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What are respiratory muscles controlled by?
Motor neurons
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What part respiration is th phrenic nerve a part of and what does it control?
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What part of respiration is the external intercostal nerve a part of and what does it control?
- Inspiration
- External intercostal muscles
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What part of respiration is the internal intercostal nerve a part of and what does it control?
- Expiration
- Internal intercostal muscles
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What are the 2 types of breathing?
- Quiet - contraction of inspiratory muscles = burst of APSs, no contraction of expiratory muscles
- Active - contraction of inspiratory muscles = large burst of APs, contraction of expiratory muscles = burst of APs
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What components generate the breathing rhythm?
- Inspiratory/Expiratory Neurons
- Respiratory Control Centres of Medulla
- Respiratory Control Centres of Pons
- Central Pattern Generator
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What does the central pattern generator establish?
Respiratory Cycle
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What are the 3 levels of control in respiration?
- 1. Respiratory rhythmicity centers - medulla oblongata (DRG & VRG), control basic breathing
- 2. Apneustil and Pneumotaxic Centers - pons, adjust output of respiration (rate and depth)
- 3. Higher Centers - hypothalamus, limbic system, cerebral cortex, important but not crucial for survival
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What receptors are a part of peripheral input to respiratory centers?
- Chemoreceptors
- Pulmonary stretch receptors
- Irritant receptors
- Muscle and join proprioceptors
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What do chemoreceptors do?
Detect blood levels of O2 and CO2
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What are the 2 types of chemoreceptors?
- Peripheral in carotid bodies
- Central in medulla oblongata
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What do peripheral chemoreceptors mainly respond to?
Changes on blood pH
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What levels of PCO2 in blood result in coma and death?
- Coma >90 mm Hg
- Death >180 mm Hg
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What do central chemoreceptors respond to?
- Changes in pH of CSF
- Not directly responsive to CO2, repsonds via pH (^CO2 = \/pH)
- Not responsive to [O2]
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What are the steps of the response to hypoventilation?
- Decreased O2 b/c less breathing
- Increased [H+] from increase CO2
- Chemoreceptors fire
- Ventilation increased
- Negative feedback to PCO2, [H+], PO2
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What are the steps of the response to hyperventilation?
- Increased PO2
- Decreased [H+] from decreased PCO2
- Chemoreceptors fire
- Ventilation decreased
- Negative feedback to PCO2, [H+], PO2
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What is ventilation?
Rate of air flow
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What is perfusion?
Rate of blood flow
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What is the ventilation-perfusion ratio?
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If there is an obstruction of an airway, what occurs?
- VA/Q decreases
- No exchange so \/ O2 ^ CO2 in blood, blood flow functioning normally
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If there is an obstruction of blood flow, what occurs?
- VA/Q increases
- Same exchange but in less blood due to lower blood flowing past alveoli so ^O2 \/CO2 in blood, alveoli are functioning normally
- Vasodilation/constriction of vessels/alveoli to compensate
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How does an increase in PO2 affect bronchioles and pulmonary arterioles?
- Bronchoconstriction
- Vasodilation
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How does an increase in PCO2 affect bronchioles and pulmonary arterioles?
- Bronchodilation
- Vasoconstriction (increase amount of blood that come in contact with alveoli)
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What is normal blood pH?
7.4
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What body systems regulate blood pH?
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What is acidosis and what can it cause?
- Blood pH < 7.35
- CNS depression
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What is alkalosis and what can it cause?
- Blood pH > 7.45
- CNS over-excitation
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What are 2 things that can act as buffers in blood?
- Hemoglobin (Hb + H+ <--> HbH)
- Bicarbonate ions (HCO3- + H+ <--> H2CO3 <--> CO2 + H2O)
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What is the Henderson-Hasselbalch Eqn?
pH = 6.1 + log [HCO3-]/[CO2]
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To maintain normal arterial pH at 7.4, what must the ratio of HCO3- and CO2 be?
20:1
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What system regulates [CO2]?
Respiratory System
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What system regulates [HCO3-]?
Renal (Kidneys)
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What is respiratory acidosis caused by?
Increased [CO2]
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What is respiratory alkalosis caused by?
decreased [CO2]
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