I. CARDIOVASCULAR SYSTEM, HEART
A. Location (mediastinum)
B. Pericardial sac, fluid, cavity (Parietal pericardium)
C. Heart wall
1. Epicardium (visceral pericardium)
2. Myocardium
– Trabeculae carneae – Irregular ridges of myocardium adding strength without weight
3. Endocardium
D. Chambers
1. Atria, Auricles, Interatrial septum
Upper chambers with “ear-like” auricles
2. Ventricles, Interventricular septum
Lower chambers
3. Coronary sulcus
External groove separating atrium from ventricle and contain coronary blood vessels
E. Valves
1. Atrioventricular (tricuspid, bicuspid or mitral)
a. Chordae tendineae
Heart strings anchoring AV valves to papillary muscles
b. Papillary muscles
Muscle columns in ventricles
2. Semilunar valves
a. Pulmonary
b. Aortic
F. Associated vessels
1. Superior vena cava
Drains superior body into RA, deoxygenated blood
2. Inferior vena cava
Drains inferior body into RA, deoxygenated blood
3. Pulmonary trunk and arteries
RV to lungs, deoxygenated blood
4. Pulmonary veins
Lungs to LA, oxygenated blood
5. Aorta
LV to systemic circuit, oxygenated blood
G. Coronary circulation
Provides nutrients to myocardium; aorta; coronary arteries serving the four chambers; deoxygenated blood is collected by cardiac veins which empty into large coronary sinus (vein), which empties into the RA
H. Cardiac muscle
1. Myocardium
2. Differences from skeletal muscle
a. Automated excitement
b. No graded responses
c. No tetany
d. No anaerobic metabolism
3. Striated, involuntary
4. Intercalated discs, Stimulus passed btwn cells
5. Refractory period prevents tetany
6. Energy
a. ATP; Aerobic metabolism
b. Coronary circulation
7. Excitation
a. Depolarization to threshold
Spontaneous, likely due to gradual decrease in membrane permeability to potassium ions causing a decreased outflow of potassium ions
b. Sinoatrial node
Specialized cardiac muscle cells in wall of right atrium
1. At rest, depolarizes every .8 sec; 60-80 x/min
2. Change in permeability [potassium ions]
3. Pacemaker
8. Conduction from SA Node:
a. AV node (.1 sec delay)
b. AV Bundle (Bundle of His)
c. Purkinje = Conduction fibers
d. Myocardial cells of ventricle
9. Cardiac cycle
a. Systole(RV=30mmHg; LV=120mmHg)
Contraction phase of cardiac cycle
b. Diastole
Heart chambers relax and refill with blood
c. Time
1. Entire cycle .8 sec
2. Atrial systole .1 sec; diastole .7 sec
3. Ventricular systole .3 sec; diastole .5
4. Pressure curves(refer to your book)
a. Atrial (Left)
b. Ventricular (Left)
c. Aortic
5. Heart sounds
a. S1= AV valves closures
b. S2= Semilunar valves closures
10. Cardiac Output
a. CO = HR x SV (5-6 liters/min=70 b/min x 80 ml/bt)
Volume of blood pumped by either ventricle per minute
b. Cardiac reserve[Increase CO 600-700%]
Difference between maximum CO and resting CO
c. Heart rate control
1. Sympathetic stimulation
Increases heart rate
2. Parasympathetic stimulation
Decreases heart rate
d. Stroke volume
Volume pumped from ventricle per beat
SV= end diastolic volume – end systolic volume
1. End-diastolic volume
– Length of diastole
– Venous return
2. End-systolic volume
– Frank- Starling Law
Stretch wall of ventricle leads to increased force of contraction
– Sympathetic N.S.
Decreases end systolic volume
– Parasympathetic N.S.
Increases end systolic volume
11. Factors influencing cardiac function
a. Cardiac center
Brain stem
b. Exercise
Chronic exercises enlarges cardiac muscle and thus increases stroke volume; can have good CO with lower HR due to increased SV
c. Temperature
Heat increases SA node discharge
d. Ions (K, Ca, Na)
e. Sex, age
HR faster in females, youngsters
12. Electrocardiography/Electrocardiogram (ECG,EKG)
a. Leads
Placement of electrodes on body for ECG
b. P wave– atrial depolarization
c. QRS– ventricular depolarization
d. T– Ventricular repolarizationInfo. derived: HR, Blocks, Orientation…
13. Heart disease – If time but not on exam.
Location and Protective Layers of the Heart Video
Conduction Pathway of the Heart Video