Physiology 4.1

Question 1

Describe the concept of ventilation in the context of the respiratory system.

Answer 1

Ventilation refers to the amount of air getting into the lungs, which can be measured as the volume of air going in and out of the respiratory system or more specifically as alveolar ventilation.

Question 2

Define perfusion in the context of the pulmonary circulation.

Answer 2

Perfusion refers to blood flow through the pulmonary circulation.

Question 3

How can ventilation and perfusion be measured?

Answer 3

Both ventilation and perfusion can be measured in litres per minute.

Question 4

Do ventilation and perfusion need to be matched for an optimal situation?

Answer 4

Ideally, the amount of air getting into the lungs per minute should match the amount of blood flowing past the lungs per minute for an optimal, efficient situation.

Question 5

Describe the ventilation-perfusion mismatch.

Answer 5

Ventilation and perfusion are not precisely matched across the whole lung, leading to a ventilation-perfusion mismatch.

Question 6

What happens to ventilation and perfusion with height across the lung?

Answer 6

Both blood flow and ventilation decrease with height across the lung, with more ventilation and perfusion at the base of the lung and less at the apex of the lung due to gravity.

Question 7

Explain the relationship between blood flow and ventilation at the base of the lungs.

Answer 7

At the base of the lungs, blood flow is higher than ventilation because arterial pressure exceeds alveolar pressure, causing the blood vessels to effectively push on and compress the alveoli.

Question 8

What causes the opposite effect at the apex of the lungs compared to the base?

Answer 8

At the apex of the lungs, blood flow is low because arterial pressure is less than alveolar pressure, leading to more ventilation than perfusion.

Question 9

Describe the impact of gravity on blood flow in the lungs.

Answer 9

Gravity causes blood to flow more to the base of the lung than to the apex of the lung, resulting in different levels of ventilation and perfusion at different heights across the lung.

Question 10

Describe the relationship between ventilation and perfusion in the lung.

Answer 10

Ventilation and perfusion are both greater at the base of the lung than at the apex. Blood flow exceeds ventilation at the base, while ventilation exceeds blood flow at the apex.

Question 11

Define the ventilation-perfusion ratio.

Answer 11

The ventilation-perfusion ratio is the ratio of ventilation to perfusion within the lung. In a perfectly matched situation, the ratio would equal 1.

Question 12

How does the ventilation-perfusion ratio change from the base to the apex of the lung?

Answer 12

In the upright position, the ratio of ventilation to perfusion within the lung increases from the base to the apex, owing to the effects of gravity that tends to pull blood to the base of the lung.

Question 13

What is the significance of the ventilation-perfusion mismatch at the base and apex of the lung?

Answer 13

The mismatch at the base and apex of the lung can lead to situations where ventilation is less than perfusion (ratio less than 1) at the base, and ventilation exceeds perfusion (ratio exceeds 1) at the apex.

Question 14

Describe the physiological processes that help minimize the ventilation-perfusion mismatch.

Answer 14

There are auto-regulatory physiological mechanisms that help maintain the ventilation-perfusion ratio close to 1, particularly at the base of the lung.

Question 15

Do ventilation and perfusion decline at the same rate from the base to the apex of the lung?

Answer 15

No, blood flow declines faster than ventilation, meaning that blood flow exceeds ventilation at the base and ventilation exceeds blood flow at the apex.

Question 16

What is the V/Q ratio and how is it measured?

Answer 16

The V/Q ratio, or ventilation-perfusion ratio, is measured by dividing ventilation by perfusion. It is used to assess the matching of ventilation and blood flow in the lungs.

Question 17

Describe the ventilation-perfusion mismatch at the apex of the lung.

Answer 17

The biggest ventilation-perfusion mismatch occurs at the apex of the lung, with a V/Q ratio difference of over 3, whereas the difference is much smaller at the base of the lung.

Question 18

Define the term ‘pulmonary artery’ and its function.

Answer 18

The pulmonary artery carries deoxygenated blood from the right side of the heart to the lungs for oxygenation.

Question 19

How does blood become oxygenated in the lungs?

Answer 19

Blood flowing through the pulmonary artery picks up oxygen from well-ventilated alveoli during gas exchange, resulting in oxygenated blood returning to the heart through the pulmonary vein.

Question 20

Describe a situation where blood flow exceeds ventilation in the lungs.

Answer 20

When blood flow exceeds ventilation, a poorly ventilated region of the lung leads to a mismatch where blood is unable to pick up oxygen and offload carbon dioxide effectively.

Question 21

Do ventilation-perfusion mismatches commonly occur at the base of the lungs?

Answer 21

Yes, ventilation-perfusion mismatches often occur at the base of the lungs, but in normal health, the mismatch is relatively minimal.

Question 22

Define a poorly ventilated region of the lung.

Answer 22

A poorly ventilated region of the lung is an area where ventilation is inhibited, leading to a buildup of carbon dioxide and a fall in the partial pressure of oxygen in the blood.

Question 23

How can a poorly ventilated region of the lung be caused?

Answer 23

A poorly ventilated region of the lung can be caused by factors such as airway blockage due to foreign body aspiration or compression by a tumor, leading to inhibited ventilation and impaired gas exchange.

Question 24

Describe the impact of a poorly ventilated region on blood flow.

Answer 24

A poorly ventilated region leads to a buildup of carbon dioxide and a fall in the partial pressure of oxygen in the blood, as it is unable to effectively offload carbon dioxide and pick up oxygen during gas exchange.

Question 25

Describe the role of partial pressure gradient in gas exchange.

Answer 25

Partial pressure gradient is crucial for exchange, as it gases like oxygen and carbon dioxide to move from areas of higher partial pressure to areas of lower partial pressure, facilitating their diffusion across membranes.

Question 26

Define shunt in the context of the respiratory system.

Answer 26

In the respiratory system, shunt refers to the movement of blood from the right side of the heart to the left side without undergoing gas exchange, often due to poorly ventilated regions of the lung.

Question 27

How does the body minimize the effects of shunt in the lungs?

Answer 27

The body responds to poorly ventilated areas of the lung by constricting the blood vessels around those areas in response to decreased partial pressure of oxygen, redirecting blood flow to better-ventilated regions and minimizing the inefficiency of gas exchange.

Question 28

Describe the impact of tissue hypoxia on blood vessels in the lungs.

Answer 28

Tissue hypoxia in the lungs triggers the constriction of smooth muscle in the blood vessels around the hypoxic area, reducing blood flow to poorly ventilated regions and redirecting it to better-ventilated areas.

Question 29

Do oxygen and carbon dioxide rely on the same partial pressure gradient for gas exchange?

Answer 29

No, they do not. Oxygen requires a large partial pressure gradient for efficient gas exchange, while the normal partial pressure gradient for carbon dioxide is very small.

Question 30

Describe the consequences of carbon dioxide buildup in the alveoli.

Answer 30

A buildup of carbon dioxide in the alveoli leads to the loss of the partial pressure gradient that would pull carbon dioxide out of the blood, hindering the removal of carbon dioxide from pulmonary arterial blood and the replenishment of oxygen, resulting in inefficient gas exchange.

Question 31

Describe the response of pulmonary vessels to hypoxia.

Answer 31

Pulmonary vessels constrict in response to hypoxia to reduce perfusion in hypoxic regions.

Question 32

What is the function of the systemic circulation compared to the pulmonary circulation?

Answer 32

The pulmonary circulation is responsible for picking up oxygen and oxygenating the blood, while the systemic circulation is focused on delivering oxygen.

Question 33

How does the increase in partial pressure of carbon dioxide affect bronchial smooth muscle?

Answer 33

It causes mild bronchial dilation, which helps to improve ventilation.

Question 34

Define alveolar dead space.

Answer 34

Alveolar dead space occurs when ventilation exceeds perfusion, leading to air in the alveoli that does not participate in gas exchange.

Question 35

Do pulmonary vessels dilate or constrict in response to hypoxia in the systemic circulation?

Answer 35

Pulmonary vessels constrict in response to hypoxia, while blood vessels in the systemic circulation dilate.

Question 36

Describe the relationship between ventilation and blood flow in alveolar dead space.

Answer 36

In alveolar dead space, ventilation exceeds blood flow, leading to an increase in the partial pressure of oxygen in the alveoli.

Question 37

How does alveolar dead space differ from anatomical dead space?

Answer 37

Anatomical dead space refers to air in airways with walls too thick to allow gas exchange, while alveolar dead space refers to air in the alveoli that does not participate in gas exchange due to ventilation exceeding perfusion.

Question 38

What is the impact of pulmonary embolism on alveolar dead space?

Answer 38

Pulmonary embolism can lead to a significant increase in alveolar dead space due to impeded blood flow in the pulmonary vessels.

Question 39

Describe the response of systemic vessels to hypoxia.

Answer 39

Systemic vessels dilate in hypoxic regions to deliver more oxygen to those areas lacking oxygen.

Question 40

Describe the relationship between partial of carbon dioxide and pulmonary vaso-dilation.

Answer 40

An increase in the partial pressure of oxygen leads to pulmonary vaso-dilation, while a decrease in the partial pressure of carbon dioxide brings about a more mild bronchial constriction.

Question 41

What is the response to alveolar dead space in terms of ventilation and perfusion?

Answer 41

The response is to try and increase perfusion by dilating the pulmonary vessels and decrease ventilation with bronchial constriction to bring about a matching of ventilation and perfusion.

Question 42

How is anatomical dead space defined in the respiratory system?

Answer 42

Anatomical dead space refers to air in the conducting zone of the respiratory tract, including nasal cavities, trachea, bronchi, and upper bronchioles, which is unable to participate in gas exchange due to thick walls.

Question 43

Describe the concept of physiologic dead space in the respiratory system.

Answer 43

Physiologic dead space is the combination of alveolar dead space and anatomical dead space, with anatomical dead space being the biggest contributor in normal situations.

Question 44

What is the impact of pulmonary embolism on physiologic dead space?

Answer 44

In situations like pulmonary embolism, anatomical dead space can increase significantly, leading to a notable impact on physiologic dead space.

Question 45

Describe Respiratory Sinus Arrhythmia.

Answer 45

Respiratory Sinus Arrhythmia describes the normal change in heart rate during the breathing cycle.

Question 46

How can you feel your own respiratory sinus arrhythmia?

Answer 46

You can feel your heart rate increasing as you breathe in and decreasing as you breathe out. Most people have a reasonably profound respiratory sinus rhythm.

Question 47

Define ventilation-perfusion mismatch and explain its significance.

Answer 47

Ventilation-perfusion mismatch refers to the imbalance between ventilation and perfusion in the lungs. It is significant as it can lead to alveolar dead space during inspiration and shunt during expiration.

Question 48

What is the role of the parasympathetic vagus nerve in respiratory sinus arrhythmia?

Answer 48

The parasympathetic vagus nerve innervates the heart and its activity changes during the breathing cycle, slowing down the heart rate during expiration and removing the brake on heart rate during inspiration.

Question 49

Do dogs have a stronger respiratory sinus arrhythmia than humans?

Answer 49

Yes, dogs have an even stronger respiratory sinus arrhythmia than humans, which can be felt more strongly when placing a hand on their chest while they are sleeping.

Question 50

Describe the relationship between vagal activity and heart rate during the breathing cycle.

Answer 50

During inspiration, there is decreased vagal activity, effectively removing the brake on heart rate and causing an increase. Conversely, during expiration, there is an increase in vagal activity, putting the brakes on heart rate and slowing it down.

Question 51

What is the significance of respiratory sinus arrhythmia in minimizing ventilation-perfusion imbalance?

Answer 51

Respiratory sinus arrhythmia helps minimize the ventilation-perfusion imbalance that would otherwise occur, ensuring that the ventilation-perfusion ratio remains close to 1.

Question 52

Explain the main cause of respiratory sinus arrhythmia.

Answer 52

Respiratory sinus arrhythmia mainly comes about due to changes in activity of the parasympathetic vagus nerve that innervates the heart, leading to the observed changes in heart rate during the breathing cycle.