Quiz 6 Regulation of Respiration Flashcards
Where does the most fundamental role in control of breathing take place?
Dorsal respiratory group of neurons located in the Medulla Oblongata.
What area of the brain is responsible for sleep?
Reticular Activating System (RAS)
Which nerves deliver sensory info to the Dorsal Respiratory Group (DRG)?
Glossopharyngeal (IX) and Vagus (X)
What are the 3 sources of peripheral sensory signals that aid in respiration control?
- Peripheral Chemoreceptors
- Baroreceptors
- Lung receptors
What does the Dorsal Respiratory Group (DRG) do?
Controls inspiration and respiratory rhythm
normal rhythmic breathing
Describe the Inspiratory “Ramp” Signal
Motor signal from DRG transmitted to Diaphram
- Weak signal begins to steadily increase in ‘ramp like’ manner for 2 sec to cause diaphragm contraction (inspiration)
- excitatory signal abruptly stops for 3 sec for diaphragm relaxation (expiration)
What is the advantage to having the “ramp” signal to the diaphragm?
Causes a steady increase in inspiratory volume
What can cause the ramp signal to the diaphragm to increase?
exerise
If the ‘ramp’ signal to the diaphram gets shorter (limiting point ceases), what happens to respiration?
The inspiration will get shorter -> shortens duration of inspiration -> increased frequency of respiration
What is the function of the Pneumotaxic Center?
functions to limit inspiratory phase and secondarily leads to increase rate of breathing.
Controls ‘on/off’ of the inspiratory point & shortens entire respiratory cycle
What will the strength of signal from the Pneumotaxic Center do to respirations?
Strong signal - shorter insp phase (0.5 sec) and increased rate (30-40bpm)
Weak signal - long insp phase (5 sec) & reduced rate (3-5 bpm)
What are the 3 groups of neurons that control respiration?
Dorsal Resp Group (DRG)
Pneumotaxic Center
Ventral Resp Group (VRG)
When is the Ventral Resp Group stimulation to breath most likely to occur?
during exercise - during high levels of pulmonary ventilation
Is the VRG active during normal quiet respirations?
No, the DRG is responsible for normal quiet respirations (VRG inactive during this time)
Does VRG contribute to respiratory drive to increase pulmonary ventilation?
Yes, it also stimulates abdominal muscles to assist in forced exhalation
What do experts believe the “Apneustic” Center, located in the lower Pons, function to be?
- Signals the DRG to prevent or retard the ‘switch off’ of the inspiratory ramp stimuli
- works in conjunction with the Pneumotaxic Center to control intensity of inspiration
What is the Hering-Breuer Reflex?
Protective feedback reflex which limits the over inflation of the lungs
- Reflex increases the rate of respiration
What is the ultimate goal of respiration?
maintain proper concentrations of oxygen, CO2, and hydrogen ions in the tissue
Excess ____________ or ___________ ions in the blood act DIRECTLY on the respiratory center to increase strength of insp and exp motor signals
Carbon Dioxde or Hydrogen ions
Does Oxygen have a direct effect on respiratory centers?
No. But it does act on peripheral chemoreceptors.
What peripheral chemoreceptors does oxygen work on?
Carotid and aortic body chemoreceptors
Where is the chemo-sensitive area of brainstem and what does it respond to?
Located in the ventral medulla surface, responds to changes in blood PCO2 and H+ concentration.
How does Hydrogen and CO2 stimulate the chemosensitive neurons in the ventral medulla surface?
Blood H+ do not cross the blood-brain barrier easily. CO2 believed to stimulate the neurons s/t H+ ion concentration.
CO2 will combine with H2O to form carbonic acid which dissociated will form H+ and bicarb. The released H+ will stimulate the resp center activity.
Which has a higher concentration of CO2, the brain or the blood?
both are equal since CO2 easily crosses the BBB.
After first 1 to 2 days of carbon dioxide exposure the stimulatory respiration response declines to a _______ of the initial response.
fifth
What causes the decline of the increased CO2 stimulatory response?
Renal adjustment of hydrogen concentration back to normal
Changes in blood CO2 concentration has potent _____ effect on controlling respiration drive but a weak _______ effect after a few days of adaptation.
Acute, Chronic
At what level of PCO2 does ventilation greatly increase?
35mm Hg
Why does O2 NOT have the effect CO2 has on the respiratory center?
This is due to the Hemoglobin-oxygen buffer system.
What is the Hemoglobin-oxygen buffer system?
Deliver normal amounts of O2 to tissues over wide range of pulmonary O2 partial pressures (60mmHG to 1000mmHg).
Blood oxygen levels below PO2 of _____mmHg are sensed by peripheral chemoreceptors.
70
Where are the peripheral chmoreceptors located?
CAROTID bodies:
- bifurcations in common carotid
- Afferent nerve fibers pass via CN IX to act on DRG
AORTIC bodies:
- Aortic arch
- CN X to DRG
Stimulation of chemo-receptors is caused by __________ arterial ________ content.
decrease, oxygen
T/F: Exact means of low PO2 stimulation of nerve endings in carotid & aortic bodies for chemo receptors stimulation is unknown.
True
If the CO2 and pH remain normal the ventilatory drive by low blood oxygen content is not significant until PO2 falls below _______mmHg.
100
Loss of sensitivity to CO2 or H ions allows ______ to drive the respiratory center.
oxygen
What effects alveolar ventilation?
- PCO2
- pH
- PO2
What does it mean when the curve on the alveolar ventilation curve is displaced to the RIGHT?
Higher pH (alkalosis)
What does it mean when the curve on the alveolar ventilation curve is displaced to the LEFT?
Lower pH (acid)
What is measure on the x-axis on the alveolar ventilation curve?
PaCO2
What is measured on the y-axis on the alveolar ventilation curve?
Ventilation L/min
What causes increases in ventilation during exercise?
- Brain transmits collateral impulses to brain stem and motor signals to contracting muscles, VRG
- During exercise the body movements of joint & muscle proprioceptors transmit excitory impulses to respiratory center
- Hypoxia in muscles during exercise elicits afferent nerve signals to excite respiration center
- The PCO2 and PO2 changes caused by exercising muscles stimulate respiration
T/F: Voluntary control is not mediated through respiratory center.
True
Describe the pathway in the brain for voluntary control of ventilation.
Starts:
Cortex/higher centers –>
cortispinal tract —>
spinal neurons that drive respiratory muscles.
What causes a cough?
Pulmonary irritant receptors that are found in the epithelium of trachea, bronchi, and bronchioles.
Pulmonary irritant receptors may also cause _______ constriction in diseases such as ______ and _________.
bronchial, asthma, emphysema
What and where are “J receptors” found?
sensory nerve endings in alveolar walls
What is believe to be the “J receptors” function?
Their excitation may give the feeling of dyspnea
What occurs to the respiratory center during brain edema?
Activity is depressed or inactivated due to decreased blood flow.
Name one form of periodic breathing.
Cheyne-Stokes breathing
T/F: The potential for Cheyne-Stoke breathing is present in everyone.
TRUE
What are two conditions that allow Cheyne-Stokes breathing?
- Delay in transport of blood from lungs to brain (low CO2)
- Eleveated negative feedback gain (brain damage) due to hypoxia or severe metabolic abnormality.
What dampens the mechanism for Cheyne-Stokes breathing?
- Large amounts of dissolved and bound CO2 and O2 in blood and tissue
- Lungs cannot build-up enough CO2 or deplete O2 supply normally
