A&P 18: The Cardiovascular System - The Heart Flashcards
Pulmonary circuit
the blood vessels that carry blood to and from the lungs
Heart
transport system pump (actually 2 pumps side by side)
Systemic circuit
the blood vessels that carry blood to and from all body tissues
Mediastinum
the medial cavity of the thorax
Base
posterior surface of the heart
Apex
pointed part of the heart; points inferiorly toward the left hip
Apical impulse
pressing your fingers between the 5th and 6th ribs just below the left nipple, you can easily feel this, caused by your beating heart’s apex where it touches the chest wall
Pericardium
the heart is enclosed by this double-walled sac
Fibrous pericardium
the loosely fitting superficial part of the pericardial sac; tough, dense connective tissue layer; protects the heart, anchors it to surrounding structures, and prevents overfilling of the heart with blood
Serous pericardium
deep to the fibrous pericardium; thin, slippery, 2-layer serous membrane that forms a closed sac around the heart
Parietal layer
lines the internal surface of the fibrous pericardium
Visceral layer
AKA epicardium; integral part of the heart wall
Pericardial cavity
between the parietal and visceral layers is this slitlike cavity containing a film of serous fluid
Epicardium
visceral layer of the serous pericardium; often infiltrated with fat, especially in older people
Myocardium
middle layer, composed mainly of cardiac muscle; forms the bulk of the heart; this is the layer that contracts
Cardiac skeleton
connective tissue fibers form this dense network that reinforces the myocardium internally and anchors the cardiac muscle fibers
Endocardium
3rd layer of the heart wall, a glistening white sheet of endothelium (squamous) resting on a thin connective tissue layer
Atria
2 superior chambers of the heart
Ventricles
2 inferior chambers of the heart
Intraatrial septum
internal partition that divides the heart longitudinally (where it separates the atria)
Interventricular septum
internal partition that divides the heart longitudinally (where it separates the ventricles)
Coronary sulcus
AKA atrioventricular groove; encircles the junction of the atria and ventricles like a crown
Anterior interventricular sulcus
cradles the anterior interventricular artery; marks the anterior position of the septum separating the right and left ventricles
Posterior interventricular sulcus
provides a landmark for the posterior interventricular artery on the heart’s posteroinferior surface
Auricles
small, wrinkled, protruding appendages which increase the atrial volume somewhat
Pectinate muscles
muscle bundles forming ridges in the walls of the atria; look like the teeth of a comb; found in the right atrium and only the auricle of the left atrium
Fossa ovalis
shallow depression in the interatrial septum that marks the spot where an opening (foramen ovale) existed in the fetal heart
Superior vena cava
blood enters the right atrium through this vein, which returns blood from body regions superior to the diaphragm
Inferior vena cava
blood enters the right atrium through this vein, which returns blood from body areas below the diaphragm
Coronary sinus
blood enters the right atrium through this vein, which collects blood draining from the myocardium
Pulmonary veins
veins entering the left atrium, which makes up most of the heart’s base; transport blood from the lungs back to the heart; best seen in a posterior view
Trabeculae carnae
irregular ridges of muscle that mark the internal walls of the ventricular chambers
Papillary muscles
conelike muscle bundles that play a role in valve function and project into the ventricular cavity
Pulmonary trunk
the right ventricle pumps blood into this, which routes blood to the lungs where gas exchange occurs
Aorta
largest artery in the body; the left ventricle ejects blood into this vessel
Atrioventricular (AV) valves
2 valves, one located at each arial-ventricular junction, prevent backflow into the atria when the ventricles contract
Tricuspid valve
right AV valve; has 3 flexible cusps (flaps of endocardium reinforced by connective tissue cores)
Mitral valve
left AV valve; 2 cusps; AKA bicuspid valve
Chordae tendinae
attached to each AV valve flap are these tiny white collagen cords; “heart strings;” anchor the cusps to the papillary muscles protruding from the ventricular walls
Aortic & pulmonary (semilunar, SL)) valves
valves which guard the bases of the large arteries issuing from the ventricles (aorta & pulmonary trunk) and prevent backflow into the associated ventricles
Coronary circulation
the functional blood supply of the heart; shortest circulation in the body
Left coronary artery
artery running toward the left side of the heart, then dividing into 2 major branches - anterior interventricular artery & circumflex artery
Anterior Interventricular artery
AKA the left anterior descending artery; follows the anterior interventricular sulcus and supplies blood to the interventricular septum and anterior walls of both ventricles
Circumflex artery
supplies the left atrium and the posterior walls of the left ventricle
Right coronary artery
artery coursing to the right side of the heart; gives rise to 2 branches - the right marginal artery and the posterior interventricular artery
Right marginal artery
serves the myocardium of the lateral right side of the heart
Posterior interventricular artery
artery running to the heart apex, supplies the posterior ventricular walls; merges (anastomoses) with the anterior interventricular artery
Cardiac veins
venous blood is collected by these veins after passing through the capillary beds of the myocardium (path roughly follows those of the coronary arteries)
Coronary sinus
the cardiac veins join to form this enlarged vessel, which empties blood into the right atrium; obvious on the posterior aspect of the heart
Great cardiac vein
large tributary of the coronary sinus in the anterior interventricular sulcus
Middle cardiac vein
large tributary of the coronary sinus in the posterior interventricular sulcus
Small cardiac vein
large tributary of the coronary sinus running along the heart’s right inferior margin
Anterior cardiac veins
several of these veins empty directly into the right atrium anteriorly
Angina pectoris
“choked chest”; thoracic pain caused by fleeting deficiency in blood delivery to the myocardium; may result from stress-induced spasms of the coronary arteries or from increased physical demands on the heart
Myocardial infarction (MI)
heart attack; cells of the heart die –> most of the dead tissue is replaced with noncontractile scar tissue
Cardiac muscle
striated tissue that contracts by the sliding filament mechanism; short, fat, branched, interconnected fibers, with 1 or 2 large, pale, centrally located nuclei and intercalated discs
Intercalated discs
dark-staining junctions containing anchoring desmosomes and gap junctions
Functional syncytium
because gap junctions electrically couple cardiac cells, the myocardium behaves as this single, coordinated unit
Automacticity (autorhythmicity)
some cardiac muscle cells can initiate their own depolarization and that of the rest of the heart as well, in a spontaneous, rhythmic way
Fast voltage-gated Na+ channels
depolarization opens a few of these channels in the sarcolemma, allowing extracellular Na+ to enter
Slow Ca2+ channels
channels allowing Ca2+ to enter from the extracellular space, though their opening is delayed a bit
Plateau
phase due to Ca2+ influx through slow Ca2+ channels; this keeps the cell depolarized because few K+ channels are open
Intrinsic cardiac conduction system
consists of noncontractile cardiac cells specialized to initiate and distribute impulses throughout the heart, so it depolarizes and contracts in an orderly, sequential manner
Cardiac pacemaker cells (autorhythmic cells)
cells making up the intrinsic conduction system having an unstable resting potential that continuously depolarizes, drifting slowly toward threshold
Pacemaker potentials (prepotentials)
spontaneously changing membrane potentials; initiate the action potentials that spread throughout the heart to trigger its rhythmic contractions
Ca2+ channels
at threshold (40mV), these channels open, allowing explosive entry of Ca2+ from the extracellular space
Sinoatrial nodes
crescent-shaped node located in the right atrial wall, just inferior to the entrance of the superior vena cava; typically generates impulses about 75 times every minute (inherent rate in the absence of extrinsic neural and hormonal factors is closer to 100 times per minute); sets the pace for the heart as a whole
Pacemaker
SA node; no other region of the conduction system or myocardium has a faster depolarization rate
Sinus rhythm
characteristic rhythm of the SA node; determines heart rate
Atrioventricular node
from the SA node, the depolarization wave spreads via gap junctions throughout the atria and via the intermodal pathway to this node, located in the inferior portion of the interatrial septum, immediately above the tricuspid valve
Atrioventricular bundle (bundle of His)
from the AV node, the impulse sweeps to this bundle in the superior part of the interventricular septum; only electrical connection between the atria and ventricles
Right and left bundle branches
the AV bundle persists only briefly before splitting into these 2 pathways, which course along the interventricular septum toward the heart apex
Subendocardial conducting network (Purkinje fibers)
long strands of barrel-shaped cells with few myofibrils; completes the pathway through the interventricular septum, penetrates into the heart apex, and then turns superiorly into the ventricular walls
Arrhythmias
irregular heart rhythms
Fibrillation
condition of rapid and irregular or out-of-phase contractions in which control of heart rhythm is taken away from the SA node by rapid activity in other heart regions; makes ventricles useless as pumps, unless the heart is defibrillated quickly, circulation stops and brain death occurs
Ectopic focus
abnormal pacemaker; may appear and take over the pacing of heart rate, or the AV node may become the pacemaker
Junctional rhythm
pace set by the AV node, ~40-60 beats per minute (slower than sinus rhythm, but adequate to maintain circulation)
Extrasystole
premature contraction (before the SA node initiates the next contraction)
Heart block
any damage to the AV node interferes with the ability of the ventricles to receive pacing impulses; no impulses get through and the ventricles beat at their intrinsic rate, which is too slow to maintain adequate circulation
Cardioacceleratory center
in the medulla oblongata; projects to sympathetic neurons in the T1-T5 level of the spinal cord
Cardioinhibitory center
sends impulses to the parasympathetic dorsal vagus nucleus in the medulla, which in turn, sends inhibitory impulses to the heart via branches of the vagus nerves
Electrocardiograph
electrical currents generated in and transmitted through the heart spread throughout the body and can be detected with this device
Electrocardiogram (ECG)
graphic record of heart activity; composite of all the action potentials generated by nodal and contractile cells at a given time (NOT the tracing of a single action potential)
P wave
lasts ~0.08s, results from movement of the depolarization wave from the SA node through the atria; 0.1s after this wave begins, the atria contract
QRS Complex
results from ventricular depolarization and precedes ventricular contraction; complicated shape because the paths of the depolarization waves through the ventricular walls change continuously, producing corresponding changes in current direction; ~0.08s
T wave
caused by ventricular repolarization, typically lasts ~0.16s (repolarization is slower than depolarization)
P-R Interval
0.16s from the beginning of atrial excitation to the beginning of ventricular excitation; includes atrial depolarization (and contraction) as well as the passage of the depolarization wave through the rest of the conduction system
P-Q interval
if the Q wave is visible (not often the case), it marks the beginning of ventricular excitation, so the P-R interval is often called this
S-T segment
segment of an ECG when the action potentials of the ventricular myocytes are in their plateau phases; entire ventricular myocardium is depolarized
Q-T interval
lasts ~ 0.38s; period from the beginning of ventricular depolarization through ventricular repolarization
Heart sounds
lub-dup sound associated with the heart valves closing (1st AV, then SL)
Heart murmurs
abnormal heart sounds that can be heard with a stethoscope; fairly common in young children and some elderly people with perfectly healthy hearts because their heart walls are relatively thin and vibrate with rushing blood; most often, these abnormal sounds indicate valve problems
Systole
periods of contraction
Diastole
periods of relaxation
Cardiac cycle
includes all events associated with the blood flow through the heart during one complete heartbeat (atrial systole and diastole followed by ventricular systole and diastole); mechanical events always follow electrical events in the ECG
Isovolumetric contraction phase
the split second period when the ventricles are completely closed and the blood volume in the chambers remains constant as the ventricles contract
Dicrotic notch
closure of the aortic valve raises aortic pressure briefly as backflowing blood rebounds off the closed valves cusps, an event beginning here on the pressure graph
Quiescent period
0.4s period of total heart relaxation
Cardiac output (CO)
amount of blood pumped out by each ventricle in 1 minute; product of heart rate (HR) and stroke volume (SV)
Stroke volume
volume of blood pumped out by 1 ventricle with each beat; correlates with the force of ventricular contraction
Cardiac reserve
difference between resting and maximal CO
End diastolic volume (EDV)
amount of blood that collects in a ventricle during diastole
End systolic volume (ESV)
volume of blood remaining in a ventricle after it has contracted; determined by arterial blood pressure and the force of ventricular contraction, ~50mL (the higher the BP, the higher this will be)
Preload
the degree to which cardiac muscle cells are stretched just before they contract; controls stroke volume
Frank-Starling law of the heart
relationship between preload and stroke volume (in a normal heart, the higher the preload, the higher the stroke volume)
Venous return
most important factor stretching cardiac muscle; amount of blood returning to the heart and distending its ventricles
Contractility
contractile strength achieved at a given muscle length
Afterload
pressure that the ventricles must overcome to eject blood; in people with hypertension, this is important because it reduces the ability of the ventricles to eject blood
Vagal tone
under resting conditions, both autonomic divisions continuously send impulses to the SA node of the heart, but the dominant influence is inhibitory; heart rate is generally slower than it would be if the vagal nerves were not innervating it
Atrial (Bainbridge) reflex
autonomic reflex initiated by increased venous return and increased atrial filling
Tachycardia
abnormally fast heart rate (more than 100 beats/minute) that may result from elevated body temperature, stress, certain drugs, or heart disease
Bradycardia
heart rate slower than 60 beats/minute; may result from low body temperature, certain drugs, or parasympathetic nervous activation
Congestive heart failure (CHF)
condition in which the heart is such an inefficient pump that blood circulation is inadequate to meet tissue needs; progressively worsening disorder; reflects weakening of the myocardium
Pulmonary congestion
if the left side of the heart fails, this occurs; left side does not adequately eject the returning blood into the systemic circulation
Peripheral congestion
if the right side of the heart fails, this occurs; blood stagnates in body organs; pooled fluids in the tissue spaces impair the ability of body cells to obtain adequate nutrients and oxygen and rid themselves of wastes; result = edema, especially in extremities
Foramen ovale
connects the 2 atria; allows blood entering the right heart to bypass the pulmonary circuit and the collapsed, nonfunctional fetal lungs
Ductus arteriosus
lung bypass in fetus; exists between the pulmonary trunk and the aorta
Ligamentum arteriosum
fibrous remnant of the ductus arteriosus
Congenital heart defects
1 of 30 birth defects of the heart; one of the most common birth defects
