1. Respiratory System Physiology
“Breathing”

2. Pulmonary Ventilation
Inspiration- in
Expiration- out
Breathing occurs because of a pressure gradient between the lungs and exterior environment
Respiratory muscles control the size of the thoracic cavity setting up the gradient

3. Inspiration
When the diaphragm contracts it increases size of thoracic cavity
Intercostal muscles aid in expanding size of rib cage

5. Expiration
Is aided by elastic recoil, tendency of thorax and lungs to return to shape
When muscles relax it causes a decrease in size of thorax
Compliance is the ability of lungs to relax or stretch

7. Breathing Patterns Eupnea- normal quiet breathing
Hyperpnea- increased breathing rate and depth to meet need for O2
Hyperventilation- increased breathing rate and depth with out need for O2
Hypoventilation- slowed breathing
Dyspnea- difficult labored breathing
Apnea- cessation of breathing

8. Exchange of Gases
O2 and CO2 move across pressure gradients from the atmosphere into the lungs
Alveolar and capillary surface area is extremely large with thin walls
Capillaries in lungs have a diameter one cell thick

10. Transport of O2
Hemoglobin greatly increases the amount of O2 that can be dissolved in the blood

11. Transport of CO2
A small amount of CO2 binds amino acid groups onto hemoglobin
Most of the CO2 in blood associates with H2O to form carbonic acid H2CO3 (bicarbonate)
H2CO3 once catalyzed by carbohydrate anhydrase (enzyme) dissociates into H+ and HCO3-
Increased CO2 in the blood causes a decrease in blood pH/increase in acidity

12. Systemic Gas Exchange
As oxygenated blood enters tissues it has high Po2 and low Pco2 relative to the tissue
O2 is pulled off the hemoglobin and CO2 binds temporary to hemoglobin to form carbaminohemoglobin

14. Respiratory Control Centers
Ventilation is the rate and depth of breathing
Ventilation is controlled by the medullary rhythmicity centers of the brain
The apneustic center stimulates the inspiratory center thus increasing respiration
The pneumotaxic center inhibits the apneustic center in the brain

16. Factors that influence Breathing
Chemoreceptors in the medulla measure levels of CO2
Low levels of CO2 will decrease rate and depth of breathing
High levels of CO2 increase rate and depth of breathing
pH plays a small role in controlling breath
Blood levels of O2 seem to have little effect on breathing rate

17. Breathing Reflexes Hering-Breuer reflex maintains normal breath depth
Once tidal volume is reached, inhalation stretch receptors trigger inhibitory impulses to the inspiratory centers of the brain

18. Breathing Reflexes
Breathing can be controlled voluntarily to a certain extent
You cannot hold your breath till you die, CO2 is too strong a stimulant
Sudden stimulation - reflex apnea
Sudden cold stimuli - reflex apnea
Stimulation of pharynx or larynx causes choking reflex
Breathing can be affected by emotions

19. Breathing Reflexes Cough reflex- caused by stimulation
Sneeze reflex- air is forced out nose and mouth(100 mph)
Hiccup- caused by a spasm of diaphragm
Yawn- slow and deep breath with similar function to a stretch