Test 3 Questions and Answers

Test 3 Questions and Answers - Test 3 Questions and Answers...

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1 Test 3 Questions and Answers 1. PNS and SNS stimulation can result in heart rates ranging from 50 to 200 beats per minute. Describe, in detail, how changing PNS and SNS stimulation would change heart rate. Diagram the relationship that this range of heart rates would have on cardiac output. Explain why this occurs. SNS and PNS innervation into SA nodal cells would change heart rate by: Vm (hyperpolarize) HR (BPM) CO 150 50 250 HR can have a positive effect on CO by: i) HR – contractility (Treppe) – SV – CO HR can have negative effects on CO by: ii) HR – duration of diastole – filling time – EDV – SV – CO iii) HR – CO – afterload – SV - CO Increased HR will have positive and negative effects on CO. The positive effects outweigh the negative effects at lower HR where there is a positive slope to the relationship between HR and CO, the positive effects equal the negative effects where there is little effect of HR on CO (around 150 BPM) and the negative effects outweigh the positive effects where there is a negative slope to the relationship between HR and CO (above 180 BPM).
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2 2. Diagram and describe the relationship between left ventricular pressure and left ventricular volume during diastole and systole. Describe in detail how an increase in SNS stimulation of ventricular myocytes would alter their function and indicate how these changes would affect the pressure-volume relationship discussed above. 1. Diastole – ventricle relaxed and filling *atrial contraction - vol and pr. 2. Systole – ventricular contraction Isovolumetric contraction pr. no change in vol., aortic pr>vent. pr. 3. Vent pr. > aortic pr., aortic valve opens and volume ejected (4.) 5. Pr (vent still contracting) - vol (ejecting blood into aorta) 6. Vent relaxation (closing of aortic valve) 7. Isovolumetric relaxation pr – no change in vol. 8. Open left AV valve, vent pr<atrial pr. 9. Period of rapid filling, vol – no change in Pr (vent still relaxing.) SNS – NE – Beta Rm – Gs – AC - cAMP – Protein kinase – phosphorylate: 1. Volt. Dep. Ca++ channels (L-type) - # of channels open per AP therefore increase trigger Ca++ therefore contractility (force).
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This note was uploaded on 12/13/2010 for the course HK 3940 taught by Professor Murrant during the Fall '10 term at University of Guelph.

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Test 3 Questions and Answers - Test 3 Questions and Answers...

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