Term
| Medullary Respiratory Center |
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Definition
* generates the spontaneous cycle of respiration
* located in reticular formation of the medulla, just under the floor of the 4th ventricle |
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Term
| Respiratory Center responds to input from: |
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Definition
* the brain
* the autonomic nervous system
* central and peripheral receptors |
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Term
| What are the 3 major groups of neurons that make up the respiratory center? |
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Definition
1. Dorsal Respiratory Group (DRG)
* deals with inspiration
2. Ventral Respiratory Group (VRG)
* deals with expiration
3. Pneumotaxic Center (located in the pons)
* controls the rate and depth of respiration |
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Term
| What is the general location of the 3 major groups of neurons that make up the respiratory center? |
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Definition
| bilaterally in the medulla oblongata and pons of the brain stem |
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Term
| Dorsal Respiratory Group (DRG) |
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Definition
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Term
| Ventral Respiratory Group (VRG) |
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Definition
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Term
| Pneumotaxic Center (located in the pons) |
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Definition
| controls the rate and depth of respiration |
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Term
| Location of Dorsal Respiratory Group (DRG) |
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Definition
| Extends the length of the medulla |
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Term
| Where are most of the neurons in the DRG located? |
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Definition
| In the nucleus of the tractus solitarius |
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Term
| What nerves transmit signals into the DRG from the peripheral chemoreceptors, baroreceptors and other lung receptors? |
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Definition
| The vagus and glossopharyngeal nerves |
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Term
| The DRG controls what aspect of respiration? |
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Definition
| the Rhythmicity of respiration (pacemaker of normal respiration) |
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Term
| How does the DRG control the Rhythmicity of respiration? |
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Definition
* works by ramping up a signal over a period of 2 seconds and then shutting down (it does not work by turning a signal on with one quick burst)
* This results in diaphragmatic stimulation and even inspiration (vs short gasps to gradually increase the lung volume)
* the shutting down is also important because it allows time for elastic passive lung recoil
* the ramping up time can be shortened during heavy breathing or exercise and the expiratory phase can also be shortened |
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Term
| Hering-Breuer Inflation Reflex |
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Definition
* when the lungs become over inflated, they signal a feedback that “switches off” the inspiratory ramp
* the over stretch leads to vagal stimulation which transmits to the DRG switching off the “ramp up” phase |
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Term
| At what point does the Hering-Breuer Inflation Reflex occur? |
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Definition
| * we think that the “over stretch” doesn’t come into play until the tidal volume is > than 1.5L (or 3x greater than normal) |
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Term
| What receptors are used in activating the Hering-Breuer Inflation Reflex? |
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Definition
| the stretch receptors in the muscle walls of the bronchi and bronchioles (they transmit important info about lung stretch to the DRG) |
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Term
| What is the main effect of the Hering-Breuer Inflation Reflex (the end result)? |
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Definition
| To protect against excessive lung inflation and barotrauma/pneumothorax |
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Term
| What can happen temporarily when the Hering-Breuer Inflation Reflex is activated? |
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Definition
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Term
| Chemical or mechanical airway irritation can result in what? |
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Definition
| A reflex cough, sneeze, hyperpnea, bronchoconstriction and increase in BP. |
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Term
| Juxtopulmonary capillary (J) receptors |
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Definition
| responsible for the subjective “shortness of breath” or dyspnea encountered during pulmonary congestion and edema due to LV failure |
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Term
| What stimulates the Juxtopulmonary capillary (J) receptors? |
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Definition
| pulmonary vascular congestion or an increase in interstitial fluid leading to tachypnea |
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Term
| Location of Juxtopulmonary capillary (J) receptors |
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Definition
| The walls of the pulmonary capillaries or interstitium |
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Term
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Definition
-innervate the pulmonary J receptors
-the afferent pathway from the J-receptors |
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Term
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Definition
| They "lie near the pulmonary microcirculation" |
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Term
| Are C-Fibers slow or fast, and are they myelinated or unmyelinated? |
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Definition
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Term
| According to the powerpoint, what nerve are C-fibers IN (within)? |
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Definition
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Term
| What lung receptors respond to interstitial fluid or pulmonary edema? (Dr. Louren's example test question from class) |
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Definition
| Juxtopulmonary capillary (J) receptors |
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Term
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Definition
| primary function is to control the switch off point of the inspiratory ramp (DPG) |
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Term
| Pneumatic Center Location |
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Definition
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Term
| What happens if the signal from the pneumatic center is strong? |
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Definition
| The inspiration lasts for a shorter period of time |
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Term
| What happens if signal from the pneumatic center is weak? |
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Definition
| The inspiration lasts for a longer period of time. |
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Term
| The pneumatic center can control respiratory rate and increase or decrease it to what levels? |
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Definition
| - Up to 30-40 bpm or as little as 3-5 bpm |
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Term
| VRG (Ventral Respiratory Group) Location |
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Definition
| In the medulla near the DRG's |
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Term
| Do the ventral respiratory group neurons fire during normal quiet breathing? |
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Definition
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Term
| VRG (Ventral Respiratory Group) |
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Definition
* Stimulation may lead to either inspiration or expiration
* These neurons provide a powerful signal to the abdominal muscles to help with exhalation during heavy breathing |
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Term
| How does the VRG "act as a contributory to the DRG"? |
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Definition
| When the respiratory drive increases, then the signals from the DRG spill over into the VRG area. |
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Term
| Ultimate goal of respiration |
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Definition
| homeostasis of oxygen, carbon dioxide, and hydrogen ions (pH) |
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Term
| The respiratory center is very sensitive to changes in the chemical concentrations of what? |
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Definition
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Term
| What effect does excessive CO2 have on the central respiratory center? |
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Definition
| Increases inspiration and expiration mechanisms |
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Term
| Does O2 directly impact the central medullary respiratory center? |
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Definition
| No, but it does act on the peripheral chemoreceptors located in the carotid and aortic bodies. |
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Term
| Can carbon dioxide directly stimulate the DRG , VRG, or pneumatic center |
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Definition
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Term
| How does carbon dioxide indirectly stimulate the DRG, VRG, and pneumatic center? |
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Definition
| Via chemosensitive neurons located near these centers that are most sensitive to changes in HYDROGEN IONS |
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Term
| Can hydrogen ions readily cross the blood brain barrier? |
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Definition
| No, because they are polar |
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Term
| Can carbon dioxide quickly cross the blood brain barrier? |
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Definition
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Term
| What happens to stimulate the respiratory center after CO2 crosses the blood brain barrier? |
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Definition
* CO2 combines with H2O to form carbonic acid
* Carbonic Acid is then dissociated into bicarbonate ions and hydrogen ions
* This is how hydrogen ions stimulate the chemoreceptors |
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Term
| Do changes in blood CO2 have a little or a huge impact on the respiratory system? |
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Definition
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Term
| What do high levels of PaCO2 do to minute ventilation? |
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Definition
| -Increase minute ventilation (in an attempt to return the pH to normal). |
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Term
| HOW LONG DOES THE CO2 DRIVEN STIMULATION OF THE CENTRAL CHEMORECEPTORS LAST? |
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Definition
| ONLY FOR A COUPLE OF DAYS |
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Term
| Why does the CO2 driven stimulation of central chemoreceptors only last for a couple of days? |
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Definition
* As levels of bicarbonate ions build, they then recombine with hydrogen ions (the formula is driven in the opposite direction).
* AND the kidneys react to the the lower pH by RETAINING bicarbonate.
* For this reason, an elevation in CO2 is a strong stimulus for a couple of days and then the effect disappears (COPD) |
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Term
True or false:
In normal circumstances, the HGB has an ability to shift its affinity and delve adequate amounts of oxygen despite changes in lung ventilation (up to a point) to tissue. |
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Definition
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Term
| What is the most effective way to impact blood oxygen concentration? |
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Definition
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Term
| What is the most effective way to impact PaCO2? |
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Definition
| By changing minute ventilation (and changing tidal volume is the most effective way to change minute ventilation) |
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Term
| What is a special mechanism for respiratory control? |
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Definition
| Peripheral chemoreceptors located OUTSIDE THE BRAIN, that work when the tissue gets in trouble due to lack of oxygen. |
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Term
| Location of peripheral chemoreceptors |
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Definition
| In the aortic root (specifically in the aortic body), and the bifurcation of the carotids (specifically the carotid bodies) |
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Term
| At what PaO2 are the peripheral chemoreceptors stimulated? |
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Definition
| When the PaO2 falls to <70mmHg |
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Term
| The peripheral chemoreceptors send signals via which nerves? |
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Definition
* Hering’s Nerve (also called the pharyngeal branch) of the GLOSSOPHARYNGEAL nerve from the carotid bodies
* AND the VAGUS NERVE from the aortic bodies. |
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Term
| When is the peripheral chemoreceptors stimulus especially important? |
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Definition
| When the PaO2 falls between 30-60 mmHg. |
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Term
| In which disease state are peripheral chemoreceptors especially important? |
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Definition
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