Chapter 18: Gas Exchange

Question 1

What 3 variables does the body respond to avoid hypoxia and hypercapnia?

Answer 1

Oxygen
Carbon Dioxide
pH

Question 2

What do the cells use oxygen for

Answer 2

Oxidative Phosphorylation

Question 3

In the pulmonary capillaries, why does CO2 move from the capillaries into the alveoli?

Answer 3

Because PCO2 is higher in the plasma

Question 4

What are the two possible causes for low alveolar Po2?

Answer 4

Inspired air has low O2 content or alveolar ventilation is inadequate.

Question 5

What is the main factor that affects atmospheric oxygen content and why is this important

Answer 5

Altitude. being above or below sea level affects the oxygen concentration of the atmosphere

Question 6

What causes hypoventilation?

Answer 6

Pathological changes such as decreased lung compliance, increased airway resistance, and CNS depression that slows ventilation rate and decreases depth.

Question 7

What are some pathological changes that adversely affect gas exchange in the alveoli

Answer 7

A decrease in alveolar surface area, increase in the thickness of alveolar-capillary exchange barrier, increase in the diffusion distance between the alveolar air space and the blood.

Question 8

Why is solubility important in physiology

Answer 8

O2 low solubility in aqueous solutions means that very little O2 can be dissolved in plasma.

Question 9

Why might there be a decreased arterial Po2 if alveolar Po2 may be normal

Answer 9

Because diffusion of O2 into alveolar capillaries does not have time to come to equilibrium before the blood has left the capillaries.

Question 10

True or false? Plasma with a PO2 of 40 mm Hg and a PCO2 of 40 mm Hg has the same concentrations of oxygen and carbon dioxide. Why?

Answer 10

Oxygen and carbon dioxide have different solubilities in plasma, with carbon dioxide being much more soluble than oxygen. Therefore, at the same partial pressures of oxygen and carbon dioxide in plasma, the concentration of carbon dioxide will be higher than that of oxygen.

Question 11

What is Ficks equation, and what is it used for

Answer 11

Related Oxygen Consumption (Qo2) = CO X (arterial oxygen content - venous oxygen content)

It is used to estimate cardiac output or oxygen consumption

Question 12

Why is hemoglobin an effective oxygen carrier

Answer 12

Hemoglobin is a tetramer molecule that has a high affinity for oxygen

Question 13

When cells increase their metabolic activity, does their PO2 decrease or increase?

Answer 13

It decreases and hemoglobin releases more oxygen to them

Question 14

What two factors influence the amount of oxygen that binds to hemoglobin?

Answer 14

the Po2 in the plasma surrounding red blood cells
number of potential Hb binding sites available in the red blood cells

Question 15

What does the total number of oxygen binding sites rely on

Answer 15

The number of hemoglobin molecules in red blood cells

Question 16

What determines the percent saturation of hemoglobin

Answer 16

Plasma Po2

Question 17

What three ways is carbon dioxide transported in the body 612

Answer 17

Dissolved in plasma, as bicarbonate ions, bound to hemoglobin.

Question 18

What groups in the brain control breathing

Answer 18

dorsal respiratory group, ventral respiratory group, pontine respiratory group

Question 19

What respiratory group is associated with inspiration

Answer 19

Dorsal Respiratory Group (DRG)

Question 20

What do peripheral chemoreceptors in the carotid and aortic bodies monitor

Answer 20

CO2, O2 and pH

Question 21

What is the primary stimulus for changes in ventilation

Answer 21

Carbon Dioxide

Question 22

what is the pre-botzinger complex

Answer 22

contains spontaneously firing neurons that act as a basic pacemaker for the respiratory system

Question 23

What do central chemoreceptors respond to

Answer 23

they respond to changes in the concentration of CO2 in CSF

Question 24

Where do the primary central receptors lie

Answer 24

On the ventral surface of the medulla

Question 25

What cells in the carotid and aorta trigger a reflex to start ventilation?

Answer 25

Type one cells otherwise called glomus cells

Question 26

What happens when a carotid body cell senses hypoxia

Answer 26

it closes the K+ channels and depolarizes the receptor cell. Then, the depolarization opens voltage-gated Ca2+ channels, and Ca2+ entry causes the exocytosis of neurotransmitters onto the sensory neuron. Neurotransmitters attach to the receptors on the sensory neuron which signals the medullary centers to increase ventilation

Question 27

Does pH changes in the plasma influence central chemoreceptors directly? Why?

Answer 27

Because plasma H+ crosses the blood-brain barrier very slowly.

Question 28

What happens if a patient is given too much oxygen

Answer 28

They may stop breathing because their chemical stimulas(low PO2) for ventilation is eliminated

Question 29

What is the Hering-Breuer inflation reflex

Answer 29

It prevents overinflation of the lung. The pulmonary stretch receptors on the wall of bronchi and bronchioles of airways respond to excessive stretching of the lung.

Question 30

What higher brain structures can have an effect on ventilation rate and depth?

Answer 30

Hypothalamus and cerebrum