TEST 1

Endocardium

The innermost layer of the heart wall.

Myocardium

The middle layer of the heart wall, consisting of cardiac muscle.

Epicardium

The outermost layer of the heart wall.

Pericardium

The fibrous sac surrounding the heart.

Systole

The phase of the heartbeat when the heart muscle contracts.

Diastole

The phase of the heartbeat when the heart muscle relaxes and fills with blood.

Atrial kick

The additional blood pushed into the ventricles when the atria contract.

Sympathetic nervous system

The division of the autonomic nervous system that increases heart rate and contractility.

Parasympathetic nervous system

The division of the autonomic nervous system that decreases heart rate.

SA node

The physiological pacemaker of the heart located in the right atrium.

AV node

The 'gate keeper' of the ventricles, responsible for delaying impulses from the atria.

QRS complex

Represents ventricular depolarization on an ECG.

T wave

Represents ventricular repolarization on an ECG.

Isoelectric line

The flat line on an ECG between waveforms, representing no electrical activity.

Artifact

Interference on an ECG that may distort the trace.

Bradycardia

A slow heart rate, defined as less than 60 beats per minute.

Tachycardia

A fast heart rate, defined as greater than 100 beats per minute.

Depolarization

The process of a cardiac muscle cell discharging an electrical impulse leading to contraction.

Repolarization

The return of cardiac cells to their resting state after depolarization.

Absolute refractory period

The phase during which cardiac cells cannot respond to any stimulus.

Relative refractory period

The phase during which a strong stimulus may cause depolarization of the cardiac cells.

Bundle of His

A collection of heart muscle cells specialized for electrical conduction that transmits impulses from the AV node.

Purkinje fibers

Fibers that spread the impulse throughout the ventricles, causing them to contract.

QRS duration

The time taken for ventricular depolarization, normally less than 0.12 seconds.

PR interval

The time from the beginning of the P wave to the beginning of the QRS complex, normal range is 0.12 to 0.20 seconds.

QT interval

Reflects the total time for ventricular depolarization and repolarization, should be less than half of the preceding R-R interval.

Einthoven's triangle

A triangle formed by the three bipolar limb leads (I, II, and III) used for cardiac monitoring.

Norepinephrine

A neurotransmitter released by sympathetic nerves that increases heart rate.

Acetylcholine

A neurotransmitter released by parasympathetic fibers that decreases heart rate.

Contractility

The ability of the heart muscle to contract.

Automaticity

The ability of cardiac cells to generate electrical impulses independently.

Excitability

The ability of cardiac cells to respond to stimuli.

Conductivity

The ability of cardiac cells to propagate electrical impulses.

Lead placement

The specific positions where electrodes are placed to monitor the heart's electrical activity.