Chapter 17 -The Cardiovascular System I: The Heart
Module 17.1 Overview of the Heart
Functions of the Heart: to pump blood
Circulation of blood through the Pulmonary and Systemic Circuits
Right side of the heart: Deoxygenated
-Pumps blood to the lungs
-Known as the pulmonary pump
-The vessels are collectively called the pulmonary circuit
-Pulmonary arteries of the pulmonary circuit delivers deoxygenated blood to the lungs
Left side of the heart: Oxygenated
-Pumps blood to the rest of the body
-Known as the systemic pump
-The vessels are collectively called the systemic circuit
-Systemic arteries deliver oxygenated blood to all of the tissues
Module 17.2 Heart Anatomy and Blood Flow Pathway
The Pericardium, Heart Wall, and Heart Skeleton
Pericardium: the membranous sack that surrounds the heart
Fibrous pericardium: the tough outer layer made of collagen, no stretch
Serous pericardium: the inner layer, a serous membrane, produces serous fluid (watery)
Parietal pericardium: the outer layer of the serous pericardium, it is fused the
fibrous pericardium, no give
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Visceral pericardium (epicardium): on the organ, is an extension of the parietal
pericardium, the most superficial layer of the heart wall
Pericardial cavity: is between the parietal & the visceral pericardium, is
filled with serous fluid called pericardial fluid, acts as a lubricant,
decreases friction as the heart moves
Myocardium: is the cardiac muscle itself, the middle layer of the heart, it houses the
fibrous skeleton that supports the valves
Endocardium: it lines the inside of the heart, is the deepest layer of the heart wall
Endothelium: inner layer of the blood vessels, special simple squamous epithelia tissue
that makes up the endocardium, it is continuous with the endothelia, tunic intima
Coronary Circulation: this is the circuit that delivers oxygen & nutrients to the heart’s cells
Coronary Arteries
Right and left coronary arteries: very first branches off of the aorta, just beyond
the aortic valve
Right coronary artery and branches supply blood to the right atrium & right
ventricle.
Left coronary artery and branches supply blood to the left atrium & left ventricle
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Coronary venous blood empties into the coronary sinus which drains into the
right atrium
The Great Vessels, Chambers, and Valves of the Heart
Great Vessels
-Superior & Inferior Vena Cava- they drain deoxygenated blood
-Pulmonary Trunk–splits into two left & right, delivers the deoxygenated blood to the
lungs
-Pulmonary Veins (4 of them) - drain oxygen rich blood into the left atrium
-Aorta- supplies the entire systemic circuit w/ oxygen rich blood
Chambers
-Atria (2 of them)- upper chambers
-Ventricles (2 of them)- lower chambers, left ventricle is the strongest because it pumps
blood to your big toe
Valves- located along the same plane, held together by a fibrous skeleton
-(AV) Atrioventricular Valves- valves between the atria & ventricles
-Tricuspid Valve (right side)- between the right atria & the right ventricle
-Bicuspid Valve (left side)- aka Mitral valve, between the left atria & the left ventricle
-Semilunar Valves- (half-moon shaped)
-Pulmonary Valves- between the right ventricle & pulmonary trunk
-Aortic Valve- between the left ventricle & the aorta (semi-hidden)
Blood flow through the heart (“Big Picture” fig 17.8)
Module 17.3 Cardiac Muscle Tissue Anatomy and Electrophysiology
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Histology of Cardiac Muscle Tissue and Cells
-Involuntary
-Striated
-Mononucleated
-Rich in mitochondria / rich in myoglobin
-Cells are joined together by intercalated discs
-Rich in gap junctions for ion distribution
Review the events along the cell membrane to cause a muscle contraction
At rest
contraction
end of contraction
(Resting Potential)
return to rest
*Heart recovery period is longer than
skeletal muscle
Pacemaker cells and the cardiac conduction system
The pacemaker cells have slow leaking sodium channels. When enough sodium leaks in, a
depolarization occurs. The depolarization spreads through the cardiac musculature. This is
followed by repolarization and return to rest. Pacemaker cells exhibit autorhymicity.
-It depolarizes 60-72 times per minute
-It is normal for an athletic person has a resting heart rate of 60
-It is not normal for an overweight / unhealthy person to have a resting heart rate of 60
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Anatomy of the Cardiac Conduction System
SA node- (Sinoatrial Node) located upper right atrium
AV node- (Atrioventricular Node) located near the tricuspid valve
Purkinje fiber system
AV bundle- located in the interventricular septum
Bundle branches- also located in the interventricular septum (will have a right & left)
Terminal branches of Purkinje fibers- located in the myocardial walls & in the papilla
Pacing the Heart: Sinus Rhythm
Conduction pathway through the heart
See figure 17.12 on page 650
1. SA Node- stimulates the atrial contraction
& the AV node
2. The action potential spreads down the
bundle branches & up the purkinje fibers
3. Ventricle contracts
**Parasympathetic NS – slows it down / Sympathetic NS – speeds it up
The Electrocardiogram
P wave- Atrial Depolarization (contraction)
QRS complex- Ventricular Depolarization (contraction)
T wave- Ventricular Repolarization or recovery (return to resting potential)
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Module 17.4 Mechanical Physiology of the Heart: The Cardiac Cycle
Heart Sounds
Ventricle
Atrium
A/V valves
SL valves
Blood Pressure
Lub (S1)
systole
diastole
close
open
systolic
Dup (S2)
diastole
systole
open
closed
diastolic
Module 17.5 Cardiac Output and Regulation
Cardiac Output:
Heart Rate X Stroke Volume = Cardiac Output
(Stroke Volume is the amount of blood pumped in one minute per ventricle)
72 beats/per min x 70 mL/per beat = 5040 mL / min
5 L / min (entire blood volume in body)
Factors that influence stroke volume
Preload- Stretch of the sarcomeres before they contract
-The greater the stretch the greater the contraction
-Frank-Sterling Law
Contractility- Pumping ability of the heart
- Increase in stroke volume
Afterload- The force of the right & left ventricle must overcome to eject the blood
- Effected by lung disease & artery disease
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Factors that influence Heart Rate
-Influences heart rate (increases it)
-Body temperature
-Parasympathetic influence (decreases it)
-Tachycardia- over 100 beats per minute & you are resting
-Bradycardia- resting heart rate of less than 60 beats per minute
Regulation of Cardiac Output
Cardiac Innervation and Regulation by the Nervous System
Sympathetic regulation: -Fight or flight
-Increases it
-Increase cardiac output by increasing SA node firing
Parasympathetic regulation: -Rest & digest
-Decreases it
-Decrease cardiac output by decreasing SA node firing
Cardiac Regulation by the Endocrine System
-Adrenal medulla- (Epinephrine & Norepinephrine) do the same thing & increase
cardiac output
-Thyroid Hormone- they increase cardiac output
-Pancreas- (Glucagon) increases cardiac output
Other Factors that Influence Cardiac Output
-Electrolyte balance
-Age
-Physical fitness
-Max heart rate = 220 – (minus) your age
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