L25. Physiology - Neural Mechanical Control of Breathing

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Questions and Answers

What is the primary function of the diaphragm during breathing?

To increase lung volume by contracting downward. (correct)

To decrease thoracic pressure by relaxing upward.

To assist in maintaining intrapleural pressure without movement.

To limit airflow by contracting during expiration.

Which of the following muscle groups actively contributes to forced expiration?

Internal intercostals and abdominal muscles. (correct)

Sternocleidomastoid and scalene muscles.

Diaphragm and external intercostals.

Accessory muscles and diaphragm.

What happens to the intrapleural pressure during normal inspiration?

It increases, causing the lungs to deflate.

It remains constant throughout the breathing cycle.

It decreases, promoting lung expansion. (correct)

It fluctuates randomly with no significant pattern.

In the respiratory cycle, when does the cessation of inspiration typically occur?

When alveolar pressure equals atmospheric pressure. Signup and view all the answers

The generation of respiratory rhythm is primarily located in which part of the brain?

Medulla oblongata. Signup and view all the answers

What physiological change occurs when air is introduced into the pleural cavity?

Decreased intrapleural pressure leading to lung collapse. Signup and view all the answers

Which pressure change is primarily responsible for airflow during normal breathing?

Decrease in intrapulmonary pressure below atmospheric pressure. Signup and view all the answers

What role do accessory muscles of inspiration play in breathing?

They provide additional force to increase airflow during deep or rapid breathing. Signup and view all the answers

What is the primary role of the diaphragm during inspiration?

To pull downward and expand the thoracic cavity Signup and view all the answers

Which muscles are primarily responsible for forced expiration?

Internal intercostals and abdominal muscles Signup and view all the answers

How are the lung and chest wall coupled in the human body?

By visceral and parietal pleura Signup and view all the answers

What happens to the chest wall during passive expiration?

It returns to a relaxed position due to compliance Signup and view all the answers

What is the functional relationship between the lung and chest wall modeled as?

Two springs coupled together Signup and view all the answers

What is one consequence of the internal intercostal muscles contracting during expiration?

They pull the ribs downward and inward, compressing the chest volume Signup and view all the answers

What is the role of accessory muscles during inspiration?

To stabilize the ribs and assist diaphragmatic movement Signup and view all the answers

Which pleura covers the thoracic wall and superior face of the diaphragm?

Parietal pleura Signup and view all the answers

During forced expiration, what is the primary function of the rectus abdominis muscle?

To compress the abdominal cavity and push the diaphragm up Signup and view all the answers

Which pressure is primarily responsible for the expansion of the lungs during inspiration?

Transpulmonary pressure Signup and view all the answers

What is the primary function of the inspiratory muscles during breathing?

To decrease intrapulmonary pressure Signup and view all the answers

Which muscle is primarily responsible for active expiration during heavy breathing?

Rectus abdominus Signup and view all the answers

Where is the respiratory rhythm primarily generated in the body?

Medulla Signup and view all the answers

Which motoneurons innervate the diaphragm?

C3 - C5 Signup and view all the answers

What type of pressure gradient primarily drives air flow during ventilation?

Alveolar pressure gradient Signup and view all the answers

What is the role of the phrenic nerve in respiration?

To innervate the diaphragm Signup and view all the answers

During heavy exercise, which of the following muscles becomes actively involved in expiration?

Internal intercostals Signup and view all the answers

Which of the following statements best describes the role of the external intercostal muscles?

They contract to elevate the ribs during inspiration. Signup and view all the answers

What happens to the intrapleural pressure during inspiration as the diaphragm and external intercostal muscles contract?

It decreases, leading to a more negative pressure. Signup and view all the answers

What effect does increased intrapleural pressure have on the respiratory system?

Prevents airflow into the lungs Signup and view all the answers

How is transpulmonary pressure calculated?

By subtracting intrapleural pressure from alveolar pressure. Signup and view all the answers

What effect does the expansion of the lungs during inspiration have on the alveolar pressure compared to atmospheric pressure?

Alveolar pressure drops below atmospheric pressure. Signup and view all the answers

What initiates the airflow into the lungs at the start of inspiration?

The creation of a negative pressure gradient between the airways and atmosphere. Signup and view all the answers

What occurs at the end of expiration regarding the alveolar pressure?

Alveolar pressure becomes equal to atmospheric pressure. Signup and view all the answers

What occurs during the uncoupling of the lung and chest wall?

The thorax expands while the lungs drop below residual volume. Signup and view all the answers

What is the functional residual capacity (FRC)?

The position of lung and chest wall at the end of expiration/beginning of inspiration. Signup and view all the answers

What is the typical intrapleural pressure at functional residual capacity (FRC)?

<ul> <li>5 cmH2O</li> </ul> Signup and view all the answers

According to Boyle’s law, how is pressure related to volume?

Pressure is inversely related to volume. Signup and view all the answers

What results from the increase in volume in the intrapleural space at FRC?

A decrease in intrapleural pressure. Signup and view all the answers

What happens to atmospheric pressure when measuring intrapleural pressure?

It is subtracted from intrapleural pressure. Signup and view all the answers

How is the pressure across the chest wall (Pcw) calculated?

Pcw = intrapleural pressure - atmospheric pressure Signup and view all the answers

What is the outcome when the lung and chest wall are uncoupled due to injury?

The lungs tend to collapse and the chest wall tends to expand. Signup and view all the answers

What defines the residual volume (RV) in terms of lung function?

The lowest lung volume that can be achieved when lungs and chest wall are coupled. Signup and view all the answers

What happens to pressure in the intrapleural space when lung volume increases?

Pressure decreases significantly. Signup and view all the answers

Study Notes

Neural Innervation of Respiratory Muscles

The respiratory rhythm is generated in the medulla by pacemaker cells and groups of neurons.
These neurons send signals to the spinal cord, where they synapse with phrenic and intercostal motoneurons.
The phrenic nerve innervates the diaphragm, originating from motoneurons in the C3-C5 spinal segments.
The external intercostal nerves innervate the external intercostal muscles, originating from motoneurons in the T1-T12 spinal segments.
Expiratory muscles like the rectus abdominus and internal intercostals are activated during increased ventilation and are innervated by motoneurons in the upper lumbar and T1-T12 segments.

Respiratory Muscle Activity

Inspiration involves contraction of the diaphragm and external intercostal muscles, pulling the ribs upward and outward.
Passive expiration relies on the relaxation of inspiratory muscles and elastic recoil of the chest wall.
Forced expiration involves contraction of the internal intercostal muscles, pulling the ribs downward and inward, along with the rectus abdominus and external oblique muscles.

Coupling of the Lung and Chest Wall

The lung and chest wall are coupled by the visceral and parietal pleura, forming a thin, double-layered serosa.
Parietal pleura covers the thoracic wall and diaphragm, while visceral pleura covers the lung surface.
The coupling of the lung and chest wall creates a resting position at functional residual capacity (FRC), the end of expiration/beginning of inspiration.

Mechanics of the Lungs and Chest Wall

When uncoupled, the lung contracts towards residual volume (RV) and the chest wall expands towards total lung capacity (TLC).
At FRC, the chest wall's tendency to expand and the lung's tendency to contract creates negative intrapleural pressure, typically around -5 cmH2O.
This negative pressure is relative to atmospheric pressure, meaning the absolute pressure in the intrapleural space is lower.

Lung Pressures and Pressure Gradients

Pressure differences are measured from inside to outside a structure.
Pressure across the chest wall (Pcw) is the difference between intrapleural pressure and atmospheric pressure.
Transpulmonary pressure is the difference between alveolar pressure (intrapulmonary pressure) and intrapleural pressure.
When there is no airflow, alveolar pressure equals atmospheric pressure.
The pressure gradient across the respiratory system is the difference between alveolar pressure and atmospheric pressure.

Pressure Changes during Respiration

During inspiration, contraction of inspiratory muscles increases intrapleural space volume, leading to more negative intrapleural pressure.
This increased negative pressure creates a positive transpulmonary pressure, expanding the lungs.
Lung expansion decompresses gas, dropping alveolar pressure below atmospheric pressure, generating airflow into the lungs.
At the end of inspiration, airflow stops when alveolar pressure equals atmospheric pressure.
During expiration, relaxation of the diaphragm and elastic recoil of the respiratory system compresses lung gas, increasing alveolar pressure above atmospheric pressure, generating airflow out of the lungs.

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Description

This quiz delves into the neural mechanisms responsible for breathing, focusing on the innervation of respiratory muscles such as the diaphragm and intercostal muscles. It covers the role of specific spinal cord segments and the activation of muscles during different respiratory phases.