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CONTROL OF VENTILATION

CONTROL OF VENTILATION. Joanne Simpson. Central Controller. Input. Output. Sensors. Effectors. Basic Sub-groups. Central Controller. Brainstem. Medullary Respiratory Centre Dorsal Respiratory Group (Inspiration) – responsible for basic ventillatory rhythm

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CONTROL OF VENTILATION

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  1. CONTROL OF VENTILATION Joanne Simpson

  2. Central Controller Input Output Sensors Effectors Basic Sub-groups

  3. Central Controller

  4. Brainstem • Medullary Respiratory Centre Dorsal Respiratory Group (Inspiration) – responsible for basic ventillatory rhythm Expiratory Area – Used for forceful breathing • Apneustic Centre Lower Pons - Impulses from here have excitatory effect on the inspiratory area of the medulla • Pneumotaxic Centre Upper Pons – regulates volume and rate of respiration (fine tuning)

  5. Cortex • Can override the function of the brainstem within limits • Able to voluntarily halve PCO2 by hyperventillation causing alkalosis • Duration of breath holding limited by many factors. Primarily PO2 and PCO2

  6. Other Parts of the Brain The Limbic System and Hypothalamus can alter the pattern of breathing in affective states such as rage and fear

  7. Effectors

  8. Effectors • Muscles of the diaphragm • Intercostal Muscles • Abdominal Muscles • Accessory Muscles Co-ordinated action is the responsibility of the central controller.

  9. Sensors

  10. Central Chemoreceptors • Surrounded by brain ECF and respond to changes in H+ concentration, (↓ [H+] suppresses ventillation) • Composition of ECF controlled by surrounding CSF, local blood flow and metabolism • Buffering effect, (↑[CO2] means ↑ liberation of H+ and resulting hyperventilation)

  11. Peripheral Chemoreceptors • Found in the carotid bodies chiefly • Respond to decreases in PO2 and pH, and increases in PCO2 • ↓PO2 results in ↑Ventilation • ↓pH results in ↑Ventilation

  12. Lung Receptors • Pulmonary Stretch Receptors Stretching of lungs causes firing of receptor and feedback via the vagus ↓respiratory frequency by ↑ expiration time • Irritant Receptors Stimulated by noxious gases, smoke and cold air. Impulses travel up the vagus causing bronchoconstriction and hyperpnea • J Receptors Respond to chemicals in the lungs. Impulses travel up the vagus and cause rapid, shallow breathing and dyspnoea

  13. Other Receptors • Nose and Upper Airway Receptors Similar to irritant receptors, initiate coughs/sneezes • Joint and Muscle Receptors Impulses from moving limbs are thought to ↑ ventillation in early stages • Gamma System Muscle spindles that sense elongation of the muscle, therfore giving sensation of dyspnoea if a large respiratoy effort is required to move chest wall • Arterial Baroreceptors ↑Arterial BP may cause hypoventillation / apnoea – converse is true • Pain and Temperature Stimulus may cause hyperventillation

  14. Questions?

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