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33 Cards in this Set
- Front
- Back
What is Intrapleural Pressure (Pip)
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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 |
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Pressure Relationships
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• Intra-alveolar pressure and intrapleural pressure fluctuate with the phases of breathing
• Intra-alveolar pressure always eventually equalizes itself with atmospheric pressure |
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What is lung collapse?
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caused by equalization of intrapleural pressure with intra-alveolar pressure
• without negative intrapleural pressure → lungs recoil and collapse |
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pneumothorax
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air enters intrapleural space
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Gas exchange in the lungs occurs because of partial pressure differences...
Concentration gradient causes: |
• O₂ to enter blood
• CO₂ to leave blood |
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Gas exchange at the tissues occurs because of partial pressure differences...
Concentration gradient causes: |
• O₂ to enter tissues
• CO₂ to enter blood |
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Control of Respiration involves neurons in the:
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medulla and pons
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Control of Respiration in the medulla .....
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sets respiratory rhythm
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Control of Respiration in the pons .....
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influences and modifies activity of medullary neurons
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What are the two respiratory groups of the Medullary Respiratory Centers?
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Ventral Respiratory Group & Dorsal Respiratory Group
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Ventral Respiratory Group (VRG)
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• 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 |
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Dorsal Respiratory Group (DRG)
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• Integrates input from:
• Peripheral Stretch receptors • Peripheral chemoreceptors to modify rhythms generated by VRG |
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Pons Respiratory Center
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• 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 |
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DRG & pons respiratory centers receive info from _____ & _____
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DRG & pons respiratory centers receive info from peripheral receptors & higher brain centers
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Breathing rate
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determined by how long inspiratory center is active (breaths per minute)
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Breathing depth
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more stimulation → more motor units excited → greater force of breath
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Factors that include breathing rate & depth are:
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• Chemical****
• CO₂ • O₂ • pH • Reflexes • Higher Brain Centers • Exercise • Pain, emotional stimuli |
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Chemoreceptos
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sensors that respond to chemical flucuations
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What are the two chemoreceptors?
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central chemoreceptors & peripheral chemoreceptors
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What are the two locations of the chemoreceptors?
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• central chemoreceptors - medulla
• peripheral chemoreceptors - aortic arch & carotid arteries |
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Factors influencing breathing rate and depth: PCO₂
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• CO₂ - most potent and closely controlled chemical
• Mediated mainly be central chemoreceptors detecting rising CO₂ |
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Hyperventilation
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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 |
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Hypoventilation
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slow and shallow breathing due to abnormally low PCO₂ levels
• Apnea (breathing cessation) - may occur until PCO₂ levels rise |
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Apnea (breathing cessation)
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may occur until PCO₂ levels rise
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Peripheral chemoreceptors
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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 |
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Factors influencing breathing rate and depth: arterial pH
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central chemoreceptors and peripheral chemoreceptors
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Central chemoreceptors
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insignificantly affected by H+ from arterial blood
• little H+ diffuses from blood into CSF |
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CO₂ and H+ are _____ → but they are distinct stimuli
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• Drop in pH may reflect an increase in CO₂ but...
• Can reflect other acid accumulation (e.g. lactic acid) |
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Body compensates for low pH by eliminating _____ by increasing breathing & respiratory rate.
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CO₂
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Body compensates for low pH by eliminating CO₂ by increasing breathing & respiratory rate.
Why does this make sense? |
CO₂ + H₂O ⇋ H₂CO₃ ⇋ H+ + HCO₃-
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Inflation reflex (Hering-Breuer reflex)
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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) |
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Pulmonary irritant reflex
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irritating physical/chemical stimuli in nasal cavity, larynx, and bronchial tree
• stimulate cough in trachea or bronchi • stimulate sneeze in nasal cavity |
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Factors influencing breathing rate and depth
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enter here
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