Chapter 18: Heart Flashcards
Heart
is a double pump that pushes blood through 2 circuits; right side of heart pumps blood through pulmonary circuit (heart to lungs to heart); left side of heart pumps blood through the systemic circuit (heart to body to heart)
Size, Location, and Orientation of the Heart
size- clinched fist and less than one pound; location- medistinum; orientation- apex angled to the left
What is the heart enclosed by?
pericardium (double walled sac)
Fibrous Pericardium
outermost; tough layer of dense CT; anchors heart to surrounding tissues; prevents it from overfilling with blood
Serous Pericardium
thin, double layered serous membrane deep to the fibrous pericardium; includes parietal pericardium and visceral pericardium
Parietal Pericardium
lines inner part of fibrous pericardium
Visceral Pericaridum
aka epicardium; forms outer laer of heart wall
What is pericarditis?
inflammation/swelling of the pericardium and can lead to cardiac tamponade (heart cant pump sufficient amt and must drain fluid to help)
What are the wall layers of the heart?
3; epicardium; myocardium; endocardium
Epicardium
visceral pericadium; outermost layer
Myocardium
bundles of cardiac muscle containing a network of collagen and elastic fibers
Endocardium
endothelial layer that lones heart chambers and is continuous with blood vessel endothelium
What are some of the external structures used to identify the chambers of the heart?
coronary sulcus; anterior interventricular sulcus
Interatria Septum
separates atria and contains a shallow depression (fossa ovalis- this is the depression that is left when the foramen ovale closes in the infant
What are the three veins that the right atria receive from?
superior vena cava; inferior vena cava; coronary sinus (on posterior side)
What are the four veins that the left atria receives from?
2 left pulmonary veins and two right pulmonary veins
Ventricles
Inferior receiving chambers; 2; thicker walls than atria; separated by interventricular septum; internally have papillary muscles and trabeculae carnae; right ventricle pumps into pulmonary trunk; left ventricle pumps into aorta
Heart Valves
flaps of endocardium reinforced with connective tissue; 2 atrioventricular valves; 2 semilunar valves; prevents backflow; ensures one way flow of blood thru heart; open and close in response to pressure changes
Tricuspid Valve
AV valve; between right atrium and right ventricle; has three flaps
Biscuspid Valve
AV valve; between left atrium and left ventricle; 2 flaps; aka mitral valve
What happens when AV valves are open?
1) blood returning to the heart fills atria, pressing against the ACV valves; the increased pressure forces AV valves to open; 2) as ventricles fill AV valve flaps have limply into ventricles; 3) atria contract forcing additional blood into ventricles
What happens when AV valves are closed?
1) ventricles contract, forcing blood against AV valve cusps; 2) AV valves close; 3) papillary muscles contract and chordae tendineae tighten, preventing valve flaps from everting into atria
Pulmonary Valve
SL valves; between right ventricle and pulmonary trunk; has 3 pocket like cusps
Aortic Valve
between left ventricle and aorta; has three pocket like cusps; SL valve
Semilunar Valves when Open
as ventricles contract and intraventricular pressure rises, blood is pushed up against semilunar valves, forcing them open
Semilunar Valves when Closed
as ventricles relax and intraventricular pressure falls blood flows back from arteries, filling the cusps of semilunar valves and forcing them to close
Incompetent Valve
valve does not function properly and you have a leak
Valcular Stenosis
valves are hardened; could need a replacement valve
Flow of Blood thru the Heart: Pulmonary Circuit
served by right ventricle; is a shot, low pressure circulation; blood comes in superior/inferior vena cava and coronary sinus then blood goes to right atrium then through tricuspid valve to right ventricle and then thorugh pulmonary valve to pulmonary trunk
Flow of Blood thru the Heart: Systemic Circuit
served by left ventricle, is a long high pressure circulation; blood comes in four pulmonary veins to left atrium and then through bicuspid (mitral) valve to left ventrile then through aortic SL valve to the aorta
Right and Left Ventricles pump….
equal volumes of blood when the contract but left ventricle works a lot harder because it hasto have more pressure/force
Coronary Circulation
myocardium needs its own blood supply to obtain o2 and nutrients
Coronary Arteries
left and right coronary. arteries branch from ascending aorta; lie in coronary sulcus; devliever blood to myocardium when relaxed
What are the two branches of the left coronary artery?
anterior interventricular artery and circumflex artery
What are the two branches of the right coronary artery?
posterior interventricular artery and right marginal artery
Anterior Interventricular Artery
supplies blood to interventriular septum and anterior walls of both ventricles
Circumflex Artery
supplies blood to left atrium and posterior walls of left ventricle
Posterior Interventricular Artery
supplies blood to posterior ventricular walls
Right Marginal Artery
supplies blood to lateral right side of heart
Coronary Veins
collect venous blood; converge to form the coronary sinus which empties into the right atria
What is angina pectoris?
chest pain due to short term o2 deprivation
What is a myocardial infarction?
heart attack
Cardiac Muscle Tissue
striated; branched cells with 1-2 nuclei per cell; many large mitochondria; cells interconnected via intercolated discs (contain demosomes and gap junctions)
Electrical Events and Basic Rhythm Controllers
contraction of the myocardium is intrinsic ( self generated ); set by noncontracting cardiac cells that depolarize spontaneously; sinoatrial node (SA), atrioventricular node (AV), atrioventricular bundle, right and left bundle branches, subendocardial conducting network (used to be purkinje fibers)
Intrinsic Cardiac Conduction System
SA node (pace maker) generates 75 impulse/min, the sinus rhythm; AV node 50 impulses /min (junctional rhythm); AV bundle and subendocardial conducting network 30 impulses/min (too low to sustain life)
Defects in the Intrinsic Conduction Sys. May Cause
arrhythmia, fibrillation, ectopic focus, heart block
Arrhythmia
irregular heart beat
Fibrillation
rapid, uncoordinated contractions
Ectopic Focus
abnormal pacemaker (junctional rhythm or extra systole)
Complete (total) Heart Block
artificial pacemaker implanted; no atrial impulses get to ventricles
Partial Heart Block
artificial pacemaker implanted; only some implance get thorugh to ventricles
Extrinsic Modification of the Basic Rhythm
cardiovascular centers in medulla oblongata modify sinus rhythm via ANS; cardioacceleratory center; cardioinhibitory center
Cardioacceleratory Center
sends impulses via sympathetic fibers to SA and AV nodes , myocardium and coronary arteries; increases HR and force of contraction
Cardioinhibitory Center
sends impulses via parasympathetic fibers to SA and AV nodes; decreases HR
Electrocardiogram
ECG; graphic record of the electrical activity of the heart; 3 distinct waves
P Wave
0.08 secs; results from atrial depolarization
QRS Complex
0.08 secs; results from ventricular depolorization
T Wave
0.16 secs; results when ventricules repolarize
Cardiac Cycle
mechanical events (pressure and volume changes) that occur during 1 heartbeat; atriale systole (contraction) and diastole (relaxation) followed by ventricular systole and diastole
Phase 1: Ventricular Filling
mid to late diastole; atria and ventricles relaxed; AV valves open; SL valves closed; blood flowing passively thru atria into ventricles; atria deporlarize and contract forcing remaining blood into ventricles; atria relax; ventricles depolarize and begin contracting; AV valves close when ventricular pressure greater than atrial pressure
Phase 2: Isovolumetric Contraction
period of time when all 4 valves are closed during ventricular contraction rising ventricular pressure forces SL valves open
Phase 3: Ventricular Ejection
blood forced from ventricles into aorta and pulmonary trunk; ventricles relax; SL valves close when ventricular pressure drops below aortic pressure
Phase 4: Isovolumetric Relaxation
early diastole; period of time when all 4 valves are claosed during ventricular relaxation; AV valves open when ventricular pressure drops below atrial pressure
What is the average length of time for the cardiac cycle?
0.8 secs; both chambers relaxed (quiescent period) 0.4 secs; atria contract 0.1 sec; ventricles contract o.3. sec
1st Heart Sound
lub; occurs when AV valves close as ventricles contract
2nd Heart Sound
dup; occurs when SL valves close as ventricles relax
What is a heart murmur?
leaky valve
Cardiac Output
amount of blood pumped out by each ventricle in 1 minute; calcualted by heart rate (HR) x stroke volume (SV)
Average CO of adutls
75 bpm x 70 ml per beat = 5250 ml/min or 5.25 l/min
Increase HR and/or SV and you…
increase CO
Decrease HR and/or SV and you…
decrease CO
Cardiac Reserve =
CO max - CO resting
Stroke Volume
aount of blood pumped out per beat; SV = EDV-ESV
End Diastolic Volume
EDV; amount of blood in each ventricle at end of diastole; about 120 ml/beat;
End Systolic Volume
amount of blood in each ventricle at end of systole; about 50 ml/beat
What are the three main factors that influence SV by altering EDV or ESV?
preload, contractility, afterload
Preload
degree of muscle stretch just before contraction; determined primarily by venous return; alters EDV; increase venous return leads to increase EDV which leads to increase SV when leads to increased CO; ensures both ventricles pump an equal volume and pulmonary/systemic circuits are balanced
Contractility
strength of contraction; alters ESV; inceased contractility leads to decreased ESV which leads to increased SV which leads to increased CO
Afterload
pressure ventricles must overcome to eject blood (~ 80 mmHg in aorta and ~10mmHg in pulmonary trunk); alters ESV; NOT a factor in healthy individuals bc it is realtively constarnt; however individuals with hypertension are affected bc blood is ejected at high pressure; increased afterload leads to increased ESV which leads to decreased SV which leads to decreased CO
What are some extrinsic factors that regulate HR?
sympathetic and parasympathetic NS; hormones; ions; age; gender; body temp
Sympathetic NS
increased SNS stimualtion leads to increased HR which increases CO
Parasympathetic NS
incrased PNS stimulation leads to decreased HR which leads to decreased CO
At rest, heart exhibits vagal tone…
PNS slowing HR from 100 to 75; if you did not have vagus nerve stimulation the heart will beat faster cuz PNS not slowing SA node
Epinephrine
increases HR and contractility
Thyroxine
(high levels) increase HR
Hypercalcemia
increased Ca2; increase HR and contractility
Hypocalcemia
decreased Ca2; cardiac arrythmia
Hyperkalemia
increased K; alter electrical activity and can lead to heart block and arrythmia
Hypokalemia
decreased K; feeble HR and arrythmia
Tachycardia
fast HR; over 100 bpm
Bradycardia
slow HR; under 60 bpm
Congestive Heart Failure
CHF; heart doesnt pump effeciently; pulmonary congestion (edema in lungs, occurs if left side of heart fails ); peripheral congestion (edema in body tissues, occurs if right side of heart fails)
Foramen Ovale
opening between right and left atria; closes to form fossa ovalis (depression)
Ductus Arteriosus
vessel connecting pulmonary trunk and aorta; closes to form ligamentum ateriosum
ADD CONGENITLA HEART DEFECTS
