Chapter 19 - Flashcards

Epicardium (Visceral Pericardium)

Outer layer of the heart wall and the visceral layer of the serous pericardium.

Myocardium

Middle and thickest layer of the heart wall composed of cardiac muscle tissue.

Endocardium

Inner endothelial layer lining the heart chambers and covering the valves.

Fibrous Pericardium

Tough, outer fibrous connective tissue layer of the pericardial sac.

Serous Pericardium Inner Layer

Divided into the parietal layer (lines the fibrous sac) and visceral layer (epicardium).

Sinoatrial (SA) Node

The natural "pacemaker" of the heart with the fastest depolarization rate.

Intrinsic Conduction System Order

1. SA Node -> 2. AV Node -> 3. AV Bundle (Bundle of His) -> 4. Right and Left Bundle Branches -> 5. Purkinje fibers.

First-Degree Heart Block

Characterized by a delayed conduction time between atria and ventricles, often seen as a prolonged PR interval on an EKG.

Second-Degree Heart Block

Characterized by intermittent dropping of ventricular beats where some atrial impulses fail to reach the ventricles.

Third-Degree (Complete) Heart Block

Total block where no impulses are transmitted from atria to ventricles, causing them to beat independently.

Reasons for Abnormal Rhythms

Ischemia, electrolyte imbalances, drug toxicity, scar tissue, and damage to the conduction system.

P Wave on an EKG

Represents atrial depolarization, which is followed by atrial contraction.

QRS Complex on an EKG

Represents ventricular depolarization (and masks atrial repolarization); precedes ventricular contraction.

T Wave on an EKG

Represents ventricular repolarization.

Atrial Contraction Timing

Occurs during atrial systole, shortly after the P wave.

Ventricular Contraction Timing

Occurs during ventricular systole, beginning shortly after the QRS complex.

AV Valves Closing Timing

Roughly close at the start of ventricular systole (beginning of QRS complex).

Semilunar Valves Closing Timing

Roughly close at the start of ventricular diastole (end of T wave).

First Heart Sound (S1)

The "lub" sound caused by the closing of the AV valves.

Second Heart Sound (S2)

The "dup" sound caused by the closing of the semilunar valves.

All 4 Valves Closed Period

Yes, during isovolumetric contraction and isovolumetric relaxation phases.

Coronary Circulation

Blood supply/circulation of the heart muscle itself.

Pulmonary Circulation

Blood circulation of the lungs.

Systemic Circulation

Blood circulation of the rest of the body.

Cardiac Cycle Pressure Rule

Blood flows through the heart chambers from areas of high pressure to areas of low pressure.

Phase 1 of Cardiac Cycle

Ventricular filling: AV valves open, semilunar valves closed, blood flows passively and via atrial contraction into ventricles.

Phase 2 of Cardiac Cycle

Isovolumetric contraction: All 4 valves closed, ventricular pressure rises sharply without a change in volume.

Phase 3 of Cardiac Cycle

Ventricular ejection: Semilunar valves open as ventricular pressure exceeds arterial pressure, blood is pumped out.

Phase 4 of Cardiac Cycle

Isovolumetric relaxation: All 4 valves closed, ventricular pressure falls as ventricles relax.

Cardiac Output Formula

CO = Heart Rate (HR) x Stroke Volume (SV).

Preload (Stroke Volume Factor)

The degree of stretch of the heart muscle before it contracts (linked to end-diastolic volume).

Contractility (Stroke Volume Factor)

The intrinsic strength of cardiac muscle contraction independent of stretch and preload.

Afterload (Stroke Volume Factor)

The arterial backpressure (resistance) that ventricles must overcome to eject blood.

Sympathetic Autonomic Control

Extrinsic control that increases heart rate (tachycardia) and contractility.

Parasympathetic (Vagus) Control

Extrinsic control via the vagus nerve that decreases heart rate (bradycardia).

Chemical Regulators (Increase HR/Force)

Epinephrine, thyroxine, and elevated calcium ions (Ca2+).

Chemical Regulators (Decrease HR/Force)

Excess potassium ions (K+) or sodium ions (Na+).

Gender Factors on Heart Rate

Females generally have a slightly higher resting heart rate compared to males.

Age Factors on Heart Rate

Infants and young individuals have significantly higher heart rates compared to older adults.

Arrhythmia

Any variation from the normal rhythm of the heart heartbeat.

Ischemia

Inadequate blood supply to an organ or tissue (such as the myocardium).

Ectopic Foci

Abnormal pacemaker sites outside of the SA node that initiate premature beats.

Fibrillation

Rapid, uncoordinated, chaotic twitching of heart muscle fibers.

Flutter

Rapid, but coordinated, regular contractions of the heart chambers (especially atria).

Myocardial Infarction

Death of myocardial tissue due to prolonged ischemia (heart attack).

Coronary Sinus

A large venous channel on the posterior heart that drains cardiac venous blood into the right atrium.

Thebesian Veins (Minimæ Cardiac Veins)

Tiny veins that drain blood directly from the myocardium into the heart chambers.

Atherosclerosis

The buildup of fatty plaques, cholesterol, and other substances in and on artery walls.

Acute Coronary Occlusion

A sudden, complete blockage of a coronary artery.

Collateral Circulation

Alternate pathways of blood vessels that develop to supply tissue when a main vessel is blocked.

Angina Pectoris

Chest pain caused by transient myocardial ischemia.

Cardiac Stretch

The stretching of myocardial fibers prior to contraction, influencing stroke volume.

Diastole

The relaxation phase of the heart chambers when they fill with blood.

Systole

The contraction phase of the heart chambers when they pump blood out.

Auscultation

The action of listening to sounds from the heart (or lungs) using a stethoscope.

Murmurs

Abnormal or unusual heart sounds resulting from turbulent blood flow (often faulty valves).

Mitral Valve Prolapse

A condition where the mitral (bicuspid) valve leaflets bulge back into the left atrium during ventricular contraction.

Frank-Starling Law of the Heart

Within physiological limits, the greater the heart muscle is stretched (preload), the greater the force of its contraction.

Cardiac Reserve

The difference between resting cardiac output and maximum cardiac output a person can achieve.

Marey's Law of the Heart

Inverse relationship between heart rate and blood pressure (an increase in BP reflexively slows the heart rate).

Bainbridge Reflex (Atrial Reflex)

An autonomic reflex where an increase in right atrial pressure/blood volume speeds up the heart rate.

Carotid Sinu Reflex

Baroreceptor-mediated reflex located in carotid sinuses that helps regulate blood pressure and heart rate.

Tachycardia

An abnormally fast resting heart rate (typically above 100 beats per minute).

Bradycardia

An abnormally slow resting heart rate (typically below 60 beats per minute).

Pulmonary Congestion & Edema

Occurs when the left side of the heart fails, causing blood to back up into the lungs.

Peripheral Congestion & Edema

Occurs when the right side of the heart fails, causing fluid backup and swelling in the feet, ankles, and fingers.