Cardiac contractility and the event s of the cardiac cycle Flashcards
How much bigger are cardiac muscle’s T-tubules in comparison to skeletal muscle?
5x greater in diameter and 25x greater in volume
What is the refractory period?
A period immediately following stimulation during which a nerve or muscle is unresponsive to further stimulation.
What is the absolute refractory period?
The period of time during which a second action potential ABSOLUTELY cannot be initiated, no matter how large the applied stimulus is
What is diastole?
The period of relaxation of the heart
What is systole?
The period of contraction of the heart
What percentage of ventricular filling is due to contraction of the atria?
20%
What is the absolute refractory period in cardiac muscle?
245ms
Why is blood pressure the pulmonary circulation much lower?
- There is much less resistance to flow
- Right side of the heart needs to do less work
- Right ventricle walls contain less muscle mass
What is the blood pressure in pulmonary circulation?
30mmHg / 12mmHg
What is the end systolic volume (ESV)
Volume in the ventricle at the end of systole
What is the end diastolic volume (EDV)
Volume in the ventricle at the end of diastole
How is stroke volume calculated?
EDV-ESV
What is the absolute refractory period of cardiac muscle?
245ms
What is the period of contraction of cardiac muscle?
250ms
What is the cardiac output?
Volume of blood pumped by the heart (L/min) (SV x HR)
When does the AV valve open?
When the atrial pressure exceeds the ventricular pressure
When does the AV valve close?
When the ventricle pressure exceeds the atrial pressure
What is the isovolumic (isometric) contraction?
The period of time during ventricular contraction where both the semilunar and AV valves are closed leading to an increased ventricular pressure.
What is the period of supranormal excitability?
The period at the end of phase 3 of the action potential during which activation can be initiated with a milder stimulus than is required at maximal repolarization, because at this time the cell is excitable and closer to threshold than at maximal diastolic potential.
