Regulation of Respiration - Quiz 6 Flashcards
How does Neurogenic Regulation work?
- Nervous System manages arterial O2 & CO2
- Adjusts Ventilation Rate
- ABG’s not really affected by Exercise or Stress
What are the Major Groups of Neurons in the Brainstem?
- Dorsal Respiratory Group - primary control of breathing
- Ventral Respiratory Group
- Pneumotaxic Center
List 1 -6
- Pneumotaxic Center
- Apneutstic Center
- VRG (Expiration & Inspiration)
- Respiratory Pathways
- DRG (Inspiration)
- Fourth Ventricle
List 1 -3
- DRG
- VRG
- VRG
What are the Functions of the Dorsal Respiratory Group?
- Inspiration & Respiratory Rhythm
- Receives surrounding signal to help control respiration
Where is the Dorsal Respiratory Group located?
Along the length of the medulla inside the Nucleus of the Tractus Solitarius
What delivers Sensory Information to the Dorsal Respiratory Group?
Vagal (X) & Glossopharyngeal (IX) Nerves
What are the peripheral signal sources of the Dorsal Respiratory Group?
- Peripheral Chemoreceptors
- Baroreceptors
- Lung Receptors
How does the Dorsal Respiratory Group generate breathing rhythm?
Neurons emit repetitive bursts of inspiratory action potential
What is the Inspiratory RAMP Signal?
- Motor signal from DRG to Diaphragm - NOT instant
- Weak signal that steadily “ramps” up for 2 seconds to contract diaphgram (Inspiration)
- Signal suddenly stops for next 3 seconds for diaphragm relaxation (expiration)
What is the advantage of the RAMP Signal?
Allows for a steady increase in inspiratory volume
What ways is the RAMP Signal controlled?
Two Ways
-
Rate of RAMP signal increases
- signal increases faster w/ activity
-
Limiting Point - when RAMP stops
- the sooner the RAMP stops, the shorter the inspiratory time
- shortens expiratory time
- ↑RR
Where is the Pneumotaxic Center located?
Dorsally in the Nucleus Parabrachialis of Upper Pons
What does the Pneumotaxic Center do?
- Limits Inspiration Phase & Increase RR
- Controls Switch Off point of Inspiration
What does the Pneumotaxic Center’s strength of inhibition determine?
Duration of filling phase & Rate of Breathing Cycle
- Strong Signal =
- ↓Inspiration Time (0.5 sec) & ↑RR (30-40 bpm)
- Weak Signal =
- ↑Inspiration Time (5 sec) & ↓RR (3-5 bpm)
Where is the Ventral Respiration Group located?
Medulla - Anterior & Lateral to DRG
What does the Ventral Respiration Group do?
VRG Stimulation = expiration & inspiration
Important during Exercise
What does the Ventral Respiration Group consist of?
Nucleus Ambiguus Rostrally
Nucleus RetroAmbiguus Caudally
Which Respiratory Group is Inactive during normal quiet breathing?
Ventral Respiration Group
Which Respiration Group does NOT participate in breathing rhythm?
Ventral Respiration Group
What Respiration Group contributes to respiratory drive?
Ventral Respiration Group - to increase pulmonary ventilation
Which Respiration Group stimulates abdominal muscles for forced exhalation?
Ventral Respiration Group
What sends signals to the DRG to prevent the switch-off of inspiratory RAMP stimuli?
Apneustic Center
What works with the Pneumotaxic Center to control Inspiration Intensity?
Apneustic Center
What limits the over-inflation of the lungs?
Hering-Breuer Reflex - a protective feedback reflex
How does the Hering-Breuer Reflex work?
- Stretch receptors in the bronchi & bronchiole muscles send signals to the DRG when the lung is overstretched
- Switches off Inspiratory RAMP to stop inflation
- Increases RR
At what Tidal Volume does the Hering-Breuer Reflex activate?
> 1.5L
The stretch receptors of the Hering-Breuer Reflex sends signals to the DRG through which nerve?
Vagus Nerve
How does the Respiratory Control signals know when to decrease or increase Intensity?
Intensity increases & decreases to match Ventilatory Needs
Excess ______ or H+ in the blood act ______ on the respiratory center to increase strength of inspiratory & expiratory motor signals
Excess Carbon Dioxide in blood act directly on respiratory center
How is Oxygen involved in Chemical Control of Respiration?
Oxygen does NOT have direct effect on Respiratory Centers
Acts on Peripheral Chemoreceptors in Carotid & Aortic Bodies
The highly sensitive area on the ventral medulla that responds to PCO2 changes is also known as?
Chemo-Sensitive Area of Brain
Hydrogen Ions
- Direct stimulus to chemosensitive neurons
- Hard to cross Blood Brain Barrier
- Has less effect than blood CO2
Effects of Blood CO2
- Potent direct effect on chemosensitive area via H+
- Highly permeable to Blood Brain Barrier
How does CO2 stimulate respiratory center in the brain?
- CO2 goes to brain, reacts with H2O to form Carbonic Acid
- Carbonic acid breaks down to H+ & Bicarb
- H+ stimulates respiratory center
How is CO2 stimulation effected by chronic exposure?
- Stimulation decreases by 1/5 after 1-2 days of CO2 exposure
- Due to renal adjustment of H+ back to normal
- COPD pts have blunted CO2 response
Changes in CO2 has a potent _______ effect on controlling respiration drive, but a weak ______ effect after a few days.
CO2 has a potent acute effect, but a weak chronic effect
What drastically increases ventilation?
Increased CO2 > 35 mmHg
Decreased pH = small ventilation increase
10x less ventilation change with pH of 7.4
Why is the respiratory center not affected by oxygen changes as drastically as it responds to PCO2 changes?
Large O2 reserve created by Hemoglobin-Oxygen Buffer System
At what PO2 does the peripheral chemoreceptors sense Blood Oxygen levels?
PO2 < 70 mmHg
Which nerves are associated with Carotid Bodies
Glossopharyngeal Nerve (IX)
Common Carotid Bifurcations
Which nerves are associated with Aortic Bodies?
Vagus Nerve (X)
What other cells may function as chemoreceptors that stimulate nerve endings?
Glomus Cells
What happens when you are at significantly higher levels of elevation?
- Respiratory centers lose PCO2 & pH sensitivty over 2 days
- Oxygen drives respiratory center
- Ventilation increases > 400% in response to low PaO2
With acidosis, Ventilation increases much faster at _______ levels of PaCO2 then it would at normal pH or alkalosis
Ventilation increases faster while acidodic at lower levels of PaCO2
How much does exercise increase O2 Consumption & CO2 formation?
20x
What is the relationship between Alveolar Ventilation & Metabolism during exercise?
Direct & Linear Relationship
PO2, PCO2 & pH stays normal
What causes increase in Ventilation during Exercise?
- Brain sends collateral impulses to brainstem & motor impulses to contracting muscles - VRG
- Joint & Muscles movement
- Hypoxia in muscles
Neurogenic vs Chemical factors during Exercise
Neurogenic = stimulate respiratory to supply O2 & remove CO2
Chemical = adjusts respiratory control to keep CO2 & pH normal
How is Voluntary Respiration Controlled?
From Cortex down through spine, NOT through Respiratory Center
What are Irritant Receptors?
Sensitive nerve endings that are stimulated by noxious environmental products - cough, sneeze, asthma, emphysema
What are J Receptors?
Sensory never endings next to pulmonary capillaries.
Stimulated by blood & edema - gives feeling of dyspnea
How does head trauma affect Respiration?
Brain edema depresses respiratory center
Treatment: mechanical hyperventilation & hypertonic diuresis
What is Cheyne-Stokes breathing?
Short deep breaths then absent breaths
What causes Cheyne-Stokes breathing?
- Low Cardiac Output - long delay in transport of blood from lungs to brain
- Brain Damage - increased negative feedback due to hypoxia
O2 acts ______ on peripheral receptors
Indirectly
Direct effect of CO2 & pH is ______ times more powerful, but peripheral stimulation occurs _____ times more rapidly
Direct effect is 7x more powerful
Peripheral stimulation is 5x more rapid
At normal CO2 & pH, when does is PO2 significant for ventilatory drive
At what PaO2 does ventilation double?
Significant when PaO2 < 100 mmHg
Ventilation doubles at < 60 mmHg
Lower PO2 = Increase in ventilation drive 5x
