Cardiovascular System: The Heart

Heart Development

I. Introduction

Functions of the Cardiovascular System:• Transportation:

• Respiratory gasses

• Nutrients

• Waste

• Hormones

• Regulation of temperature

• Protection (immune system)

Components of the Cardiovascular System

• Cardiovascular System = heart and the vessels

• Lymphatic system = lymph vessels, lymph nodes, lymph organs

Heart Anatomy

• General Features:

• Size

• It's a dual pump

Coverings of the Heart:

• Parietal pericardium

• Visceral pericardium (epicardium)

• Pericardial sac

Heart in Cross-Section

Epicardium (visceral pericardium)

Myocardium

Endocardium

Chambers of the Heart

• Atria receive blood

• Ventricles pump blood

• Right ventricle pumps blood to the pulmonary circuit

• Left ventricle pumps oxygenated blood to the systemic circuit

• NOTE: Arteries Always carry blood Away from the heart

Heart Valves

• Atrioventricular(AV) valves prevent backflow from ventricles to atria

• Tricuspid valve

• Bicuspid valve (mitral valve)

• Chordae tendineae originate from papillary muscles

• Semilunar valves

• Aortic semilunar valve

• Pulmonary semilunar valve

Cardiac Circulation

Electrical Events in the Heart

Compare and Contrast Skeletal vs. Cardiac Muscle

• Purpose

• Basic principles (all-or-none)

• Time

• Summation / Tetanus

• Refractory period

• Source of stimulus / role of NS

Extrinsic Regulation

Autonomic nervous system

• Sympathetic system

• Parasympathetic

Intrinsic regulation (nodal system)

• Sinoatrial (SA) node contains pacemakers

• Atrioventricular (AV) node

• Atrioventricular bundle (Bundle of His)

• Bundle branches

• Purkinje fibers

The Cardiac Cycle

• Cardiac cycle = contraction, relaxation cycle of the heart

• Systole = contraction

• Diastole = relaxation

• Stroke volume = volume of blood ejected by a ventricle as it contracts

• Cardiac Output = heart rate x stroke volume

The Cardiac Cycle

• 1. Atrial and Ventricular Diastole

• Atria are filling with blood, AV valves are open and blood passively fills the ventricles.

• 2. Early Ventricular Systole

• Ventricles begin to contract, forcing the AV valves to close

• Isovolumic ventricular contraction: ventricles contract, but AV and semilunar valves are closed

The Cardiac Cycle• 3. Ventricular Systole and Blood Ejection

• When ventricular contraction generates enough pressure to open the semilunar valves, blood enters the arteries

• 4. Ventricular Diastole

• Ventricles relax, pressure decreases

• Blood remaining in ventricles is called end-diastolic volume, EDV

• Blood flows back into the heart, closing the semilunar valves

Electrocardiogram (ECG)

• P wave = atrial depolarization

• QRS wave = depolarization of ventricles (and repolarization of atria).

• T wave = repolarization of ventricles

Arteriosclerosis and Cardiac Arrhythmia

• Plaques can clog the arteries, causing restricted blood flow

• Smoking, hypertension, and a diet high in cholesterol and fats contribute

• High ratio of HDL to LDL is desirable

• Myocardial ischemia

• Myocardial infarction = heart attack.

Tight stenosis of RCA. This can cause an inferior wall myocardial infarction. Since this is a short lesion, usually percutaneous coronary intervention will be used - balloon dilatation & stinting.

Cardiac Arrhythmias

• Arrhythmias

• Bradycardia = heart rate less than 60 beats/ min

• Tachycardia = heart rate more than 100 / min

• Flutter = rapid, controlled contractions of atria or ventricles

• Fibrillation = rapid, uncontrolled contractions

• Electrical defibrillation can sometimes re-regulate the myocardial cells to become synchronous again.