Carbon Dioxide Transport and Control of Respiration

Question 1

What are the 4 factors that affect the binding of O2 to heme?

Answer 1

PO2
PCO2
pH
Temperature

Question 2

What is a right shift in the oxyhemoglobin dissociation curve?

Answer 2

Shift in the original dissociation curve, causing more O2 to be dissociated due to the increase in pH

Question 3

What is the Bohr effect?

Answer 3

In the presence of CO2 or protons (H+), hemoglobin has a decreased affinity for O2
-aka: more H+ causes the blood to become more acidic, lowering pH or if the level of CO2 increases in the blood O2 will want to dissociate from hemoglobin

Question 4

What does CO2 turn into when released from body into the blood?

Answer 4

Combines with water to make carbonic anhydrase(H2CO3) and then quickly converts to bicarbonate(HCO3) and H+

Question 5

What happens when O2 levels are high?

Answer 5

Hemoglobin wants to bind O2

Question 6

What happens when CO2 is high in the blood and pH is low at tissues?

Answer 6

Hemoglobin no longer wants to bind to O2, so O2 dissociates from the oxyhemoglobin

Question 7

What happens when O2 dissociates from oxyhemoglobin?

Answer 7

O2 can leave the blood and enter the cells of the tissues for use

Question 8

What are the 3 ways in which CO2 carried in the blood?

Answer 8

1. Dissolved form: 7% because CO2 is better at dissolving in plasma
2. Carbamino form: 23% CO2 binds to globing subunits
3. Bicarbonate form: 70% bicarbonate formed in the blood with the help of carbonic anhydrase which speeds up the reaction

Question 9

How is ventilation regulated?

Answer 9

Nervous system adjusts pulmonary ventilation and consequently alveolar ventilation to match O2 demands and CO2 production
-Does this through a negative feedback loop

Question 10

describe the 6 steps to the negative feedback that regulates ventilation

Answer 10

1. Set Point: Normal PO2 and PCO2 values
2. Integrating Centre: Respiratory centre in the medulla
3. Effector: Respiratory muscles (diaphragm and intercostals)
4. Response: Alter pulmonary ventilation
5. Stimulus/Controlled Variables: PO2 and PCO2 levels
6. Receptors: Chemoreceptors sense blood chemical levels

Question 11

What are chemoreceptors?

Answer 11

Special receptors that respond to changes in the chemical composition of the blood or other fluid around the receptors

Question 12

What are the 2 kinds of chemoreceptors?

Answer 12

Peripheral chemoreceptors in aortic arch and carotid body (outside CNS). Signal transmission to respiratory centre based on blood PO2 PCO2 and pH levels detected in carotid bodies and aortic arch

Central chemoreceptors located in the medulla

Question 13

How does the regulation of ventilation by central chemoreceptors differentiations from peripheral receptors?

Answer 13

Not directly affected by CO2, H+ and O2 in the blood. There is a chemosensitive area in the medulla that is highly sensitive to H+
-Central only responds to pH

Question 14

Why can’t CO2rxn be sensed in the blood at the central receptor?

Answer 14

Because of the BBB, conversion of CO2–> H+ and HCO3 requires a channels/transported to get the end products across the BBB.

Question 15

What can CO2 do in terms of the BBB?

Answer 15

CO2 can diffuse across the BBB, and the same run can be done in the spinal fluid, producing the H+ for the chemoreceptors to sense.