Unit 4 Health Science: The Heart- EKG, Cardiac Output, Na+, K+

What is the cardiac output formula?

CO = HR × SV (heart rate × stroke volume).

What is an EKG?

A recording of the heart's electrical activity over time. NOT BLOOD FLOW.

What is cardiac conduction?

The movement of electrical impulses through the heart to coordinate contractions.

What is the normal resting heart rate?

60-100 beats per minute (bpm) in adults.

Which EKG component is used to determine heart rate?

R wave in QRS complex.

Polarized Cardiac cell (resting)

The inside of the cell is negative relative to the outside.

What are sodium and potassium levels at rest?

More Na+ outside the cell; more K+ inside the cell.

What is depolarization?

Electrical activation of heart cells; in working cardiac muscle, rapid Na+ entry causes depolarization.

What is repolarization?

Heart cells return toward their resting electrical state, primarily as K+ leaves the cells.

What does the P wave represent?

Atrial depolarization; electrical activation leading to atrial contraction.

What does the QRS complex represent?

Ventricular depolarization; electrical activation leading to ventricular contraction.

What does the T wave represent?

Ventricular repolarization; electrical recovery of the ventricles.

What is stroke volume (SV)?

Amount of blood ejected by one ventricle during one heartbeat.

What is the normal stroke volume?

Approximately 60-100 mL per beat.

What is preload?

Stretch of the ventricular muscle before contraction, related to ventricular filling.

What is contractility?

Strength of heart muscle contraction independent of preload.

What is afterload?

Resistance or pressure the ventricle must overcome to eject blood.

What is Frank-Starling's Law?

Within normal limits, more ventricular filling causes greater stretch and a stronger contraction.

How does increased preload affect stroke volume?

More preload generally increases stroke volume through Frank-Starling's Law.

How does increased afterload affect stroke volume?

Higher afterload generally decreases stroke volume if other factors remain unchanged.

What is cardiac output (CO)?

Volume of blood pumped by one ventricle every minute.

How does increased heart rate affect cardiac output?

CO increases if stroke volume stays constant; extremely fast rates can reduce filling and CO.

What is atrial fibrillation (A-Fib)?

Disorganized atrial electrical activity causing quivering atria and an irregularly irregular heartbeat.

How does A-Fib affect cardiac output?

Loss of effective atrial contraction can reduce ventricular filling, stroke volume, and CO.

What is ventricular fibrillation (V-Fib)?

Chaotic electrical activity causes the ventricles to quiver without pumping effectively; effective CO is zero.

What is ventricular tachycardia (V-Tach)?

A rapid rhythm originating in the ventricles; reduced filling can decrease stroke volume and cardiac output.