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33 Cards in this Set

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What is Intrapleural Pressure (Pip)
pressure in space between parietal & visceral pleura (also fluctuates with breathing) (~ slight vacuum)
• Should be ~ −4 mm Hg at rest
** remains below atmospheric pressure (Patm) throughout respiratory cycle
Pressure Relationships
• Intra-alveolar pressure and intrapleural pressure fluctuate with the phases of breathing
• Intra-alveolar pressure always eventually equalizes itself with atmospheric pressure
What is lung collapse?
caused by equalization of intrapleural pressure with intra-alveolar pressure
• without negative intrapleural pressure → lungs recoil and collapse
pneumothorax
air enters intrapleural space
Gas exchange in the lungs occurs because of partial pressure differences...

Concentration gradient causes:
• O₂ to enter blood
• CO₂ to leave blood
Gas exchange at the tissues occurs because of partial pressure differences...

Concentration gradient causes:
• O₂ to enter tissues
• CO₂ to enter blood
Control of Respiration involves neurons in the:
medulla and pons
Control of Respiration in the medulla .....
sets respiratory rhythm
Control of Respiration in the pons .....
influences and modifies activity of medullary neurons
What are the two respiratory groups of the Medullary Respiratory Centers?
Ventral Respiratory Group & Dorsal Respiratory Group
Ventral Respiratory Group (VRG)
• Rhythm generating
• Integrative center
• Excites "quiet" inspiratory muscles & sets normal respiratory rate & rhythm
• Inspiratory neurons (2 seconds)
• signal contraction of diaphragm & external intercostals
• Expiratory neurons (3 seconds)
• output stops, inspiration ceases
• passive expiration
Dorsal Respiratory Group (DRG)
• Integrates input from:
• Peripheral Stretch receptors
• Peripheral chemoreceptors

to modify rhythms generated by VRG
Pons Respiratory Center
• influences & modifies activity of medullary respiratory center
• "smooths out" inspiration and expiration transitions
• e.g. modifies breathing rhythm set by VRG during vocalization, sleep & exercise

• DRG & pons respiratory centers receive info from peripheral receptors & higher brain centers
DRG & pons respiratory centers receive info from _____ & _____
DRG & pons respiratory centers receive info from peripheral receptors & higher brain centers
Breathing rate
determined by how long inspiratory center is active (breaths per minute)
Breathing depth
more stimulation → more motor units excited → greater force of breath
Factors that include breathing rate & depth are:
• Chemical****
• CO₂
• O₂
• pH
• Reflexes
• Higher Brain Centers
• Exercise
• Pain, emotional stimuli
Chemoreceptos
sensors that respond to chemical flucuations
What are the two chemoreceptors?
central chemoreceptors & peripheral chemoreceptors
What are the two locations of the chemoreceptors?
• central chemoreceptors - medulla
• peripheral chemoreceptors - aortic arch & carotid arteries
Factors influencing breathing rate and depth: PCO₂
• CO₂ - most potent and closely controlled chemical
• Mediated mainly be central chemoreceptors detecting rising CO₂
Hyperventilation
increased depth and rate of breathing
• Quickly flushes CO₂ from blood
• Occurs in response to high CO₂
➤ Though a rise in CO₂ act as original status → control of breathing is actually regulated by H+ concentration in the brain
Hypoventilation
slow and shallow breathing due to abnormally low PCO₂ levels
• Apnea (breathing cessation) - may occur until PCO₂ levels rise
Apnea (breathing cessation)
may occur until PCO₂ levels rise
Peripheral chemoreceptors
in aortic bodies & carotid bodies
• Sensitive to O₂ changes (and CO₂)
• Usually only respond to large changes in O₂ (vs very sensitive CO₂ receptors)
• ok because we have large O₂ reservoir bound to Hb
• drop in pH results in an increase in respiratory and breathing rate
Factors influencing breathing rate and depth: arterial pH
central chemoreceptors and peripheral chemoreceptors
Central chemoreceptors
insignificantly affected by H+ from arterial blood
• little H+ diffuses from blood into CSF
CO₂ and H+ are _____ → but they are distinct stimuli
• Drop in pH may reflect an increase in CO₂ but...
• Can reflect other acid accumulation (e.g. lactic acid)
Body compensates for low pH by eliminating _____ by increasing breathing & respiratory rate.
CO₂
Body compensates for low pH by eliminating CO₂ by increasing breathing & respiratory rate.

Why does this make sense?
CO₂ + H₂O ⇋ H₂CO₃ ⇋ H+ + HCO₃-
Inflation reflex (Hering-Breuer reflex)
stretch receptors in airways respond to changes in lung volume
• lungs stretched during inspiration
• send signal to control center to inhibit inspiration

• lungs recoil during expiration
• send signal to control center to stimulate inspiration

Thought to be a protective response (to prevent excessive stretching of lungs)
Pulmonary irritant reflex
irritating physical/chemical stimuli in nasal cavity, larynx, and bronchial tree
• stimulate cough in trachea or bronchi
• stimulate sneeze in nasal cavity
Factors influencing breathing rate and depth
enter here