Functions of the Circulatory System

• Transport oxygen to cells• Transport nutrients from the

digestive system to body cells• Transport hormones to body cells• Transport waste from body cells to

excretory organs• Distribute body heat

Energy Requirements:• lots of mitochondria • aerobic respiration

Mechanisms and events of contractions:

1. All or none law- at organ level, not cellular level

2. Means of stimulation- autorhythmicy

3. Length of refractory period- cardiac (250ms), skeletal (1-2ms)

Location of Heart

Visceral pericardium • Outer protective layer composed of a serous

membrane • Includes blood capillaries, lymph capillaries, and

nerve fibers.

Layers of Cardiac Tissue

Myocardium • Relatively thick. • Consists largely of cardiac muscle tissue

responsible for forcing blood out of the heart chambers.

• Muscle fibers are arranged in planes, separated by connective tissues that are richly supplied with blood capillaries, and nerve fibers.

Layers of Cardiac Tissue

Endocardium • Consists of epithelial and connective tissue that

contains many elastic and collagenous fibers. • Connective tissue also contains blood vessels

and some specialized cardiac muscle fibers called Purkinje fibers.

• Lines all of the heart chambers and covers heart valves.

Layers of Cardiac Tissue

Pericardial Cavity

Layers of Cardiac Tissue

Heart Anatomy

Heart Anatomy

Heart Anatomy

Rightventricle

Leftventricle

Interventricularseptum

Heart Anatomy

CirculationCirculation

Components of the Human Components of the Human Circulatory SystemCirculatory System

The HeartBlood Vessels

BloodLymphatic Vessels

Lymph

Mechanisms & Events of Contraction

1. Means of stimulation2. Organ vs motor unit

contraction3. Length of absolute

refractory period

Microscopic Anatomy of Cardiac Muscle

Cardiac muscle cells are striated, short, fat, branched, and interconnected

Connective tissue matrix (endomysium) connects to the fibrous skeleton

T tubules are wide but less numerous; SR is simpler than in skeletal muscle

Numerous large mitochondria (25–35% of cell volume)

Figure 18.11a

Nucleus

DesmosomesGap junctions

Intercalated discs Cardiac muscle cell

(a)

Microscopic Anatomy of Cardiac Muscle

Intercalated discs: junctions between cells anchor cardiac cells • Desmosomes prevent cells from separating

during contraction• Gap junctions allow ions to pass;

electrically couple adjacent cells Heart muscle behaves as a functional

syncytium

Microscopic Anatomy of Cardiac Microscopic Anatomy of Cardiac MuscleMuscle

Microscopic Anatomy of Cardiac Microscopic Anatomy of Cardiac MuscleMuscle

Figure 18.8a

Pulmonary valveAortic valveArea of cutaway

Mitral valveTricuspid valve

Myocardium

Tricuspid(right atrioventricular)valveMitral(left atrioventricular)valveAorticvalve

Pulmonaryvalve

(b)

Pulmonary valveAortic valveArea of cutaway

Mitral valveTricuspid valve

Myocardium

Tricuspid(right atrioventricular)valve

(a)

Mitral(left atrioventricular)valveAortic valve

Pulmonaryvalve

Fibrousskeleton

Anterior

VALVES

Figure 18.8c

Pulmonaryvalve

AorticvalveArea ofcutawayMitralvalve

Tricuspidvalve

Chordae tendineaeattached to tricuspid valve flap

Papillarymuscle

(c)

VALVES

left ventricle

left atrium

pulmonary arteries

aorta

superior vena cava

inferior vena cava

right atrium

right ventricle

pulmonary vein

pulmonary arteries

bicuspid valve

aortic semilunar valve

tricuspid valve

pulmonary semilunar

valve

Heart ValvesHeart Valves

ContractioContraction Cycle of n Cycle of the Heartthe Heart

ContractiContraction Cycle on Cycle

of the of the HeartHeart

Contraction Contraction Cycle of the Cycle of the

HeartHeart

Cardiac OutputCO = the vol. of blood ejected from the l. or r. ventricle into the aorta or pulmonary trunk each min.

CO= SV x HR

SV= stroke vol.; the vol of blood ejected from the ventricle during each contraction (ml/beat)HR= heart rate; # beats/min, at rest ~60, exercise ~100

Cardiac Output (at rest)

SV = 75 ml/beat

HR = 75 beats/min

CO = 75 ml/b x 75 b/min

CO = 5250 ml/min = 5.25 L/min

Cardiac Output (exercise)

SV = 100 ml/beat

HR = 100 beats/min

CO = 100 ml/b x 100 b/min

CO = 10 L/min

Electrical Conductivity of the Heart

medulla

oblongata

pons

vagus

Nerve Nerve Innervation:Innervation:

Vagus nerve from medulla (parasympathetic division)

acetylcholine (slows heart)

Cardioacceleratory center in medulla (sympathetic) adrenaline from adrenal glands (speeds up heart)

• P = atrial depolarization ~ 0.1 sec atria contracts• QRS = ventricular depolarization ventricles contract

(lub), contraction stimulated by Ca++ uptake• T = ventricular repolarization ventricles relax (dub)

Electrocardiogram (ECG)

0.1 sec 0.3 sec 0.4 sec

Figure 18.17, step 1

Atrial depolarization, initiated bythe SA node, causes the P wave.

P

R

T

QS

SA node Depolarization

Repolarization

1

Excitation of the Excitation of the HeartHeart

Figure 18.17, step 2

Atrial depolarization, initiated bythe SA node, causes the P wave.

P

R

T

QS

SA node

AV node

With atrial depolarization complete,the impulse is delayed at the AV node.

P

R

T

QS

Depolarization

Repolarization

1

2

Figure 18.17, step 3

Atrial depolarization, initiated bythe SA node, causes the P wave.

P

R

T

QS

SA node

AV node

With atrial depolarization complete,the impulse is delayed at the AV node.

Ventricular depolarization beginsat apex, causing the QRS complex.Atrial repolarization occurs.

P

R

T

QS

P

R

T

QS

Depolarization

Repolarization

1

2

3

Figure 18.17, step 4

Ventricular depolarization iscomplete.

P

R

T

QS

Depolarization

Repolarization

4

Figure 18.17, step 5

Ventricular depolarization iscomplete.

Ventricular repolarization beginsat apex, causing the T wave.

P

R

T

QS

P

R

T

QS

Depolarization

Repolarization

4

5

Figure 18.17, step 6

Ventricular depolarization iscomplete.

Ventricular repolarization beginsat apex, causing the T wave.

Ventricular repolarization iscomplete.

P

R

T

QS

P

R

T

QS

P

R

T

QS

Depolarization

Repolarization

4

5

6

Figure 18.18

(a) Normal sinus rhythm.

(c) Second-degree heart block. Some P waves are not conducted through the AV node; hence more P than QRS waves are seen. In this tracing, the ratio of P waves to QRS waves is mostly 2:1.

(d) Ventricular fibrillation. These chaotic, grossly irregular ECG deflections are seen in acute heart attack and electrical shock.

(b) Junctional rhythm. The SA node is nonfunctional, P waves are absent, and heart is paced by the AV node at 40 - 60 beats/min.

Heart Sounds

Two sounds (lub-dup) associated with closing of heart valves• First sound occurs as AV valves close and

signifies beginning of systole• Second sound occurs when SL valves

close at the beginning of ventricular diastole

Heart murmurs: abnormal heart sounds most often indicative of valve problems

Coronary Artery Disease(CAD)

• Arteriosclerosis• HDL vs LDL

Homeostatic Imbalances

Angina pectoris• Thoracic pain caused by a fleeting

deficiency in blood delivery to the myocardium

• Cells are weakened Myocardial infarction (heart attack)

• Prolonged coronary blockage• Areas of cell death are repaired with

noncontractile scar tissue

Coronary Artery Disease(CAD)Diagnosis

• Stress test• Echocardiography• Cardiac catheterization• Coronary angiography

Coronary Artery Disease(CAD)Treatment

• Coronary bypass grafting (CABG)

• Percutaneous transluminal coronary angioplasty (PTCA)

Procedures for reestablishing blood flow in occluded coronary heart disease

Defibrillator

Inquiry

1. Name the 2 pacemakers of the heart.2. What is the QRS wave?3. What is the middle layer of heart tissue

called?4. What is the parietal pericardium?5. Why is the left ventricle thicker walled than

the right?6. What blood vessel returns blood from the

lungs to the heart?7. What is the function of the chordae tendinae?8. How does the heart avoid going into tetanus?9. What function does serous fluid serve?