Lecture 13 - Respiratory Flashcards
What is atmospheric pressure?
760 mmHg
Percent of nitrogen in the atmospheric air
79% N2
- About 600 mmHg
Percent of oxygen in the atmospheric air
21% O2
- About 160 mmHg
Pressure gradient for the atmosphere
Pressure must be greater in the external environment than compared to the internal environment
If the summit of Mt. Everest is approximately 30,000 and the atmospheric pressure is 226mmHg, what is the partial pressure of oxygen at the summit?
21% of 226
= 47 mmHg
Steps of external respiration
- Ventilation or gas exchange between the atmosphere and the lungs
- Exchange of oxygen and carbon dioxide between air lungs and the blood
- Transport of oxygen and CO2 between the lungs and tissues
- Exchange of O2 and CO2 between the blood and tissues
What is the anatomical dead space?
Area where no gas exchange occurs
- usually nares to the lung tissues
Pressure in the lungs during equilibrium
The lungs have a pressure of 760mmHg and the pleural sac around the lungs have a pressure of 756mmHg
Pulmonary capillaries
Where gas exchange occurs
- 100% of the cardiac output flows through these
How do nutrients diffuse throughout the pulmonary capillaries and alveolus?
There is a very thin membranous layer between them which allows for the diffusion of nutrients
Diaphragm’s role in breathing
Involved in every inspiration
- relaxation causes passes expiration
Muscles involved with forceful inspiration
Sternocleidomastoid
Scalenus
Muscles involved in active expiration
Internal intercostal muscles
Abdominal muscles
Process of inspiration
- Contractions of external intercostal muscles causes elevation of ribs, which increases side-to-side dimension of thoracic cavity
- Contractions of external intercostal muscles
- Elevation of ribs causes sternum to move upward and outward which increases dimension of thoracic cavity
- Diaphragm contracts
- Lowering of diaphragm on contraction increases vertical dimension of thoracic cavity
Negative pressure process
Pressure in the lung drops from 760 to 759 and pleural cavity drops from 756 to 754 becoming more negative. Both pull air in from the atmosphere
- During expiration: lung goes to 761 causing gas to move out of the lungs
Type 2 alveolar cells
Produces alveolar fluid lining with pulmonary surfactant
Law of Laplace
P = (2y)/r P = gas pressure required to keep equilibrium y = gamma, surface tension r = radius of the sphere
Volume of lungs at the end of normal respiration
2,700 mL
Volume of lungs at the end of normal expiration
2,200 mL
Tidal Volume
Difference between end-expiratory and end inspiratory volume (about 500mL)
Area in which perfusion is greater than airflow affects:
- Increased CO2, decreased O2
- Dilation of airways, constriction of blood vessels
- Decreased airway resistance, increased vascular resistance
- Increased airflow, decreased blood flow
CO2 is ____ in plasma
Solube
H2O is _____ in plasma
insoluble
Average resting PO2 at systemic capilaries
40mmHg
Normal PO2 at pulmonary capillaries
100 mmHg
Myoglobin curve
Binds O2 more tightly due to only 1 heme group, steeper curve
Hemoglobin curve
Shows cooperative binding due to 4 heme groups, sigmoidal shape.
What factors decrease hemoglobin saturation
- increased CO2
- increased acid
- increased temperature
- increased 2,3-BPG
During Hypoventilation
- Increased Co2 partial pressure
During Hyperventilation
- increased O2 partial pressures
What does the ventral respiratory group control
Controls nerves that regulate inspiration and expiration
Neural control of respiration
- Inspiratory neurons in DRG are rhythmically firing and signal travels to the medulla
- Integrator neuron travels to the phrenic nerve in the spinal chord.
- Phrenic nerve travels out of the spinal chord and stimulates the diaphragm to contract.
What so the carotid and aortic bodies sense?
Sense BP
- If BP goes up then they stimulate fibers going to the cardiovascular center
What happens when the arterial PO2 drops below 60mmHg?
Peripheral chemo receptors are stimulated which stimulates the medullary respiratory center which increased ventilation and arterial PO2
