L9 part 1 physiology

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Questions and Answers

What primarily stimulates the dorsal respiratory group (DRG) during normal breathing?

Relaxation of respiratory muscles

Contraction of diaphragm and external intercostal muscles (correct)

Inhibition of lung distension

Increased tidal volume

Which center in the pons inhibits inspiration?

Pneumotaxic center (correct)

Ventral respiratory group

Dorsal respiratory group

Apneustic center

What is the main function of peripheral chemoreceptors?

Regulate the activity of the pneumotaxic center

Respond directly to decreased PaO2 (correct)

Detect changes in lung volume

Monitor blood pH levels indirectly

What effect does decreased pH have on central chemoreceptors?

Increase tidal volume Signup and view all the answers

Which of the following is NOT a type of mechanical sensor involved in breathing?

Ventral respiratory group Signup and view all the answers

What does the Hering-Breuer reflex primarily prevent?

Over-inflation of the lungs Signup and view all the answers

What happens during intense breathing, such as during exercise?

The VRG stimulates forced inhalation and exhalation Signup and view all the answers

Which pressures are primarily responsible for maintaining lung stability?

Intra-alveolar and intra-pleural pressure Signup and view all the answers

What is transpulmonary pressure defined as?

The difference between intrapulmonary pressure and intrapleural pressure Signup and view all the answers

Which of the following is NOT an importance of intrapleural pressure?

Increases the resistance of the airways Signup and view all the answers

Which muscle is primarily responsible for inspiration?

Diaphragm Signup and view all the answers

What effect does the central nervous system have on breathing?

It regulates breathing through signals from multiple brain regions Signup and view all the answers

Which of the following describes the Hering-Breuer reflex?

A mechanism that prevents overinflation of the lungs during deep breathing Signup and view all the answers

What occurs during the process of inspiration?

Pressure inside the lungs is lower than atmospheric pressure Signup and view all the answers

How does chronic obstructive pulmonary disease (COPD) affect lung mechanoreceptors?

It diminishes their ability to detect lung inflation Signup and view all the answers

What is a characteristic of Kussmaul breathing?

Deep, labored breaths regardless of metabolic state Signup and view all the answers

Which muscle is considered the principal muscle of inspiration?

Diaphragm Signup and view all the answers

Which type of chemoreceptors are sensitive to changes in arterial partial pressure of carbon dioxide (PCO2)?

Peripheral chemoreceptors Signup and view all the answers

How does expiration occur during quiet breathing?

It is a passive process due to muscle relaxation Signup and view all the answers

What is the range of normal respiratory rates in adults?

12-20 breaths/min Signup and view all the answers

What is the average intrapleural pressure in humans?

-4 mmHg Signup and view all the answers

Which of the following describes trans-pulmonary pressure?

The difference between intrapulmonary and intrapleural pressure Signup and view all the answers

Which muscles contract during forced expiration?

Internal intercostals and abdominal muscles Signup and view all the answers

What defines tachypnea?

Abnormally rapid breathing Signup and view all the answers

Study Notes

Mechanics of Respiration I

This presentation covers the mechanics of breathing.
Learning Objectives include describing the functions of inspiration and expiration muscles, explaining inspiration and expiration processes, defining and describing the importance of intra-alveolar, intrapleural, and transpulmonary pressures.
Breathing is a mechanical process for moving air in and out of the lungs.
Respiratory rate is 12-20 breaths per minute.

Breathing Movements

The body uses thoracic cavity muscles to change the volume of the chest.
This alters pressure inside the lungs.
An increase in volume = a decrease in pressure (and vice versa).

Basics of the Respiratory System

Diagrams show the muscles and membranes involved in respiration. Images include the diaphragm, sternocleidomastoids, scalenes, and intercostals (internal and external).

Muscles of Inspiration

The diaphragm is the principal inspiratory muscle.
During inspiration, it contracts and increases the vertical diameter of the thoracic cage.
External intercostals move the ribs, increasing both the transverse and anteroposterior diameters of the chest.
Inspiration is an active process.

Muscles of Expiration

Expiration is a passive process during quiet breathing, brought about by relaxation of inspiratory muscles.
During forced expiration (coughing, blowing), expiration muscles (abdominal muscles and internal intercostals) contract to reduce thoracic cage volume.
Contraction of abdominal muscles increases intra-abdominal pressure, pushing the diaphragm upward.
Internal intercostals contract, pulling ribs downwards, further decreasing the chest size.

Lung Pressures

Intrapulmonary pressure (intra-alveolar) measures pressure within alveoli.
Normal range is -1 to +1 mm Hg, with 0 mmHg corresponding to atmospheric pressure.
Intrapleural pressure is the pressure in the intrapleural space. Typical range is -6 to -3 mmHg.
Average intrapleural pressure is -4 mmHg, which is always negative.
Transpulmonary pressure is the pressure difference across the wall of the lung. It's always positive.
This difference prevents lung collapse.

Importance of Intrapleural Pressure

Helps inflate the lungs during inspiration.
Prevents lung collapse.
Decreases the work required for breathing.
Aids venous and lymphatic drainage.

Regulation of Respiration

Learning objectives include explaining the importance of breath control, outlining how the central nervous system controls breathing, listing anatomical locations of ventilation control chemoreceptors, describing the Hering-Breuer reflex, and chronic obstructive pulmonary disease (COPD) effects on lung mechanoreceptors, and defining breathing patterns (Kussmaul, Cheyne-Stokes, and Biot).

Case Presentation

Patient GB is brought to an emergency department with altered mental status, history of illicit drug use, decreased respiratory rate, irregular breathing and episodes of apnea.
Given the presentation, the reason for the abnormally deep breathing must be determined.

Why is Breath Control Important?

Breathing is mostly an involuntary process.
Respiratory muscles (diaphragm, intercostals, and abdominal muscles) receive signals from the brainstem (pons and medulla).
Some voluntary control like breathing in activities (swimming, singing, yoga) exists.

How Does the Central Nervous System Control Breathing?

Each brain region has specific neuronal groups for respiration.
Medulla and pons stimulate respiratory muscles.
Diagram of brain regions (medulla oblongata, pons, midbrain) is shown.

Medulla

Dorsal Respiratory Group (DRG) controls inspiration and sets the normal breathing rhythm.
Efferent DRG sends impulses via phrenic and intercostal nerves to stimulate inspiration by contracting the diaphragm and external intercostal muscles.
Ventral Respiratory Group (VRG) is inactive during normal breathing but stimulates forced inhalation and exhalation in intense situations like exercise or illness.

Pons

Pneumotaxic Center (PNC): located in the upper pons, inhibits inspiration by decreasing tidal volume and respiratory rate.
Apneustic Center (APC) in lower pons stimulates inspiration, leading to deep gasping inspirations with occasional expirations.

What Chemical Sensors Control Breathing?

Peripheral chemoreceptors detect decreased PaO2, increased PaCO2, and increased hydrogen ion concentration.
They send impulses to the solitary nucleus in the brainstem for initiating inspiration.
Decreased PaO2 is the primary and most important signal detected by peripheral chemoreceptors.

Central Chemoreceptors

Located in the brain (ventral medulla).
Sensitive to decreased pH of cerebrospinal fluid (CSF): acidic pH.
This decreased pH stimulates central chemoreceptors to increase respiratory rate and tidal volume.
Peripheral chemoreceptors are affected directly by low blood PaO2, high PaCO2, and low blood pH.
Central chemoreceptors are affected indirectly by high PaCO2.

What Mechanical Sensors Control Breathing?

Sensory receptors detect mechanical pressure or distortion.
These include pulmonary stretch receptors, irritant receptors, and J receptors.

Pulmonary Stretch Receptors

Stimulated by lung distension during inspiration.
Send impulses via the vagus nerve to inhibit inspiration and prevent overinflation of the lungs.
Typically not active at low tidal volumes, but importantly affect patients with COPD, a respiratory condition causing trapped air and increased lung volume/distension, therefore the reflex is diminished.

Irritant Receptors

Found in upper respiratory airways (trachea, bronchi).
Respond to mechanical and chemical irritants (chemicals, dust, pollens, cold air).
Initiates coughing and bronchoconstriction for clearing harmful substances.

J Receptors

Located near capillaries in alveolar septa.
Sensitive to increased pulmonary capillary pressure.
Initiates rapid, shallow breathing when stimulated.
Important in conditions like heart failure with pulmonary edema and pulmonary emboli.

Mechanical Receptors that Control Breathing

Pulmonary stretch receptors, irritant receptors, and J receptors (summary). Their stimuli and responses are listed.

What Are Some Pathological Breathing Patterns?

Kussmaul, Cheyne-Stokes, and Biot breathing illustrated in a graph.

Case Connection

GB's history and Biot breathing pattern are suggestive of opioid overdose.
Opioid intoxication can cause respiratory arrest, and is reversed with an opioid receptor antagonist (naloxone).

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Description

This quiz covers the mechanics of breathing, focusing on the roles of inspiration and expiration muscles, as well as the processes involved. Learn about the importance of pressures in the respiratory system and the muscles responsible for breathing movements. Understanding these fundamentals is crucial for grasping the mechanics of respiration.