Oxygen Transport & Neural Respiratory Control

How is oxygen transported in the blood?

98% bound to hemoglobin; 2% dissolved in plasma.

How is carbon dioxide transported in the blood?

7% dissolved in plasma, 23% bound to hemoglobin as carbaminohemoglobin, 70% as bicarbonate (HCO3-) in plasma.

What does the oxygen-hemoglobin saturation curve show?

Positive cooperative binding, represented by a sigmoidal (S-shaped) curve.

Why is hemoglobin cooperative in binding oxygen?

Binding of one O2 molecule causes a conformational change that increases affinity of remaining heme units.

Where is myoglobin found?

In cardiac and skeletal muscle.

How does myoglobin's affinity for oxygen compare to hemoglobin's?

Myoglobin has a higher binding affinity for oxygen.

Why does fetal hemoglobin bind oxygen more strongly than adult hemoglobin?

Different protein structure gives fetal Hb a higher affinity, allowing it to "steal" oxygen from maternal blood.

How does CO2 affect O2 release from hemoglobin?

CO2 binds to hemoglobin and promotes oxygen release; carbonic anhydrase speeds the reaction by 10^6.

How does pH affect hemoglobin's affinity for oxygen?

Lower pH (more acidic) weakens the Hb-O2 bond; increased H+ binds to Hb and promotes oxygen release.

How does temperature affect hemoglobin's oxygen affinity?

Higher temperature decreases affinity and promotes O2 release.

What is the role of 2,3-BPG in oxygen release?

2,3-BPG binds hemoglobin and decreases its affinity for O2; its production increases with high temperature and low pH.

What causes a left shift in the oxygen-hemoglobin dissociation curve?

Decreased temperature, 2,3-BPG, H+, and CO2; increased pH; increased Hb affinity.

What causes a right shift in the oxygen-hemoglobin dissociation curve?

Increased temperature, 2,3-BPG, H+, and CO2; decreased pH; reduced Hb affinity.

What is the function of carbonic anhydrase in blood?

It catalyzes CO2 + H2O → H2CO3 to help maintain blood pH.

What is normal blood pH?

7.35-7.45.

What is acidosis?

Blood pH below 7.35.

What is alkalosis?

Blood pH above 7.45.

What does the Haldane Effect describe?

How oxygen concentration determines hemoglobin's affinity for CO2.

What happens when oxygen binds to hemoglobin in the Haldane Effect?

It displaces CO2 and reduces hemoglobin's affinity for CO2.

Why is the Haldane Effect useful in the lungs?

Hemoglobin shifts left (higher O2 affinity) to help load oxygen.

What does the Bohr Effect describe?

The effect of pH on the hemoglobin-oxygen saturation curve.

What causes the Bohr Effect?

High CO2 entering RBCs at tissues.

How does decreased pH affect hemoglobin?

Decreases hemoglobin's O2 affinity (right shift), promoting O2 release to tissues.

How does PCO2 affect bronchiole diameter?

Higher PCO2 causes bronchodilation; lower PCO2 causes bronchoconstriction.

Why do bronchioles dilate when PCO2 increases?

To direct airflow to lobules actively engaged in gas exchange.

Where is respiration controlled in the brain?

The brainstem.

What crosses the blood-brain barrier to stimulate central chemoreceptors?

CO2.

How does CO2 activate central chemoreceptors?

CO2 → H+ via carbonic anhydrase in CSF; H+ stimulates chemoreceptors.

What is the effect of increased CO2 on ventilation rate?

It increases ventilation.

Where are peripheral chemoreceptors located?

Carotid bodies and aortic bodies.

What do peripheral chemoreceptors detect?

Low O2 and high CO2.

How does low O2 affect ventilation?

It increases ventilation rate.

What inputs does the respiratory center in the brainstem receive?

Central and peripheral chemoreceptors.

What muscles does the respiratory center control?

The diaphragm and intercostal muscles.

What is hypercapnia?

Excess CO2 in arterial blood.

What commonly causes hypercapnia?

Hypoventilation (low respiratory rate).

How does the body respond to hypercapnia?

Increases ventilation rate.

What is hypocapnia?

Low arterial CO2 levels.

What causes hypocapnia?

Hyperventilation.

How does the body respond to hypocapnia?

Decreases respiratory rate.

What are the major functions of the respiratory system?

Move air to and from the lungs; provide extensive gas exchange surface area; protect respiratory surfaces; maintain acid-base balance; produce sounds; participate in smell (olfaction); help regulate blood volume and blood pressure via angiotensin II.

How does the respiratory system contribute to sound production?

Air movement through the vocal cords generates sound.

How does the respiratory system help maintain acid-base balance?

By regulating CO2 levels, which influence blood pH.

How do the lungs participate in blood pressure regulation?

Capillaries in the lungs help produce angiotensin II, which affects BP.

What role does hemoglobin (Hb) play in gas transport?

It transports O2 and CO2 but uses different mechanisms for each gas.

What determines hemoglobin saturation with oxygen?

PO2, temperature, pH, CO2 levels, and 2,3-BPG.

What is the Bohr Effect?

Decreased pH (increased CO2) shifts the Hb-O2 curve right, promoting O2 release in tissues.

What is the Haldane Effect?

High O2 levels in the lungs reduce Hb's affinity for CO2, promoting CO2 release.

Where does the Bohr Effect primarily occur?

In systemic tissues.

Where does the Haldane Effect primarily occur?

In the lungs.

What is the main factor used by the body to control respiration rate?

CO2 levels in the blood.

How do CO2 levels control respiration rate?

High CO2 increases ventilation; low CO2 decreases ventilation.

Which muscles does CO2 regulation primarily act on to affect breathing?

The diaphragm and intercostal muscles.