BIO Heart Notes - A&P PDF

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BIO Heart Notes

Quiz 2 Exam 1

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Blood flows from the heart through arteries  arterioles  capillaries

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Blood flows from capillaries to the heart through  venules  veins

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Arteries carry oxygen rich blood from the heart, while veins carry deoxygenated blood back to the heart

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Arteries o Blood flows away from heart o Thicker walls (provide strength from high pressure)

o Elastic & stretchable (maintains blood pressure even when heart relaxes) 

Three tunics (layers) of an artery o Tunica adventitia (outer) o Tunica intima (middle) o Tunica media (inner)

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Veins o Return blood back to heart o Thinner walls (blood travels with low pressure/flows because muscles contract when we move) o Valves in large veins (one-ways valves allow blood to flow only one way)

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Pulmonary Circuit: blood vessels that carry blood to and from alveoli of lungs for gas exchange (right side of the heart)

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Systemic Circuit: transport blood to and from rest of body (left side of heart)

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Heart o Beats about 100,000 times/day, pumping 8,000 liters of blood o Approx. the size of a fist o Made up of 4 chambers  Left & right atria  Left & right ventricles o Located in mediastinum between lungs o Base: broad superior portion of heart o Apex: inferior end, tilts to the left, tapers to point

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Pericardium: parietal; covers the heart; thin, tough sac

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Heart walls o Epicardium: visceral; covers outer surface of the heart

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o Myocardium: muscle wall of the heart; forms both atria and ventricles that contains blood vessels and nerves o Endocardium: inner surface of heart including valves 

Anterior

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Posterior

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Sulci o Coronary sulcus: divides atria and ventricles o Anterior and posterior interventricular sulci: separate left and right ventricles; contain blood vessels of cardiac tissue

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Interatrial septum: wall between atria

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Interventricular septum: thicker wall between ventricles

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Atrioventricular (AV valves): fibrous valves that connect atria to ventricles and only permit blood flow in one direction

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Right atrium: receives blood from superior and inferior vena cava

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SVC: opens into posterior/superior portion of right atrium, delivering blood from head, neck, upper limbs, and chest

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IVC: posterior/inferior delivers blood from rest of trunk, viscera, and lower limbs

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Coronary sinus: large vein that returns from cardiac veins into right atrium

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Right ventricle: blood travels here from right atrium through the tricuspid valve (right AV valve) o Each cusp has attached chordae tendineae that also attach to papillary muscles o Inner surface of ventricles contain muscular ridges called trabeculae carneae (prevent suction which would impair the heart’s ability to pump)

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From the right ventricle that blood flows to the pulmonary trunk through the pulmonary valve o Pulmonary trunk divides into right and left pulmonary arteries o These arteries branch into capillaries in the lungs where o2 enters the blood and co2 exits

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Right and left pulmonary veins: blood travels here from the lungs after they are oxygenated

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Left atrium: blood travels here from the pulmonary veins

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Left ventricle: blood travels here from the left atrium via Mitral/Bicuspid valve (left AV valve)

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Blood leaves left ventricle through aortic valve into the ascending aorta then to the aortic arch

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Aortic arch: serves the upper body by passing into the o Brachiocephalic trunk o Left common carotid artery o Left subclavian artery o Descending aorta

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Descending aorta: blood travels from here to the lower body

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From the body, the blood (capillary level) travels through venules, veins, then to the superior and inferior vena cava (deoxygenated)

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Regurgitation: failure of valves; causes backflow of blood into atria o Prolapse: valve opens backwards o I.e. systolic heart murmur

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Myocardium needs its own constant supply of oxygen-rich blood

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The left and right coronary arteries originate at base of ascending aorta

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Blood pressure here is highest in all systemic circuit

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Blood returned to right atrium from myocardium by great cardiac vein, posterior cardiac vein, middle cardiac vein, and small cardiac vein—by dumping it into the coronary sinus

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Angina Pectoris: partial obstruction of coronary blood flow can cause chest pain; pain cause by ischemia (restricted blood flow), often activity dependent

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Myocardial Infarction (heart attack): complete obstruction causes death of cardiac cells in affected area; pain or pressure in chest that often radiates down left arm

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Coronary artery bypass graft (CABG): involves bypassing major blocks in blood vessels of the heart to improve the blood to the cardiac muscle (myocardium) o Plaques have been removed before bypass in a procedure called coronary endarterectomy o Endarterectomy: fatty deposits in the shape of coronary arteries removed from within arteries

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Cardiac conduction system o Myogenic: heartbeat originates within heart o Auto-rhythmic: regular, spontaneous depolarization o Components: sinoatrial node (pacemaker), atrioventricular node, atrioventricular bundle, bundle branches, purkinje fibers

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SA node: pacemaker, initiates heartbeat, sets heart rate

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AV node: electrical gateway to ventricles (brief delay so atria can contract before ventricles)

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AV bundle: pathway for signals from AV node o Right and left bundle branches: divisions of AV bundle that enter interventricular septum

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Purkinje fibers: upward from apex spread throughout ventricular myocardium in order to maximize ventricular ejection

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Myocytes have stable resting potential of -90 mV

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Step 1: Depolarization o Stimulus opens voltage regulated Na+ gates (Na+ rushes in) membrane depolarizes rapidly o Action potential peaks at +30 mV o Na+ gates close quickly

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Step 2: Plateau (200-250 msec long—sustains contraction) o Slow Ca+ channels open, Ca+ binds to channels on SR, releases Ca+ into the cytosol—contraction

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Step 3: Repolarization o Ca+ channels close, K+ channels open, rapid outflux returns cell to resting potential

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Role of Calcium Ions in Cardiac Contractions o 20% of calcium ions required for a contraction comes from calcium entering through the plasma membrane during the plateau phase o Arrival of extracellular Ca+ triggers release of calcium ion reserves from SR o Ca+ channels close slowly and intracellular Ca+ is absorbed by the SR or pumped out of cell

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Cardiac muscle is very sensitive to extracellular Ca+ concentrations

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K+ leak permeability out of the cell and Na+ leak permeability into the cell—balance of the two determines resting membrane potential

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Pacemaker Action Potentials (resting is at -60 to -70 mv) o Step 1: depolarization  K+ leak channels allow K+ out of the cell slowly and Na+ leak channels allow Na+ in the cells of the SA node o Step 2: threshold  -40 and -50mv; voltage sensitive calcium channels open generating a slow depolarization o Step 3: repolarization  the calcium channels are rapidly inactivated, potassium is increases, and the loss of positive ions slowly repolarizes the cell

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Differences to remember between cardiac muscle and skeletal muscle AP’S o 1. All-or-None Law - Gap junctions allow all cardiac muscle cells to be linked electrochemically, so that activation of a small group of cells spreads like a wave throughout the entire heart. This is essential for "synchronistic" contraction of the heart as opposed to skeletal muscle.

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o 2. Automacity (Autorhythmicity) - some cardiac muscle cells are "self-excitable" allowing for rhythmic waves of contraction to adjacent cells throughout the heart. Skeletal muscle cells must be stimulated by independent motor neurons as part of a motor unit. o 3. Length of Absolute Refractory Period - The absolute refractory period of cardiac muscle cells is much longer than skeletal muscle cells (250 ms vs. 2-3 ms), preventing wave summation and tetanic contractions which would cause the heart to stop pumping rhythmically. 

EKG o 1. Atrial depolarization begins o 2. Atrial depolarization complete (atria contracted) o 3. Ventricles begin to depolarize at apex; atria repolarize (atria relaxed) o 4. Ventricular depolarization complete (ventricles contracted) o 5. Ventricles begin to repolarize at apex o 6. Ventricular repolarization complete (ventricles relaxed)

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 o P wave - atria depolarize o P–R interval - from start of atrial depolarization to start of QRS complex o QRS complex - ventricles depolarize o Q–T interval - from ventricular depolarization to ventricular repolarization o T wave - ventricles repolarize 

Cardiac Arrhythmias o Ectopic foci: region of spontaneous firing (not SA)  Nodal rhythm: set by AV node, 40 to 50 bpm  Intrinsic ventricular rhythm: 20 to 40 bpm o Arrhythmia: abnormal cardiac rhythm o Heart Block: failure to conduction system  Bundle branch block or total heart block (damage to AV node)

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ECG: Long QT syndrome: ventricles aren’t repolarizing fast enough o ST segment elevation equals injury (myocardial infarction) o ST segments depression equals ischemia (reduced blood flow through coronary artery)

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Hyperkalemia: ECG tracing has tall, thin, T-waves; prolonged PR intervals, ST segment depression; widened QRS; loss of P-wave

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Cardiac Cycle: is the period between the start of one heart beat and the beginning of the next; includes both contraction and relaxation o Systole: atrial/ventricular contraction o Diastole: atrial/ventricular relaxation o Sinus Rhythm: set by SA node at 60-100 bpm; adult resting is 7080 bpm

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Atrial systole: SA node fires, atria depolarize, P-wave appears on ECG, atria contract & force blood into the ventricles, ventricles now contain end-diastolic volume (EDV) of about 130 ml of blood

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Isovolumetric contraction of ventricle: atria repolarize and relax, ventricles depolarize, QRS complex appears on ECG, ventricles contract, rising pressure closes AV valvues (lub), no ejection of blood yet

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Ventricular ejection: rising pressure opens semilunar valves, rapid ejection of blood, reduced ejection of blood (less pressure), stroke

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volume (SV) amount ejected (70ml), SV/EDV= ejection fraction, end systolic volume (ESV) amount left in heart 

Isometric relaxation of ventricles: t-wave appears in ECG, ventricles repolarize and relax, semilunar valves close (dub), AV valves remain closed, ventricles expand but do not fill yet

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Phases of cardiac cycle o Quiescent period o Ventricular filling (atrial kick) o Isovolumetric contraction

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o Ventricular ejection o Isovolumetric relaxation 

Heart Sounds o Auscultation: listening to sounds made by body o S1 First Heart Sound: louder and longer “lub” occurs with closure of the AV (tricuspid and bicuspid) valves o S2 Second Heart Sound: softer and sharper “dup” occurs with closure of semilunar valves (aortic and pulmonary veins) o Softer Sounds  S3: blood flow into ventricles  S4: atrial contraction (kick)  Rarely heard in people >30

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Heart Valve Abnormalities o The type of murmur will depend on the valve involved

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Cardiac Output (CO): amount of blood ejected by the ventricle in 1 minutes o Heart rate X stroke volume  About 4-6 L/min at rest  Exercise increases CO to 21-35 L/min o Cardiac reserve: difference between a person’s maximum and resting CO

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Heart Rate o Pulse: surge of pressure in artery  Infants: 120 bpm or more

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 Young adult female: 72-80 bpm  Young adult male: 64-72 bpm  HR rises in elderly o Tachycardia: resting adult HR above 100  Stress, anxiety, drugs, heart disease, increase body temp o Bradycardia: resting adult HR...