Respiratory system PartII

Question 1

Dalton’s law -

Answer 1

in a mixture of gases each gas exerts its own partial pressure that is independent of the other gases present.

Question 2

Exchange of Oxygen and Carbon dioxide

Answer 2

atmospheric pressure - (760mmHg) = P oxygen + P nitrogen + P carbon dioxide + P water + P other gases,
The partial pressure is caculated by multipling the percent of gas and the total pressure. Gaseswill move from one area from high partial pressure to low partial pressure for the individual gas.

Question 3

Henry’s law -

Answer 3

the amount of a gas that disolves in a solution is dependent upon the partial pressure and its solubility coefficient. The greater the partial pressure (concentration) and solubility , the more gas will be dissolved.

Question 4

External (pulmonary) respiration -

Answer 4

the exchange of oxygen and carbon dioxide between the alveoil and the blood.
Deoxygenated blood - depleted of oxygen by about 25%
Oxygenated blood ( saturated) - All four hemes have oxygen attached.
Net diffusion is from high partial pressure to low partial pressure.
Blood entering the alveolar capillaries - the partial pressure of CO2 is higher in the blood than the alveoli so the net diffusion of CO2 is into the alveoli, the partial pressure of O2 is higher in the alveoli than the blood so the net diffusion of O2 is into the blood.
Blood exiting the alveolar capillaries - partial pressure of oxygen is 100mm Hg and the partial pressure of carbon dioxide is 40 mm Hg as a result of the diffusion of the gases.

Question 5

The rate of diffusion of gases depends upon -

Answer 5

1. The partial pressure diffrence between the gases - the steepness of the pressure gradient ( high to low) affects rate of the diffusion of the gases.
2. Surface area for gas exchange - an increase in surface area provides area more gas exchange. In emphysema, alveoli are destroyed which decreases the surface area.
3. Diffusion distance - thickness of the respiratory membrane, a thinner membrane results in faster diffusion. Pulmonary edema and pneumonia both increase the thickness of the membrane and decrease the rate of diffusion.
4. Solubility and molecular weight of gases - a combination of these two factors contributes to the rate.

Question 6

Rate of diffusion of gases -

Answer 6

Even though oxygen has a lower molecular weight, carbon dioxide diffuses 20 times faster in liquid because of its high solubility. For this reason , hypoxia is more common than hypercapnia ( high levels of carbon dioxide). Remember Henry’s Law.

Question 7

Ventilation - perfusion coupling -

Answer 7

ventilation - specifically the amount of oxygen entering the alveoli.
Perfusion - the amount of bloob flowing in the alveolar capillaries. Ideally, these two variables should match.
Autoregulatory mechanism - local mechanisms alter the flow of blood (perfusion) to match the amount of ventilation. If ventilation is low, perfusion decreases by constriction of the arterioles to slow the flow of blood to allow time to maximize the gas exchange. If ventilation is greater than perfusion, the arterioles dilate.

Question 8

Internal (tissue) respiration -

Answer 8

the exchange of oxygen and carbon dioxide between the tissues and the blood.
Net diffusion of oxygen - into the tissue. Since oxygen doen’t diffuse quickly, only about 25% of the oxygen diffuses into the tissue. This means that deoxygenated blood still has about 75% of the oxygen still present.
Net diffusion of carbon dioxide is into the capillaries. Net diffusion of oxygen is into the tissues. Blood entering tissues so net diffusion is into the tissues, the net diffusion for CO2 is out of the tissues ad into the blood. Blood exiting tissue capillaries- the partial pressure of oxygen is 40 mm Hg and the partial pressure of carbon dioxide is 45mmHg.

Question 9

Oxygen Transport -

Answer 9

Oxygen has a low solubility coefficient and so very little is dissolved in the blood (only 1.5%). therefore, oxygen is better transportyed using a carrier such as hemoglobin, specifically the iron connected to the heme(pigment). The partial pressure of the oxygen partially determines how much oxygen is attached by shifting the equilibrium. This is directly affected by altitude. Other factors that affect the affinity(stickiness) of hemoglobin (Hb) for oxygen: 1. pH- with an increase in acidity (decrease in pH) the 3D structure of hemoglobin changes, decreasing the affinity of hemoglobin to oxygen. The opposite is also true.

2. Partial pressure of carbon dioxide - carbon dioxide can bind to hemoglobin on the globin part of the molecule, an increase in the partial pressure of carbon dioxide, decreases the affinity of hemoglobin for oxygen. The converse is also true. Bohr effect- a decrease in pH or an increase in partial pressure of carbon dioxide both result in a decreases affinity of hemoglobin for oxygen. The results in a decrese in the amount of oxygen bound to the iron on the heme( aka oxygen unloading)
3. Temperature - high temperature results in decreased affinity and oxygen unloading , low temperature results increased affinity and more oxygen bound.

Question 10

Fetal Hemoglobin-

Answer 10

This form of Hb- F naturally has a higher affinity for oxygen which contributes to better transfer of oxygen from the placenta.

Question 11

Carbon monoxide poisoning-

Answer 11

this occurs because CO binds the same place on hemoglobin as oxygen and CO has an affinity 200 times grater than oxygen.

Question 12

Hypoxia-

Answer 12

insufficient oxygen delivery to the tissues.

Question 13

Anemic hypoxia -

Answer 13

low delivery due to too few RBCs or low or abnormal hemoglobin.

Question 14

Ischemic hypoxia -

Answer 14

low delivery due to blockage of blood vessels.

Question 15

histotoxic hypoxia -

Answer 15

poisons that prevent oxygen from being utilized such as cyanide.

Question 16

Hypoxemic hypoxia -

Answer 16

inadequate perfusion ventilation coupling most commonly due to ventilation abnormalities but can also be due to carbon monoxide poisoning.

Question 17

Carbon dioxide transport -

Answer 17

1. dissolved in the plasma - only about 7%
2. attached to the globin part of the Hb (aka Carbaminohemoglobin) 23%
3. in the bicarbonate ion form 70%

Chloride ion shift- diffusion of bicarbonate ion into the plasma results in chloride ion diffusing into the red blood cells to balance the negativity.

Question 18

Haldane effect-

Answer 18

Increases in carbon dioxide decreases the pH of the blood which decreases the affinity of hemoglobin for oxygen (the Bohr effect). With oxygen released from hemoglobin, it allows more carbon dioxide to bind to the globin portion of the hemoglobin molecule. Note: the Haldane effect refers to the loading of carbon dioxide that results from oxygen unloading.

Question 19

Control of respiration -

Answer 19

1. medullary rhythmicity area, in the medulla oblongata, sets the basic rhythm of respiration.
2. pneumotaxic area, in the pons, coordinates the transition from inspiration to expiration.
3. apneustic area - in the pons, prolongs inspiration and inhibits expiration (a back-up system)
4. cortical influences- the cerebral cortex provides some voluntary control, to a point. It is limited by the build-up of carbon dioxide and acid which stimulates breathing
   Pulmonary irritants reflexes- chemoreceptors stimulated in the lower respiratory system stimulate a cough and chemoreceptors stimulated in the upper respiratory system stimulate a sneeze.

Question 20

Chemoreceptors that regulate breathing -

Answer 20

Central chemoreceptors located in the medulla oblongata and peripheral chemoreceptors located in the wall of systemic arteries stimulate the respiratory centers to make the appropriate changes. Aortic and carotid bodies play a key role.
Increase in carbon dioxide (hypercapina) can make the blood more acidic (increase in H+). Remember the Bohr affect. This results in an increase in the rate of respirations, hyperventilation, to compensate. Hyperventilation- carbon doixide( a volatile acid) is leaving the body more rapidly, this increases th pH of the blood because the acid potential of the body is decreasing. Decreases in oxygen don’t normally have a large effect on the rate of respirations because of the multiple binding sites of oxygen on the hemoglobin protein.