The Cardiovascular System:
The Heart
A.
B.
C.
D.
E.
F.
Location and size of the heart
Pericardium
Heart wall
Chambers of the heart
Blood flow through the heart
Valves of the heart
1. Atrioventricular valves
2. Semilunar valves
G. Heart blood supply
1. Coronary arteries
2. Coronary veins
H. Conduction system and
pacemaker
1. Autorhythmic cells: the
conduction system
I. Electrocardiogram
J. Cardiac cycle
1. Phases of the cardiac
cycle
2. Timing of systole and
diastole
K. Cardiac output
1. Regulation of stroke
volume
a. Preload: effect of
stretching
b. Contractility
c. Afterload
2. Regulation of heart rate
a. Autonomic control of
heart rate
b. Chemical regulation of
heart rate
The heart is the center of
cardiovascular system.
1. double pump
a. systemic circulation
b. pulmonary circulation
2. 1,800 gallons of blood per day through
about 60,000 miles of blood vessels
The Pulmonary and Systemic Circuits
Cardiac and Pulmonary Circuits
Heart Location and Size
1. middle mediastinum
2. apex vs base
Gross Anatomy of the Heart
(Anterior and Lateral View)
Pericardium
1. outer fibrous
2. inner serous
a. parietal layer
b. visceral layer
(epicardium)
__________________
3. pericardial cavity
4. pericardial fluid
Pericardium peeled back
Heart Wall
1. epicardium
2. myocardium
a. involuntary
b. striated
c. branched
d. intercalated discs
e. 2 muscle masses
3. endocardium
(endothelium)
Epicardium
Fat and connective Tissue + simple squamous epithelium
Myocardium
Endocardium
Heart Chambers
1. right and left atrium
2. atrial appendages
3. right and left ventricles
____________________
4. coronary sulcus
5. interventricular sulci
Septa of the Heart
1. interatrial septum
a. fossa ovalis
b. foramen ovale
2. interventricular septum
a. membranous
b. muscular
Heart Valves
1. atrioventricular (AV) valves (2)
a. tricuspid & bicuspid (mitral)
b. base vs apex
c. chordae tendineae
d. papillary muscles
2. semilunar (SL) valves (2)
a. pulmonary valve & aortic valve
______________________
b. 3 half-moon cusps
(pockets)
The Heart Valves and Associated
Structures
Gross Anatomy of the Heart
Valves
Blood Flow Through the Heart
Blood Flow Through the Heart
Coronary Circulation(Arteries)
1. left coronary artery
a. anterior interventricular a.
b. circumflex a.
2. right coronary artery
a. marginal a.
b. posterior interventricular a.
_________________________
anastomoses
Coronary Circulation(Veins)
1.
2.
3.
4.
great cardiac v.
middle cardiac v.
small cardiac v.
coronary sinus
Small cardiac vein
Conduction System and
Pacemaker
1. heart stimulates itself with autorhythmic cells
2. ANS and hormones can only modify, not
establish, the fundamental rhythm
3. 1% of cardiac muscle cells lose the ability to
contract during early development (specialized
autorhythmic cells)
4. those cells that cannot contract form the
pacemakers (primary and secondary) and the
conduction system
Conduction System Components
1. sinoatrial (SA) node
(90 - 100 action potentials/min)
(primary pacemaker)
2. atrioventricular (AV) node
(40 - 50 action potentials/min)
(secondary pacemaker)
3. atrioventricular (AV) bundle
4. right and left bundle branches
5. Purkinje fibers
Conduction System of the Heart
Timing of Conduction Events
Times are in seconds
0.07
0.00
0.09
0.01
0.04
0.05
0.22
0.16
0.07
0.19
0.17
0.21
0.19
0.18
0.18
Where does the cardiac muscle contract first? Last?
Why is there a 0.12 sec delay across the AV node?
What separates the atrial muscle mass from the ventricular muscle mass?
Why does the interventricular septum begin to contract before the apex?
Electrocardiogram (ECG)
1.
2.
3.
4.
5.
6.
P wave = atrial depolarization
QRS complex = ventricular depolarization
T wave = ventricular repolarization
P-R interval
S-T segment
quiescent period
Relationship of ECG to Electrical
Activity and Contraction
Normal and Pathological ECGs
Cardiac Cycle
Two phenomena control blood flow
through the heart.
1. contraction and relaxation
2. opening and closing of the AV and
SL valves
The Cardiac Cycle Phenomena
Operation of the Heart Valves
due to Pressure Changes
Blood flows from an area of higher pressure
to an area of lower pressure.
The pressure developed within a heart
chamber is related to two things.
1. volume of blood within the chamber
2. size of the chamber
Pressures to Keep in Mind
1.
2.
3.
4.
venous pressure
atrial pressure
ventricular pressure
arterial pressure
In a normal cardiac cycle, the two atria contract
while the two ventricles relax, then the two
ventricles contract while the atria relax and then
all chambers are relaxed until the next P wave
1. systole vs. diastole
2. Four phases of the cardiac cycle:
a. Ventricular filling
b. Isovolumetric contraction
b. Ventricular ejection
c. Isolvolumetric relaxation

Ventricular Filling
1. In diastole, ventricles expand and pressure decreases.
AV valves open when atrial pr. > ventricular pr.
2. Three phases of ventricular filling
a. rapid ventricular filling
b. diastasis
c. atrial systole (30%)
70%
3. end-diastolic volume (EDV)
= 130 ml of blood
70% of filling occurs during quiescent period- time period
In which all four chambers are in diastole
Isovolumetric Contraction
1. Atrial diastole begins and
Ventricular systole begins
2. AV valves close when
ventricular pr. > atrial pr.
3. No blood is ejected because
arterial pr. > ventricular pr.
Ventricular Ejection
 1. Ventricular pr. > arterial pr.
 2. SL valves open when
ventricular pr. > arterial pr.
 3. Rapid ejection, then
reduced ejection
 Stroke volume (SV) = 70 ml
 Ejection fraction
= SV/EDV x 100 = 54%
 End-systolic volume
ESV = 60 ml
Isovolumetric Relaxation
1. Early ventricular diastole
2. Ventricles expand, pr. decreases
3. SL valves close when
arterial pr. > ventricular pr.
4. Isovolumetric because the
SL valves are closed and
AV valves are still closed
The quiescent period begins when
atrial pr. > ventricular pr.
AV valves open and the period
of rapid ventricular filling begins
for the next cycle.
Cardiac Cycle Events Continued
Overview of Volume Changes
End-systolic volume
(left from previous heart beat)
60 ml
Passively added during atrial diastole +
(rapid ventricular filling + diastasis)
30 ml
Atrial systole
+
40ml
_____________________________________________________________
total = end-diastolic volume
130 ml
Stroke volume
(ejected by ventricular systole)
Leaves the end-systolic volume
-
70 ml
60 ml
Timing of the Cardiac Cycle
1. resting heart rate = 75 beats/minute
2. one cardiac cycle requires 0.8 sec.
3. first 0.4 sec. = quiescent period
4. next 0.4 sec. = atrial and ventricular
systole
Chamber Volume and Pressure Changes
8 sec.
0 sec.
aortic
valve
closes
aortic
valve
opens
pressure
aortic pressure
AV valve
closes
AV valve
opens
atrial pressure
ventricular
pressure
volume
R
R
P
ventricular
volume
P
T
ECG
Q
T
Q
S
lubb
dupp
heart sounds
ventricular systole
ventricular diastole
S
lubb
dupp
Cardiac output (CO) = amount of blood
ejected from the left ventricle into the
aorta per minute
Cardiac output is determined by two factors:
1. stroke volume (SV)
2. heart rate (HR)
So how is cardiac output calculated?
CO = SV x HR
= (70 ml/beat) x (75 beats/minute)
= 5,250 ml/minute or 5.25 liters/minute (L/min)
Cardiac Reserve
1. difference between maximum
cardiac output and resting cardiac
output
2. expressed as percent of normal
Normal cardiac reserve = 15-20L/min =
200-300%
endurance athlete = 35L/min = 600%
Regulation of SV: Preload
increased venous pressure
increased venous return
increased ventricular filling
increased preload
increased ventricular stretch
Frank-Starling mechanism
increased force of contraction
increased stroke volume
increased cardiac output
Regulation of SV: Contractility
increased sympathetic activity
increased epinephrine
other factors
increased contractility
increased force of contraction
increased stroke volume
increased cardiac output
Regulation of SV: Afterload
increased arterial pressure
increased afterload
decreased blood volume
ejected into artery
decreased stroke volume
decreased cardiac output
Autonomic Regulation of the
Heart
1. CO = SV x HR
2. sensory input
a. baroreceptors
b. chemoreceptors
3. cardiovascular center
4. motor output
a. cardioacceleratory nerves
(sympathetics)
b. cardioinhibitory nerves
(parasympathetics)
Chemical Regulation of the
Heart Rate
Ions
– Increased K+ decreases heart rate
– Moderate increase in Ca2+ increases heart
rate
,
Hormones- epinephrine,
norepinephrine, throxine, and glucagon
increase heart rate