Unit 4 - A & P Module - Cardiac Cycle and Regulation of Cardiac Output Flashcards
Ventricular contractility is influenced by __________.
calcium and epinephrine
End diastolic volume is influenced directly or indirectly by __________.
heart rate, preload, afterload, sympathetic nerve activity
Put the following events of the cardiac cycle in the correct order, starting with the ventricular filling phase:
first heart sound
P wave of ECG
ventricular pressure > atrial pressure
isovolumetric relaxatio
b, c, a, d
Starling’s law of the heart can be stated as: __________.
if end diastolic volume increases, stroke volume will increase and if venous return decreases, end diastolic volume will decrease and stroke volume will decrease
Which of the following would result in an increase in cardiac output?
Increased end diastolic volume
The actions of norepinephrine and acetylcholine on pacemaker cells is similar in that both transmitters __________.
utilize G proteins and affect calcium channels
Stroke volume can be influenced by __________.
preload, contractility, afterload, and sympathetic nerve activity
The effect of parasympathetic input to the heart is to __________.
open additional potassium channels in pacemaker cells
Starling’s law states that __________.
stroke volume increases as end-diastolic volume increases
Regarding ventricular volumes __________.
the larger the end diastolic volume, the larger the stroke volume becomes and an increase in the force of ventricular contraction decreases the end systolic volume
Which of the following will increase the force of contraction of the ventricles?
Increasing end diastolic volume
The pulmonary semilunar valve opens in response to __________.
right ventricle pressure > pulmonary artery pressure
Cardiac output is increased by __________.
increasing venous return and increasing ventricular filling time
Which of the following may increase heart rate?
Norepinephrine and epinephrine
Abnormalities within the SA node can cause which of the following symptoms?
Bradycardia or tachycardia
Which of the following would result in an increase in cardiac output?
Increased end diastolic volume
Sympathetic activity increases ventricular contractility by __________.
increasing the rate of myosin ATPase activity and increasing the flow of calcium into the cytosol
Which of the following are the same for the left and right ventricles?
Cardiac output, heart rate, and stroke volume
During the plateau phase of the action potential in cardiac contractile cells __________.
calcium channels are open, the membrane potential remains depolarized, inward rectifier potassium channels are closed, sodium channels are inactivated
The second heart sound occurs during which aspect of the ECG?
T wave
When you begin to exercise, the working tissue will need an increased delivery of blood in order to obtain the oxygen and nutrients necessary for the maintenance of the increased metabolism. Which of the following will occur in order to help enhance the blood flow to the working tissue?
Increased heart rate and stroke volume
During isovolumetric contraction __________.
pressure in the ventricles is increasing
During exercise, sympathetic input to the heart is increased. Stroke volume is often maintained, or even increased, even though heart rate is also increasing. How is this possible?
Sympathetic input increases ventricular contractility, thereby increasing stroke volume, and sympathetic input decreases conduction time within the heart, decreasing the delay between atrial and ventricular contractions, and
Sympathetic input increases the speed of ventricular contraction.
Give the mechanistic explanation as to why tetanus does NOT occur in myocardial contractile cells?
Calcium entry depolarizes the cell and lengthens the refractory period, which prevents the summation of the tension developed from repeated action potentials.
