3. Structure of the Heart
Four chambers
a. Right atrium (RA): receives deoxygenated
blood from the body
b. Right ventricle (RV): receives blood from RA
and pumps deoxygenated blood to the lungs
c. Left atrium (LA): receives oxygenated blood
from the lungs
d. Left ventricle (LV): receives blood from LA and
pumps oxygenated blood to the body
4. Structure of the Heart
Fibrous skeleton
a. Separates atria from ventricles. The atria
therefore work as one unit, while the ventricles
work as a separate unit.
b. Forms the annuli fibrosi rings, which hold in
heart valves
c. Attachment for cardiac muscles
d. Insulates extra electrical impulses from traveling
to and from the ventricles and atria
5.
6. Pulmonary and Systemic Circulations
Pulmonary: between heart and lungs
a. Deoxygenated blood pumped to lungs via
pulmonary arteries.
b. Oxygenated blood returns to heart via
pulmonary veins.
Systemic: between heart and body tissues
a. Oxygenated blood pumps to body tissues via
aorta.
b. Deoxygenated blood returns to heart via
superior and inferior venae cavae.
9. Atrioventricular & Semilunar Valves
Atrioventricular (AV) valves: located between the
atria and the ventricles
a. Tricuspid (right atrioventricular valve):
between right atrium and ventricle
b. Bicuspid or mitral (left atrioventricular
valve): between left atrium and ventricle
c. Papillary muscles and chordae tendineae
prevent the valves from everting
10. Atrioventricular & Semilunar Valves
Semilunar valves: located between the ventricles
and arteries leaving the heart
a. Pulmonary valve: between right ventricle and
pulmonary trunk
b. Aortic valve: between left ventricle and aorta
12. Heart Sounds
1. Produced by closing valves
a. “Lub” = closing of AV valves; occurs at
ventricular systole
b. “Dub” = closing of semilunar valves; occurs at
ventricular diastole
14. Heart Murmur
Abnormal heart sounds produced by abnormal
blood flow through heart.
• Many caused by defective heart valves.
a. Aortic stenosis – calcified or defective aortic
valve that doesn’t open completely
• Systolic murmur radiates to right carotid area
b. Aortic regurgitation – defective aortic valve that
doesn’t close completely
• Diastolic murmur best heard at the left sternal
border
15. Heart Murmur
c. Mitral stenosis – calcified or defective mitral
valve that doesn’t opening completely.
• Diastolic murmur best heard at the apex
• May result in pulmonary hypertension.
d. Mitral regurgitation – defective mitral valve that
doesn’t close completely
• Systolic murmur best heard at apex and radiates
to axilla
• May be due to damaged papillary muscles
• Mitral valve prolapse – most common cause of
chronic mitral regurgitation
16. Heart Murmur
e. Septal defects: holes in interventricular or
interatrial septa which allows blood to cross sides.
1. Atrial septal defect
• Systolic murmur best heard at upper sternal
border
2. Ventricular septal defect
• Systolic murmur best heard at lower sternal
border
f. Patent ductus arteriosus
• Machinery-like murmur best heard at right upper
sternal border
19. Introduction
1. Cardiac cycle
a. Repeating pattern of contraction and
relaxation of the heart.
b. Systole: contraction of heart muscles
c. Diastole: relaxation of heart muscles
2. End-diastolic volume – total volume of blood
in the ventricles at the end of diastole
3. End-systolic volume – the amount of blood left
in the left ventricle after systole (1/3 of the end-
diastolic volume)
21. Pressure Changes During the Cardiac Cycle
1. Ventricles begin contraction, pressure rises, and
AV valves close (lub); isovolumetric contraction
2. Pressure builds, semilunar valves open, and blood
is ejected into arteries.
3. Pressure in ventricles falls; semilunar valves close
(dub); isovolumetric relaxation
4. Dicrotic notch – slight inflection in pressure during
isovolumetric relaxation
5. Pressure in ventricles falls below that of atria, and
AV valve opens. Ventricles fill.
6. Atria contract, sending last of blood to ventricles
29. Introduction
1. Cardiac muscle cells are interconnected by gap
junctions called intercalated discs.
2. Once stimulation is applied, the impulse flows
from cell to cell.
3. The area of the heart that contracts from one
stimulation event is called a myocardium or
functional syncytium.
4. The atria and ventricles are separated electrically
by the fibrous skeleton.
30. Electrical Activity of the Heart
1. Automaticity – certain areas of the heart
contains specialized cardiac tissues that have
the ability to generate action potentials on their
own Pacemaker potential
2. Sinoatrial node (SA node) - “natural
pacemaker”; located in right atrium
• Average about 80 beats per minute
3. AV (atrioventricular) node and Purkinje fibers
(subendocardial fibers) are secondary
pacemakers of ectopic pacemakers; slower rate
than the “sinus rhythm”
31. Conducting Tissues of the Heart
a. Action potentials spread via intercalated discs
(gap junctions).
b. SA node to AV node to stimulate atrial
contraction
c. AV node at base of right atrium and bundle of
His conduct stimulation to ventricles.
d. In the interventricular septum, the bundle of His
divides into right and left bundle branches.
e. Branch bundles become Purkinje fibers, which
stimulate ventricular contraction.
33. Conduction of Impulses
a. Action potentials from the SA node spread rapidly
1) 0.8–1.0 meters/second
b. At the AV node, things slow down.
1) 0.03−0.05 m/sec
2) This accounts for half of the time delay
between atrial and ventricular contraction.
c. The speed picks up in the bundle of His, reaching
5 m/sec in the Purkinje fibers.
d. Ventricles contract 0.1–0.2 seconds after atria.
34. Pacemaker potential
a. A slow, spontaneous depolarization; also called
diastolic depolarization
b. Triggered by hyperpolarization of preceding AP,
which opens “funny channels” at -60mV
c. “Funny channels” (HCN channels) allow for both
Na+ and Ca2+ to flow into and depolarize the cell
d. Once threshold is reached at −40mV, voltage-
gated Ca2+ channels open, triggering action
potential and depolarization atrial contraction
e. Repolarization occurs with the opening of voltage-
gated K+ channels.
36. Pacemaker potential
Pacemaker cells in the sinoatrial node depolarize
spontaneously, but the rate at which they do so
can be modulated:
1) Epinephrine and norepinephrine increase the
production of cAMP, which keeps cardiac
pacemaker channels open.
a) Called HCN channels – hyperpolarization-
activated cyclic nucleotide-gated channels
b) Speeds heart rate due to Na+ inflow
2) Parasympathetic neurons secrete acetylcholine,
which opens K+ channels to slow the heart rate.
37. Myocardial (Ventricular) Action Potentials
a. Cardiac muscle cells have a resting potential of
−85mV.
b. They are depolarized to threshold by action potentials
from the SA node.
c. Voltage-gated Na+ channels (fast Na+) open causes
rapid depolarization
d. At the peak, fast Na+ channels close, but slow Ca2+
channels and voltage-gated K+ channels open at
-15mV , which maintains the plateau phase for
200−300 msec.
e. More voltage-gated K+ channels are opened, and
repolarization occurs.
40. Excitation-contraction Coupling
a. Ca2+-stimulated Ca2+ release
b. Action potentials conducted along the sarcolemma
and T tubules, open voltage-gated Ca2+ channels
c. Ca2+ diffuses into cells and stimulates the opening
of calcium release channels of the SR
d. Ca2+ (mostly from SR) binds to troponin to
stimulate contraction
e. These events occur at signaling complexes on the
sarcolemma where it is close to the SR
42. Repolarization
a. Ca2+ concentration in cytoplasm reduced by active
transport back into the SR and extrusion of Ca2+
through the plasma membrane by the Na+-Ca2+
exchanger
b. Myocardium relaxes
43. Refractory Periods
a. Because the atria and ventricles contract as single
units, they cannot sustain a contraction.
b. Because the action potential of cardiac cells is
long, they also have long refractory periods before
they can contract again.
45. Electrocardiogram (ECG or EKG)
The electrocardiograph records the electrical
activity of the heart by picking up the movement
of ions in body tissues in response to this activity.
a. Does not record action potentials, but
results from waves of depolarization
b. Does not record contraction or relaxation,
but the electrical events leading to contraction
and relaxation
46. Electrocardiogram waves and intervals
a. P wave - atrial depolarization
b. P-Q interval – atrial systole
c. QRS wave - ventricular depolarization
d. S-T segment - plateau phase, ventricular systole
e. T wave - ventricular repolarization
49. Electrocardiograph leads
a. Bipolar limb leads record voltage between
electrodes placed on wrists and legs.
1) Lead I: between right arm and right leg
2) Lead II: between right arm and left leg
3) Lead III: between left arm and left leg
50. Electrocardiograph leads
b. Unipolar leads record voltage between a single
electrode on the body and one built into the
machine (ground).
1) Limb leads go on the right arm (AVR), left arm
(AVL), and left leg (AVF).
2) There are six chest leads.
56. Tunics of blood vessels
1. Tunica interna – inner layer; composed of simple
squamous endothelium on a basement membrane
and elastic fibers
2. Tunica media – middle layer; composed of
smooth muscle tissue
3. Tunica externa – outer layer; composed of
connective tissue
57. Arteries
1. Elastic arteries: closer to the heart; allow stretch
as blood is pumped into them and recoil when
ventricles relax
2. Muscular arteries: farther from the heart; have
more smooth muscle in proportion to diameter;
also have more resistance due to smaller lumina
3. Arterioles: 20−30 µm in diameter; provide the
greatest resistance; control blood flow through the
capillaries
59. Capillaries
1. Smallest blood vessel: 7−10 µm in diameter
2. Single layer of simple squamous epithelium tissue
in wall
3. Where gases and nutrients are exchanged
between the blood and tissues
4. Blood flow to capillaries is regulated by:
a. Vasoconstriction and vasodilation of arterioles
b. Precapillary sphincters
60. Types of Capillaries
a. Continuous capillaries: Adjacent cells are close
together; found in muscles, adipose tissue, and
central nervous system (add to blood-brain
barrier)
b. Fenestrated capillaries: have pores in vessel
wall; found in kidneys, intestines, and endocrine
glands
c. Sinusoidal capillaries: have large pores and
gaps between cells; found in bone marrow, liver,
and spleen; allow the passage of proteins
61. Veins
1. Most of the total blood volume is in veins,
therefore also known as Blood resevoirs
2. Lower pressure (2 mmHg compared to 100
mmHg average arterial pressure)
3. Thinner walls than arteries, larger lumen; collapse
when cut
62. Veins
4. Blood returns back to the heart via:
a. Skeletal muscle pumps: Muscles
surrounding the veins help pump blood.
b. Venous valves: Ensure one-directional flow
of blood
c. Breathing: Flattening of the diaphragm at
inhalation increases abdominal cavity
pressure in relation to thoracic pressure and
moves blood toward heart.
65. A. Atherosclerosis
1. Most common form of arteriosclerosis (hardening
of the arteries)
a. Contributes to 50% of the deaths due to heart
attack and stroke
b. Plaques protrude into the lumen and reduce
blood flow.
c. Serve as sites for thrombus formation
d. Plaques form in response to damage done to
the endothelium of a blood vessel.
e. Caused by smoking, high blood pressure,
diabetes, high cholesterol
67. 2. Developing Atherosclerosis
a. Lipid-filled macrophages and lymphocytes
assemble at the site of damage within the tunica
interna (fatty streaks).
b. Next, layers of smooth muscle are added.
c. Finally, a cap of connective tissue covers the
layers of smooth muscle, lipids, and cellular
debris.
d. Progress promoted by inflammation stimulated by
cytokines and other paracrine regulators.
68. 3. Cholesterol and Lipoproteins
a. Low-density lipoproteins (LDLs) carry
cholesterol to arteries.
1) People who consume or produce a lot of
cholesterol have more LDLs.
2) This high LDL level is associated with
increased development of atherosclerosis
70. Cholesterol and Lipoproteins, cont
b. High-density lipoproteins (HDLs) carry
cholesterol away from the arteries to the liver for
metabolism.
1) This takes cholesterol away from the
macrophages in developing plaques (foam
cells).
2) Statin drugs (e.g., Lipitor), fibrates, and niacin
increase HDL levels.
71. 4. Inflammation in Atherosclerosis
a. Atherosclerosis is now believed to be an
inflammatory disease.
b. C-reactive protein (a measure of inflammation) is
a better predictor for atherosclerosis than LDL
levels.
c. When endothelial cells engulf LDLs, they become
oxidized LDLs that damage the endothelium
d. Antioxidants may be future treatments for this
condition.
72. 5. Ischemic Heart Disease
a. Ischemia is a condition characterized by
inadequate oxygen due to reduced blood flow.
1) Atherosclerosis is the most common cause.
2) Associated with increased production of lactic
acid and resulting pain, called angina pectoris
(referred pain).
3) Eventually, necrosis of some areas of the heart
occurs, leading to a myocardial infarction (heart
attack or MI).
73. Ischemic Heart Disease, cont
4) Nitroglycerin produces vasodilation
a) Improves blood flow
b) Dead myocardial cells can not be replaced by
mitosis of neighboring cells
c) Reperfusion injury may cause death of
neighboring cells to enlarge the infarct
74. b. Detecting Ischemia
1) Depression of the S-T segment of an
electrocardiogram
2) Plasma concentration of blood enzymes
a) Creatine phosphokinase – 3-6 hours, return to
normal in 3 days
b) Lactate dehydrogenase – 48-72 hours, elevated
about 11 days
c) Troponin I – today’s most sensitive test
d) Troponin T
76. B. Heart Arrhythmias Detected by ECG
1. Abnormal heart rhythms
a. Bradycardia: slow heart rate, below 60 bpm
b. Tachycardia: fast heart rate, above 100 bpm
c. These heart rhythms are normal if the person is
active, but not normal at rest.
d. Abnormal tachycardia can occur due to drugs or
fast ectopic pacemakers.
77. Heart Arrhythmias, cont
e. Ventricular tachycardia occurs when
pacemakers in the ventricles make them
contract out of synch with the atria.
f. This condition is very dangerous and can
lead to ventricular fibrillation and sudden
death.
78. 2. Flutter and Fibrillation
a. Flutter: extremely fast (200−300 bpm) but
coordinated contractions
b. Fibrillation: uncoordinated pumping between the
atria and ventricles
80. 3. Types of Fibrillation
a. Atrial fibrillation:
1) Can result from atrial flutter
2) Atrial muscles cannot effectively contract.
3) AV node can’t keep pace with speed of atrial
contractions, but some stimulation is passed on.
4) Only reduces cardiac output by 15%
5) Associated with increased risk of thrombi,
stroke, and heart failure
81. Types of Fibrillation, cont
b. Ventricular fibrillation
1) Ventricles can’t pump blood, and victim dies
without CPR and/or electrical defibrillation to
reset the heart rhythm.
2) Caused by circus rhythms – continuous cycling
of electrical waves
3) Refractory period prevented
4) Sudden death progresses from ventricular
tachycardia, through ventricular fibrillation,
ending in astole (straight-line ECG)
82. 4. AV Node Block
a. Damage to the AV node can be seen in
changes in the P-R interval of an ECG.
b. First degree: Impulse conduction exceeds 0.2
secs.
c. Second degree: Not every electrical wave can
pass to ventricles
d. Third degree/complete: No stimulation gets
through. A pacemaker in the Purkinje fibers
takes over, but this is slow (20−40 bpm).
85. Functions of the Lymphatic System
1. Transports excess interstitial fluid (lymph) from
tissues to the veins
2. Produces and houses lymphocytes for the
immune response
3. Transports absorbed fats from intestines to blood
87. Vessels of the Lymphatic System
1. Lymphatic capillaries: smallest; found within
most organs
a. Interstitial fluids, proteins, microorganisms, and
fats can enter.
2. Lymph ducts: formed from merging capillaries
a. Similar in structure to veins
b. Lymph is filtered through lymph nodes
