THE HEART
Chapter 18
The Pulmonary and Systemic Circuits
 ______________________________: receives blood returning from
______________________________ oxygen poor blood from the tissues
 ______________________________: receives blood returning from
______________________________, oxygen rich blood from the lungs
 ______________________________: pumps blood through
______________________________pumps to lungs to get rid of CO2 and pick
up O2
 ______________________________: pumps blood through systemic circuit
Heart Anatomy
 Rests on the superior surface of _______________
 _______________ leans toward right shoulder
 _______________ points toward left hip
Coverings of the Heart: Pericardium
 _____________________________________________: protects and anchors the
heart to surrounding structures
 Deep two-layered ______________________________
o ______________________________: lines internal surface of fibrous
pericardium
o _______________ _______________ (epicardium): lines the external
surface of the heart
o Two layers separated by fluid-filled _______________ _______________
(decreases friction)
Three Layers of the Heart Wall
 _______________ (visceral layer of serous pericardium): lines the external surface
of the heart
 _______________: spiral bundles of contractile cardiac muscle cells
 _______________: lines heart chambers; covers cardiac skeleton of valves
______________________________: crisscrossing, interlacing layer of connective tissue
 _______________cardiac muscle fibers
 _______________ great vessels and valves
 Limits spread of ______________________________to specific paths
Four chambers of the heart:
 Two superior atria separated by the ______________________________
o ______________________________: remnant of foramen ovale of fetal
heart
 Two inferior ventricles separated by the ______________________________
Coronary Sulci:
 _______________ _______________ (atrioventricular groove): encircles junction
of atria and ventricles
 _____________________________________________: anterior position of
interventricular septum
 _____________________________________________: posterior position of
interventricular septum
Atria: The Receiving Chambers
 _______________: appendages that increase atrial volume, contribute little to
propulsion of blood
 ______________________________: contain
______________________________; posterior and anterior regions separated by
______________________________
o Three veins empty into right atrium:
_____________________________________________,
_____________________________________________,
______________________________
 ______________________________: no pectinate muscles
o Four ______________________________empty into left atrium
Ventricles: The Discharging Chambers
 Most of the _______________ of heart
 ______________________________than atria
 ______________________________: irregular ridges of muscle on walls
 ______________________________: anchor chordae tendineae
 ______________________________: most of anterior surface, pumps blood into
pulmonary trunk
 ______________________________: posterior inferior surface, pumps blood into
aorta (largest artery in body)
Heart Valves
 Ensure_______________blood flow through heart
 Open and close in response to ______________________________within the heart
chambers
 Two ______________________________: prevent backflow into atria when
ventricles contract
o ______________________________: between the
_______________atrium and _______________ ventricle
o _______________ _______________ (bicuspid valve): between the
_______________ atrium and _______________ ventricle
 ______________________________anchor cusps to
______________________________; hold valve flaps in closed
position
Heart Valves
 _____________________________________________: prevent backflow into
ventricles when ventricles relax
 Open and close in response to ______________________________within the heart
chambers
o _____________________________________________: between the left
ventricle and aorta
o _____________________________________________: between the right
ventricle and pulmonary artery
______________________________: blood backflows so heart repumps same blood
over and over
______________________________: stiff flaps constrict opening; heart must exert more
force to pump blood
Pulmonary circuit: ______________________________to
______________________________to ______________________________to
_____________________________________________to
______________________________to ______________________________to
_______________to ______________________________to
______________________________
Systemic circuit: ______________________________to
______________________________to
______________________________
______________________________________
_______to _______________ to ______________________________
Pathway of Blood Through the Circuits
 Pulmonary circuit short, ______________________________circulation
 Systemic circuit long, ______________________________circulation
o Left ventricle walls ______________________________than right
ventricle walls
Coronary Circulation: functional blood supply to ____________________________itself
 Delivered when heart is _______________
 ______________________________receives most blood supply
 Contains many _______________ (junctions) which provide additional routes for
blood delivery
Coronary Circulation: Arteries arise from ______________________________
 _____________________________________________branches into the
_____________________________________________ and
______________________________
 _____________________________________________branches into the
_____________________________________________ and
_____________________________________________
Coronary Circulation: Veins collect blood from ______________________________
 ______________________________empties into right atrium; formed by merging
cardiac veins
 ______________________________vein in anterior interventricular sulcus
 ______________________________vein in posterior interventricular sulcus
 Several _____________________________________________empty directly into
right atrium anteriorly
______________________________: thoracic pain caused by fleeting deficiency in
blood delivery to myocardium, cell weakened
______________________________: heart attack; prolonged coronary blockage, areas
of cellular death repaired with noncontractile scar tissue
Cardiac muscle cells:
 _______________, short and _______________
 1 (perhaps 2) ______________________________
 Numerous large _______________
 _______________ connects cardiac muscle cells to the cardiac skeleton
 ______________________________: junctions between cells, allows heart to
behaves as single coordinated unit
o _______________: prevent cells from separating during contraction
o ______________________________: allow ions to pass from cell to cell;
electrically couple adjacent cells
Three differences between cardiac muscle and skeletal muscle:
1. _______________: do not need nervous system stimulation
2. All cardiomyocytes contract as ______________________________, or none do
3. Long absolute _______________ _______________ (prevents tetanic contractions)
Cardiac Muscle Contraction (starting at -90V resting potential)
1. ______________________________allow initial small depolarization by allowing
_______________and _______________into the cell
2. At -70V (threshold) _________________________________________________
open (Na+ in) depolarizing cell quickly to +20V
3. Fast voltage-gated Na+ channels close quickly _______________ (K+ out) bring cell
down to +5V
4. ____________________________________________________________ (Ca2+ in)
open to counteract the __________________ (K+ out) prolongs the depolarization
phase (_______________)
5. ____________________________________________________________close and
_______________ (K+ out) bring cell back to -90V
6. _______________close
Intrinsic cardiac conduction system
 Network of _____________________________________________
 Initiate and distribute impulses which coordinate _______________ and
_______________of heart
______________________________: autorhythmic, have unstable resting membrane
potentials and continuously depolarize
Three parts of action potential in pacemaker cells:
 ______________________________: at -60V K+ channels close and slow Na+
channels open (Na+in)
o Does not reach resting potential of -90V
 ______________________________: at threshold (-40V) Ca2+ channels open,
huge influx of Ca2+; rising phase of action potential
o Higher threshold, -40V vs. -90V
 _______________: at +10V inactivation of Ca2+ channels and K=+ channels open;
efflux of K+ until cells reach -60V
______________________________cells pass impulses, in order, across heart in ~220
ms______________________________to ______________________________to
______________________________to
____________________________________________________________to
_____________________________________________
(______________________________)
______________________________located in the right atrial wall
 Depolarizes _______________than rest of myocardium
 Generates impulses about 75X/minute (______________________________)
______________________________: located in the inferior interatrial septum
 40-60 bts/min without SA intervention
 Delays impulses approximately_______________because fibers are
______________________________and have fewer
______________________________
 Allows atrial contraction _______________to ventricular contraction
______________________________: located in superior interventricular septum
 Only ______________________________between atria and ventricles
Right and left ______________________________: two pathways in interventricular
septum
 Carry impulses toward _______________of heart
Subendocardial conducting network (______________________________): complete
pathway through ______________________________into apex and
______________________________
 More elaborate on ______________________________of heart
_______________: irregular heart rhythms; uncoordinated atrial and ventricular
contractions
_______________: rapid, irregular contractions; useless for pumping blood; circulation
ceases resulting in brain death
Electrocardiogram (_______________): composite of all
______________________________generated by nodal and contractile cells at given
time
 Three waves:
o _______________: SA node depolarization
o ______________________________: ventricular depolarization and atrial
repolarization
o _______________: ventricular repolarization
 Three intervals:
o _______________interval: beginning of atrial excitation to beginning of
ventricular excitation
o _______________segment: entire ventricular myocardium depolarized
o _______________interval: beginning of ventricular depolarization
through ventricular repolarization
Extrinsic Innervation of the Heart
 Heartbeat modified by ANS via ______________________________in
______________________________
 _______________ increase rate and force
o ______________________________: affects SA, AV nodes, heart muscle,
coronary arteries
o Activated by emotional or physical stressors
o Release of _______________ causes faster HR
 _______________ decreases rate
o ______________________________: inhibits SA and AV nodes via
vagus nerves
o Opposes sympathetic effects (______________________________)
o Heart at rest exhibits ______________________________
o _______________ causes slower HR
_______________: abnormally fast heart rate (>100 bts/min); if persistent, may lead to
fibrillation
_______________: heart rate slower than 60 bts/min; may result in grossly inadequate
blood circulation in nonathletes
Heart Sounds: two sounds (lub-dup) associated with closing of _____________________
 First as _______________close (mitral, bicuspid)
 Second as _______________close (aortic, pulmonary)
______________________________: abnormal heart sounds; usually indicate
incompetent or stenotic valves
______________________________blood flow through heart during one complete
heartbeat
 _______________systole (contraction) and diastole (relaxation) followed by
_______________ systole (contraction) and diastole (relaxation)
 Series of _______________ and ______________________________changes
Three stages of the cardiac cycle:
1. ______________________________
 Pressure in the heart is _______________
 _______________are open
 Blood _______________ moves from the atria into the ventricles (80%)
 Atria_______________delivering remaining blood to ventricles (20%)
 _____________________________________________volume of blood remaining
in each ventricle after atrial systole
2. ______________________________
 Atria _______________; ventricles begin to contract
 Rising ventricular pressure closes _______________
 _____________________________________________ (all valves are closed)
 In ______________________________ventricular pressure exceeds pressure in
large arteries, forcing _______________open
 _____________________________________________volume of blood remaining
in each ventricle after ventricle systole
3. ______________________________
 Ventricles _______________; atria relaxed and _______________
 Backflow of blood in aorta and pulmonary trunk closes _______________
(ventricles totally closed chambers)
 When atrial pressure exceeds that in ventricles _______________open; cycle
begins again with ______________________________
______________________________: volume of blood pumped by each ventricle in one
minute
 CO = ______________________________× ______________________________
 _______________ = number of beats per minute
 _______________ = volume of blood pumped out by one ventricle with each beat

____________________________
 ______________________________: difference between resting and maximal CO
Regulation of Stroke Volume (______________________________)
 EDV affected by _______________of ventricular diastole and
______________________________
o Longer ventricle _______________means more time for filling (greater
EDV)
o Stronger venous pressure forces _______________ blood into ventricles
(greater EDV)
 ESV affected by _______________and force of ____________________________
o _______________arterial BP impedes movement of blood out of
ventricles (greater ESV)
o _______________ ventricular contractions moves less blood out of
ventricles (greater ESV)
Three factors affecting stroke volume:
1. _______________force distending ventricles
 Force of the contractions of the myocytes depends on the _______________ to
which they are stretched
 _______________ _______________ (within limits) results in a greater force of
contraction
 More efficient creation of cross-bridges between actin and myosin
 Most important factor stretching cardiac muscle is
______________________________
o ______________________________and _______________ increase
venous return which distends (stretches) ventricles and _______________
2. _______________y: measure of the ability of the muscle to contract, independent of
muscle
stretch
 ______________________________: sympathetic stimulation positive inotropic
agents (thyroxine, glucagon, epinephrine, high extracellular Ca2+)
 ______________________________: negative inotropic agents (acidosis, increased
extracellular K+, calcium channel blockers)
3. _______________: force against which the ventricle must act to eject blood
 Main factor is _______________
_____________________________________________: progressive condition; CO is so
low that blood circulation inadequate to meet tissue needs
______________________________: left side of the heart fails results in blood backing
up in lungs (edema)
______________________________: right side of the heart fails results in blood pooling
in body organs (edema)