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Chapter 20
The Heart
59
Anatomy
Undergraduate 2
01/22/2018
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Term
Parietal pericardium
 Definition
- outer layer of pericardium, inner layer of
pericardial sac
Term
Visceral pericardium
 Definition
inner layer of pericardium
Term
Pericardial cavity
 Definition
between parietal and visceral layers
contains pericardial fluid (lubricant)
Term
Auricle
 Definition
Atrial appendage
Term
Coronary sulcus
 Definition
divides atria and ventricles
Term
Anterior & posterior interventricular sulcus
 Definition
separate ventricles, contain blood vessels
Term
Characteristics of cardiac muscle cells
 Definition
-Small size
-Single, central nucleus
-branching interconnections between cells
-Intercalated discs
Term
Atrioventricular (AV) valves
 Definition
Connect right atrium to right ventricle and left atrium to left ventricle
 The fibrous flaps that form bicuspid (2) and tricuspid (3) valves
 Permit blood flow in one direction: atria to ventricles
Term
Superior vena cava
 Definition
Receives blood from head, neck, upper
limbs, and chest
Term
Inferior vena cava
 Definition
Receives blood from trunk, viscera, and
lower limbs
Term
Coronary sinus
 Definition
Cardiac veins return blood to coronary
sinus
 Coronary sinus opens into right atrium
Term
Foramen ovale
 Definition
Before birth- opening through interatrial septum
 Connects the two atria
 Seals off at birth, forming fossa ovalis
Term
Pectinate muscles
 Definition
Contain prominent muscular ridges
 On anterior atrial wall and inner surfaces of right auricle
Term
Trabeculae carneae
 Definition
 Muscular ridges on internal surface of right (and left) ventricle
 Includes moderator band:
– Ridge contains part of conducting system
– Coordinates contractions of cardiac muscle cells
Term
The Pulmonary circuit
 Definition
Conus arteriosus (superior end of right ventricle) leads to pulmonary trunk
 Pulmonary trunk divides into left and right pulmonary arteries
 Blood flows from right ventricle to pulmonary trunk through pulmonary valve
 Pulmonary valve has three semilunar cusps
 Pulmonary semilunar valve
Term
The Left Atrium
 Definition
Blood gathers into left and right pulmonary veins
 Pulmonary veins deliver to left atrium
 Blood from left atrium passes to left ventricle through left atrioventricular (AV) valve
 Two-cusped bicuspid valve or mitral valve
 Prevents backflow during ventricular contraction
Term
The Left Ventricle
 Definition
Holds same volume as right ventricle
 Much larger; muscle is thicker and more powerful
 Similar internally to right ventricle but does not have moderator band
Term
Systemic circulation
 Definition
Blood leaves left ventricle through aortic valve into ascending aorta
 Ascending aorta turns (aortic arch) and becomes descending aorta
Term
Atrioventricular (AV) valves
 Definition
Blood pressure closes valve cusps during ventricular contraction
 Papillary muscles tense chordae tendineae: prevent valves from swinging into atria
Term
Semilunar valves
 Definition
pulmonary & aortic tricuspid valves
 Prevent backflow from pulmonary trunk and aorta into ventricles, have no muscular support
Term
Cardiac (fibrous) skeleton
 Definition
4 bands around heart valves & bases of pulmonary trunk & aorta- stabilize valves
 Electrically insulate ventricular cells from atrial cells
Term
Coronary Arteries
 Definition
Originate at aortic sinuses at base of aorta
 Highest blood pressure in systemic circuit
 Elastic rebound forces blood through coronary arteries between contractions
Term
Left coronary artery
 Definition
Supplies blood to left ventricle, left
atrium, interventricular septum
 2 main branches of left coronary artery
 Circumflex artery
 Anterior interventricular artery
Term
Right coronary artery
 Definition
- Supplies blood to right atrium,
portions of both ventricles, and cells of sinoatrial (SA) and atrioventricular nodes
Term
Anterior cardiac veins
 Definition
Empties into right atrium
Term
Anterior cardiac veins
 Definition
Empties into right atrium
Term
Anterior cardiac veins
 Definition
Empties into right atrium
Term
Anterior cardiac veins
 Definition
Empties into right atrium
Term
Anterior cardiac veins
 Definition
Empties into right atrium
Term
2 types of cardiac muscle cells
 Definition
Conducting system
 Controls and coordinates heartbeat
 Contractile cells
 Produce contractions that propel blood
Term
Conducting system
 Definition
Step 1:SA node activity and atrial activation begin Step 2: Stimulus spreads across the atrial surfaces and reaches the AV node. Step 3:There is a 100 msec delay at the AV node. Atrial contraction begins.After traveling through AV node, impulse conducted through the AV bundle and bundle branches in the interventricular septum to Purkinje fibers. Step 4: The impulse travels along the interventricular septum within the AV bundle and the bundle branches to the purkinje fibers and, via the moderator band, to the papillary muscles of the right ventricle. Step 5: Purkinje fibers distribute impulse through ventricles. Atrial contraction completed, ventricular contraction begins.
Term
Ectopic pacemaker
 Definition
Abnormal cells generate high rate of action potentials
 Bypass conducting system, disrupt ventricular contractions
 Results in pumping efficiency reduction
Term
Features of an EKG
 Definition
P wave: atria depolarization
QRS complex: ventricles depolarize, ventricles contracting shortly after R wave
T wave: ventricles repolarize
Term
Role of calcium ions
 Definition
Contraction of a cardiac muscle cell is produced by an increase in Ca2+ concentration around myofibrils
1. calcium ions crossing plasma membrane during plateau phase provide about 20% of Ca required for a contraction
2. Arrival of extracellular Ca2+ triggers release of calcium ion reserves from sarcoplasmic reticulum.
Term
4 phases of the cardiac cycle
 Definition
atrial systole, atrial diastole, ventricular systole, ventricular diastole
Term
8 steps in the cardiac cycle
 Definition
1. atrial systole
2. atria eject blood into ventricles
3. Atria systole ends
4. Ventricular systole
5. Ventricular ejection
6. ventricular pressure falls
7. Ventricular diastole
8. Atrial pressure is higher than ventricular pressure
Term
End-diastolic volume (EDV)
 Definition
Amount of blood in each ventricle at end of ventricular diastole
Term
S1 (Lubb)
 Definition
Produced by AV valves closing, start of ventricular contraction
Term
S2 (Dubb)
 Definition
produced by semilunar valves closing, beginning of ventricular filling
Term
End-systolic volume (ESV)
 Definition
Amount of blood remaining in each ventricle at end of ventricular systole
Term
Stroke volume
 Definition
Amount of blood pumped out of each ventricle during a single beat
SV=EDV-ESV
Term
Absolute refractory period
 Definition
membrane cannot respond at all
 Na+ channels already open, closed or inactivated
 Usually lasts the duration of plateau and initial period of rapid repolarization
Term
Relative refractory period
 Definition
Na+ channels closed but can open if stronger than normal stimulus
 Action potential lasts 30 X’s longer than skeletal muscle
Term
Cardioacceleratory center
 Definition
controls sympathetic neurons
(increases heart rate)
Term
Cardioinhibitory center
 Definition
controls parasympathetic neurons
(slows heart rate)
Term
Effects on the SA Node (heart rate)
 Definition
Any factor that changes rate of spontaneous depolarization
or duration of repolarization will alter heart rate by changing
time required to reach threshold
 Resting membrane potential
 Rate of depolarization
Term
Ach- parasympathetic stimulation
 Definition
Open chemically gated K+ channels- slowing depolarization, extending repolarization- Slows the heart
Term
NE- sympathetic stimulation
 Definition
Binds beta-1 receptors, open Na+ -Ca2+ channels, increases rate of depolarizaton, shortens repolarization- speeds the
heart
Term
Bainbridge reflex
 Definition
adjusts heart rate in response
to increase in venous return
-Stretch receptors in right atrium trigger increase
in heart rate through increased sympathetic activity
 Rate of venous return to heart increases, heart rate &
cardiac output increase as well
Term
Factors affecting the stroke volume
 Definition
The greater the EDV, the larger the stroke volume
 At rest EDV is low, myocardium stretches less
 Stroke volume is low
 With exercise, EDV increases, myocardium stretches more
 Stroke volume increases
Term
Frank-Starling principle
 Definition
As EDV increases, stroke volume increases
Term
Ventricular expansion is limited by:
 Definition
Myocardial connective tissue
 The cardiac (fibrous) skeleton
 The pericardial sac
Term
Three Factors Affect ESV
 Definition
Preload- Ventricular stretching during diastole
 Contractility- Force produced during contraction, at a given preload
 Afterload- Tension the ventricle produces to open the semilunar valve and eject blood
Term
Contractility is affected by:
 Definition
Autonomic activity
 Hormones
 Increase contractility- positive inotropic action
 Stimulate Ca2+ entry into cardiac muscles, increasing force
& duration of ventricular contraction
 Decrease contractility- negative inotropic action
 Block Ca2+ entry into cardiac muscles
 Factors include: ANS activity, hormones, changes in extracellular ion concentration
Term
Effects of Autonomic Activity on Contractility
 Definition
Sympathetic stimulation- POSITIVE effect
 NE released by cardiac nerves
 E and NE released by suprarenal medullae
 Causes ventricles to contract with more force
 Increases ejection fraction and decreases ESV
Term
Effects of Autonomic Activity on Contractility
 Definition
Parasympathetic stimulation- NEGATIVE effect
 Acetylcholine released by vagus nerves
 Produces hyperpolarization & inhibition
 Reduces force of cardiac contractions
Term
 Pharmaceutical drugs mimic hormone actions
 Definition
Stimulate beta receptors- mimic E, NE
 Stimulate Ca2+ channels alpha-1 receptor
 Treat hypertension- beta or alpha blockers (negative effect)
 Calcium channel blockers- negative effect
Term
Effects of Autonomic Activity on Contractility
 Afterload
 Definition
tension ventricle produces to open semilunar valve
and eject blood
 Afterload increased by any factor that restricts arterial blood flow
 As afterload increases, stroke volume decreases
 Indirect relationship
Term
Cardiac Reserve
 Definition
difference between resting and maximal cardiac output
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