Respiration during Exercise (1) Flashcards
What is the primary purpose of the respiratory system?
To maintain arterial blood-gas homeostasis
maintenance of arterial blood-gas
homeostasis is accomplished by a 4-step process. What are the 4 steps?
- Pulmonary ventilation
- Alveolar gas exchange
- Gas transport
- Systemic gas exchange
What does the epiglottis do?
Separates the upper and lower respiratory tracts.
The lungs are enclosed within membranes called..?
Pleura
Is intrapleural pressure > or < than atmospheric pressure?
Intrapleural pressure < atmospheric pressure, which prevents the alveoli from collapsing
There are ~23 airway generations. What is the main bronchi?
The main bronchi is Z1; the conducting zone extends to the terminal bronchioles (Z16)
In terms of the airways, where does gas exchange occur?
Gas exchange occurs in the respiratory zone (Z17-23)
Where does pulmonary gas exchange take place?
Across the pulmonary capillary
How do O2 and CO2 move between air and blood?
Simple diffusion (high to low partial pressure)
There are 2 types of alveolar cell (pneumocytes), what are they?
o Type I cells cover ~95% of the internal
surface of the alveolus and are critical for gas exchange
o Type II cells release surfactant—a molecule that lowers the surface tension (like soap) - without surfactant alveoli would collapse.
What is the volume of gas passing through a sheet dependent upon?
- Surface area (A)
- Thickness (T)
- Diffusion coefficient (D)
- Pressure gradient (alveolar to arterial)
Alveolar gas has a diffusion path to the erythrocyte and includes 5 layers, what are these ?
- Surfactant (not shown)
- Alveolar epithelium (EP)
- Interstitium (IN)
- Capillary endothelium (EN)
- Plasma
The blood-gas barrier is very thin (0.3 μm) and has a vast surface area (50-100 m2) making it ideal for gas exchange/diffusion (Fick’s law)
The mechanics of breathing is concerned with the movement of air into and out of the lungs by changes in..?
pressure, flow and volume
contraction length = change in volume
contraction velocity = change in flow
contraction force = change in pressure
What does the bucket handle motion do?
increases the transverse (lateral) diameter of the thorax during
inspiration
What does the pump handle motion of the ribs do?
increases the anteroposterior diameter of the thorax during inspiration
What muscle is responsible for the majority of pulmonary ventilation at rest?
Diaphragm contraction (expiration is passive)
During exercise, what muscle are the diaphragm assisted by?
external intercostal muscles, scalenes,
sternocleidomastoid and many others in
order to increase pulmonary ventilation 10 20-fold above resting levels
When expiration become active, contraction of what muscles happen?
contraction of the rectus abdominis, internal intercostal muscles and external oblique (among others)
What is Ohm’s law?
o Current = voltage/resistance, applied to breathing
o Airflow is dependent upon a pressure gradient and airway resistance
What is Poiseuille’s law?
o Resistance is dependent upon length and radius of a tube
o Radius is raised to the fourth power, thus the major determinant of airway resistance
What is the difference between a volume and a capacity?
- A volume is one segment
- A capacity is two or more segments
What is ‘dead space’?
Not all air breathed reaches the alveoli; the volume of air not participating in gas
exchange is called dead space.
What is forced vital capacity ?
the maximum volume air that can be forcefully expired after a maximum inspiration
COPD is characterised by increased airway resistance and a reduced FEV1/FVC
