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Ch. 20 The Heart
Anatomy
79
Anatomy
Undergraduate 3
02/24/2014

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Term
What is the size of the heart?
Definition
250-300 g (size of fist)
Term
Where is the heart located?
Definition
Between lungs, displaced 2/3 to the left.
Term
What is cardiology?
Definition
Study of heart and associated diseases.
Term
What two layers make up the pericardium?
Definition
Outer fibrous layer, inner serous layer: consists of parietal layer and visceral layer which contain the pericardial cavity.
Term
What is pericarditis?
Definition
Inflammation of pericardium.
Term
What is cardiac tamponade?
Definition
When blood or fluid gets into the pericardial cavity, life threatening.
Term
What this difference in pre-birth blood circulation of the heart?
Definition
Ductus arteriosus which goes from pulmonary trunk to the aorta, bypasses lungs.
Term
What are auricles?
Definition
Small pouches on top of each atrium that increase atrial capacity.
Term
What are sulci?
Definition
Grooves containing blood vessels and fat, separate chambers from each other.
Term
What are functions of the fibrous skeleton of the heart?
Definition
Surrounds valves, valve attachment, cardiac muscle insertion, prevents valve ocerstretching, electrical insulator to prevent AP spread from atria to ventricles.
Term
How do heart valves open/close and what is their function?
Definition
Open/close due to pressure changes, papillary muscles contract on chordae tendinae to prevent back-flow through valves.
Term
What are the atrioventricular valves and where are they?
Definition

Tricuspid: between right atrium and ventricle

Bicuspid: between left atrium and ventricle

Term
What are the semilunar valves and where are they?
Definition

Pulmonary: between right ventricle and pulmonary artery

Aortic: between left ventricle and aorta

Term
What is the path of coronary circulation and what are vessels that are a part of it?
Definition
Right and left coronary arteries branch from ascending aorta to supply blood to cardiac muscle, coronary veins go to coronary sinus which empties into right atrium
Term
Describe the histology of cardiac muscle.
Definition
Shorter than skeletal muscle fibers, larger diameter, branched, same sarcomere arrangement, mitochondria larger and more numerous, less sarcoplasmic reticulum, intercalated disks which function as desmosomes and gap junctions.
Term
What is the function of the cardiac conduction system?
Definition
Controlled systematic contraction of different parts of heart, atrial contracts first then ventricular.
Term
Where is the SA node found and what is its function?
Definition
Found in right atrial wall just below superior vena cava, functions as pacemaker, establishes fundamental rhythm (90-100 bpm), atria contract after action potential.
Term
Where is the AV node found?
Definition
Located in septum between atria, similar histology to SA node.
Term
What is the AV bundle?
Definition
Only electrical connection between atria and ventricles, fibrous skeleton electrically insulates atria from ventricles in rest of heart.
Term
What are the right and left bundle branches?
Definition
Extend through interventricular septum, impulses travel to apex of ventricles.
Term
What are purkinje fibers?
Definition
Large diameter, rapid conduction.
Term
Where does the action potential in the heart begin and what are contractile fibers?
Definition
Begins in SA node, contractile fibers cause atrial and ventricular contractions and are brough to threshold by excited neighboring cells.
Term
What are the 4 stages of the action potential in hearts?
Definition

Depolarization: rapid, voltage-gated Na+ channels open, Na+ floods into cell, membrane potential changes from -90 to +20 mV

Plateau: Ca2+ channels open in sarcolemma and sarcoplasmic reticulum, Ca2+ levels rise in cytosol inside muscle cells, K+ channels close, cardiac muscle reamins depolarized 250x longer than skeletal

Repolarization: recovery of RMP (back to -90mV), voltage gated K+ channels open and Ca2+ channels close

Refractory period: time during which cardiac muscle cannot contract, lasts longer than contraction itself, no tetanus possible in cardiac muscle, another contraction cannot occur until relaxation underway

Term
What is an electrocardiogram?
Definition
Graphic representation of electrical changes in heart measured on surface of body, function to detect normal conduction pathway/enlarged heart/heart damage.
Term
Describe the P wave.
Definition
Atrial depolarization, AP from SA to the atria, atria contract.
Term
Describe the T wave.
Definition
Ventricular repolarization, prior to ventricular relaxation, if too low heart not getting enough O2, if too large may be too much K+ present.
Term
Describe the PQ interval.
Definition
Conduction time from beginning of atrial excitation to ventricular excitation, time for AP to travel through SA node/AV node/and rest of system, if long may indicate CAD or rheumatic fever.
Term
Describe the QRS interval.
Definition
Ventricular depolarization, AP spreads through ventricles, ventricle contraction.
Term
Describe the QT interval.
Definition
Beginning of ventricle depolarization to end of repolarization, too long may indicate MI damage/coronary ischemia/conduction damage.
Term
Describe the ST interval.
Definition
Time that ventricular fibers are fully depolarized, too long indicates MI, too short indicates heart is O2 starved.
Term
What is the cardiac cycle?
Definition
Events associated with one heartbeat, includes systole and diastole.
Term
Describe relaxation in the cardiac cycle.
Definition
At end of the heart beat, all 4 chambers relaxe, all 4 valves close, relaxation takes up half of cardiac cycle.
Term
Describe atrial systole in the cardiac cycle.
Definition
Atrial pressure is greater than ventricular pressure, AV valves open, takes up 1/8 of cardiac cycle.
Term
Describe ventricular systole in the cardiac cycle.
Definition
AV valves shut which is first heart sound, then all valves close, ventricular pressure then rises, semilunar valves then open which is ejection, then semilunar valves close which is second heart sound, ventricular systole takes up 3/8 of cardiac cycle.
Term
What is auscultation?
Definition
Listening to sounds of body's interior, heart sounds caused by blood turbulence from valve closures, lubb is AV closure and dupp is semilunar valve closure, heart murmur is sounds other than lubb dupp
Term
What is cardiac output and the equation for it? What is the equation for SV?
Definition
Volume of blood ejected from left or right ventricle each minute, equation is CO = HR X SV, SV is amount of blood ejected with each contraction and is equal to EDV - ESV.
Term
What is cardiac reserve?
Definition
Ratio between max CO and CO at rest.
Term
What is preload and how does it relate to SV?
Definition
Degree of stretching on cardiac muscle fibers before contraction, preload is proportional to EDV, increase in preload leads to increase in SV.
Term
What is myocardial contractility?
Definition
Force of contraction of individual fibers, strength of heartbeat, increase in cotractility leads to increase in SV.
Term
What are positive inotropic agents?
Definition
Increase contractility which leads to increase in SV, epinephrine increases Ca2+ inflow into cardiac muscle cells, sympathetic stimulation of ANS.
Term
What are negative inotropic agents?
Definition
Decrease contractility which will decrease SV, inhibition of sympathetic ANS, anoxia (lack of O2) and acidosis (lower pH) both leade to lower force of contraction, elevated K+ extracellular levels.
Term
What is afterload and how does it relate to SV?
Definition
Pressure needed to overcome in ventricles to open semilunar valves, increased by hypertension and artherosclerosis, increase in afterload causes decrease in SV.
Term
What is congestive heart failure?
Definition
Heart fails to pump, blood remains in ventricles, increases preload, leads to overstretching of heart over long period of time which leads to less forceful contractions.
Term
What are congestive heart failure symptoms?
Definition
Leads to weaker contraction, can't supply O2 demands of body, pulmonary edema (if left ventricle fails), peripheral edema (if right ventricle fails)
Term
Describe the autonomic regulation of HR including the receptors involved.
Definition
Receptors send signals to medulla oblongata, proprioceptors indicate physical activity, baroreceptors measure BP, chemoreceptors deal with blood chemistry.
Term
What does sympathetic stimulation do to the heart?
Definition
Increases HR.
Term
What does parasympathetic stimulation do to the heart?
Definition
Decreases HR.
Term
What hormones and ions are involved in the chemical regulation of HR?
Definition
Epinephrine, norepinephrine, and thyroid hormones are involved. Excess Na+ and K+ decrease contractibility, excess Ca2+ increases contractibility.
Term
What are 4 other factors in HR regulation?
Definition

Age - HR decreases with age until too old

Gender - females faster than males

Physical fitness - bradycardia is less than 50 bpm, tachycardia is greater than 100bpm

Temperature - fever or strenuous activity increase HR, hypthermia decreases HR

Term
What is coronary artery disease?
Definition
#1 cause of death in US, caused when heart receives inadequate O2 due to obstructed blood vessels, symptoms include hypertension/angina/stroke/MI (heart attack)
Term
What are risk factors for coronary artery disease?
Definition
High blood cholesterol, high blood pressure, cigarette smoking, obesity, sedentary lifestyle, diabetes mellitus, males more likely to get this until 70 where women more likely cause of menopause.
Term
What are the long term effects of plasma lipids in coronary artery disease?
Definition
Plaque formation, block lumen, restrict blood flow, increased risk for thrombus.
Term
What is the function of lipoproteins in blood?
Definition
Transport lipids.
Term
What do low density lipoproteins do and are they good or bad?
Definition
Transport lipids from liver to arteries, bad.
Term
What do high density lipoproteins do and are they good or bad?
Definition
Transport excess lipids back to liver, good.
Term
What is the formula for total cholesterol?
Definition
TC = LDL + HDL + VLDL
Term
Above what number is total cholesterol considered a high risk?
Definition
Greater than 200.
Term
What is arteriosclerosis?
Definition
Thickening of artery walls and loss of elasticity.
Term
What is atherosclerosis?
Definition
Excess LDLs accumulate in walls of medium/large arteries, endothelial and smooth muscle cell damage which leads to plaque formation which obstructs blood flow which attracts platelets for clotting.
Term
What is a coronary spasm?
Definition
Intermittent smooth muscle spasm of coronary artery, atherosclerosis which leads to MI which can lead to sudden death.
Term
What is thrombosis?
Definition
Formation of a clot.
Term
How is coronary artery disease diagnosed?
Definition
Stress test, echocariography which is listening through ultrasound, cardiac catheterization which will help visualize the artery, cardiac angiography which views inside vesicles/ventricles.
Term
What are coronary artery disease treatments?
Definition
Drugs such as nitroglycerine and beta blockers, bypass grafting, percutaneous transluminal coronary angioplasty, lase angioplasty.
Term
What is a myocardial ischemia?
Definition
Partial obstruction of blood flow in coronary arteries, hypoxia is reduced oxygen supply which is the result of ischemia, weakens cells without killing them, angina pectoris occurs which is chest pain.
Term
What is a myocardial infarction?
Definition
Also called heart attack, complete obstruction to blood flow in coronary artery, tissue death occurs, treated with clot-busting agents/heparin/PTCA/CABG.
Term
What are congenital heart defects?
Definition
Exist at birth, examples are: coarctation of the aorta which is extreme aortic stenosis (narrowing of blood vessel) that strains the heart and leads to high BP, patent ductus arteriosus which is embryonic connection between aorta and pulmonary trunk which normally closes at birth but fails to resulting in aortic blood flow into pulmonary trunk to lungs and overworking of both ventricles.
Term
What are other congenital heart defects?
Definition
Septal defects such as ASD which is an opening between right and left atria or VSD which is an opening between the right and left ventricles.
Term
What is arrhythmias?
Definition
Abnormal or irregular heart beat, causes include improper impulse conduction/production, chemicals such as caffeine/nicotine/alcohol, anxiety, and hyperthyroidism.
Term
What is a heart block?
Definition
AV block is most common, 1st degree block results in long PQ, 2nd degree results in dropped beats, 3rd degree results in no SA impulse through the AV node and atria and ventricles contracting independently and dizziness and convulsions.
Term
What is an atrial flutter?
Definition
240-360 bpm, 2nd degree heart block accompanies this, atria contracting too fast resulting in not every beat getting through to ventricles.
Term
What is an atrial fibrillation?
Definition
Asynchronous atrial contractions and sometimes the atrial pumping ceases altogether, up to 300-600 bpm.
Term
What are ventricular premature contractions?
Definition
Ectopic region begins action potential, results in extra systoles, usually harmless.
Term
What is a ventricular fibrillation?
Definition
Asynchronous ventricular contraction resulting in ventricle pumping to cease, death imminent unless medical intervention, defibrillation can save victim.
Term
What is an angiography?
Definition
Image of heart and vessels using x-rays and dye.
Term
What is cardiac arrest?
Definition
Loss of effective heartbeat, ventricular fibrillation, cardiac standstill.
Term
What is cardiomegaly?
Definition
Enlarged heart.
Term
What is cor pulmonale?
Definition
Right ventricular hypertrophy, caused by pulmonary hypertension.
Term
What is a palpitation?
Definition
Awareness of strong fast irregular or galloping heartbeat, usually brief, may be caused by underlying heart-related condition.
Term
What is paroxysmal tachycardia?
Definition
Sudden racing of heartbeat.
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