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Phys2 Cont of Vent

QuestionAnswer
Why is ventilation control necessary? To maintain BL PO2 and PCO2 levels. B/c O2 demand and CO2 production vary depending on what we are doing. **Hypoventilation can cause Dec PO2, Inc PCO2, and Dec pH.
What type of control system is ventilatory control? NEGATIVE feedback
Ventilatory control system: Effector Repiratory muscles (diaphragm, ext intercostals)
Ventilatory control system: Sensor 1.Chemoreceptors (regulate arterial PO2 and PCO2). 2.Lung receptors: respond to inflation and irritants.
Ventilatory control system: Controller Respiratory center in the Medulla and pons (brainstem).
Ventilatory control system: variables Arterial PO2 and PCO2.
Location of respiratory control center? Medulla and Pons
2 basic types of neurons in the respiratory control center? 1.Pattern generator: responsible for generating basic pattern breathing. 2.Integrators: integrate sensory feedback from chemorecep, lung recep, hypothalamus/Limbic system, cortex (emotions).
3 main groups of neurons controlling inspiration and expiration and their functions 1.Medullary respiratory center (most important). 2.Pneumotaxic center (upper pons): Turns off inspiration, tweeks Vt and RR. 3.Apneustic center (lower pons): Prolongs inspiration.
2 types of neurons in the medullary respiratory center 1.Dorsal respiratory group (dorsal medulla): trigger inspiration. 2.Ventral respiratory group (ventral medulla): involved with expiration, so they are inactive at rest.
What activates the inspiratory neurons? Integrator neurons. They synch up inspiration and expiration. Get EXCITATORY input from chemorecep and lung irritant recep and IHIBITORY input from "switch off" neurons. Net input determines action.
What controls the "off switch" neurons that send inhibitory signals to the Integrator neurons? Activated by: 1.Lung stretch receptors, 2.Pneumotaxic center in the upper pons. Inhibited by: 1.Apneustic area of lower pons.
Hering-Breuer reflex 1.Inflation stim lung stretch receptors. 2.CN X carries impulses to activate "off switch" n. 3.Off-swith n. inhibit intergratory n. (turning off inspir). 4.deflation of lungs leads to loss of stim of stretch recep and inh of intergrator n.
How much stretch during inhalation must occur to activate the Hering-Breuer reflex? Tidal Volume (Vt) >1L.
Hering-Breuer reflex: What affects does cigarrette smoke and cold air have on lung irritant receptors? Promoting inspiration and coughing. they accomplish this by directly activating integrator neurons.
Lung receptors: J-receptors 1.Location: Alveolar wall. 2.Stimuli: Inc interstitial fluid (Edema). 3.Neuronal pathway: CN X. 4.Effects: Rapid shallow breathing
Lung receptors: C-receptors 1.Location: Bronchioles. 2.Stimuli: chemical composition of bronchiole BL, Inflammatory mediators. 3.Neuronal pathway: 4.Effects: Bronchoconstriction and rapid shallow breathing.
What are the most important receptors in ventilation control? CHEMORECEPTORS (central and peripheral)
Central chemoreceptors Location: ventral medulla close to medullary respiratory center. Stimuli: H+ (indirectly, PCO2) in CSF, CO2 creates more H+ here than interstitially b/c of the lack of proteins. Effect: Inc Ventilation **more important for minute by minute chages.
Peripheral chemoreceptors Location: Carotid sinus, Aortic bodies. Stimuli: Dec PO2/hypoxia (ex: COPD and altitude), Inc PCO2 & H+
Can H+ ions in the BL stimulate central chemorecpetors? NO, their ionic charge wont allow them to cross the BBB
Why does CO2 have a greater H+ production effect in CSF than BL? Lower protein content in CSF to buffer the H+ (Hb does this in BL). Effect: Increased ventilation.
Which parameter is most important for control of breathing under normal conditions? Arterial PCO2 **b/c relationship b/w PCO2 and ventilation is very steep (2mmHg PCO2 Inc DOUBLES ventilaion)
Are peripheral chemoreceptors sensative to O2? why or why not? Not really, arterial PO2 must be reduced to <50mmHg in order to significantly Inc ventilation.
Why does pure O2 decrease ventilation in COPD patients? B/c they have no central chemorecep (due to body's adjustment to chronic Inc PCO2), they must rely only on peripheral chemorecep. Chronic Inc O2 will cause those receptors to dec activation & the drive to breathe is diminshed (hypoventilation, Inc PCO2)
Peripheral Vs Central Chemoreceptor's response to PCO2 Peripheral respond faster but only contribute 20% of total response to CO2. **May be due to closeness to lungs.
What chemoreceptors will be activated: Inc PCO2 1.Central 80%. 2.Peripheral 20%.
What chemoreceptors will be activated: Dec PO2 **Peripheral ONLY**
What is a typical Cheyne-stokes breathing pattern? rapid increases and then decreases in ventilation followed by prolonged apnea.
When is Cheyne-stokes commonly seen? 1.End of Life (goodbye). 2.HF.
Mechanism behind Cheyne-stokes 1.Dec CO causes slowed circulation. 2.This Dec central response time to PCO2 change. 3.Hypoxemia stimulates peripheral. 4.J-receptors cause hypervent. 5.Dec PCO2. 6.Delayed central detection of dec PCO2, then they inhibit breathing. 7.Starts over
Created by: WeeG