1. Control of Respiration Dr. Meg-angela Christi Amores

2. Control of Respiration Central o Respiratory Center o Bilaterally in the medulla oblangata and pons 1.Dorsal Respiratory Group – dorsal medulla – Mainly inspiration and rhythm of breathing 2.Ventral Respiratory Group – ventrolateral medulla – Either inspiration or expiration 3.Pneumotaxic Center – dorsal superior pons – Controls rate and pattern of breathing

4. Dorsal Respiratory Group Generates basic rhythm of respiration Operates on a “ramp” signal Begins weakly and increases steadily for about 2 seconds, then ceases abruptly for next 3 secs. Turns off excitation of diaphram, allows elastic recoil 2 ways of control: 1.Control of rate of increase of ramp signal 2.Control of limiting point at which ramp signal ceases

5. Pneumotaxic Center Control “switch off” point of inspiratory ramp If strong, inspiration is 0.5 seconds, filling lungs only slightly Primary function is to limit inspiration

6. Ventral Respiratory Group Inactive during normal quiet respiration No participation in rhythm control Contributes to respiratory drive when pulmonary ventilation increases Some neurons excite – inspire Other neurons excite – expire Useful in heavy breathing

7. Chemical Substances Oxygen No significant direct effect, instead, regulates respiration on its effect on peripheral chemoreceptors Carbon Dioxide Potent indirect effect Excess concentration in blood acts directly on respiratory center itself Hydrogen Excites sensory neurons in chemosensitive areas Cannot cross blood brain barrier

8. Control of Respiration Peripheral – Chemoreceptors – special nervous chemical receptors located in several areas outside brain Detects changes in oxygen concentration in blood Transmits nervous signals to the respiratory center to the brain Mostly in Carotid bodies and Aortic bodies – Decreased arterial O 2 concentration in blood – Increased CO 2 and H ion concentration

9. Chemoreceptors

10. Factors that Affect Respiration Voluntary control One can hyperventilate/hypoventilate Nervous pathway for voluntary control passes directly from cortex and down the corticospinal tract, not through the respiratory center

11. Factors that Affect Respiration Effect of Irritant receptors in Airways Epithelium in trachea, bronchi, bronchioles – sensitive Cause cough and sneeze Also cause bronchial constriction – as in BA and Emphysema

12. Factors that Affect Respiration Function of lung “J” receptors Sensory nerve endings in alveolar walls, in juxtaposition to pulmonary capillaries Excitation gives feeling of dyspnea Effect of brain edema Activity of respiratory center may be decreased or inactivated by acute brain edema due to blockage of blood supply Anesthesia Most prevalent cause of respiratory depression and arrest Eg Na pentobarbital, morphine overdose

13. Abnormalities in Respiratory Control Periodic breathing (e.g. Cheyne-Stokes breathing) Waxing and waning respiration 40-60 seconds – Due to: 1.Long delay of transport of blood carrying O2 – As in severe heart failure 2.Increase negative feedback gain – Brain damage