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Medicine 1 - Respiratory > Physiology 5.1 > Flashcards

Physiology 5.1 Flashcards

1
Q

Describe the role of phrenic nerve in ventilatory control.

A

The phrenic nerve innervates the diaphragm, a key muscle of inspiration, and is essential for stimulating the skeletal muscles of inspiration.

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2
Q

Define passive expiration and provide an example of when it occurs.

A

Passive expiration occurs at rest when there is no neural input to the muscles of expiration. An example is quiet breathing while sitting.

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3
Q

How does voluntary modulation affect ventilatory control?

A

Voluntary modulation can override the brain stem respiratory centers to some extent, allowing conscious control over breathing.

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4
Q

Describe the impact of severing the spinal cord above the origin of the phrenic nerve.

A

Breathing ceases if the spinal cord is severed above the origin of the phrenic nerve, indicating the dependence of breathing on neural signaling from the brain.

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5
Q

Do the muscles of respiration have intrinsic rhythm similar to the heart?

A

No, the muscles of respiration require somatic motor neuron input to activate them, unlike the heart which has intrinsic rhythm.

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6
Q

Define the stimuli that can alter the rhythm set by the respiratory centers in the brain stem.

A

Emotion is a stimulus that can alter the rhythm set by the respiratory centers in the brain stem, indicating a connection between the limbic system and the respiratory centers.

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7
Q

Describe the impact of emotion on breathing patterns.

A

Emotion, such as fear, laughter, or crying, can affect breathing patterns, indicating a connection between the limbic system and the respiratory centers in the brain stem.

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8
Q

Explain the role of the limbic system in ventilatory control.

A

The limbic system, the home for emotion, connects to the respiratory centers in the brain stem and can bring about changes in breathing patterns in response to strong emotions.

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9
Q

Describe the role of voluntary in the respiratory system.

A

Voluntary override in the respiratory system originates from the cortex of the brain and allows conscious thought to exert control over breathing.

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10
Q

Define mechano-sensory input in the context of the respiratory system.

A

Mechano-sensory input refers to the stretch receptors in the thoracic cage that monitor the stretch of the thoracic wall and trigger reflex inhibition of ventilation when a threshold is reached.

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11
Q

How does the chemical composition of the blood impact the respiratory centers?

A

The chemical composition of the blood, including the partial pressure of carbon dioxide, oxygen, and pH, is detected by chemoreceptors and impacts the rhythm of the respiratory centers.

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12
Q

Describe the function of the Dorsal Respiratory Group of neurons in the respiratory system.

A

The Dorsal Respiratory Group primarily stimulates the inspiratory muscles, including the diaphragm and external intercostal muscles.

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13
Q

What is the role of the Ventral Respiratory Group during inspiration?

A

During inspiration, the Ventral Respiratory Group stimulates a basal muscular tone in the muscles of the tongue, pharynx, and larynx to maintain a patent airway.

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14
Q

Explain the significance of maintaining a basal tone in the muscles of expiration.

A

Maintaining a basal tone in the muscles of expiration, including the tongue, pharynx, and larynx, helps to maintain a patent airway and allows for easy air exchange between the atmosphere and the lungs.

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15
Q

Describe the impact of respiratory load on the muscles of expiration.

A

During an increase in respiratory load, the Ventral Respiratory Group actively recruits the muscles of expiration to facilitate expiration.

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16
Q

How do stimuli such as emotional input and mechano-sensory input alter the basal rhythm set by the respiratory centers?

A

Stimuli such as emotional input and mechano-sensory input can alter the basal rhythm set by the respiratory centers, along with voluntary inputs and chemoreceptor input.

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17
Q

Describe the role of basal in the expir muscles during expiration.

A

The basal tone in the expiratory muscles allows expiration to happen in a smooth, controlled manner, preventing abrupt exhalation.

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18
Q

How does the Dorsal Respiratory group contribute to the process of expiration?

A

The Dorsal Respiratory group switches off, causing the inspiratory muscles to relax, decreasing the volume of the thoracic cavity, and increasing pressure, which allows air to flow out down the pressure gradient.

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19
Q

Define the primary ventilatory drive and its relation to the central chemoreceptors.

A

The primary ventilatory drive is provided by the central chemoreceptors, which respond to changes in hydrogen ion concentration in the cerebrospinal fluid surrounding the brain, reflecting the partial pressure of carbon dioxide in systemic arterial blood.

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20
Q

What are the two types of chemoreceptors involved in the respiratory process?

A

The two types of chemoreceptors are Central chemoreceptors and Peripheral chemoreceptors.

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21
Q

Describe the location and primary stimuli for the peripheral chemoreceptors.

A

The peripheral chemoreceptors are found in the carotid and aortic bodies, and they primarily respond to changes in the partial pressure of oxygen, with less sensitivity to changes in the partial pressure of carbon dioxide.

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22
Q

Explain the significance of the blood brain barrier in regulating the composition of the cerebrospinal fluid.

A

The blood brain barrier tightly regulates the composition of the cerebrospinal fluid surrounding the brain, ensuring a stable environment for brain tissue by controlling the exchange of substances between the plasma of the blood vessels supplying the brain and the interstitial fluid.

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23
Q

What is the role of the peripheral chemoreceptors in the respiratory process?

A

The peripheral chemoreceptors provide the secondary ventilatory drive, responding to changes in the partial pressure of oxygen and plasma hydrogen ion concentration.

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24
Q

Describe the function of the central chemoreceptors in detecting changes in hydrogen ion concentration.

A

The central chemoreceptors detect changes in hydrogen ion concentration in the cerebrospinal fluid surrounding the brain, which is tightly regulated and reflects the partial pressure of carbon dioxide in systemic arterial blood.

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25
Q

Do the central chemoreceptors directly respond to carbon dioxide?

A

No, the central chemoreceptors respond directly to hydrogen ions, which originate from carbon dioxide, reflecting changes in the partial pressure of carbon dioxide in systemic arterial blood.

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26
Q

Describe the role of central chemoreceptors in to changes in hydrogen concentration in the cerebrospinal fluid.

A

The central chemoreceptors respond to an increase in hydrogen ion concentration in the cerebrospinal fluid by increasing the rate and depth of breathing.

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27
Q

What is hypercapnea and what causes it?

A

Hypercapnea refers to an increase in the partial pressure of carbon dioxide in the blood, which is caused by an increase in the partial pressure of carbon dioxide in systemic arterial blood.

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28
Q

How does carbon dioxide in plasma lead to the stimulation of central chemoreceptors?

A

Carbon dioxide in plasma reacts with water to form carbonic acid, which then dissociates into hydrogen ions and bicarbonate ions. The central chemoreceptors respond to these hydrogen ions derived from carbon dioxide.

29
Q

Define the blood-brain barrier and its role in regulating ion composition.

A

The blood-brain barrier forms a tight barrier between plasma and interstitial fluid in the brain, preventing ions from crossing. It regulates the composition of cerebrospinal fluid and protects the brain from fluctuations in ion concentration.

30
Q

Do changes in arterial PCO2 affect ventilation?

A

Yes, a decrease in arterial PCO2 leads to a reduction in hydrogen ion concentration in the cerebrospinal fluid, which reduces the stimulation of central chemoreceptors and inhibits ventilation.

31
Q

Describe the impact of voluntary hyperventilation on breathing.

A

Voluntary hyperventilation, by blowing off carbon dioxide, switches off the primary stimulus for breathing, leading to a temporary cessation of breathing. Once carbon dioxide levels start to build up again, normal breathing resumes.

32
Q

Describe the role the blood-brain barrier in the exchange of gases and ions between the capillary and the cerebrospinal fluid.

A

The blood-brain barrier allows gas to freely exchange between the capillary and the cerebrospinal fluid, but it restricts the movement of ions from the plasma into the cerebrospinal fluid.

33
Q

Define the negative feedback loop involved in regulating the partial pressure of carbon dioxide in the blood.

A

The negative feedback loop involves an increase in carbon dioxide in the cerebrospinal fluid, leading to an increase in hydrogen ion concentration, which stimulates the central chemoreceptors and respiratory control centers, ultimately increasing ventilation to reduce carbon dioxide levels.

34
Q

How do central chemoreceptors respond to changes in carbon dioxide levels in the blood?

A

Central chemoreceptors respond directly to hydrogen ions, which are derived from carbon dioxide, and they reflect the levels of carbon dioxide in the blood. An increase in carbon dioxide levels activates the central chemoreceptors, leading to an increase in ventilation.

35
Q

Describe the relationship between carbon dioxide levels and the activity of central chemoreceptors.

A

An increase in the partial pressure of carbon dioxide in the blood activates the central chemoreceptors, leading to an increase in ventilation. Conversely, a decrease in carbon dioxide levels due to hyperventilation switches off the activity in the central chemoreceptors, resulting in reflex inhibition of breathing.

36
Q

What is the significance of the body’s sensitivity to changes in the partial pressure of carbon dioxide?

A

The body is highly sensitive to changes in the partial pressure of carbon dioxide because high levels of carbon dioxide can be toxic and lethal to cells. Excessive carbon dioxide buildup can have a destructive effect on cells, making it crucial to regulate and eliminate carbon dioxide from the body.

37
Q

Describe the normal minute ventilation and arterial partial pressure of carbon dioxide in the blood.

A

The normal minute ventilation is around five liters per minute, and the normal arterial partial pressure of carbon dioxide is 40 millimeters of mercury. An increase of arterial PCO2 by 10 percent to 44 millimeters of mercury almost doubles the minute ventilation.

38
Q

Do hydrogen ions in the plasma affect the central chemoreceptors?

A

No, hydrogen ions in the plasma do not affect the central chemoreceptors because they do not cross the blood-brain barrier. The central chemoreceptors respond directly to hydrogen ions derived from carbon dioxide, reflecting the levels of carbon dioxide in the blood.

39
Q

Describe the relationship between the partial pressure of carbon dioxide ventilation.

A

A 10 percent increase in the partial pressure of carbon dioxide causes a percent increase in ventilation, as the body is supersensitive to changes in the partial pressure of carbon dioxide.

40
Q

Define ‘Hypoxic drive’ in the context of chronic lung disease.

A

In chronic lung disease, individuals become desensitized to increased levels of carbon dioxide and start relying on their peripheral chemoreceptors to affect their breathing pattern, a condition known as ‘Hypoxic drive’.

41
Q

How do individuals with chronic lung disease on ‘Hypoxic drive’ differ from others in terms of breathing pattern regulation?

A

Individuals with chronic lung disease on ‘Hypoxic drive’ have their breathing pattern set by hypoxia, as their tissues become hypoxic, rather than being driven by hypercapnea like most individuals.

42
Q

Describe the role of peripheral chemoreceptors in ventilation.

A

Peripheral chemoreceptors, found in the carotid artery and aorta, provide secondary ventilatory drive for most individuals and become much more important in individuals with chronic lung disease who are on ‘hypoxic drive’.

43
Q

Do central chemoreceptors or peripheral chemoreceptors play a more significant role in setting the breathing pattern for most individuals?

A

Most individuals rely predominantly on their central chemoreceptors to set their breathing pattern, although they also use their peripheral chemoreceptors to some extent.

44
Q

Describe the impact of chronic exposure to elevated levels of carbon dioxide on central chemoreceptors.

A

Chronic exposure to elevated levels of carbon dioxide can lead to desensitization of central chemoreceptors, causing them to stop responding to the increase in carbon dioxide.

45
Q

Define the term ‘hypercapnea’ in the context of breathing pattern regulation.

A

Hypercapnea refers to the condition where individuals are driven by increased levels of carbon dioxide in terms of setting their breathing pattern, as opposed to hypoxia.

46
Q

How do peripheral chemoreceptors respond to changes in arterial PO2 and hydrogen ion concentration?

A

Peripheral chemoreceptors detect changes in arterial PO2 and hydrogen ion concentration in systemic plasma, and reflexively stimulate ventilation when there is a significant fall in the partial pressure of oxygen in arterial blood.

47
Q

Describe the location of peripheral chemoreceptors in the body.

A

Peripheral chemoreceptors are found in the carotid arteries and in the aorta, specifically in the carotid bodies and in an aortic body, as opposed to the central chemoreceptors found in the medulla of the brain stem.

48
Q

Describe the relationship partial pressure of oxygen and the saturation ofemoglobin.

A

As the partial pressure of oxygen falls below 60 mmHg, the saturation ofemoglobin decreases significantly, leading to a more pronounced impact on the total oxygen content of the blood.

49
Q

Define the role of peripheral chemoreceptors in regulating ventilation based on arterial PO2 levels.

A

Peripheral chemoreceptors stimulate ventilation when arterial PO2 falls below 60 mmHg, leading to an exponential increase in ventilation.

50
Q

How does the response of peripheral chemoreceptors to changes in partial pressure of oxygen differ from their response to changes in partial pressure of carbon dioxide?

A

Unlike carbon dioxide, a significant decrease in partial pressure of oxygen (40% decrease) is required to stimulate a significant increase in ventilation.

51
Q

Describe the impact of haemoglobin saturation on the response of peripheral chemoreceptors.

A

Peripheral chemoreceptors do not stimulate ventilation significantly until the haemoglobin saturation falls below 90%, as adding more oxygen into the plasma when haemoglobin is already more than 90% saturated does not significantly impact the total oxygen content of the blood.

52
Q

Do peripheral chemoreceptors respond to total oxygen content or arterial PO2 levels?

A

Peripheral chemoreceptors respond to arterial PO2 levels, specifically to the oxygen in solution in the blood plasma, rather than the total oxygen content which is largely determined by the amount of oxygen bound to haemoglobin.

53
Q

Describe the conditions under which peripheral chemoreceptors start stimulating ventilation.

A

Peripheral chemoreceptors start stimulating ventilation when arterial PO2 falls below 60 mmHg, equivalent to an altitude of about 3000 meters.

54
Q

How does the response of peripheral chemoreceptors change at high altitudes?

A

At high altitudes, peripheral chemoreceptors start stimulating ventilation at rest when arterial PO2 falls below 60 mmHg, due to the decreased availability of oxygen in the atmosphere.

55
Q

Define the impact of anemia on respiration rate in a patient with normal lung function and half the normal blood oxygen content.

A

In an anemic patient with normal lung function and half the normal blood oxygen content, the respiration rate would increase to compensate for the reduced oxygen-carrying capacity of the blood.

56
Q

Describe the impact of a 10% increase in PCO2 on ventilation compared to a 40% decrease in PO2.

A

A 10% increase in PCO2 leads to a 100% increase in ventilation, while a 40% decrease in PO2 is required to stimulate a significant increase in ventilation.

57
Q

Describe the impact of ana on ventilation in a patient with healthy lungs and reduced blood oxygen content.

A

Ventilation will stay the same as the peripheral chemoreceptors respond to the partial pressure of oxygen, not the total oxygen content.

58
Q

Do gaseous anaesthetic agents increase or decrease tidal volume, and what is the impact on alveolar ventilation?

A

Gaseous anaesthetic agents increase respiration rate but decrease tidal volume, negatively impacting alveolar.

59
Q

Define the impact of barbiturates and opioids on centers.

A

Barbiturates and opioids depress the respiratory centers, decreasing sensitivity to pH and reducing the response to PCO2.

60
Q

How do barbiturates and opioids affect the sensitivity of peripheral chemoreceptors?

A

Barbiturates and opioids decrease the sensitivity of peripheral chemoreceptors, resulting in a decreased response to falling partial pressure of oxygen.

61
Q

Describe the effect of nitrous oxide on peripheral chemoreceptors.

A

Nitrous oxide blunts the peripheral chemoreceptor response to falling PaO2, essentially knocking out the peripheral chemoreceptor response.

62
Q

Explain the safety of nitrous oxide for most individuals in terms of ventilatory control.

A

Nitrous oxide is safe for most individuals as it has a detrimental effect on the peripheral chemoreceptors, which most individuals are not relying on.

63
Q

Describe the impact of nitric oxide on chemoreceptors.

A

Nitric oxide has no impact on central chemoreceptors, which are relied upon for monitoring carbon dioxide in the blood and determining ventilatory breathing patterns.

64
Q

What is the ‘hypoxic drive’ in individuals with chronic lung disease?

A

Individuals with chronic lung disease who become desensitized to carbon dioxide rely on ‘hypoxic drive’ for regulating their blood gas composition.

65
Q

Define the role of peripheral chemoreceptors in individuals on ‘hypoxic drive’ when given nitric oxide.

A

When given nitric oxide, individuals on ‘hypoxic drive’ lose their peripheral chemoreceptor response, leading to an inability to regulate their blood gas composition.

66
Q

How does administering oxygen to individuals on ‘hypoxic drive’ affect their condition?

A

Administering oxygen to individuals on ‘hypoxic drive’ can make their condition worse by stopping their breathing and reassuring the peripheral chemoreceptors that everything is okay with oxygen.

67
Q

Describe the danger of nitric oxide administration in certain situations.

A

In individuals with chronic lung disease who are on ‘hypoxic drive’, nitric oxide administration can lead to dangerously high carbon dioxide levels and disrupted brain function.

68
Q

What is the role of peripheral chemoreceptors in responding to increasing plasma hydrogen ion concentration?

A

Peripheral chemoreceptors also have a role in responding to increasing plasma hydrogen ion concentration, which will be further explored in the context of acid-base balance in the second part of the lecture.

Medicine 1 - Respiratory (23 decks)

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