Presentation Transcript

1. Physiology Laws

   Dr. S. Parthasarathy MD., DA., DNB, MD (Acu), Dip. Diab.DCA, Dip. Software statistics PhD (physio)
2. Some are described Laplace law Frank starling law Bainbridge relex Bezoldjarisch reflex Baro receptor reflex
3. Laplace's Law Surface tension properties are described mathematically by Laplace's law, This states that the pressure inside a bubble (or alveolus) necessary to keep it expanded is directly proportional to the tension on the wall of the bubble, which tends to collapse it, divided by the radius of the bubble. P = 2T/r
4. P = 2T/r pressure Tension
5. Surfactant If alveolar surface tension properties were not modified by the presence of surfactant the lungs would eventually become collapsed, stiff, and fluid filled. lipoprotein secreted by type II alveolar cells (pneumocytes) lining the alveoli. It is a complex consisting of about 85% to 90% lipids and 10% to 15% proteins. The lipid portion is about 85% phospholipid, approximately 75% of which is dipalmitoylphosphatidylcholine.
6. Laplace law- 2 T/ R = P ----- PR/2T = stress
7. Aortic stenosis – obstruction- higher pressure- more tension – but LVH occurs to decrease stress In aortic stenosis, afterload is increased. The ventricle has to generate far higher pressure to overcome the increased load opposing systolic ejection of blood. To generate such high performance, the ventricle increases its wall thickness (LV hypertrophy). By applying Laplace's law, increased LV wall thickness will decrease wall stress despite the necessary increase in LV pressure to overcome the aortic stenosis
8. Failing heart
9. Vessels and GI tract( P = 2T/R ) if an aneurysm forms in a blood vessel wall, the radius of the vessel has increased. This means that the inward force on the vessel decreases, and therefore the aneurysm will continue to expand until it ruptures. A similar logic applies to the formation of diverticuli in the gut
10. Frank starling law E. H. Starling, using an isolated heart-lung preparation as a model, observed in 1914 that “the mechanical energy set free on passage from the resting to the contracted state is a function of the length of the muscle fibre ability of the heart to change its force of contraction and therefore stroke volume in response to changes in venous return is called the Frank-Starling mechanism
11. LVEDP – 8 mm Hg SV of around 70 ml.
12. Starling concluded that the increased twitch force was the result of a greater interaction of muscle bundles. cardiac reduction in force is only 10% even if cardiac muscle is at 80% sarcomere length
13. Frank starling law A common clinical application of Starling's law is the relationship of left ventricular end-diastolic volume (LVEDV) and stroke volume. increase in actin and myosin cross-bridging . The Frank-Starling mechanism may remain intact even in a failing heart. ventricular remodelling after injury or in heart failure may modify the Frank-Starling relationship.
14. Frank starling law
15. CARDIAC FUNCTION CURVE THE FRANK- STARLING “LAW OF THE HEART” 15- 10- Decreased Heart Rate CARDIAC OUTPUT (L/min) 5- -4 0 +4 +8 RAP mmHg
16. CARDIAC FUNCTION CURVE THE FRANK- STARLING “LAW OF THE HEART” 15- Increased Heart Rate 10- CARDIAC OUTPUT (L/min) 5- -4 0 +4 +8 RAP mmHg
17. Laplace law and frank starling law – OK
18. Bainbridge Reflex Francis Arthur Bainbridge described this reflex in 1915 when he was experimenting on dogs. Bainbridge found that infusing blood or saline into the animal increased heart rate. Increase blood volume – increase heart rate
19. Bainbridge Reflex stretch receptors located in the right atrial wall and the cavoatrial junction. An increase in right-sided filling pressure sends vagal afferent signals to the cardio vascular center in the medulla. These afferent signals inhibit parasympathetic activity, thereby increasing the heart rate.
20. Bainbridge Reflex Acceleration of the heart rate also results from a direct effect on the SA node by stretching the atrium. The changes in heart rate are dependent on the underlying heart rate before stimulation.
21. Bainbridge Reflex the Bainbridge reflex does occur in humans, as in after delivery of an infant when a large volume (up to 800 mL) of uteroplacental blood is put back into the mother's circulation, resulting in tachycardia.
22. Bainbridge Reflex Bainbridge Reflex is involved in Respiratory Sinus Arrhythmia. During inhalation intrathoracic pressure decreases. It triggers increased venous return --- stretch receptors, ---- Bainbridge Reflex increases the heart rate momentarily during inspiration.
23. Reverse Bainbridge Reflex Spinal Sympathetic block Vasodilation Decreased venous return Decreased atrial stretch receptors Bradycardia
24. The Bezold-Jarisch reflex Response to noxious ventricular stimuli sensed by chemo receptors and mechano receptors within the LV wall induced the triad of hypotension, bradycardia, and coronary artery dilatation. The activated receptors communicate along unmyelinatedvagal afferent type C fibers. These fibers reflexively increase parasympathetic tone.
25. The Bezold-Jarisch reflex Because it invokes bradycardia, the Bezold-Jarisch reflex is thought of as a cardioprotective reflex. implicated in the physiologic response to conditions such as myocardial ischemia or infarction, thrombolysis, or revascularization and syncope. Natriureticpeptide receptors stimulated by endogenous ANP or BNP may modulate the Bezold-Jarisch reflex. less pronounced in patients with cardiac hypertrophy or atrial fibrillation.
26. The baroreceptor reflex The baroreceptor reflex is responsible for maintenance of blood pressure. This reflex is capable of regulating arterial pressure around a preset value through a negative-feedback loop
27. Bain and baro The Bainbridge reflex and the baroreceptor reflex act antagonistically to control heart rate. The baroreceptor reflex acts to decrease heart rate when blood pressure rises. When blood volume is increased, the Bainbridge reflex is dominant; When blood volume is decreased, the baroreceptor reflex is dominant. The Bainbridge reflex is seen in dogs, but experiment has shown that it is not as significant in primates.
28. Summary Laplace law Frank starling law Bainbridge relex Bezoldjarisch reflex Baro receptor reflex
29. Thank you all