35 Questions
What happens at 0mV in the cardiac cycle?
Ca++ channels close and K+ channels open
What is the role of Ca++ in muscle contraction?
Ca++ binds to troponin to allow myosin and actin cross bridge
Which part of the heart has the lowest firing rate?
Purkinje fibers
What is the purpose of an ECG or EKG?
Record electrical signals of the heart
If the SA node was not under endocrine control, how many times would it fire per minute?
100 - 120 times
Where is the heart located?
In a space called mediastinum
Which chamber of the heart collects blood and pushes it into the lower chambers?
Atria
What is the purpose of auricles in the heart?
To hold blood and empty into atria
Which layer of the heart is the most superficial?
Epicardium
Where does CO2 leave and O2 enter in the pulmonary capillaries?
In the pulmonary arteries
Which vessel is the only vein to carry oxygenated blood?
Pulmonary vein
What does the P wave represent in the cardiac cycle?
Depolarization of the atria
Which phase of the cardiac cycle involves the closure of semilunar valves and ventricular relaxation?
Ventricular diastole
What is the main function of an artificial pacemaker in the heart?
To ensure effective heart contractions
Which phase marks the pumping of blood into circulation during the cardiac cycle?
Ventricular systole
What is the primary purpose of AEDs in relation to the heart?
To correct fibrillations
What represents the amount of blood left in the ventricles after stroke volume is pushed out?
End systolic volume (ESV)
Which of the following is responsible for the first heart sound, S1?
Closing of atrioventricular valves
What does S4 indicate in terms of heart function?
Blood being pushed into a stiff ventricle
What is the normal range for cardiac output (CO) in liters per minute?
4 - 8 L/min
What is the formula to calculate stroke volume (SV) based on end-diastolic volume (EDV) and end-systolic volume (ESV)?
$SV = EDV - ESV$
Which factor can decrease heart rate according to the text?
Hypoxia (lack of O2)
Where does nervous control of heart rate primarily originate from?
Medulla oblongata
What is the term used to describe increased ventricular stretch leading to more powerful contractions?
$Starling mechanism$
During exercise, what happens to stroke volume as heart rate increases?
$SV$ decreases as $HR$ increases
What is the percentage range for normal ejection fraction?
$50% - 70%$
'S7' is a term used when referring to which condition according to the text?
$S3$ and $S4$ occurring together
What cell type in the heart is responsible for initiating and propagating the action potential through the heart?
Myocardial conducting cells
Which structure ensures that cardiac muscle cells do not rip apart during contractions?
Desmosomes
What is the primary function of the Sinoatrial (SA) node in the heart?
Create a normal cardiac rhythm
Which structure receives impulses from the AV node and branches into right and left bundle branches?
Bundle of His
What is the function of semilunar valves in the heart?
Ensure unidirectional blood flow
During which phase of depolarization do cardiac contractile cells experience a plateau?
At peak depolarization
What causes a heart murmur during auscultation?
Altered blood flow due to valve disorders
Which heart chamber receives deoxygenated blood from systemic circulation?
Right atrium
Test your knowledge on the cardiac action potential, refractory period, calcium channels, and the conduction system of the heart. Learn about the role of calcium ions, SA node, AV node, and bundle branches in regulating the heart's electrical activity.
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