Unit 11

Question 1

Differentiate between internal and external respiration.

Answer 1

Internal respiration refers to the exchange of gases between tissues and blood, whereas, external respiration refers to gas exchange between air and blood in the lungs.

Question 2

ventilation

Answer 2

process of moving air in and out of the lungs (i.e. breathing)

Question 3

gas exchange

Answer 3

process where gases are transferred across a surface in the opposite direction (based on diffusion gradient). This takes place between air and blood in the lungs and between blood and tissues.

Question 4

oxygen utilization

Answer 4

use of oxygen by tissue through cellular respiration.

Question 5

inspiration

Answer 5

movement of air into lungs through contraction of diaphragm

Question 6

expiration

Answer 6

movement of air out of lungs through relaxation of diaphragm

Question 7

compliance

Answer 7

ability to distend/expand when stretched

Question 8

Describe the anatomy of the lungs.

Answer 8

Lungs are located in the thoracic cavity, suspended in the pleural cavity. They are open to the external environment via the trachea. Lungs have a series of tubes that systematically branch out into smaller and smaller airways that carry air to millions of interconnected sacs called alveoli, where gas exchange occurs

Question 9

Identify: mouth, nose, pharynx, larynx, trachea, primary bronchus, terminal bronchioles, respiratory bronchioles, and alveolus in the conducting zone and respiratory zone.

Answer 9

Conducting Zone: brings air to the respiratory zone; includes the mouth/nose, pharynx, larynx, trachea, bronchi and bronchioles (including terminal bronchioles).

Respiratory Zone: site of gas exchange; includes respiratory bronchioles and alveolar sacs.

Question 10

Describe the morphology of the alveolus and identify the type I and type II alveolar cells and indicate their function.

Answer 10

Alveoli make up the majority of the lung and are the reason for the spongy texture. They are clustered together in the shape of a polyhedral, similar to a honeycomb. To facilitate efficient diffusion of gas molecules, alveoli are thin walled and their basement membrane fuse with the endothelial cells of capillaries.

Type I alveolar cells make up the majority of the surface area of the lungs and is the site for gas exchange. Type II alveolar cells secrete surfactant to reduce surface tension caused by hydrogen bonds between water molecules at the water/air interface; this prevents the collapse of alveolus.

Question 11

Describe the relationship between lung alveoli and pulmonary capillaries.

Answer 11

Pulmonary capillaries and lung alveoli are closely associated with a large number of capillaries enveloping the entire alveolus. In addition, capillaries and alveoli are only separated by a very small distance (0.3mm). Both features allow for rapid gas exchange between air in the alveoli and blood in the pulmonary capillary.

Question 12

List the homeostatic functions of the conducting zone of the respiratory system.

Answer 12

1) Warming
2) Humidification
3) Filtration
4) Cleaning

Question 13

diaphragm

Answer 13

separates the abdominal and thoracic cavity; it is a dome-shaped striated muscle that is used during inspiration/expiration.

Question 14

mediastinum

Answer 14

group of structures located in the middle of the thoracic cavity (between the lungs).

Question 15

thoracic cavity

Answer 15

region above the diaphragm that contains the heart and associated large vessels, the respiratory system (including the lungs, trachea) as well as the esophagus and thymus.

Question 16

pleural membranes

Answer 16

wet epithelium membranes that line the mediastinum; the parietal pleura line the inside wall of the thoracic cavity and the visceral pleura covers the surface of the lung.

Question 17

intrapleural space

Answer 17

very small space between the parietal and visceral membrane that contains a thin layer of fluid that lubricates lungs during ventilation. Under normal circumstances, the visceral pleura is pushed against the parietal pleura with both membranes essentially stuck together, eliminating this space. If lungs collapse, the intrapleural space would become a real space.

Question 18

lung lobes

Answer 18

the lung is divided into lobular regions. The right lung has 3 lobes, whereas the left lung has 2 lobes.

Question 19

atmospheric pressure

Answer 19

pressure in the atmospheric air; remains constant

Question 20

intrapleural pressure

Answer 20

pressure within the intrapleural space caused by contraction/recoil of diaphragm. During inspiration, pressure within the intrapleural space is lower (negative) than atmospheric. During expiration, pressure within the intrapleural space is higher than atmospheric.

Question 21

transpulmonary pressure

Answer 21

pressure difference between intrapulmonary (pressure within the lungs) and intrapleural pressures (pressure within the intrapleural space); causes lungs to stick to thoracic cavity wall.

Question 22

negative pressure

Answer 22

pressure that is less than atmospheric pressure

Question 23

State Boyle’s Law.

Answer 23

Pressure of any given gas is inversely proportional to its volume.

Question 24

Discuss how Boyle’s law impacts ventilation.

Answer 24

Movement of air into and out of the lungs is dependent on pressure differences between the atmosphere and lungs. The contraction and relaxation of the diaphragm during ventilation causes a change in lung volume, which ultimately changes transpulmonary pressure.

Inspiration: contraction of diaphragm, ↑ lung volume, ↓ transpulmonary pressure, which is < atmospheric pressure, air moves into lungs

Expiration: relaxation of diaphragm, ↓ lung volume, ↑ transpulmonary pressure, which is > atmospheric pressure, air moves out of lungs

10.12 List the physical properties of the lung and how they influence ventilation

Compliance: ability of lungs to distend under pressure; allows for changes in lung volume

Elasticity: ability of lung to return to its normal size after being distended; allows for distension during inspiration and recoil during expiration.

Surface Tension: partially collapses alveoli during expiration, causing an increase in transpulmonary pressure.

Question 25

State Laplace’s Law

Answer 25

Pressure is proportional to surface tension and inversely proportional to the radius of alveoli. P = 2T/r P= pressure; T= surface tension; r= radius

Question 26

Describe the role of surfactant in maintaining normal alveolar function

Answer 26

Surfactant is a fluid made up lipoprotein complexes that is secreted on the surface of alveoli. Surfactant will decrease surface tension by disruption the hydrogen bonds between water molecules. If surface tension becomes too high, it would collapse the alveoli.

Question 27

Discuss the actions of the diaphragm, intercostals, rib cage, intrathoracic pressures, intrapleural pressures and movement of air during inspiration

Answer 27

Inspiration: contraction of diaphragm and intercostal muscles raises the rib cage, increase in thoracic volume, decrease in intrapulmonary pressure (below atmospheric pressure) and movement of air into lungs.

Question 28

Discuss the actions of the diaphragm, intercostals, rib cage, intrathoracic pressures, intrapleural pressures and movement of air during expiration

Answer 28

Expiration: relaxation of diaphragm and intercostal muscles lowers the rib cage (recoil of lungs), decrease in thoracic volume, increase in intrapulmonary pressure (above atmospheric pressure) and movement of air out of the lungs.

Question 29

Define tidal volume

Answer 29

volume of air expired in each breath

Question 30

State Dalton’s Law

Answer 30

Pressureair = sum of partial pressure of gases contained in the air mixture

Question 31

pressure

Answer 31

the amount of force within a given area exerted against a surface

Question 32

partial pressure

Answer 32

the amount of pressure that a specific gas within a mixture exerts on its own. It is equal to the product of the total pressure relative to its percentage within of the mixture (x% of total pressure)

Question 33

atmospheric pressure

Answer 33

the amount of pressure that a specific gas within a mixture exerts on its own. It is equal to the product of the total pressure relative to its percentage within of the mixture (x% of total pressure)

Question 34

State specifically the partial pressure of oxygen in the atmosphere (PatmosphereO2), alveoli (PAO2), pulmonary arterial blood (PaO2) and pulmonary venous blood (PvO2)

Answer 34

PatmosphereO2 = 159 mmHG Palveoli (PAO2) = 105 mmHG Pulmonary arterial blood (PaO2) = 100 mmHG Pulmonary venous blood (PvO2) = 40 mmHG

Question 35

Discuss how Henry’s Law predicts movement of O2 during alveolar gas exchange

Answer 35

According to Henry’s law, the maximum amount of gas dissolved in air or blood is dependent on 1) the solubility of gas in liquid, 2) the temperature of fluid and, 3) the partial pressure of the gas. Given that solubility and temperature are constants, the movement of oxygen during gas exchange is driven by differences in partial pressure between air and blood. (Ch. 16.4) 10.23 Identify the major atmospheric gases and indicate the proportions relative to atmospheric pressure O2 = 21% (159 mmHG) N2 = 78% (593 mmHG)

Question 36

Describe how oxygen is transported in the blood

Answer 36

Oxygen is transported primarily by hemoglobin; however there is also a small amount of oxygen that is also dissolved in the blood.

Question 37

Discuss how hemoglobin transports oxygen in the blood

Answer 37

Hemoglobin is found in red blood cells. It is composed of four polypeptide chains, each with a heme group that contains an iron molecule that can bind and transport oxygen.

Question 38

Describe the role of iron in oxygen transport

Answer 38

Iron (Fe2+) is found within in the centre of each heme group in a hemoglobin. Iron will share its electrons to bind with oxygen; thus, for each hemoglobin molecule there will be 4 heme groups, 4 iron atoms and 4 oxygen molecules.

Question 39

oxyhemoglobin

Answer 39

a molecule of hemoglobin that has oxygen bound

Question 40

deoxyhemoglobin

Answer 40

a molecule of hemoglobin with no bound oxygen

Question 41

methemoglobin

Answer 41

hemoglobin molecule with an oxidized iron atom (Fe3+); methemoglobin is not able to bind oxygen since it does not have a free electron to share.

Question 42

carboxyhemoglobin

Answer 42

hemoglobin molecule that is bound to carbon monoxide (CO); the CO has a very tight bond with hemoglobin and is therefore difficult for an oxygen molecule to displace the carbon monoxide molecule.

Question 43

percent oxyhemoglobin saturation

Answer 43

the percent of total hemoglobin that is bound to oxygen.

Question 44

Discuss loading and unloading reactions

Answer 44

Loading Reactions: takes place in the lungs; deoxyhemoglobin combines with oxygen to form oxyhemoglobin Unloading Reaction: takes places at the tissue level; oxygen dissociates from oxyhemoglobin to enter tissue cells to yield deoxyhemoglobin

Question 45

Describe the oxyhemoglobin dissociation curve

Answer 45

The oxyhemoglobin dissociation curve is a graphic representation of the percent oxyhemoglobin saturation at different oxygen partial pressures (P02); it demonstrates the% unloading reactions based on oxygen content. Under normal conditions, the dissociation curve is a sigmoidal or S-shaped curve. At high P02 (arterial blood), hemoglobin is 97% saturated with oxygen. As blood passes through tissues which have a lower P02, oxygen will dissociate (unloading reaction) from hemoglobin (75% saturated). During exercise, a low P02 levels in returning venous blood correspond to higher level of dissociation (unloading) at tissues.

Question 46

Describe hemoglobins affinity to oxygen with altering levels of PC02, pH and temperature

Answer 46

An increase in PC02 and temperature and a decrease in pH, which is typically seen during exercise, will decrease hemoglobin’s affinity to oxygen. This results in slightly less oxygen being loaded at the lungs and higher unloading of oxygen at tissues. The net effect is that tissues will receive more oxygen.

Question 47

Predict oxyhemoglobin curve shifts under differ PC02, pH and temperature environments

Answer 47

Hide Feedback increase PC02, decrease pH, ­increase temperature: oxyhemoglobin dissociation curve will shift to the right derease PC02, ­increase pH, decrase temperature: oxyhemoglobin dissociation curve will shift to the left

Question 48

Identify methods of CO2 transport in the blood

Answer 48

Bicarbonate (HCO3-), dissolved CO2 in plasma, carbamino compounds

Question 49

Discuss the role of carbonic anhydrase in the formation of bicarbonate

Answer 49

Carbonic anhydrase catalyzes the reaction of carbon dioxide and water to form carbonic acid within red blood cells. As carbonic acid concentrations rises following blood flow through systemic capillaries, there is the dissociation of carbonic acid into bicarbonate and hydrogen atom.

Question 50

Reproduce the chemical reaction of bicarbonate formation by carbonic anhydrase

Answer 50

CO2 + H2O ----------> H2CO3 ----------------> H+ + HCO3-

Question 51

Describe the chloride shift and reverse chloride shift

Answer 51

Following the dissociation of carbonic acid into hydrogen ions and bicarbonate, bicarbonate diffuses out of the red blood cell into plasma, whereas the hydrogen atom remains within the red blood cell bonded to deoxyhemoglobin, creating a net positive charge. As a result, chloride ions are attracted into the red blood cell; this process is known as the chloride shift. The reverse chloride shift takes place in pulmonary capillaries when hydrogen atom dissociates from deoxyhemoglobin; H+ attracts bicarbonate ions from plasma in exchange for chloride ions (Cl- moves out of red blood cell into plasma); this process is known as the reverse chloride shift and allows H+ to bind to bicarbonate to form carbonic acid. Carbonic acid is then converted into carbon dioxide gas and water.

Question 52

Discuss how the respiratory system can maintain acid base balance

Answer 52

The respiratory system maintains acid base balance by regulating the concentration of carbon dioxide in the blood.

Question 53

acidosis

Answer 53

blood pH < 7.35

Question 54

alkalosis

Answer 54

blood pH > 7.45

Question 55

respiratory acidosis

Answer 55

decrease in blood pH due to an increase in plasma concentration of CO2 and carbonic acid caused by a decrease in ventilation (hypoventilation).

Question 56

respiratory alkalosis

Answer 56

increase in blood pH due to a decrease in plasma concentration of CO2 and carbonic acid caused by an increase in ventilation (hyperventilation).

Question 57

metabolic acidosis

Answer 57

decrease in pH due to metabolic factors such as increased production of nonvolatile acids (i.e. ketone bodies) or a decrease in bicarbonate.

Question 58

metabolic alkalosis

Answer 58

increase in pH due to metabolic factors such as low levels of nonvolatile acids or high levels of bicarbonate.

Question 59

buffers

Answer 59

molecule, such as bicarbonate ion that binds to H+ in order to maintain blood pH

Question 60

Predict changes to blood pH based on changes in ventilation

Answer 60

↑ ventilation : ↑ pH ↓ ventilation : ↓ pH

Question 61

Describe the respiratory centers of the brain stem and cerebral cortex

Answer 61

Brain Stem receives sensory information from the body to regulate ventilation and has 3 respiratory centers. 1) Apneustic Center: located in pons 2) Pneumotaxic center: located in pons 3) Rhythmicity center: located in medulla oblongata and controls automatic ventilation Cerebral Cortex: controls voluntary breathing and can override the medulla oblongata.

Question 62

Describe the role of the rhythmicity center, apneustic center, pneumotaxic center in the regulation of breathing

Answer 62

hythmicity center: controls automatic ventilation; may be influenced by apneustic and pneumotaxic centers Apneustic Center: promote inspiration by stimulating I neurons Pneumotaxic center: inhibit inspiration by antagonizing the apneustic center

Question 63

Identify the location of chemoreceptors in the mammalian body

Answer 63

Central chemoreceptors: ventrolateral surface of the medulla oblongata Peripheral chemoreceptors: located in small nodules known as aortic and carotid bodies associated with aorta and carotid arteries, respectively.

Question 64

Differentiate between central and peripheral chemoreceptors

Answer 64

* chart *

Question 65

Identify molecules recognized by chemoreceptors

Answer 65

PCO2, H+, PO2 (only detected by carotid bodies)

Question 66

Predict changes in PC02, pH and oxygen content detected by chemoreceptors will have on ventilation

Answer 66

↑ PC02, ↑ ventilation ↓ pH, ↑ ventilation ↓ P02, ↑ ventilation

Question 67

Describe the feedback regulation of chemoreceptor control of breathing

Answer 67

Chemoreceptors found in brain and arterial system will detect increases in PC02 through changes in plasma carbon dioxide content and blood pH, respectively. The respiratory centres will increase ventilation accordingly through the activation of respiratory muscles. As ventilation increases, there will be a negative feedback loop caused by the clearance of CO2 leading to a decrease in arterial PC02 and subsequent increase in pH to normal levels.

Question 68

Describe the Hering-Breuer reflex

Answer 68

The Hering-Breuer reflex is a mechanism stimulated by pulmonary stretch receptors that inhibits over distention of the lungs.

Question 69

Discuss the effects of exercise on ventilation

Answer 69

At the onset of exercise, there is an increase in ventilation frequency and depth to increase the total minute volume of air; this allows delivery of oxygen and removal of carbon dioxide in exercising tissue. The increase in ventilation has been suggested to be triggered by two mechanisms: 1) neurogenic which stimulates respiratory muscles through sensory nerve activity from exercising limbs, and 2) humoral, where the cerebral cortex stimulates brain stem respiratory centres. At the end of exercise, there is a gradual decrease in ventilation once the balance between oxygen and carbon dioxide is restored.

Question 70

Describe the homeostatic response to high altitude exposure

Answer 70

At high altitudes, the atmosphere has a lower PO2. To compensate for the lower oxygen content, the respiratory system will gradually become acclimatized through the following mechanisms: 1) Upon immediate exposure to high altitudes the respiratory system, triggered by the carotid bodies (low PO2), will increase ventilation (hyperventilation). This will increase the total minute volume. In turn, hyperventilation will cause respiratory alkalosis where the kidneys compensate by excreting more bicarbonate ions to return pH to normal, allowing for continued hyperventilation. In addition, respiratory alkalosis will increase hemoglobin’s affinity for oxygen at the level of the lung (i.e. improved oxygen loading). 2) At high altitudes, hemoglobin has a lower affinity for oxygen (% oxyhemoglobin saturation decreases from 97% to 92-93%). Triggered by low oxyhemoglobin, 2,3 DPG production is increased, causing a decrease in hemoglobin’s affinity for oxygen and more unloading of oxygen into tissues. 3) After a few days/week, kidneys will detect the decrease in tissue oxygen content and will secrete erythropoietin to stimulate production of red blood cells and hemoglobin to increase blood oxygen content.