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40 Neural Regulation of Breathing

40 Neural Regulation of Breathing - PSL302 Lecture 40 by...

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Neural Regulation of Breathing Outline - What factors can affect breathing? - What is the final common pathway for all systems attempting to control the respiratory muscles? - How is respiratory rhythm generated? - What feedback pathways modulate respiratory rhythm? - What are the types of airway & lung receptors and what are their functions? Textbook reading: 612-614, 617 1. What factors can affect breathing? All of these involve the CNS Factor Effect Motor cortex Voluntary control, i.e. speech Chemoreceptors Chemical control, i.e. blood pH Reflexes I.e. Sneezing & coughing Posture Affects intercostal & abdominal muscles Behaviour Startling events, i.e. flight-or-fight (gasp!) Emotions I.e. Fear, anxiety, sorrow Exercise Immediately breathing Pain breathing (rapid & shallow) Recall: Respiratory muscles Diagram: Inspiratory muscles on L, expiratory muscles on R - For quiet (passive) breathing: diaphragm (inspiration) + elastic recoil of lungs (expiration) Respiratory muscles directly controlled by spinal respiratory motoneurons (skeletal muscles controlled by spinal motoneurons) - Anatomy: soma in sp. cord axons in nerves neuromuscular jxn - Inhalation: Phrenic motoneurons (axons make up phrenic nerve) - Drives the diaphragm - Soma found in cervical spinal cord segments C3, C4 & C5 - Expiration: Motoneurons for intercostal nerves - Drive intercostal muscles - Soma found in thoracic spinal cord segments T1 to T12 - Activity of spinal motoneurons regulated by diff pathways that impinge on these neurons (i.e. from cerebral cortex or from brainstem) - Voluntary vs. chemoreflexes Lectu Respirato Airways and lungs alveoli Mus pleura fun Pulmonary ventilation Gas excha alveoli/blo blood/tissu ± pressures lung how much? properties Respiratory contr Exercise and l P l i l i ure 5 ory system structures scles Pulmonary circulation nctions ange Gas Defense Vocalization ange ood ues Gas transport Acid/base balance O 2 CO 2 + H 2 0 H + + HCO3 ± ol d High Altitude Sternocleido- Sternocleido mastoids Scalenes External intercostals Diaphragm Muscles of inspiration Internal intercostals Abdominal Muscles of expiration muscles PSL302: Lecture 40, by French Wednesday, Jan. 19, 2010 1 of 6
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- Recall: breath holding experiment - When you breathe rhythmically - Regulated by brainstem, which drives diaphragm contraction - When you hold your breath - Voluntary signals from cerebral cortex impinged on spinal cord - Inhibited activity of spinal motoneurons = inhibit pathway to hold breath - After hyperventilation - PCO 2 = drive to breathe via chemoreceptors - Eventually chemoreflexes kick in when PCO 2 - Central chreceptors in medulla, & peripheral chreceptors carotid & aorta - Influence medulla oblongata & pons (respiratory center has neurons that regulate rhythmic breathing) - Impact on somatic motor neurons (more for inspiratory than expiratory) - Respiratory motoneurons in spinal cord: last step for control of breathing - But many systems can influence these: i.e. voluntary (cerebral cortex), posture (cerebellum), coughing & sneezing (via receptors) - Two forms of regulation: -
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