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KINE 3012 (22)
Tara Haas (22)
Lecture 14

Lecture 14 - Feb 13th.docx

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Humber College
Kinesiology & Health Science
KINE 3012
Tara Haas

Page 73 - Instead of plotting length of muscle, we measure diastolic volume - We exist at a very low level of our maximal tension compared to skeletal muscles where they are usually at optimal - We activate more motor units to gain more tension so not all the muscles are contracting sometimes, cardiac muscles activate all the muscles during contraction - We exercise to increase strength of contraction, we get more blood into the heart, we get an increase in stroke volume, *25% increase in stroke volume* - As you lengthen that muscle, you have a greater myosin actin overlap. That gives you more tension - Conclusion, if you get more blood into the heart, you're going to increase your stroke volume - Reason we don't live at optimal level because if we exceed, we'll lose tension - Professional athletes can squeeze 150ml of blood, so there's still room for improvements to reach optimal length - Another way to increase heart rate, affect the parasympathetic/sympathetic nervous system Page 74 - Greater increase in intracellular calcium, reach threshold faster - More calcium in the cell = stronger contraction - Greater stroke volume and higher diastolic volume dependent on the amount of intracellular calcium - Sympathetic stimulation during exercise causes increased stroke volume Second Graph - Rate of rise in calcium is higher and higher rise *Faster threshold and stronger contraction* - Faster threshold allows contractions to occur more frequently *more heartbeats* Page 75 - Knowing is systolic/diastolic we can identify our ejection fraction - Ejection fraction, amount of blood we can squeeze out during every beat - We generally squeeze 50% blood out of the heart during ejection fraction - During disease, ejection fraction can change *Remember disease, homeostasis is gone, inability to react to changes* - Parasympathetic only affects heart rate *Does not affect stroke volume* - Venous return, pulls blood back from the vein - If the ejection fraction is at 25% instead of 50%, we would increase are heart rate to match homeostasis of cardiac output Page 76 - The heart can't maintain adequate flow - Progressive disease, starts mild and then gets worse - Chronic elevated MAP --> Constantly the heart is working very hard - Coronary artery flow, blood that is supplied to the heart muscles - Heart attack/Cardiac arrest No blood to the muscle, it dies and part of the heart doesn't work - e.g. 30% of the heart muscle died. The other 70% of the heart has to work harder to make up for it everyday Diastolic dysfunction - e.g. when you tear a muscle and repair a muscle, it sometimes replaced as connective tissue - And connective
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