3.4 Levitzsky
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Questions and Answers

What initiates breathing in the central nervous system?

  • Commands from the hypothalamus
  • Neurons located in the brainstem (correct)
  • Information from receptors in contact with the cerebrospinal fluid
  • Reflexes arising in the lungs

    • In eupneic states, how does breathing occur?

  • By reflex actions in the lungs and airways
  • By information from receptors in contact with the cerebrospinal fluid
  • Without a conscious initiation of inspiration and expiration (correct)
  • Through commands from higher centers of the brain

    • What forms the 'final common pathway' for respiratory control in the brainstem?

  • Spinal cord, phrenic nerves, and respiratory muscles (correct)
  • Cerebrospinal fluid receptors
  • Airway reflexes
  • Higher centers of the brain

    • What determines the depth of respiration or tidal volume?

    <p>Frequency of neural discharges transmitted by individual nerve fibers</p> Signup and view all the answers

    Where are the centers that initiate breathing located?

    <p>In the reticular formation of the medulla</p> Signup and view all the answers

    Which area is known as the medullary center or medullary respiratory center?

    <p>Nucleus of the Tractus Solitarius</p> Signup and view all the answers

    What is the function of inspiratory neurons in the dorsal respiratory groups?

    <p>Responsible for maintaining activity of diaphragm</p> Signup and view all the answers

    What happens if the brainstem is transected below the area where breathing initiation centers are located?

    <p>Breathing ceases</p> Signup and view all the answers

    Where do inspiratory neurons in the dorsal respiratory groups mainly project to?

    <p>Contralateral spinal cord</p> Signup and view all the answers

    What do the dorsal respiratory groups consist mainly of?

    <p>Inspiratory neurons</p> Signup and view all the answers

    Where is the primary projection site of visceral afferent fibers of the ninth and tenth cranial nerves?

    <p>Dorsal respiratory group</p> Signup and view all the answers

    Which neurons primarily innervate the ipsilateral laryngeal, pharyngeal, and tongue muscles for breathing?

    <p>Vagal motorneurons in the nucleus ambiguus</p> Signup and view all the answers

    What is the main function of the Ventral Respiratory Group (VRG) neurons?

    <p>To drive spinal respiratory neurons</p> Signup and view all the answers

    Which population of cells in the DRG increase their activity if lung inflation is withheld?

    <p>I   cells</p> Signup and view all the answers

    Where are the expiratory neurons located in the ventral respiratory groups?

    <p>Nucleus retroambigualis</p> Signup and view all the answers

    What is the role of I   cells if lung inflation is withheld?

    <p>Increase their activity</p> Signup and view all the answers

    Which neurons are involved in maintaining the patency of the upper airway?

    <p>Vagal motorneurons in the nucleus ambiguus</p> Signup and view all the answers

    What is the location of DRG within the NTS responsible for?

    <p>Integration of various inputs affecting respiratory rhythm</p> Signup and view all the answers

    What is the main function of the pontine respiratory groups in the brainstem?

    <p>Fine-tuning the breathing pattern</p> Signup and view all the answers

    What is the result of apneusis when induced by the transection in the brainstem?

    <p>Prolonged inspiratory efforts interrupted by occasional expirations</p> Signup and view all the answers

    Where are the pontine respiratory groups located in the brainstem?

    <p>Upper pons</p> Signup and view all the answers

    What is the likely role of pulmonary inflation afferent information in relation to the pontine respiratory groups?

    <p>Inhibition of the pontine respiratory group activity</p> Signup and view all the answers

    Which group of neurons is suggested to be associated with the normal 'inspiratory cutoff switch'?

    <p>Apneustic center neurons</p> Signup and view all the answers

    What is suggested to be the cause of apneusis according to the text?

    <p>Sustained discharge of medullary inspiratory neurons</p> Signup and view all the answers

    'Apneusis' is a result of what according to the text?

    <p>'Inactivation of inspiratory cutoff mechanism'</p> Signup and view all the answers

    Which receptors are activated in the Hering-Breuer inflation reflex?

    <p>Slowly adapting pulmonary stretch receptors</p> Signup and view all the answers

    What is the afferent pathway in the Hering-Breuer inflation reflex?

    <p>Vagus nerve</p> Signup and view all the answers

    What is the efferent limb of the Hering-Breuer inflation reflex responsible for?

    <p>Bronchodilation and increased heart rate</p> Signup and view all the answers

    What is the threshold tidal volume range required to elicit the Hering-Breuer inflation reflex in unanesthetized humans?

    <p>$800-1500$ mL</p> Signup and view all the answers

    What effect does abrupt deflation of the lungs have on ventilatory rate?

    <p>Increases ventilatory rate</p> Signup and view all the answers

    Which receptors might play a role in periodic spontaneous deep breaths that help prevent atelectasis?

    <p>$J$ receptors</p> Signup and view all the answers

    'Sighs' consisting of slow deep inspirations followed by slow deep expirations are important for maintaining what in infants?

    <p>$FRCs$ (functional residual capacities)</p> Signup and view all the answers

    Where are the receptors for the paradoxical reflex of the head located?

    <p>In the lungs</p> Signup and view all the answers

    What effect does lung inflation have on inspiratory effort according to the Hering-Breuer inflation reflex?

    <p>Cessation of inspiratory effort</p> Signup and view all the answers

    What is the effect of low PaO2 and high PaCO2 on arterial chemoreceptors?

    <p>Apnea or tachypnea; bronchoconstriction</p> Signup and view all the answers

    What reflex is triggered by mechanical or chemical irritation of the airways?

    <p>Cough or sneeze reflex</p> Signup and view all the answers

    Where are the receptors responsible for the J receptors reflex believed to be located?

    <p>Pulmonary capillaries or interstitium</p> Signup and view all the answers

    Which nerve is responsible for transmitting information from the carotid body, one of the arterial chemoreceptors?

    <p>Glossopharyngeal nerve</p> Signup and view all the answers

    What physiological response may be caused by stimulation of J receptors?

    <p>Tachypnea</p> Signup and view all the answers

    What causes apnea or rapid shallow breathing in response to pulmonary embolism?

    <p>Pulmonary vascular congestion</p> Signup and view all the answers

    What is the primary stimulus to ventilation that is very powerful and surpasses minute ventilations obtained with hypercapnia?

    <p>Elevated level of carbon dioxide</p> Signup and view all the answers

    What is the most important input to the ventilatory control system in establishing breath-to-breath levels of tidal volume and ventilatory frequency?

    <p>Arterial PCO2</p> Signup and view all the answers

    What happens to arterial PCO2 during severe exercise according to the text?

    <p>It changes little</p> Signup and view all the answers

    Which stimuli is postulated to produce dyspnea in patients with congestive heart failure?

    <p>Right ventricular strain</p> Signup and view all the answers

    What is the effect of stimulation of the arterial baroreceptors by elevated blood pressure?

    <p>Apnea</p> Signup and view all the answers

    What type of pain generally causes hyperpnea according to the text?

    <p>Somatic pain</p> Signup and view all the answers

    Which stimuli leads to bronchoconstriction based on the information provided?

    <p>Hypoxemia</p> Signup and view all the answers

    How can spontaneous rhythmicity generated in the medullary respiratory center be temporarily overwhelmed?

    <p>By influences from higher brain centers</p> Signup and view all the answers

    What is the effect of stimulating the arterial chemoreceptors according to the text?

    <p>Dilation of upper airway</p> Signup and view all the answers

    How does metabolic acidosis affect ventilation?

    <p>Increases ventilation</p> Signup and view all the answers

    What is the primary mechanism responsible for the depressed ventilatory response to hypercapnia in chronic obstructive lung diseases?

    <p>Central acid-base changes</p> Signup and view all the answers

    How does the respiratory control system respond to increased metabolic production of carbon dioxide?

    <p>Increases alveolar ventilation</p> Signup and view all the answers

    In the context of the text, what is exemplified by the negative feedback system of the respiratory control system?

    <p>Response to carbon dioxide</p> Signup and view all the answers

    Why does anemia (without acidosis) not stimulate ventilation according to the text?

    <p>Because arterial PO2 is normal</p> Signup and view all the answers

    What is the primary reason for ventilation increasing above oxygen consumption at high work levels during exercise?

    <p>Increased lactic acid production</p> Signup and view all the answers

    What characterizes the ventilatory response to constant work-rate exercise?

    <p>A final steady-state phase if exercise is too severe</p> Signup and view all the answers

    What contributes to the immediate increase in ventilation at the beginning of exercise?

    <p>Neural component</p> Signup and view all the answers

    What is a possible explanation for the unexplained aspects of the ventilatory response to exercise according to the text?

    <p>Neural factors</p> Signup and view all the answers

    How does hypoxia alone influence arterial PCO2 according to the text?

    <p>It may lead to respiratory alkalosis</p> Signup and view all the answers

    What is the 'set point' for the respiratory control system as mentioned in the text?

    <p>Normal PaCO2 of 40 mm Hg</p> Signup and view all the answers

    Where are the central chemoreceptors located, according to the text?

    <p>Near the ventrolateral surface of the medulla in the brainstem</p> Signup and view all the answers

    What is the main response of peripheral chemoreceptors to elevated PCO2, decreased PO2, or decreased pH?

    <p>Increase their firing rate</p> Signup and view all the answers

    What may stimulate the arterial chemoreceptors apart from elevated PCO2?

    <p>Increased potassium ion concentration</p> Signup and view all the answers

    What is suggested to be the reason behind certain drugs like cyanide stimulating the carotid body?

    <p>Blockage of ATP formation</p> Signup and view all the answers

    How do peripheral and central chemoreceptors differ in terms of exposure to substances?

    <p>Peripherally exposed to cerebrospinal fluid, centrally exposed to arterial blood</p> Signup and view all the answers

    How does the blood-brain barrier affect the transmission of arterial PCO2 to cerebrospinal fluid?

    <p>It separates hydrogen ions from CO2 diffusion</p> Signup and view all the answers

    Why does the cerebrospinal fluid have a lower buffer line compared to blood?

    <p>Higher bicarbonate concentration</p> Signup and view all the answers

    What is the main function of central chemoreceptors?

    <p>Detect changes in arterial PCO2</p> Signup and view all the answers

    How do alterations in arterial pH affect the cerebrospinal fluid?

    <p>May show opposite changes to blood in some cases</p> Signup and view all the answers

    Why are the peripheral chemoreceptors considered less important in the short-term response to elevated carbon dioxide?

    <p>They contribute only 10% to 20% of the steady-state response</p> Signup and view all the answers

    What is the primary buffer in the cerebrospinal fluid?

    <p>Bicarbonate</p> Signup and view all the answers

    What receptors do NOT play a significant role in the initial immediate ventilatory response to exercise?

    <p>Arterial chemoreceptors</p> Signup and view all the answers

    What is a probable reason for the slower increase in ventilation during constant work-rate exercise in patients who had their carotid bodies surgically removed?

    <p>Elevated arterial potassium concentration</p> Signup and view all the answers

    What type of receptors may respond to increased carbon dioxide load in mixed venous blood during exercise?

    <p>Pulmonary circulation receptors</p> Signup and view all the answers

    Which receptors are believed to send information about increased muscle metabolism to the respiratory controllers?

    <p>Metaboreceptors</p> Signup and view all the answers

    What may stimulate the arterial chemoreceptors during exercise levels above the anaerobic threshold?

    <p>Elevated potassium concentration</p> Signup and view all the answers

    What receptors are not believed to be significant in the ventilatory response to exercise during mild or moderate levels?

    <p>Cardiac receptors</p> Signup and view all the answers

    Which receptors could potentially respond to the metabolites released during exercise, leading to stimulation of pain receptors?

    <p>Nociceptors</p> Signup and view all the answers

    Which group of receptors has NOT been conclusively demonstrated according to the text?

    <p>'Mixed venous chemoreceptors'</p> Signup and view all the answers

    What may stimulate the arterial chemoreceptors during exercise levels above the anaerobic threshold?

    <p>Elevated potassium concentration</p> Signup and view all the answers

    What receptors are believed to send information about increased muscle metabolism to the respiratory controllers? What may stimulate the arterial chemoreceptors during exercise levels above the anaerobic threshold?

    <p>Metaboreceptors, elevated potassium concentration</p> Signup and view all the answers

    What is the role of the central chemoreceptors in monitoring the balance of arterial PCO2, cerebral blood flow, and cerebral metabolism?

    <p>Detecting interstitial pH of the brain</p> Signup and view all the answers

    What is the primary stimulus to ventilation that is influenced by alterations in hydrogen ion concentration?

    <p>Arterial pH</p> Signup and view all the answers

    Which condition results in an initial hyperpnea that mainly arises from the peripheral chemoreceptors?

    <p>Metabolic acidosis of nonbrain origin</p> Signup and view all the answers

    What effect does acidotic stimulation of the peripheral chemoreceptors have on alveolar ventilation?

    <p>Increases ventilation</p> Signup and view all the answers

    Where does the ventilatory response to hypoxia primarily arise from?

    <p>Carotid bodies</p> Signup and view all the answers

    Which factor potentiates the response to hypoxia at higher arterial PCO2 levels?

    <p>Increased arterial PO2</p> Signup and view all the answers

    What happens to ventilation with increasing degrees of hypoxia when the peripheral chemoreceptors are intact?

    <p>Increases progressively</p> Signup and view all the answers

    How does a progressive increase in hypoxia affect the central respiratory controller in the absence of peripheral chemoreceptor response?

    <p>Directly depresses it</p> Signup and view all the answers

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