10.2.13 kin 272 class notes- EDV: end diastolic volumeo 120 mL starting value before contraction- ESV: end systolic volume =/~o 40% of 120 = 48 mL (about 50 mL)- SV: stroke volume =/~o 60% of 120 = 72 mL (about 70 mL)- Cardiac output (per min)o 70 mL * 60 seconds= 4.2 L/min- EF = 60%- HR = 60 bpmo To increase: Sickness Exercise- Preload CO increases, increase needs of tissueso Increase heart rateo Increase ejection fraction, increase stroke volume 1. Frank/starling mechanism- fancy term for preload- realized that it operates based on the length/tension relationshipo stretch muscle to optimal length – it will producethe most amount of forceo beyond optimal you get no forceo two words about how it works titin and nebulin- elastic in nature- in between actin and myosin- stretch sarcomere – engages these- when actin and myosin interact, its- identical to skeletal muscleo more fluid into the ventricle, increase preload, you stretch ventricle outo contracts with more force, ejection fraction goes up!o Auricles of atria hold more fluid, prefill the ventricle more alsoo Only works up to a heart rate around 160 bpm Filling time is so compromised – have very little time, can’t prefill enough to get a good contraction Excessively high heart rate Feel numbness… Stroke volume goes down… Makes the heart rate go up SV* HR =cardiac output 2. After load- increase recoil in aorta- pushes blood forward faster- more fluid in aorta stretches it more- (high pressure)- afterload has less resistance! Decrease afterload 3. Increase contractility- Most confusing- Increase ejection fractiono Message from axon bulb to sarcolemmao Activates T-tubuleo Activates the SR to release Ca++ Increasing contractility does this! CICR – calcium induced, calcium released Needs to rely on getting calcium from extracellular spaces Spaces outside the muscle cello Ca++ binds to troponin causes a conformational change in tropomyosin (open sites on actin)o Myosin head binds to actino Myosin head bendso Myosin head breaks off actino Myosin head bounces backo Ca++ back to SR (sarcoplamic reticulum)o Neurotransmitter chain reaction Brain says I need more ejection fraction because the preload isn’t working and the body is demanding more cardiac output Brain will release hormones- Secondary messengerso Norepinephrine Causes g-protein linked receptor Linked next to norepinephrine receptors is g protein! G protein is mobile Moves from norepinephrine receptor over to the effector receptor It moves using energy! GTP GDP Other high end energy source, other than ATP Effector won’t work until g protein is attached to it Adenylate cyclase – part of effector, takesATP and turns it intoAMP Cyclic AMP is one of the most common 2nd messengers in your body – chemical that does other things Norepinephrine works on 2nd messanger AMP does all the
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