respiration

Question 1

Name the muscles involved in quiet breathing - and their actions.

Answer 1

• the diaphragm and the intercostal muscles cause inhalation

- exhalation is passive and occurs without muscular contraction

Question 2

Quiet breathing uses approximately ____ % of the daily Caloric intake; forced
breathing, if it continued all day, could consume _____% of the normal daily Caloric
intake.

Answer 2

5% for “quiet”

20% for “forced”

Question 3

Describe the muscles involved in forced breathing – and their actions.

Answer 3

• forced breathing uses the same muscles as quiet breathing AS WELL AS
  1) the pectoralis minor, sternocleidomastoid and scalenes for inhalation and
  2) the rectus abdominus and obliques for exhalation

Question 4

Explain the mechanism of inspiration; in your answer, refer to atmospheric pressure,
intrapulmonary pressure and pleural pressure (2 marks).

Answer 4

as the chest expands, the lungs also expand, because the lungs are held to the inner lining of the chest by pleural fluid (the pressure in this fluid is termed pleural pressure)

• as the lungs expand, the pressure of the gas molecules in the lungs (intrapulmonary pressure) decreases
• because the pressure of the gas molecules in the lungs is less than the pressure of gas molecules in the atmosphere (atmospheric pressure), air flows from the atmosphere into the lungs

Question 5

Explain the mechanism for expiration; in your answer, refer to atmospheric pressure,
intrapulmonary pressure and intrapleural pressure (2 marks

Answer 5

• the chest decreases in volume, increasing the pressure in the fluid between the chest wall and lungs (pleural pressure)
• the volume of the lungs decreases causing the pressure of gas within them (intrapulmonary pressure) to increase
• when the intrapulmonary pressure becomes greater than the atmospheric pressure, air flows out of the lungs

Question 6

Explain what airway resistance is and explain its impact on ventilation

Answer 6

• airway resistance opposes the flow of air
• airway resistance increases as the diameter of the airways decreases
• increased resistance results in slower movement of air in and out of the lungs

Question 7

Analyze the three main forces acting on the alveolus (3 marks

Answer 7

• pleural pressure, generated by the expansion of the chest, is negative, meaning that it tends to inflate the alveoli
• surface tension results from the thin film of water that lines the alveoli, tending to deflate them
• elasticity results from the elastic fibers that surround the alveoli and tends to deflate them

Question 8

Explain what surfactant is and describe its physiological role.

Answer 8

• surfactant is a molecule composed of lipid and protein (lipoprotein) that is secreted by specialized cells in the lining of the alveolus
• surfactant reduces the force of surface tension, making it easier to inflate the alveoli (especially important in the newborn)

Question 9

Air typically consists of ____ % oxygen, _____% nitrogen and _____ % carbon
dioxide.

Answer 9

~20% oxygen
~80% nitrogen
less than 1 % carbon dioxide

Question 10

The following OR similar Question: A metal cylinder contains an equal number of
oxygen and nitrogen molecules and the overall pressure in the cylinder is 1000 mm
of Hg. The pressure of oxygen in the cylinder is _______.

Answer 10

500 mm of Hg

Question 11

The partial pressure of O2 in air (PO2) is ______ mm Hg and the partial pressure of
PCO2 in air is _____ mm Hg a) 0.01; 10
b) 10,0.01 c) 0.3;160 d) 160;0.3

Answer 11

d) 160; 0.3

Question 12

Describe the composition of the respiratory membrane of the lungs and explain how its structure is related to its function (2 marks).

Answer 12

composed of two simple squamous epithelia (one from the lining of the alveolus; the other from the endothelium of the capillary around the alveolus) and a thin layer of basement membrane between them
- the respiratory membrane is very thin to allow for the movement of oxygen and carbon dioxide across it by diffusio

Question 13

How do oxygen and carbon dioxide compare with respect to solubility in aqueous solutions?

a) neither is very soluble
b) both are very soluble
c) onlyoxygenisverysoluble
d) only carbon dioxide is very soluble

Answer 13

d) only carbon dioxide is very soluble

Question 14

Explain how the alveoli adjust so that the air supply and the blood supply are optimal.

Answer 14

-if air stops reaching an alveolus, the blood vessels that supply it will constrict…until air returns

Question 15

Explain what carbon dioxide loading and unloading are and where, in the body, each occurs.

Answer 15

• CO2 loading is movement of CO2 from the tissues to the systemic blood
• CO2 unloading is movement of CO2 from the pulmonary blood to the air in the alveoli

Question 16

Explain what oxygen loading and unloading refers to and where, in the body, each occurs.

Answer 16

O2 loading is movement of O2 from the air in the alveoli to the pulmonary blood
-O2 unloading is movement of O2 from the systemic blood to the tissues

Question 17

List the forms in which oxygen is transported in the blood and the approximate proportions of each (2 marks).

Answer 17

• 99% of the oxygen in the blood is bound to hemoglobin

- the rest is dissolved in the plasma

Question 18

Explain what oxygen saturation is, how it depends on the partial pressure of oxygen in the surrounding medium and how it varies in the blood during normal physiological conditions (3 marks)

Answer 18

oxygen saturation is the percentage of oxygen binding sites on the hemoglobin of blood that are ACTUALLY bound to oxygen

• oxygen saturation increases with the partial pressure of oxygen but it is not a straight line relationship (plotted on a graph, it appears as an S shaped curve (I can’t draw it on a sticky note)
• oxygenated blood has an oxygen saturation of more than 95%
• deoxygenated blood has an oxygen saturation of about 70%

Question 19

19)The following two panels show the exchange of respiratory gases. In each panel, PO2 and PCO2 are indicated in three regions. Complete the diagram by adding the missing concentrations of the O2 and CO2 (in mm of Hg).

Answer 19

look at notes

Question 20

Explain what the Bohr effect is and the role that it plays in respiratory physiology (2 marks).

Answer 20

as the pH decreases, hemoglobin is less saturated with oxygen
-as cells respire more, they release more acid - this causes greater release of oxygen from the blood supplying those cells

Question 21

List three factors that promote the release of oxygen from the blood to the cells of a contracting muscle (3 marks).

Answer 21

1) H+
2) heat
3) BPG

Question 22

Explain how a child in utero is adapted to obtain oxygen

Answer 22

before birth, red blood cells contain a specialized form of hemoglobin called fetal hemoglobin
-fetal hemoglobin has a stronger attraction for oxygen than adult hemoglobin, making it easier for the fetal blood to absorb oxygen from the mothers blood as they both pass through the placenta

Question 23

List the forms in which carbon dioxide is transported in the blood and the
approximate proportions of each (2 marks).

Answer 23

• most (~70%) CO2 is converted to bicarbonate ion and transported in the plasma
• about 20% of CO2 is bound to hemoglobin
• about 10% of CO2 is dissolved in the plasma

Question 24

Explain what carbonic anhydrase is, where it is located and why it is important in
respiration (2 marks).

Answer 24

carbonic anhydrase is an enzyme located inside the red blood cells

• it catalyzes the conversion of CO2 and H2O to carbonic acid, which dissociates to form bicarbonate ion (the main transport from of CO2)
• carbonic anhydrase converts CO2 to bicarbonate rapidly in the tissues allowing more to be transported in the blood
• it also rapidly converts bicarbonate ion back to CO2 in the lungs for rapid removal from the blood

Question 25

)Explain what the chloride shift is.

Answer 25

• chloride shift is the transport of chloride ion in the opposite direction to bicarbonate ion
• chloride shift prevents the movement of bicarbonate from changing the charge inside the red blood cell

Question 26

The neurons that control breathing are located in ___________________

Answer 26

medulla oblongata
(you could also argue that they are present in the phrenic nerve)

Question 27

The medical term for failure to maintain normal ventilation is ___________

Answer 27

asphyxia

Question 28

Describe the physiological effects of hyperventilation (2 marks)

Answer 28

• decrease in plasma concentration of CO2 and increase in pH

- increased pH can result in increased excitability of nervous system

Question 29

Describe the locations of chemoreceptors that are involved in respiratory reflexes,
the substances that they are stimulated by and how they regulate respiration (3 marks).

Answer 29

• central chemoreceptors (stimulated by CO2 and H+) are located in the hypothalamus
• peripheral chemoreceptors (stimulated by CO2, H+ and O2) are located in the aorta and carotid sinus
• stimulation of chemoreceptors transmits impulses along cranial nerves IX and X to medulla oblongata (and pons) where reflexes that result in increased rate and depth of ventilation are triggered