Copyright 2010, John Wiley & Sons, Inc. Chapter 15 The Cardiovascular System: The Heart.

Copyright 2010, John Wiley &

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Chapter 15

The Cardiovascular System: The Heart


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Location of the Heart Thoracic cavity between two lungs

~2/3 to left of midline surrounded by pericardium: Fibrous pericardium -

Inelastic and anchors heart in place Inside is serous pericardium - double

layer around heart Parietal layer fused to fibrous pericardium Inner visceral layer adheres tightly to heart Filled with pericardial fluid - reduces friction

during beat.


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Position of the Heart


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Position of the Heart


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Heart Wall

Epicardium - outer layer Myocardium - cardiac muscle

Two separate networks via gap junctions in intercalated discs - atrial & ventricular

Networks- contract as a unit Endocardium - Squamous epithelium

lines inside of myocardium


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Pericardium


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Cardiac Muscle Fibers


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Cardiac Muscle Tissue


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Chambers of the Heart 4 chambers 2 upper chambers = Atria

Between is interatrial septum Contains fossa ovalis - remnant of foramen ovalis

2 lower chambers = ventricles Between is interventricular septum

Wall thickness depends on work load Atria thinnest Right ventricle pumps to lungs & thinner than left


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Structure of the Heart


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Great Vessels Of Heart-Right

Superior & inferior Vena Cavae Delivers deoxygenated blood to R. atrium

from body Coronary sinus drains heart muscle veins

R. Atrium R. Ventricle pumps through Pulmonary Trunk R & L pulmonary arteries lungs


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Great Vessels Of Heart-Left

Pulmonary Veins from lungs oxygenated blood

L. atrium Left ventricle ascending aorta body Between pulmonary trunk & aortic arch is

ligamentum arteriosum fetal ductus arteriosum remnant


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Posterior View of Heart


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Anterior View of Frontal Section


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Valves

Designed to prevent back flow in response to pressure changes

Atrioventricular (AV) valves Between atria and ventricles

Right = tricuspid valve (3 cusps) Left = bicuspid or mitral valve Semilunar valves near origin of aorta &

pulmonary trunk Aortic & pulmonary valves respectively


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Atrioventricular Valves: Bicuspid Valves


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Atrioventricular Valves: Superior View


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Blood Flow Through Heart


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Blood Flow


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Blood Supply Of Heart

Blood flow through vessels in myocardium = coronary circulation

Left & right coronary arteries branch from aorta branch to carry blood throughout muscle

Deoxygenated blood collected by coronary sinus (posterior)

Empties into right atrium


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Conduction System 1% of cardiac muscle generate action

potentials= Pacemaker & Conduction system

Normally begins at sinoatrial (SA) node Atria & atria contract AV node - slows AV bundle (Bundle of His) bundle branches Purkinje fibers apex and up- then ventricles contract


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Pacemaker

Depolarize spontaneously sinoatrial node ~100times /min also AV node ~40-60 times/min in ventricle ~20-35 /min Fastest one run runs the heart = pacemaker Normally the sinoatrial node


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Frontal plane

Right atrium

Right ventricle

Left atrium

Left ventricle

Anterior view of frontal section

Frontal plane

Left atrium

Left ventricle


SINOATRIAL (SA) NODE1

Right atrium

Right ventricle

Frontal plane

Left atrium

Left ventricle


SINOATRIAL (SA) NODE

ATRIOVENTRICULAR(AV) NODE

1

2

Right atrium

Right ventricle

Frontal plane

Left atrium

Left ventricle




ATRIOVENTRICULAR (AV)BUNDLE (BUNDLE OF HIS)

1

2

3

Right atrium

Right ventricle

Frontal plane

Left atrium

Left ventricle





RIGHT AND LEFTBUNDLE BRANCHES

1

2

3

4

Right atrium

Right ventricle

Frontal plane



Left atrium

Left ventricle



RIGHT AND LEFTBUNDLE BRANCHES

PURKINJE FIBERS

1

2

3

4

5

Right atrium

Right ventricle


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Electrocardiogram Recording of currents from cardiac

conduction on skin = electrocardiogram (EKG or ECG)

P wave = atrial depolarization Contraction begins right after peak Repolarization is masked in QRS

QRS complex = Ventricular depolarization Contraction of ventricle

T-wave = ventricular repolarization Just after ventricles relax


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ECG


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Cardiac Cycle after T-wave ventricular diastole

Ventricular pressure drops below atrial & AV valves open ventricular filling occurs

After P-wave atrial systole Finishes filling ventricle (`25%)

After QRS ventricular systole Pressure pushes AV valves closed Pushes semilunar valves open and ejection

occurs Ejection until ventricle relaxes enough for

arterial pressure to close semilunar valves


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Action Potential

Review muscle Heart has addition of External Ca2+

Creates a plateau Prolonged depolarized period Can not go into tetanus


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Cardiac Cycle


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Flow Terms

Cardiac Output (CO) = liters/min pumped

Heart Rate (HR) = beats/minute (bpm) Stroke volume (SV) = volume/beat CO = HR x SV


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Controls - Stroke Volume (S.V.)

Degree of stretch = Frank-Starling law Increase diastolic Volume increases strength

of contraction increased S.V. Increased venous return increased S.V.

increased sympathetic activity High back pressure in artery decreased

S.V. Slows semilunar valve opening


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Controls- Heart Rate Pacemaker adjusted by nerves

Cardiovascular center in Medulla parasympathetic- ACh slows

Via vagus nerve Sympathetic - norepinephrine speeds Sensory input for control:

baroreceptors (aortic arch & carotid sinus)- B.P.

Chemoreceptors- O2, CO2, pH


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Other Controls Hormones:

Epinephrine & norepinephrine increase H.R.

Thyroid hormones stimulate H.R. Called tachycardia

Ions Increased Na+ or K+ decrease H.R. &

contraction force Increased Ca2+ increases H.R. &

contraction force


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Autonomic Nervous System Regulation of Heart Rate


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Exercise and the Heart

Aerobic exercise (longer than 20 min) strengthens cardiovascular system

Well trained athlete doubles maximum C.O.

Resting C.O. about the same but resting H.R. decreased


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End of Chapter 15

Copyright 2010 John Wiley & Sons, Inc.All rights reserved. Reproduction or translation of this work beyond that permitted in section 117 of the 1976 United States Copyright Act without express permission of the copyright owner is unlawful. Request for further information should be addressed to the Permission Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publishers assumes no responsibility for errors, omissions, or damages caused by the use of theses programs or from the use of the information herein.

Copyright 2010, John Wiley & Sons, Inc. Chapter 15 The Cardiovascular System: The Heart.

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