Cardiovascular System Overview

Major Circuits of Blood Flow

The cardiovascular system consists of two main circuits that transport blood throughout the body and lungs.

• Systemic Circuit: Pumps blood from the heart to the body and back.

• Pulmonary Circuit: Pumps blood from the heart to the lungs and back.

• Cardiac Circuit: Refers to the flow of blood within the heart itself (coronary circulation).

Functions of the Heart

The heart is a muscular organ responsible for maintaining blood flow and pressure throughout the body.

• Maintains one-way blood flow via valves.

• Circulates blood based on the body's needs.

• Creates blood pressure to drive circulation.

• Oxygenates blood and removes carbon dioxide via pulmonary circulation.

Heart Anatomy

Layers and Coverings of the Heart

The heart wall consists of three layers, surrounded by protective membranes.

• Endocardium: Innermost layer lining the heart chambers.

• Myocardium: Thick muscular middle layer responsible for contraction.

• Epicardium (Visceral Pericardium): Outermost layer of the heart wall.

• Pericardial Membranes: Include the fibrous pericardium (outermost), parietal pericardium (middle), and visceral pericardium (innermost, also called epicardium).

Chambers of the Heart

The heart has four chambers:

• Right Atrium: Receives deoxygenated blood from the body.

• Right Ventricle: Pumps deoxygenated blood to the lungs.

• Left Atrium: Receives oxygenated blood from the lungs.

• Left Ventricle: Pumps oxygenated blood to the body; has the thickest wall.

Heart Valves

Valves ensure unidirectional blood flow and prevent backflow.

• Atrioventricular (AV) Valves: Separate atria from ventricles (tricuspid on right, bicuspid/mitral on left).

• Semilunar Valves: Separate ventricles from arteries (pulmonary semilunar on right, aortic semilunar on left).

Blood Vessels

Types and Structure of Blood Vessels

Blood vessels transport blood throughout the body and are classified by structure and function.

• Arteries: Carry blood away from the heart; thick muscular walls (tunica media).

• Veins: Carry blood toward the heart; have valves to prevent backflow.

• Capillaries: Microscopic vessels for exchange of gases, nutrients, and wastes.

Layers of Blood Vessels

• Tunica intima: Innermost layer, includes endothelium.

• Tunica media: Middle muscular layer, controls vessel diameter.

• Tunica externa (adventitia): Outermost layer, provides support.

Cardiac Physiology

Cardiac Cycle and Heart Sounds

The cardiac cycle describes the sequence of events in one heartbeat.

• Systole: Contraction phase; blood is pumped out.

• Diastole: Relaxation phase; chambers fill with blood.

• Heart Sounds: "Lub" (closing of AV valves), "Dub" (closing of semilunar valves).

Electrical Conduction System

The heart's electrical system coordinates contraction.

• SA Node: Natural pacemaker, initiates impulse.

• AV Node: Delays impulse, allows atria to contract before ventricles.

• AV Bundle (Bundle of His): Transmits impulse to ventricles.

• Purkinje Fibers: Distribute impulse throughout ventricles.

Electrocardiogram (ECG/EKG)

An ECG records the electrical activity of the heart.

• P wave: Atrial depolarization

• QRS complex: Ventricular depolarization

• T wave: Ventricular repolarization

Blood Pressure and Cardiac Output

Definitions and Formulas

• Cardiac Output (CO): Volume of blood pumped by a ventricle per minute.

• Stroke Volume (SV): Volume of blood pumped by a ventricle in one contraction.

• Blood Pressure (BP): Force exerted by blood on vessel walls.

Key Formulas:

• Cardiac Output:

• Stroke Volume: (End-diastolic volume minus end-systolic volume)

Factors Affecting Blood Pressure

• Peripheral Resistance: Resistance to blood flow in vessels.

• Blood Volume: Total amount of blood in the body.

• Heart Rate: Number of beats per minute.

• Vessel Diameter: Smaller diameter increases resistance and pressure.

Regulation of Cardiovascular Function

Neural and Hormonal Control

• Medulla Oblongata: Location of the cardiac control center.

• Sympathetic Nervous System: Increases heart rate and contraction strength.

• Parasympathetic Nervous System: Decreases heart rate.

• Hormones: ADH, aldosterone, and ANH regulate blood volume and pressure.

Renin-Angiotensin-Aldosterone System (RAAS)

This system regulates blood pressure and fluid balance.

• Angiotensin II increases blood pressure by vasoconstriction and stimulating aldosterone release.

• Aldosterone increases sodium and water reabsorption, raising blood volume.

Vascular Physiology

Capillary Exchange

Capillaries allow exchange of gases, nutrients, and wastes between blood and tissues.

• Diffusion: Movement of substances from high to low concentration.

• Osmosis: Movement of water across a semipermeable membrane.

• Filtration: Movement of fluid out of capillaries due to hydrostatic pressure.

Venous Return Mechanisms

• Skeletal Muscle Pump: Muscle contractions help push blood toward the heart.

• Respiratory Pump: Changes in thoracic pressure during breathing aid venous return.

Common Cardiovascular Conditions

Atherosclerosis

Atherosclerosis is the abnormal hardening and narrowing of arterial walls due to plaque buildup.

• Can be caused by smoking, high cholesterol, and hypertension.

• Leads to reduced blood flow and increased risk of heart attack and stroke.

Heart Murmurs

Heart murmurs are abnormal heart sounds due to faulty valves or turbulent blood flow.

• May indicate valve disease or congenital heart defects.

Phlebitis

Phlebitis is inflammation of veins, which can lead to serious complications like thrombosis.

• Symptoms include pain, swelling, and redness along the affected vein.

Pulse Points and Blood Pressure Measurement

• Common Pulse Points: Radial artery, carotid artery, brachial artery.

• Blood Pressure Measurement: Usually taken at the brachial artery using a sphygmomanometer.

Summary Table: Key Terms and Definitions

Additional info: These notes expand upon the multiple-choice questions by providing definitions, explanations, and context for each concept, suitable for college-level Anatomy & Physiology students.