expiration center, and vice versa. This reciprocal inhibition allows the body to alternate between inhalation and exhalation.

What role do peripheral chemoreceptors play in respiration?

Peripheral chemoreceptors detect changes in blood CO2 levels and send signals to the respiratory centers in the brain. High CO2 levels activate the inspiration center, which increases the rate and depth of breathing to reduce CO2 concentration.

What is the Hering-Breuer reflex?

The Hering-Breuer reflex prevents over-inflation of the lungs by using stretch receptors in the alveoli. When these receptors detect lung inflation, they send signals via the vagus nerve to inhibit further inhalation and initiate exhalation.

How does carbon dioxide accumulation lead to a newborn's first breath?

When a newborn is delivered, the oxygen supply through the umbilical cord stops, leading to CO2 accumulation in the blood. This stimulates chemoreceptors, which activate the inspiration center in the medulla oblongata, prompting the newborn to take its first breath.

How does the body adapt to high altitudes?

At high altitudes, the body responds to lower oxygen levels (hypoxia) by increasing heart rate, respiratory rate, and red blood cell production. Over time, hemoglobin levels also increase to improve oxygen transport, but full adaptation may take weeks.

What happens during diving at high pressures, and what is the risk of air embolism?

During diving, increased pressure increases the solubility of gases like oxygen and nitrogen in the blood. Rapid ascent can cause nitrogen to form bubbles, leading to air embolism, which can block circulation and be fatal. To avoid this, divers must ascend slowly or use decompression stops.

How is the respiratory center involved in both narrow and wide senses?

In the narrow sense, the respiratory center is located in the medulla oblongata, regulating inspiration and expiration. In the wide sense, many parts of the CNS, including the pons, limbic system, neocortex, and spinal cord, are involved in modulating breathing patterns and voluntary control.

Why is hyperventilation followed by a period of reduced breathing (apnea)?

During hyperventilation, CO2 is expelled rapidly, reducing its levels in the blood. This decrease in CO2 causes the respiratory centers to reduce the drive for breathing, leading to a temporary period of apnea (reduced or stopped breathing) until CO2 levels normalize.