Term
| What is functional residual capacity? |
|
Definition
| The amount of air found in the lungs at rest just before inspiration begins |
|
|
Term
| Why are the lungs and thoracic wall in stable equilibrium at rest? |
|
Definition
| There is a negative intrapleural pressure (-4) |
|
|
Term
| How does inspiration begin? |
|
Definition
Diaphragm contracts down, inspiratory intercostals expand out --> increase in thoracic cavity volume
Intrapleural pressure becomes -6! |
|
|
Term
|
Definition
| At an increase in Pip, lungs are no longer in equilibrium with the thoracic wall and expand |
|
|
Term
| How is pressure related to volume? |
|
Definition
| An increase in volume causes a DECREASE in pressure --> P = 1/V |
|
|
Term
| When does air flow into the alveoli? |
|
Definition
| Pressure decreases to a negative pressure in the alveoli as lung volume expands --> F = Patm - Palv/R. Since F is positive, air flows into alveoli until pressure is atmospheric again. |
|
|
Term
| How does expiration occur? |
|
Definition
The diaphragm and inspiratory intercostals relax, and lungs recoil
Air is compressed as volume decreases, thus air flows OUT into the atmosphere to equalize |
|
|
Term
| When do expiratory intercostals and abdominal muscles contract? |
|
Definition
Only under strenuous conditions
Normally expiration is a passive process. |
|
|
Term
| What 3 physical factors affect air passage and ventilation? |
|
Definition
- Lung compliance
- Alveolar surface tension
- Airway resistance |
|
|
Term
|
Definition
| The ability of a substance to be stretched or distended |
|
|
Term
|
Definition
Cl - Compliance = volume/ (Ppul - Pip). Volume / pressure.
Higher = easier to expand. Lower = requires more energy, rapid breathing
**Caused by thickening of connective tissue due to scarring |
|
|
Term
| What is alveolar surface tension? |
|
Definition
Surfaces of alveoli are lined with a film that breaks tension. Alveolar surfectant disrupts the properties of water, reducing surface tension! Comprised of 90% lipid, 10% protein
**Surfectant INCREASES lung compliance
IRDS - infants did not produce surfectant |
|
|
Term
| What is airway resistance? |
|
Definition
| Friction or drag in response to flow: Flow = Pressure/Resistance |
|
|
Term
| What factors increase airway resistance? |
|
Definition
- Decreased diameter
- Increased length
- Decreased pressure
- Decreased Lateral traction - fibers pulling outwards
- Increased mucous
- Tumors/blockage
- Chemicals that constrict - Histamine, Ach, irritants |
|
|
Term
| Where is airway resistance greatest? |
|
Definition
|
|
Term
|
Definition
| Hyperresponsiveness of SM --> bronchospasms. Inflammation and mucous accumulation. |
|
|
Term
|
Definition
- Chronic bronchitis - excess mucous production in the bronchi leads to inflammation. Chronic cough
- Emphysema - Deterioration of alveolar walls, collapse of small air ways |
|
|
Term
| How do infections/tumors affect resistance? |
|
Definition
| Blockage of airways increases resistance |
|
|
Term
| What are the different kinds of pressure relationships in the thoracic cavity? |
|
Definition
- Transpulmonary - +4, The pressure difference between Ppul and Pip --> 0 - (-4) = 4. The force that holds lungs open.
- Intrapleural = -4 less that Patm, inside the pleural cavity. Always negative!
- Intrapulmonary - 0, pressure within the alveoli. Equilibrates with atmospheric pressure (0) at end of expiration |
|
|
Term
| What is absolute and relative scale? |
|
Definition
- Absolute - 760
- Relative - 0 mmHg |
|
|
Term
| Why is Pip perpetually negative? |
|
Definition
The visceral pleura recoils inward, while the parietal pleua recoils outward, creating a vacuum.
**Negative pressure and surface tension keeps pleural sac from pulling apart |
|
|
Term
| What are properties of the lungs and thoracic wall? |
|
Definition
- Elasticity - resists stretching, attempts to return to original position
- Lungs recoil inwards due to elastin and collagen
- Thoracic wall recoils outwards due to bone and muscle |
|
|
Term
| What are the anatomical differences between inspiration and expiration? |
|
Definition
- Inspiration - inspiratory intercostals and diaphragm
- Expiration - Expiratory intercostals and abdominal muscles |
|
|
Term
| What controls rhythmic excitation of breathing? |
|
Definition
Medullary inspiratory neurons discharge w/ inspiration, stop with expiration - via direct input or interneurons.
**Sensitive to barbs and morphine |
|
|
Term
| What chemoreceptors affect inspiratory medullary neurons? |
|
Definition
- Peripheral chemoreceptors - carotid bodies (in the neck) and aortic bodies, sensitive to PO2, PCO2
- Central chemoreceptors - in MEDULLA, provide input to medullary inspiratory neurons. |
|
|
Term
| What affects peripheral chemoreceptors? |
|
Definition
- Low O2 - increases discharge, stimulating medullary neurons to increase ventilation
- Increased CO2 - increases ventilation |
|
|
Term
| What affects central chemoreceptors? |
|
Definition
| H+ - increase H+ increases ventilation |
|
|
Term
| What are protective reflexes? |
|
Definition
A cough or sneeze, deep inspiration followed by violent expiration
**Stretch receptors are inhibitory, in the lungs
**Sensory in the muscles are stimulatory |
|
|
