Cardiovascular System

The HeartThe Heart

Both Sides (now)

Functions of the Heart

Generating blood pressureRouting blood

–Heart separates pulmonary and systemic circulationsEnsuring one-way blood flow

–Heart valves ensure one-way flowRegulating blood supplyChanges in contraction rate and force match blood delivery to changing metabolic needs

Size, Shape, Location of the Heart

Size of a closed fist

Shape–Apex: Blunt rounded point of cone–Base: Flat part at opposite of end of cone

Located in thoracic cavity in mediastinum

Pericardium

Heart WallThree layers of tissue–Epicardium: This serous membrane of smooth outer surface of heart–Myocardium: Middle layer composed of cardiac muscle cell and responsibility for heart contracting–Endocardium: Smooth inner surface of heart chambers

Heart Wall

External Anatomy

• Four chambers– 2 atria

– 2 ventricles

• Major veins– Superior vena

cava

– Pulmonary veins

• Major arteries– Aorta

– Pulmonary trunk

External Anatomy

Coronary Circulation

Heart ValvesAtrioventricular

– Tricuspid

– Bicuspid or mitral

Semilunar– Aortic

– Pulmonary

Prevent blood from flowing back

Heart Valves

Function of the Heart Valves

Blood Flow Through Heart

Systemic and PulmonaryCirculation

Heart Skeleton

Consists of plate of fibrous connective tissue between atria and ventricles

Fibrous rings around valves to support

Serves as electrical insulation between atria and ventricles

Provides site for muscle attachment

Conducting System of Hearthttp://www.youtube.com/watch?v=te_S

Y3MeWys&feature=related

Electrical PropertiesAction potentials are:

Sodium ions enter the cell and begin the depolarization

Calcium ions follow and extend the depolarization even further.

Once Calcium stops moving inward, Potassium ions move out and repolarization begins

Specific to the Heart...

•Action Potential is:–Rapid depolarization of heart muscle–Rapid, partial early repolarization of heart muscle –Via Voltage-gated channels–CONFUSED?

Refractory PeriodThe important part of

this cycle is the period where the cells reset and prepare for the next wave. This is called the refractory period because the cells are refractory to (or unaffected by) further stimulation

Refractory Period

• The time between • Absolute: Cardiac muscle cell completely insensitive to further stimulation• Relative: Cell exhibits reduced sensitivity to additional stimulationLong refractory period prevents tetanic contractions

Imagine, if you will, a toilet.

When you pull the handle, (initiate an impulse) water floods the bowl(kinda' like contraction!). This event takes a couple of seconds and you cannot stop it in the middle. Once the bowl empties, the flush is complete. Now the upper tank is empty. If you try pulling the handle at this point, nothing happens (absolute refractory?) Wait for the upper tank to begin refilling (Potassium moves back). You can now flush again, but the intensity of the flushes increases as the upper tank refills (relative refractory...)

ECGAction potentials through myocardium during cardiac cycle produces electric currents than can be measured

Pattern

– P wave

Atria depolarization-firing

– QRS complex

Ventricle depolarization

Atria repolarization

T wave:

Ventricle repolarization-reloading

PQRSTthe P-Wave, representing the impulse across the atria to the A/V Node;The QRS representing the impulse as it travels across the ventricles;the T-Wave, representing the repolarization of the ventricles

Cardiac Arrhythmias

• Tachycardia: Heart rate in excess of 100bpm• Bradycardia: Heart rate less than 60 bpm• Atrial Fibrillation:

describes a condition in which the atrial tissue randomly generates action potentials from many different regions

Alterations in Electrocardiogra

m

Cardiac Cycle

Heart is two pumps that work together, right and left halfRepetitive contraction (systole) and relaxation (diastole) of heart chambersBlood moves through circulatory system from areas of higher to lower pressure.

–Contraction of heart produces the pressure

Cardiac Cycle

Heart Sounds• First heart sound or “lub” (S1-closing

of the tricuspid and mitral valves)– Atrioventricular valves and surrounding fluid vibrations

as valves close at beginning of ventricular systole

• Second heart sound or “dub” (S2- closing of the pulmonic and aortic valves as blood leaves right and left ventricles)– Results from closure of aortic and pulmonary semilunar

valves at beginning of ventricular diastole, lasts longer

• Third heart sound (occasional)

– Caused by turbulent blood flow into ventricles and detected near end of first one-third of diastole

Location of Heart Valves

Heart Homeostasis• Effect of blood pressure– Baroreceptors monitor blood pressure

• Effect of pH, carbon dioxide, oxygen

– Chemoreceptors monitor • Effect of extracellular ion concentration– Increase or decrease in extracellular K+

decreases heart rate

• Effect of body temperature– Heart rate increases when body

temperature increases, heart rate decreases when body temperature decreases

Effects of Aging on the Heart

Gradual changes in heart function, minor under resting condition, more significant during exerciseHypertrophy of left ventricleMaximum heart rate decreasesIncreased tendency for valves to function abnormally and arrhythmias to occurIncreased oxygen consumption required to pump same amount of blood

Pathology (1)

Cardiomyopathy- disease of the heart musclePhlebitis - inflammation of a veinAneurysm - local widening of an arteryCyanosis- bluish color of skinIschemia- diminished blood flowAngina - chest pain

Pathology (2)Petichiae- small, pinpoint hemorrhagesCoronary Artery Disease-blocked arteries leads to ischemiaCongestive heart failure- inability of heart to pump adequatelyClaudication- pain and weakness in a limb as result of decreased blood flow

END

Let’s Do Respiratory!