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15 Cards in this Set
- Front
- Back
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Ca, troponin mechanism
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influx of Ca binds Troponins -> moves Tropomysin -> opens a spot on actin so it can bind myosin. after an MI, TnI and TnT (specific to heart) are elevated
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sequence of events in cardiac myocyte contraction
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Ca enters via transverse tubule, binds dihydropyridine receptor @ L-type channel. then, Ca binds Ryanidine receptor on SR. Ca release, stims sarcomere, then reenters SR via SERCA or expelled via Na/Ca pump.
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name two sympathetic effects on Heart (on myocyte, not pacemaker cells). how are these mediated w/in the cell?
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-increase force/contractility
-increase rate of relaxation via: -activate L-type channels, and sarcomere -activate SERCA |
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frank-starling mechanism
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increased preload -> increased contraction force.
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contractility - 2 indices
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-change in dP/dt, or the rate of change in Ventricular P during an ejection at given preload
- change in EF = SV/EDVV |
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CO = HR * SV. in a healthy person, response to increased MAP is via?
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increased HR. SV barely changes. this is opposite in transplant patients, as their heart is denervated
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how does sympathetic change HR , 2 mechanisms:
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1. increase slope of pacemaker Na channels
2. lower AP threshold in pacemaker cells (lusitropic effects on SERCA do not directly affect rate; these help the myocytes meet the rate demanded by the pacemaker cells) |
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3 determinants of Stroke Volume:
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1. afterload
2. contractility 3. preload (decreased by compliance problems) |
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at what HR is ventricular filling compromised? which heart phase loses more time in increased HR?
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above 180 BPM, ventricular filling is compromised. as HR rises, diastole time decreases moreso than systole
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what has a greater O2 demand - pressure or volume work by the heart?
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pressure. unexplained event
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chronotropic
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affecting heart rate
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dromotropic
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affecting conduction velocity
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inotropic
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affecting contractility or force
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lusitropic
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affecting rate of relaxation
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systolic vs diastolic dysfunction
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systolic - due to decreased contractility, thus decreased SV. compensate by slightly increasing EDVV thus SV
diastolic - due to decreased compliance, thus decreased EDVV (filling) thus decreased SV and decreased CO |
