Cardiac Physiology Practice Flashcards

Vocabulary-style flashcards covering cardiac nerve transmission, ECG components, the cardiac cycle, hemodynamics, and cardiac abnormalities based on the lecture transcript.

Resting membrane potential of cardiac contractile fibers

$$-90\,mV$$

Threshold potential of cardiac contractile fibers

$$-75\,mV$$

Depolarization (Cardiac Muscle)

The phase initiated when threshold potential is reached and sodium channels open, causing sodium ions to rush into contractile fibers.

Intercalated disks

Structures used to carry nerve impulses throughout cardiac muscle.

Plateau

Phase where calcium channels open and calcium enters contractile fibers from extracellular fluid and the sarcoplasmic reticulum, maintaining depolarization for $250\,mS$.

Repolarization (Cardiac Muscle)

Phase where potassium channels open and potassium diffuses out of contractile fibers while sodium and calcium channels close, restoring the resting membrane potential.

Epinephrine

A chemical that increases contraction force by increasing calcium influx into the contractile fibers.

Calcium channel blockers

Agents that reduce calcium influx to diminish contraction force.

Refractory Period

The time following a contraction when a second contraction cannot be triggered, allowing ventricles to relax and fill with blood.

Electrocardiogram

A recording of electrical changes occurring in the myocardium during a cardiac cycle, used to determine if conduction pathways are normal or heart regions are damaged.

P Wave

The portion of an ECG tracing representing atrial depolarization.

QRS Complex

The portion of an ECG tracing representing ventricular depolarization; it also contains atrial repolarization.

T Wave

The portion of an ECG tracing representing ventricular repolarization, occurring just before ventricles relax.

Systole

The contraction phase of the cardiac cycle.

Diastole

The relaxation phase of the cardiac cycle.

Relaxation Period

Phase following the T wave where all four chambers are relaxed and semilunar valves are closed.

End-diastolic volume

The maximum amount of blood each ventricle contains, approximately $130\,ml$ in a normal adult.

Isovolumetric contraction phase

The phase from the start of ventricular contraction to the opening of the semilunar valves.

Stroke Volume

The volume of blood ejected from each ventricle, measuring approximately $70\text{-}80\,mL$.

Isovolumetric relaxation

Period where all heart valves are closed and ventricular pressures are higher than atrial pressures, preventing blood flow into the ventricles.

First heart sound

A loud and long sound representing the closing of the atrioventricular (AV) valves.

Second heart sound

A short and sharp sound representing the closing of the semilunar (SL) valves.

Heart murmur

A sound caused by blood regurgitation back through a valve.

Cardiac Output (CO)

The volume of blood pumped by a ventricle in one minute, calculated as $CO = HR \times SV$; normal is $5\,\text{liters}$.

Vagus nerve

A parasympathetic nerve that decreases the heart rate.

Ischemia

Low blood flow.

Hypoxia

Low oxygen content.

Angina Pectoris

Chest pain related to cardiac abnormalities.

Myocardial Infarction

Commonly known as a heart attack.

Tachycardia

A heart rate greater than $100$.

Bradycardia

A heart rate lower than $60$.

Premature Ventricular Contractions (PVC’s)

Ventricular contraction that occurs before atrial contraction.

Ventricular Fibrillation

Electrical activity in the heart without true contraction.

Asystole

The absence of electrical activity, often called a "flat line".