Module 9 critical care

1. Module 9 critical care Homeostasis, The respiratory system, vascular system, renal system

4. Homeostasis eg thirst

5. The Respiratory System Upper Respiratory Tract Air conducting passages nose, Pharynx, Larynx Warm, moisten and filter the air Lower Respiratory Tract Trachea C shaped cartilage rings Primary bronchi left and right Air is cleansed, mucus traps dust in inspired air, cilia waft mucus towards mouth, air is moistened, air is conducted

6. Physical factors that influence pulmonary ventilation: 1.Respiratory passageway resistance 2.Lung compliance & elasticity 3.The pulmonary / alveolar membrane surface tension

7. Neural regulation of Airway size parasympathetic neurons(acetylcholine)contraction of smooth muscle increased resistance (mucus secretion & chemical irritants also cause smooth muscle resistance) sympathetic  epinephrine(noradrenaline) airway dilatation

8. Changes in ventilation mediated by:1.Neurological Control Central respiratory centres in Medulla Oblongata consists of two groups of identifiable cells :- Dorsal Respiratory Group DRG (Inspiratory Centre) Function to generate basic respiratory rhythm. Sends inf. to Pneumotaxic centre of the pons and the ventral group and upper motor neurones to the resp muscles during quiet breathing. Ventral Respiratory Group VRG(expiratory centre) sends inf. to the upper motor neurones to the resp mms during forced inspiration and expiration.

9. PONS Fine tune breathing and smoothe transition from inspiration to expiration Pneumotaxic centre fine tuning of breathing rhythm & prevents over inflation, continuously sends inhibitory information to the DRG when signals are particularly strong duration of inspiration[ shorterned increasing them. Apneustic centre provides inspiratory drive continuously stimulates dorsal group, prolongs respiration, breath hold on inspiration

10. 2.Chemical control central chemoreceptors situated anterolateral side of medulla sensitive to changes in the cerebro spinal fluid in CO2 and H+ CO2 crosses the blood brain barrier then dissociates into H+ ions but CSF has very poor buffer mechanisms unlike the blood and CSF pH will fall Minute fall in CSF pH will produce a huge response to ventilation i.e. increase it Response is slow 10-20 seconds or lag phase of 5 breaths

11. ADAPTATION if blood PaCO2 is maintained abnormally high for a long time weeks CSF pH will gradually return to normal as CSF HCO3 levels will rise slowly in order to balance CSF pH Chronic respiratory disease: chronic ventilatory failure CO2 may not be their drive for resp.  Peripheral chemoreceptors situated in the bifurcation of the carotid artery also in arch of aorta well perfused rapidly respond to second by second changes in arterial CO2 pH and O2 more responsive to PCO2 than O2

12. The Vascular System The vascular system is made up of the vessels that carry our blood. Arteries carry the blood out from the heart to all parts of our bodies.

27. A fall in blood pressure (1) causes the release of renin--a kidney enzyme. Renin (2) in turn activates angiotensin (3), a hormone that causes the muscular walls of the small arteries (arterioles) to constrict, increasing blood pressure. Angiotensin also triggers the release of the hormone aldosterone from the adrenal gland (4), which causes the kidney to retain salt (sodium) and excrete potassium. The sodium retains water, thus expanding the blood volume and increasing blood pressure.