Mechanisms of Depressed Ventilation in Sleep

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Questions and Answers

What contributes to the inhibition of the wakefulness drive during sleep?

Increased muscle tension in the upper airways
The increased activity of the medullary centre
Decreased tonic discharge from the ascending reticular formation (correct)
Enhanced excitatory signals from the midbrain

How do CO2 response coefficients change during sleep?

They increase significantly
They fluctuate based on ambient conditions
They decrease leading to a right shift in the CO2 response curve (correct)
They remain constant

What happens to upper airway muscles during sleep that contributes to sleep apnea?

Their activity levels are heightened, increasing resistance
They maintain high tension preventing any collapse
Their tonic activity decreases, leading to relaxation and potential collapse (correct)
Their activity becomes erratic and unpredictable

What is primarily responsible for maintaining control of breathing when awake?

<p>The tonic discharge generated by the ascending reticular formation (A)</p> Signup and view all the answers

What impact does active inhibition during sleep have on ventilation?

<p>It decreases ventilation causing potential breathing issues (A)</p> Signup and view all the answers

Flashcards

How sleep affects breathing: Wakefulness drive suppression

The brainstem's wakefulness drive, coming from the ascending reticular formation, normally keeps breathing going while awake. During sleep, this drive is suppressed, leading to reduced ventilation.

How sleep affects breathing: Depressed O2/CO2 response

The sensitivity to oxygen and carbon dioxide levels in the blood decreases during sleep. This means the body responds less strongly to changes in these gases, leading to reduced ventilation.

How sleep affects breathing: Upper airway muscle relaxation

The muscles in the upper airway (like the tongue, soft palate, and nasopharyngeal wall) normally stay contracted, keeping the airway open. However, during sleep, these muscles relax, making them more likely to collapse, leading to airway obstruction and sleep apnea.

How sleep affects breathing: Reduced muscle activity

The brain's signals to the muscles in the upper airway are weaker during sleep, causing a decrease in muscle tension, which leads to a higher chance of airway obstruction.

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How sleep affects breathing: Shifted CO2 response curve

During sleep, the sensitivity of the body to changes in oxygen and carbon dioxide levels decreases, which means it takes a larger change to trigger a response. This is called a shifted CO2 response curve, and it means the body is less likely to adjust breathing to maintain proper oxygen levels.

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Study Notes

Mechanisms of Depressed Ventilation in Sleep

Inhibition of Wakefulness Drive: Wakefulness maintains breathing control through a connection between brain stem neurons and the ascending reticular formation (midbrain). This pathway generates constant signals (action potentials) to the medullary breathing center. In sleep, this pathway is actively inhibited, resulting in reduced ventilation.
Reduced Oxygen and Carbon Dioxide Responses: The body's response to changes in oxygen and carbon dioxide levels during sleep are reduced. The sensitivity to these changes, measured by response coefficients, decreases. The carbon dioxide response curve also shifts to the right, indicating a reduced sensitivity to carbon dioxide buildup.
Weakened Upper Airway Muscle Activity: Normally, accessory muscles of the upper airway (tongue, nasopharyngeal wall, soft palate) maintain open airways, this keeps airway resistance low. Brain activity to these muscles decreases during sleep, causing muscle relaxation and potential airway collapse. This relaxation can lead to partial airway blockage, contributing to sleep apnea.

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Description

Explore the mechanisms behind reduced ventilation during sleep, focusing on the inhibition of wakefulness drive, decreased sensitivity to oxygen and carbon dioxide, and weakened upper airway muscle activity. Understand how these factors contribute to airflow resistance and respiratory efficiency during sleep.