Lecture 19: Gas transport and respiratory control Flashcards
What two forms can oxygen be transported in the blood?
- Dissolved O2 (Oxygen dissolves poorly, especially because blood is warm)
- Bound to Haemoglobin in RBCs (primary transport)
What are the Functions & Characteristics of Red Blood Cells (RBCs, Erythrocytes)?
- Contain large amounts of hemoglobin (One-third weight of RBC)
- Uses iron as part of the heme structures to bind oxygen
- Four heme units, so each hemoglobin can bind four oxygen molecules
What is haemoglobin’s binding curve and where would it pick up and give away oxygen?
It is a sigmoidal binding curve due to the cooperative nature of haemoglobin.
Haemoglobin picks up oxygen in the pulmonary circuit where pO2 is very high
Haemoglobin gives away oxygen in the systemic circuit where pO2 is low (oxygen is distributed to the tissues that need it most)
What are two ways that haemoglobins binding curve can be shifted?
Lower pH = Reduced O2 affinity and the curve shifts to the right
Higher temperature = Reduced O2 affinity shifts the curve to the right
Exercise causes pH to drop and temperature to rise in
skeletal muscle! This means that haemoglobin is more likely to offload O2 to the muscles
Emily goes to the gym and runs on the treadmill, pushing
herself to her aerobic limit. Which of the following
statements is most likely to be CORRECT as she is
exercising?
A. Her alveolar ventilation is decreased.
B. Her breathing frequency is decreased.
C. Her tidal volume is decreased.
D. Her hemoglobin affinity for oxygen near her skeletal
muscle is decreased.
D
What are the three ways CO2 is transported?
- Dissolved in plasma (small amount)
- Bound to hemoglobin (most in RBC, some bind to haemoglobin but not much as affinity for CO2 is low)
- Converted to bicarbonate (once it moves into RBC its combined with water to form bicarbonate ion)
What is the process for the formation of bicarbonate ions?
- Carbon dioxide and water combine to form carbonic acid (H2CO3)
- Carbonic acid dissociates into bicarbonate and a hydrogen ion (HCO3- and H+)
- This lowers the pH…the blood is getting more acidic
How are O2 and CO2 are normally kept within close limits. Despite very variable usage?
By tight control of ventilation (breathing)
What is the central controller of breathing?
Pons, medulla, other part of brain
What are the four sensors for regulation of breathing
- Chemoreceptors
- Baroreceptors
- Lung stretch receptors
- Protective reflexes
How do chemoreceptors help regulate breathing?
Chemoreceptors are Receptors that monitor O2 and CO2
levels in our blood
- If O2 is down or CO2 is up, chemoreceptors send afferent input to the brain, resulting in increased breathing frequency and tidal volume
- It is our most critical system that regulates breathing, as
it can override your voluntary control!
IMPORTANT!!
* CO2 receptors play the primary role…O2 receptors
are secondary
Where are the baroreceptors and how do they regulate breathing rate?
The left and right Carotid sinus receptors and the Aortic arch receptors
Arterial BP goes down which means reduced blood flow:
* Sensed by the baroreceptors
* Respiratory minute volume goes up
* Increased uptake of air
Arterial BP goes up, which means increased blood flow:
* Sensed by the baroreceptors
* Respiratory minute volume goes down
* Decreased uptake of air
How do the lung stretch receptors manage breathing?
- As the lungs inflate or deflate, they send afferent input from stretch receptors to the Dorsal/Ventral Respiratory Group in the brainstem
- The brain then sends efferent output preventing them from stretching too far either way to prevent damage!
How do the protective reflexes receptors impact breathing?
- Receptors also detect irritation
- Brain sends efferent signal that triggers a sneeze or
cough
