Regulation Of Heart Pumping Flashcards
At rest how much blood the heart pumps?
4 to 6 litters
What are the basic mechanism of cardiac pumping regulation?
A) intrensic cardiac regulation of pumping through the Frank starling mechanism
B) The control of heart rate and strength of heart pumping by the autonomic nervous system
Explain frank starling mechanism?
The greater the ventricular muscles stretched during diastole, the greater the force of cardiac contraction and the quantity of blood pumped.
What is the explanation of Frank starling mechanism?
When the ventricles are stretched during diastole,the actin and myosin filaments are brought to an optimal degree of angle for Force generation.
The relationship between ventricular function curves and Frank starling mechanism?
As the ventricles fill in response to higher atrial pressure each ventricles volume and strength of cardiac contraction increases leading to an increased ejection volume.
What is the maximum range of heart rate increase due to sympathetic stimulation?
180-200 beats / min. Rarely 250 beats per minute.
What is the effect of normal sympathetic stimulation on cardiac pumping?
Under normal conditions the sympathetic nerve fibers of the heart discharge continuously at a slow rate which increases cardiac output at 30% higher than with no sympathetic stimulation.
What is the effect of sympathetic inhibition on cardiac pumping?
Inhibition of baseline sympathetic stimulation will cause a 30% reduction in cardiac contraction force, rate and cardiac output
What is the effect of strong parasympathetic stimulation on the heart?
It can stop the heart beat for a few seconds. The SA node usually escape the vagal inhibition and beat at a rate of 20-40 beats per minute.
What is the effect of strong parasympathetic stimulation on the strength of cardiac contraction?
It decreases by 20 to 30 %
What is the combined effect of greater decrease in HR and mild reduction in cardiac contraction strength due to strong parasympathetic stimulation on cardiac output ?
It can cause 50% or more reduction in cardiac output
Effect of excessive extracellular potassium ions on heart function?
A) Excess potassium in the cardiac extracellular fluid causes the heart to become dilated and flaccid causing slow heart rate.
B) hyperkalemia can causes AV conduction block.
C) An elevation of potassium levels to 8-12 mEq/ L can cause dangerous dysrhythmias and death.
What is the mechanism of hyperkalemic cardiac dysfunction?
The high potassium in the extracellular fluid partially depolarizes the cell membrane and causes the membrane potential to be less negative. As the membrane potential decreases from partial depolarization state the intensity of AP also decreases which make the heart more weaker.
What is the effect of excess calcium on the heart function?
It has the exact opposite effect of potassium as it leads to spastic contraction of the heart.
