BPK 305 Lecture Notes - Lecture 3: Aortic Valve, Afterload, Cardiac Muscle

• School: Simon Fraser University
• Department: Biomedical Physio & Kines
• Course: BPK 305
• Professor: Damon Poburko

Document Summary

Preload = changing the stretch of the myocyte: example -> bicep curl on bench, preload = arms resting on bench, weight stretching muscle. Afterload = how much force the heart has to contract against: preload is related to length of sarcomere and related to edv, *anything that increases edv will increase preload4, *preload is not pressure! It is a stretch (ex. stretch from blood filling heart and stretching myocytes: afterload = blood pressure (plv needed to open aortic valve) = force that muscle must overcome, plv = pressure in left ventricle. In declining phase -> the muscle finishes relaxing. Increased preload = increased force of contraction: as preload increases it takes longer to generate enough force to lift weight, so shorter amount of time is spent actually lifting the weight. Increased afterload = increased isometric contraction, decreased velocity of contraction (lighter load = move faster), and decreased time of shortening.