BIO 132 – Anatomy and Physiology II

LECTURE 10: PHYSIOLGY OF THE RESPIRATORY SYSTEM: GAS EXCHANGE, TRANSPORT, AND CONTROL OF BREATHING

Study Outline

10.1. Dalton’s Law of Partial Pressures:

a. Atmospheric air is a mixture of ___________________________________, ________________________________ and trace amounts of other gases including argon and CO₂.

b. Dalton’s Law states that the total pressure of a gas mixture is the sum of ____________________________.

c. The pressure exerted by each component gas is called the __________________________ and is equal to the total pressure of all gases in the mixture multiplied by the ________________________________.

d. Within alveoli, the partial pressure of water vapor is ___________________ at an atmospheric pressure of 760 mmHg.

e. As one moves to higher altitudes, the partial pressure of oxygen ________________________ compared to what it is at sea level; because while the fractional concentration of oxygen is ____________, the total pressure of air at altitude is _____________.

10.2. Composition of Alveolar Air:

a. The P_O2 within the alveolus is less than that in inspired air because __________________________________________________________.

b. The P_O2 within the alveolus is less than that in expired air because ___________________________________________________________.

c. Typically, the P_CO2 of alveolus air is _________________________ which is equivalent to the P_CO2 of blood within the ___________________________.

d. Blood leaving pulmonary capillaries has a P_O2 of ______________________, and a P_CO2 of ________________________.

e. Blood entering pulmonary capillaries has a P_O2 of _______________________, and a P_CO2 of __________________________.

10.3. Henry’s Law and Pulmonary Diffusion:

a. According to Henry’s Law, the amount of a gas that is absorbed by a liquid is directly proportional to the ______________________________ and the __________________________ of the gas.

b. CO₂ is about ____________________ times more soluble in plasma than O₂. Nitrogen on the other hand has ____________________ solubility.

c. Fick’s Law of Diffusion states that the volume of gas diffusing through a barrier per unit time is proportional to the _________________________, ________________________________, __________________________; and inversely proportional to the ____________________________________.

d. The diffusion constant of Fick’s Law is proportional to the solubility of the solute divided by the square root of _______________________________.

e. Diseases like emphysema reduce the total surface area for pulmonary diffusion, which would be expect to _________________________ diffusion.

f. The typical thickness of the diffusion barrier is about ___________________________. Factors like pulmonary edema or interstitial fibrosis are expected to ___________________________ diffusion.

g. Increases in the partial pressure gradient will __________________ diffusion.

h. Even though the molecular weight is greater for CO₂ compared to O₂, the diffusion coefficient for CO₂ is higher because of _____________________________________.

i. Blood spends an average of ____________________________ seconds in a pulmonary capillary which decreases to ___________________________ seconds with exercise.

j. Even though CO₂ is 20 times more soluble than O₂, it has a similar time course of diffusion because _____________________________________.

10.4. Transport of O₂ in Blood:

a. Most O₂ is carried in blood ___________________________________.

b. Hemoglobin can bind __________________________ oxygen molecules, each bound to a ______________________________ atom.

c. The relationship between O₂ bound to hemoglobin and the _____________________ is called the oxy-hemoglobin dissociation curve.

d. The P₅₀ is the P_O2 at which hemoglobin is ________________________.

e. The shape of the oxy-hemoglobin dissociation curve is ___________________________.

f. At a P_O2 of about 100 mmHg, hemoglobin is about ___________________ saturated whereas at 40 mmHg, it is only ___________________ saturated.

10.5. Factors that Affect the Oxy-hemoglobin Dissociation Curve:

a. A decrease in pH will shift the curve to the ___________________________.

b. An increase in temperature will shift the curve to the ___________________.

c. A decrease in P_CO2 will shift the curve to the ________________________.

d. An increase in 2,3-DPG will shift the curve to the ______________________.

e. A shift of the curve to the left means that there is _____________________ affinity of O₂ for hemoglobin.

f. The Bohr effect refers to the ________________ shift of the curve in response to _______________________ and _______________________________. A right shift in the curve means that there is ___________ affinity of O₂ for hemoglobin.

10.6. Transport of CO₂ in Blood:

a. Most CO₂ is transported in the form of _________________________ present in __________________________________. The remainder is present as ________________________ and bound to ___________________________.

b. The conversion to bicarbonate depends on the enzymatic action of ______________________ present within _________________________.

c. The protein which forms most of the carbamino complexes with CO₂ is ________________________________.

d. The CO₂ dissociation curve is shifted to the _____________________ with an increase in the amount of oxy-hemoglobin. The Haldane effect however mostly refers to the shift to the ________________________ with decreased amounts of oxy-hemoglobin.

e. Within systemic capillaries, most CO₂ is taken up into _________________ where it is converted to _________________________ which then enters plasma. In this case the chloride shift is directed ___________________________________.

f. Within pulmonary capillaries, ___________________ enters RBCs where it is converted to carbonic acid and ultimately CO₂. In this case the chloride shift is directed ___________________________.

10.7. Control of Breathing:

a. Inspiratory neurons send nerve impulses to the diaphragm via the ___________________ nerve and the ___________________ muscles via intercostal nerves.

b. The depth of breathing is controlled by ______________________ while the breathing rate is controlled by the ______________________________ and _________________________.

c. The presumed pacemakers for respiration are found within the __________________________ located within the medulla. Also present within the medulla are the ___________________________.

d. Two other centers located in the pons are called the ___________________ and the _____________________ centers.

e. Medullary respiratory centers receive input from many sources including ____________________________, _________________________________, ______________________________,________________________________, ______________________________, and ____________________________.

f. Our ability to hold our breath comes from the __________________________

g. Increased respiration due to emotions, pain, or even in thermoregulation stems from input from the _______________________________________.

h. Chemoreceptors sense ___________________________________________, _______________________________, and _________________________. Of these the __________________________ level has the greatest influence on breathing.

i. The condition of elevated P_CO2, known as ___________________________, results in a(n) _________________________ in breathing. This response is initiated mostly by chemoreceptors located in the _______________________.

j. The response to a low P_O2, also called _______________________, isn’t really effective until the P_O2 falls to __________________________. Low P_O2 will augment the response to ______________________.