Respiratory homeostasis
- Created by: kpritchard16
- Created on: 24-12-18 16:11
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- Respiratory homeostasis
- Steps in external respiration
- 2. Gas exchange between lungs and blood via diffusion
- 1. Pulmonary ventilation
- 3. Transport of oxygen and carbon dioxide in blood to tissues
- 4. Gas exchange between blood and tissues via diffusion
- Aortic bodies
- peripheral chemoreceptors responsible for sensing changes in blood gases are called 'glomus cells'.
- Aortic bodies are several small clusters of chemoreceptors, baroreceptors, and supporting cells located along the aortic arch.
- What can effect the response of ventilation?
- H+
- Peripheral receptors are highly sensitive to fluctuations in [H+]. ? [H+] stimulate ventilation ? [H+] repress ventilation- these changes are far less important than CO2's central effects
- H+ cannot influence central chemoreceptors. Changes in arterial CO2 will produce changes in arterial H+
- PCO2
- only weakly stimulates peripheral, more responsive
- potently stimulates (major ventilation control), chemoreceptors found next to medullary respiratory centres
- PO2
- peripheral only stimulated in life threatening conditions (40% reduction, < 60mmHg)
- directly depresses both central chemoreceptors and respiratory centres themselves
- H+
- respiratory centres
- primary centre is medullary respiratory centre
- collection of aggregations of neuronal cell bodies within medulla and in the pons
- different centres
- Apneustic centre (pons)
- Prevents inspiratory neurones from being 'switched off'This provides a boost to inspiration. Pneumotaxic centre dominates over apneustic
- pneumotaxic centre (pons)
- Sends signals to the DRG to 'switch off' inspiratory neuronesThis limits the duration of inspiration, prevents lungs from over expanding
- Dorsal respiratory group (medulla) DRG
- Consists mostly of inspiratory neurones
- Firing causes inspiratory muscles to contract, causing inspiration
- Subsequent cessation of firing causes inspiratory muscles to relax leading to passive expiration
- Neurones fire again and inspiration restarts (cycle)
- Ventral respiratory group (medulla) VRG
- Consists of both inspiratory and expiratory neurones
- Especially involved in active expiration- VRG is innervated by DRG and can response in times of need to increase inspiration - e.g. exercise
- Both types remain inactive during normal 'quiet' breathing. Only used in times of increased demand
- Apneustic centre (pons)
- 3 distinct components
- factors that generate inspiration-expiration rhythm
- factors that regulate the magnitude of ventilation
- factors that modify respiration to serve other purposes
- primary centre is medullary respiratory centre
- HCRG
- consists of motor neurones, increased CO2 in blood causes pH to decrease - causes acidosis - spinal cord can take over in extreme cases, can mediate small amount of respiration
- Steps in external respiration
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