The Cardiovascular system: Heart

Chapter 13Pages 339-373

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Chapter 13 Wordbytes

1. Angio- = vessel2. Auri- = ear3. Cardio-, cor- = heart4. -emia = in the blood5. Endo- = within6. Epi = on top of7. Ische- = to obstruct

8. Myo = muscle9. Papill- = nipple10.Peri = around11.Pulmon- = lung12.Tend- = tendon13.Ventr- =underside

About the size of a fist; weighs less than a pound

Found in thoracic cavity between two lungs = mediastinum (medial cavity of thorax)◦ ~2/3 to left of midline

Surrounded by pericardium:1. Fibrous pericardium-

◦ Inelastic; protects and anchors heart in place2. 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.

Size, Location, Orientation

Homeostatic Imbalance p.683

•Pericarditis inflammation of pericardium

–Creates a creaking sound heard by a stethoscope–Can compress fluid and limit heart’s ability to pump blood

Figure 15.1

p. 682

1. Epicardium- outer layer (contains fat)

2. Myocardium- cardiac muscle = bulk of heart; what contracts ◦Two separate networks via gap junctions

in intercalated discs- atrial & ventricular◦Networks- contract as a unit

3. Endocardium- Squamous epithelium◦Lines inside of myocardium

3 Heart Wall Layers: p. 684

Figure 15.2a

Figure 15.2b

Figure 15.2c

2 superior chambers= atria (receiving chambers)◦Contains auricles small, wrinkled, protruding appendages

◦2 Parts:◦ 1.smooth-walled posterior◦ 2.anterior = ridged by bundles of muscles

◦Between is interatrial septum◦Contains fossa ovalis- remnant of foramen ovalis (opening in fetal heart)

4 Chambers of Heart

Blood enters right atria via 3 veins:1. Superior vena cava (from body regions

superior to diaphragm)2. Inferior vena cava (from body areas below

diaphragm)3. Coronary sinus (collects blood from

myocardium)

4 pulmonary veins enter the left atrium◦ Transport blood from the lungs back to the heart

2 inferior chambers = ventricles (discharging chambers = pumps)◦Make up most of the mass of the heart◦Between is interventricular septum◦Right ventricle pumps blood into the

pulmonary trunk (to lungs for gas exchange)

◦Left ventricle pumps blood into the aorta = largest artery in the body

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

left

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

Great Vessels Of Heart- Right p. 687

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

Great Vessels –Left p. 687-8

Figure 15.3a

p. 685 - 687

Figure 15.3b

p. 685 - 687

Figure 15.3c

p. 685 - 687

Blood flow through vessels in myocardium = coronary circulation

L. & R. coronary arteries◦ branch from aorta◦ branch to carry blood throughout muscle

Deoxygenated blood collected by Coronary Sinus (posterior)

Empties into R. Atrium

Blood Supply Of Heart

Figure 15.5a

Figure 15.5b

p. 688

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◦ Chordae tendineae – “heart strings”

= anchor cusps to muscles Semilunar valves near origin of aorta &

pulmonary trunk ◦ Aortic & pulmonary (semilunar)

valves respectively

Valves p.690

Figure 15.4ab

p. 691

Figure 15.4c

p. 691

Figure 15.4d

p. 691

Striated Contracts by sliding Short, fat, branched, interconnected Contains 1 or 2 centrally located nuclei Large mitochondria = high resistance to

fatigue

Properties of Cardiac Muscle

1% of cardiac muscle generate action potentials= Pacemaker & Conduction system

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

Conduction System

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

Pacemaker

Figure 15.6

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

Electrocardiogram

Figure 15.7

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

Cardiac Cycle

Review muscle Heart has addition of External Ca2+

creates a plateau prolonged depolarized period. Can not go into tetanus.

Action Potential

Figure 15.8

Cardiac Output (CO) = liters/min pumped Heart Rate (HR) = beats/minute (bpm) Stroke volume (SV) = volume/beat CO = HR x SV

Flow Terms

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

Controls- Stroke Volume (S.V.)

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

Controls- Heart Rate

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

Other Controls

Figure 15.9

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

Exercise

Figure 15.10