Lesson 3 - Introduction to Cardiovascular Disease

CARDIOVASCULAR SYSTEM

Dr. Poland Room 3-007, Sanger Hall, Phone: 828-9557E-mail: [email protected]

Departemen Fisiologi

Fakultas Kedokteran

Universitas Sumatera Utara

CARDIOVASCULAR SYSTEM

• heart, which serves as a pump for the • blood, • blood vessels, which transport blood

throughout the body.• a continuous and closed circuit,

Functions of the Cardio-Vascular System

©Delivery of O2, Glucose and other nutrients to active tissues.

©Transport of metabolites and other substances to and from storage sites.

©Transport of hormones, antibodies and other substances to site of action.

Dr Peter K. McFawn Department of Physiology Queen’s University Botterell Hall 4 th floor

[email protected] http://meds.queensu.ca/physiol/underg.html

Transport

HEARTheart consists of two separate pumps; right and left side

right side; pumps blood to the lungs through the pulmonary gas exchange, uptake of oxygen and elimination of carbon dioxide can take place

left side; pumps blood to the rest of the tissues of the body through the systemic circulation oxygen and nutrients are delivered to the tissues to sustain their activities and carbon dioxide and other metabolic waste products are removed from the tissues

BLOOD VESSELS

arterial system, arteries and arterioles, carry blood away from heart and toward tissues.

arterioles deliver blood to the capillaries where exchange of substances between blood and tissues takes place.

From capillaries, blood flows into the vessels of the venous system, veins and venules, which carry blood back to the heart.

BASIC PHYSICS OF BLOOD FLOW

To function mechanically as a pump, the heart must have: • Receiving chambers ; atria• Delivery chambers; ventricles• Valves; ensure the one-way, or forward, flow of the blood

Cardiac output (CO); amount of blood from each ventricle pumped/minute depends on volume of bood ejected per minute (stroke volume, SV) and number of heart beats per minute (heart beat, HR)

CO = SV x HR

Systole; phase of cardiac cycle during which ventricle cells are contracting

Diastole; when ventricle cells relax

Conducting System of the Heart

AV Node

Posterior Inferior Fascicle

Anterior Superior Fascicle

Septal Depolarization Fibers

Purkinjie Fibers

Inter- nodal Tracts

Bundle of HIS

Left Bundle Branch

Right Bundle Branch

SA Node

• Diastolic Filling

Autonomic Neural Influences

• Adrenergic sympathetic nerve fibers release norepinephrine on cardiac cells which interacts with β1 adrenergic receptors to increase heart rate, action potential conduction velocity, force of contraction and rates of contraction and relaxation.

• increase cardiac pumping

• Cholinergic parasympathetic nerve fibers travel to heart via vagus nerve and innervate SA node, AV node, and atrial muscle. When active, release acetylcholine which interacts with muscarinic receptors on cardiac muscle cells to decrease heart rate (SA node) and action potential conduction velocity (AV node), force of contraction of atrial (not ventricular) muscle cells.

The Circulatory System2 main divisions

• Pulmonary circulation (heart lungs)– Pulmonary artery: deoxygenated blood from the heart to

the lungs– Pulmonary vein: oxygenated blood from the lungs to the

heart

• Systemic circulation: (Heart rest of the body)– Aorta: feeds oxygenated (arterial) blood to the body – Venae cavae: returns deoxygenated (venous) blood from

the body

PULMONARYCIRCULATION

1. LOW RESISTANCE

2. LOW PRESSURE(25/10 mmHg)

SYSTEMICCIRCULATION

1. HIGH RESISTANCE

2. HIGH PRESSURE(120/80 mmHg)

PARALLELSUBCIRCUITS

UNIDIRECTIONALFLOW

THE SYSTEMIC CIRCULATION

CAPACITY VESSELS

NORMAL

THE PULMONARYCIRCULATION

1. LOW RESISTANCE

2. LOW PRESSURE(25/10 mmHg)

1. HIGH RESISTANCE

2. HIGH PRESSURE(120/80 mmHg)

VALVES

Atrioventricular (AV) valves; between the atria and the ventricles: Right side: tricuspid valve Left side: bicuspid valve (mitral valve)

Semilunar valves; separate the ventricles from their associated arteries. Right side: pulmonary valve Left side: aortic valve

ATRIOVENTRICULAR VALVE

When ventricles contract, the pressure within them increases substantially, creating a pressure gradient for blood flow from ventricles back into the atria where the pressure is very low.

Closure of the AV valves prevents this potential backward flow of blood.

When ventricles are stimulated to contract, the papillary muscles also contract, pulling downward on chordae tendinae

In this way, the flaps of valves are not pushed open into the atria, but instead are held in place in the closed position.

Blood is now forced to continue its forward progression and move from ventricles into their respective arteries

SEMILUNAR VALVES

These valves prevent backward flow of blood from the pulmonary artery or the aorta into their preceding ventricles when the ventricles relax.

HEART SOUNDS

Two sounds are normally heard through a stethoscope during each cardiac cycle.

First sound, a low, slightly prolonged “lub” caused by vibrations set up by sudden closure of AV valves at start of ventricular systole. Duration 0,15 s and frequency 25 to 40 Hz.

Second sound, a shorter, high-pitched “dup” caused by vibrations associated with closure of aortic and pulmonary valves just after the end of ventricular systole. Duration 0,12 s and frequency 50 Hz.

Third sound, a soft, low-pitched, is heard about one third of the way through diastole in many normal young individuals. It coincides with period of rapid ventricular filling and is probably due to vibrations set up by the inrush of blood.

Fourth sound can sometimes be heard immediately before first sound when atrial pressure is high or ventricle is stiff in conditions such as ventricular hypertrophy. It is due to ventricular filling and is rarely heard in normal adults.

MURMURBlood normally flows in a laminar

fashion; that is, layers of fluid slide smoothly over each other (lamina means “layer”). Laminar flow does not produce any sound up to a critical velocity; above this velocity and beyond an obstruction, blood flow is turbulent and creates sounds.

Blood flow speeds up when an artery or a heart valve is narrowed.

Murmurs (abnormal heart sounds) are usually (but not always) associated with cardiac disease.

Murmurs not involving heart pathology, so-called functional murmurs, are more common in young people (and some elderly people) with perfectly healthy hearts, probably because their heart walls are relatively thin and vibrate with rushing blood.

Systolic murmurs are also heard in anemic patients as a result of the low viscosity of the blood and associated rapid flow.

HEART MURMURHeart murmurs can be either systolic

or diastolic. During systole, while left ventricle is

contracting, aortic valve is open and the mitral valve is closed.

Turbulent flow can occur either because of an incompetent mitral valve, leading to regurgitation of blood back into the atrium, or from a narrowed aortic valve.

HEART MURMURIn diastole, the situation is reversed, with filling of the left ventricle through an open mitral valve while the aortic valve is closed.

Turbulent flow occurs when there is narrowing of the mitral valve or incompetence of the aortic valve.

Let it beat!