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82 Cards in this Set

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Oxygen is transported in ? between ? and ?.
Oxygen is transported in blood between alveoli and tissues.
What percentage of O2 is physically dissolved? What happens to the rest?
1.5% physically dissolved. The other 98.5% is bound to hemoglobin.
Oxygen and CO2 are both bound by what?
Both are bound by hemoglobin. HOWEVER they do not occupy the same space.
CO2 is transported in ? between ? and ?.
CO2 is transported in blood between tissues and alveoli.
What percentage of CO2 is physically dissolved? What happens to the rest?
10% of CO2 is physically dissolved.

30% is bound to hemoglobin.

60% is transported as bicarbonate (HCO3-)
What happens to most of the O2 in blood?
Most O2 is bound to hemoglobin (98.5%)
When hemoglobin (Hb) combines with oxygen to form what?
Forms Oxyhemoglobin (HbO2)
The formation of oxyhemoglobin is what kind of process?
It is a reversible process.
Where is oxyhemoglobin formation favored?
In the lungs. (so the rxn moves to the right in the lungs)

Hb + O2 --> HbO2
When does Hb combine with O2?
Hb combines with O2 as O2 diffuses from alveoli into pulmonary capillaries.
Where does the dissociaton of oxyhemoglobin occur?
Dissociation of oxyhemoglobin into Hb and free molecules of oxygen occurs at tissue cells. (so rxn moves from right to left)

HbO2 --> Hb + O2
Most O2 is in blood bound to hemoglobin what happens to the rest? What does this contribute to?
Less O2 is dissolved in the plasma (1.5%). This percentage contributes to the Po2 of the blood.

So the O2 that is bound to Hb contributes nothing to partial pressure in the blood...only the 1.5% contributes)
The partial pressure of oxygen is the main determinant of the percent of ? ?.
Po2 is the main determinant of the percent hemoglobin saturation. (ie, how much O2 is assoc. with hemoglobin)
Where is the percent of Hb saturation high?
Percent Hb saturation is high where Po2 is high. This occurs in the lungs. (in the alveoli O2 tends to associate with Hb)
Where is te percent of Hb saturation low?
Percent Hb saturation is low where Po2 is low. This occurs in tissue cells. (at tissue cells O2 tends to dissociate from Hb...this is good b/c it delivers O2 to cells)
The relationship between the Po2 and hemoglobin saturation is illustrated by what?
Relationship is shown in the oxygen-hemoglobin dissociation curve.
Hemoglobin promotes the net transfer of what?
Promotes net transfer of O2 at both alveolar and tissue levels.
There is a net diffusion of O2 from the ? to ?.
From the alveoli to blood. This occurs continously until hb is saturated (97.5% at 100 mm of Hg)
At tissue level there is a diffusion of O2 from ? into ? and on to ?.
Diffusion of O2 from hemoglobin into blood and on to tissue cells at tissue level.
Under normal metabolic conditions, hemoglobin is ?% saturated with O2 at the tissues.
? factors promote O2 unloading.
Various factors promote O2 unloading.
Increased CO2 from tissue cells into systemic capillaries increases what?
Increased CO2 from tissue cells into systemic capillaries increases Hb dissociation from O2. This shift the dissociation curve to the right. This is the Bohr (haldane) effect.
How does increased acidity affect O2 unloading (the dissociation curve)?
Shifts the curve to the right.

Hbs affinity for O2 differs at different pHs. This is good for us b/c we have a more acidic environment at tissue level.

At lower pH (acidic), Hb has less affinity for O2, releasing more O2 to tissues.
How do higher temp.s affect O2 unloading?
Higher temp.s produce a shift to the right for the dissociation curve. This is also good for us b/c cells have a higher temp at tissue level.
BPG is produced by what? What does BPG do to the dissociation curve?
BPG is produced by RBCs and causes a shift to the right.
What is BPG aka?
2,3-Bisphosphoglycerate...enhances the off-loading of O2 from Hb but can happen anywhere in the body (not just at the tissue level).
Most CO2 is transported as what?
60% is transported as bicarbonate ion.
CO2 combines with water to form what?
CO2 combines with water to form carbonic acid (H2CO3).

(enzyme, carbonic anhydrase, facilitates rxn in RBC)
What does carbonic acid dissociate into?
Hydrogen ions (H+) and bicarbonate ion (HCO3-)
The dissociation of carbonic acid is what kind of process? Where is it favored?
It is a two-step reversible process that is favored at tissue cells.
The reverse process of carbonic acid dissociation occurs where?
Reverse process occurs in the lungs. So bicarbonate ions forming free molecules of carbon dioxide.
Write the carbonic acid chemical eqn.
CO2 + H2O <--(carbonic anhydrase)--> H2CO3 <--> H+ + HCO3-
What percentage of CO2 is bound to hemoglobin in blood?
What percent of transported CO2 is dissolved in plasma?
What is a chloride shift?
RBC plasma membrane has a carrier that passively facilitates diffusion of bicarbonate and chloride ions (in opposite directions) (so exchange bicarb for Cl-)(Via HCO3-Cl carrier)
What is a haldane effect?
O2 removal from Hb at tissue cells increases the ability of Hb to bind CO2 and H+.
Abnormal blood gas levels involves abnormalities in what?
Abnormalities in arterial Po2.
What is hypoxia?
Insufficient O2 at the cellular level. (4 general categories)
Is Po2 always low with hypoxia?
No, you can have normal Po2 adn still have hypoxia.
List the 4 general categories of hypoxia.
1. Hypoxic hypoxia

2. Anemia hypoxia

3. Circulatory hypoxia

4. Histotoxic hypoxia
What is hypoxic hypoxia?
Low Po2 in arterial blood.

(this also occurs at high altitudes because the atmosphere Po2 is reduced)

(this is also seen in respiratory issues like pneumonia and emphysema)
What is anemia hypoxia?
Reduced oxygen-carrying capacity in the blood. Because of decreased RBCs or decreased availability of Hb. An ex. would be CO poisoning.
What is circulatory hypoxia?
Too little oxygenated blood delivered to tissues. (ex. ischemia)(ex. hemorrhage)
What is histotoxic hypoxia?
O2 delivery to tissues is normal, but cells can't use it. So something is wrong with the cell. (ex. cyanide poisoning)
What is hyperoxia?
Above-normal arterial Po2.
What is hypercapnia?
(an abnormality in arterial Po2)

Excess CO2 in arterial blood. Caused by hypoventilation. AKA respiratory acidosis.

(so will increase H+ and HCO3-)

(increases acidity)

(decreases pH)
What is hypocapnia?
Below-normal CO2 in arterial blood. (rxn moves to left)(decrease H+)

AKA respiratory alkylosis.

Caused by hypERventilation.
What is hyperpnea?
Increased need for O2 delivery and CO2 removal.

(an ex. is fever --> increased metabolism)

Occurs during time of increased metabolic need.
Respiratory centers are where?
Respiratory centers in brain stem. (this indicates a very basic level of function)
The respiratory centers in the brain stem establish what?
Est. rhythmic breathing pattern via cyclical activity.
Respiration can be modified via what?
Via voluntary activity. (ex. speaking, singing)(but can also be modified via a need like a fever)
List two respiratory control centers found in the brain stem.
1. Medullary respiratory center

2. Two respiratory centers in Pons.
Describe the medullary respiratory center?
Aggregation of neuronal cell bodies in medulla, provide output to respiratory muscles:


Pre-Botzinger Complex

Dorsal Respiratory Group

Ventral Respiratory Group
Describe the two respiratory centers in the pons?
Influence output from medullary respiratory center.


Pneumotaxic center

Apneustic center
Inspiration is an ? process.

Expiration is a ? process.
Inspiration is an active process.

Expiration is a passive process.
What are the inspiratory neurons?
Phrenic and intercostal.
What are the inspiratory muscles?
Diaphragm and external intercostals.
Inspiratory neurons (phrenic and intercostal) signal what?
Inspiratory neurons signal inspiratory muscles (diaphragm and external intercostals).
Explain how the inspiratory neurons control breathing by signaling inspiratory muscles.
1. Impulses from medullary center terminate on phrenic and intercostal motor neurons

2. Cell bodies for neurons located in spinal cord

3. Signal sent to inspiratory muscles

4. If there is no signal from inspiratory neurons, then the inspiratory muscles relax (= expiration)
During inspiration what is the diaphragm doing?
List the 3 parts of the medullary respiratory center.
1. Dorsal Respiratory Group (DRG)

2. Ventral Respiratory Group (VRG)

3. Pre-Botzinger Complex
What is the Dorsal Respiratory Group (DRG)?
Mostly inspiratory neurons, descending fibers terminate on inspiratory motor neurons.

Responsible for inspiration.

Connected to VRG.
What is the Ventral Respiratory Group (VRG)?
Both inspiratory and expiratory neurons.

Both inactive during quiet breathing.

Utilized during increased demand for ventilation.

Especially important for ACTIVE EXPIRATION.
What is the Pre-Botzinger Complex?
Region in upper end of medullary respiratory center, believed to establish basic respiratory rhythm.

Neurons here display pacemaker activity.
List 3 areas of Pons involved in the control of breathing.
("these kind of smooth out medulla actions")

1. Pneumotaxic center

2. Apneustic center

3. Hering-Breuer reflex
What is the pneumotaxic center?
Area of pons.

Sends impulses that switch off inspiratory neurons.

Limits duration of inspiration.
What is the Apneustic center?
Area of the pons.

Prevents inspiratory neurons from being switched off.

Provides extra boost to inspiratory drive.
What is the Hering-Breuer Reflex?
Stretch receptors in lungs activated with large tidal volumes (TVs) (>1L) during inspiration.

Signals travel from receptors to medullary center by afferent neurons, inhibiting the inspiratory center.

Expiratory center then dominates.
What is the magnitude of ventilation adjusted in response to?
Adjusted in response to 3 chemical factors.

1. Po2

2. Pco2

3. [H+] (which is a reflection of CO2 if you think about the eqn)
Describe the magnitude of ventilation?
It is adjusted in response to Po2, Pco2, and [H+].

CO2 generated H+ in the brain is the primary regulator.

The peripheral and central chemoreceptors detect chemical changes in the blood and signal to medulla to change repiratory rate.
Which is more important for magnitude, peripheral or central chemoreceptors?
Central chemoreceptors of the brain are more important.
What are the peripheral chemoreceptors important for concerning ventilation?
They monitor arterial Po2.

Stimulated only when arterial Po2 life-threateningly low (<60 mm Hg...this will stimulate the peripherals because normal is ~100 mm Hg)
Where are the central chemoreceptors located?
In the medulla.
What do the central chemoreceptors monitor?
Monitor increased [H+] in brain ECF. CO2-generated H+ in brain: normally primary regulator of ventilation.
Again, what is the eqn for bicarbonate ions forming free molecules of carbon dioxide?
CO2 + H2O <-> H2CO3 <-> H+ + HCO3-
What does elevated H+ in the brain ECF directly stimulate?
Directly stimulates central chemoreceptors to increase ventilation by stimulating respiratory center.
Peripheral chemoreceptors are highly responsive to ? [H+], but less important than ?.
Peripheral chemoreceptors are highly responsive to arterial[H+], but less important than central chemoreceptors.

Elevated arterial [H+] also stimulates ventilation.
What is apnea?
Transient interruption in ventilation.

A complete cessation would be Respiratory Arrest.
What is respiratory arrest?
A complete cessation of ventilation.
What is sleep apnea?
Breathing can cease for few seconds up to 2 minutes as many as 500 times a night.
What is dyspnea?
A SUBJECTIVE feeling of 'shortness of breath'.
What does dyspnea often accompany? (not always)
Often accompanies other conditions.

ex. COPD
ex. pulmonary edema from CHF