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2012-05-06 13:21:09
circulatory system heart

circulatory system: the heart
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  1. State the location and position of the heart:
    • location: thoracic cavity, in mediastinum, between lungs, behind sternum, ribs 2 - 5
    • position: tilted to the left, so 2/3 rds of the heart is to the left of the median plane
  2. describe the external anatomy of the heart:
    • pericardial sac: tough, fibrous layer of dense irregular connective tissue, and a deep serous layer. dense connective tissue anchors heart to- diaphram, sternum, mediastinum, secrets serous fluid to lubricate/reduce friction
    • heart wall: epicardium, myocardium - cardiac muscle, thickest layer, left ventricle 3x thicker than the R ventricle, endocardium
    • great vessels: major vessels entering/leaving the heart, vena cava, plumonary trunk, pulmonary veins, aorta
    • coronary vessels: fills grooves between chambers
    • arteries: blood flow away from the heart
    • veins: blood flow towards the heart
  3. describe the internal anatomy of the heart:
    4 chambers: two superior are R and L atria- receving chambers for blood returing to the heart, two inferior chambers R and L ventricles- pumps that eject blood to arteries

    • valves
    • R atrioventricular (AV, tricuspid),
    • L atrioventricular (AV, bicuspid, mitral valve)
    • plumonary valve: opening from R ventricle into pulmonary trunk, (semilunar)
    • aortic valve: opening from L ventricle into aorta (semilunar)

    chordea tendineae: connects the AV valves to papillary muscles (prevents AV valves from flipping inside out)
  4. describe the structure of the pericardium:
    • pericardium: encloses heart in a double-walled sac
    • pericardial sac: tough, fibrous layer of dense irregular connective tissue, and a thin deep serous layer
    • pericardial sac is anchored: to diaphram, sternum, mediastinum
    • * secrets serous fluid lubricates/reduces friction
  5. describe the structure of the heart wall:
    • epicardium: serous membrane of the external heart surface
    • myocardium: under edpicardium, thickest layer, cardiac muscle, L ventricle is 3x thicker than R ventricle
    • endocardium: lines interior of the heart chambers, covers valve surfaces, continuous with endothelium of the blood vessels
  6. describe the location, structure, and fxn of the heart vavles:
    • location: Atrioventricular (AV) valves regulate the openings between the atria and ventricles, Semilunar valves regulate the flow of blood from the ventricles into the great artieries
    • structure:
    • fxn: ensure one way blood flow, open/close due to pressure not muscle contraction,
  7. distinguish between the pulmonary and systemic circuits:
    • pulmonary circuits: carries blood to the lungs for gas exchange and returns it to the heart, right side of the heart, lower pressure pump, thicker walls
    • systemic circuit: supplies blood to every organ of the body, including parts of the lungs, and part of the heart itself, left side of heart, higher pressure pump, thinner walls

    • pulmonary circulation flow
    • pulmonary trunk - low O2
    • lungs - load O2, unload CO2
    • aorta- high O2
    • body - unload O2, load CO2
    • vena cava- low O2

    pulmmonary trunk > lungs > pulmonary veins > L atrium > L AV valve > L ventricle > aortic valve > aorta > body > vena cava > R atrium > R AV valve > R ventricle > pulmonary valve > pulmonary trunk > over again

    * distribution of blood: pulmonary 18%, heart 12%, 2/3 systemic - arteries 11%, capillaries 5%, veins 54% (70% systemic)
  8. describe and identify the major vessels that carry blood into and out of the heart:
    • blood enters the R atrium from the superior and inferior venae cavae
    • blood in the R atrium flows through R AV valve into the R ventricle
    • contraction of the R ventricle forces the pulmonary valve to open
    • blood flows thru pulmonary valve into pulmonary trunk
    • blood is distribued by R and L pulmonary arteries to the lungs where it unloads CO2 and loads O2
    • blood returns from lungs via pulmonary veins to L atrium
    • blood in the L atrium flows through left AV valve to left atrium
    • blood in L atrium flows thru L AV valve into L ventricle
    • contraction of L ventricle (simultaneous with step 3) forces aortic valve open
    • blood flows through the arotic valve into ascending aorta
    • blood in arota is distribued to every organ in the body, where it unloads O2 and loads CO2
    • blood returns to the heart via venae cavae
  9. Put the following structures of the heart in the correct order from deep to superficial:

    • endocardium
    • myocardium
    • epicardium
    • pericardium
  10. The________ valve separates the right ventricle and pulmonary trunk, whereas the _______ valve separates the
    left atrium and left ventricle.

    atrioventricular; semilunar
    right AV; left AV
    aortic; right AV
    pulmonary; left AV
    right AV; pulmonary
    pulmonary; left AV
  11. Blood returning to the heart from the lungs enters which chamber of the heart?

    left atrium
    right ventricle
    left ventricle
    right atrium
    left atrium
  12. Which of the following is NOT characteristic of cardiocytes (cardiac muscle cells)?

    intercalated discs
    short, branched cells
    uses anaerobic fermentation
    uses anaerobic fermentation
  13. Which of the following structures distributes electrical signals throughout the ventricles of the heart?

    atrioventricular bundle
    Purkinje fibers
    sinoatrial node
    atrioventricular node
    prukinje fibers
  14. Compared to skeletal muscle cells, action potentials in cardiac muscle cells (cardiocytes) are _________ and have a _______ refractory period.

    shorter; shorter
    longer; shorter
    shorter; longer
    longer; longer
    longer; longer
  15. In an ECG, the ______ represents atrial depolarization and the T wave is generated by ___________.

    P wave; atrial repolarization
    T wave; atrial depolarization
    P wave; ventricular repolarization
    QRS complex; ventricular depolarization
    P wave; ventricular repolarization
  16. A person with a resting heart rate below 60 beats/min has which of the following?

  17. The amount of blood pumped by each ventricle in 1 min is called _______ and can be calculated as _________.

    auscultation; age x heart rate
    cardiac output; heart rate + stroke volume
    ventricular ejection; blood pressure x heart rate
    cardiac output; stroke volume x heart rate
    ventricular filling; heart rate ÷ stroke volume
    cardiac output; stroke volume x heart rate
  18. The autonomic nervous system (ANS) directly influences heart rate. The firing of which nerve keeps the resting heart rate at ~70 beats/min?

  19. which of the following is NOT one of the great vessels entering or leaving the heart?

    A. common carotid artery
    B. pulmonary trunk
    C. superior vena cava
    D. aorta
    A. common carotid artery
    (this multiple choice question has been scrambled)
  20. which structure attaches to the AV valves to prevent them from turning inside out?

    A. interventricular septum
    B. cordate tendineae
    C. interatrial septum
    D. pericardium
    B. cordate tendineae
    (this multiple choice question has been scrambled)
  21. the right ventricle has a _________ wall than the left ventricle because the right ventricle pump against ______ pressure than the left ventricle.

    A. thicker; more
    B. thinner; more
    C. thinner; less
    D. thicker; less
    C. thinner; less
    (this multiple choice question has been scrambled)
  22. the pulmonary semilunar valve separates the pumonary trunk from which heart chamber?

    A. right atrium
    B. left atrium
    C. right ventricle
    D. left ventricle
    C. right ventricle
    (this multiple choice question has been scrambled)
  23. the coronary arteries that supply the heart with blood originate from which vessel?

    A. pulmonary trunk
    B. superior vena cava
    C. common carotid atery
    D. arota
    E. inferior vena cava
    D. arota
    (this multiple choice question has been scrambled)
  24. in fetal circulation, the foramen ovale diverts the blood flow from the _____ to the _____.

    A. right atrium; left atrium
    B. left atrium; left ventricle
    C. left ventricle; right ventricle
    D. right atrium; right ventricle
    A. right atrium; left atrium
    (this multiple choice question has been scrambled)
  25. which part of the anatomy contains oxygenated blood?

    A. inferior vena cava
    B. right atrium
    C. pulmonary trunk
    D. pulmonary vein
    D. pulmonary vein
    (this multiple choice question has been scrambled)
  26. the systemic circulation consists of each of the following EXCEPT:

    A. pulmonary trunk
    B. vena cavae
    C. aorta
    D. carotid atery
    A. pumonary trunk
    (this multiple choice question has been scrambled)
  27. the heart is located in which cavity:

    A. pleural
    B. peritoneal
    C. thoracic
    D. pulmonary
    C. thoracic
    (this multiple choice question has been scrambled)
  28. contrast the prenatal heart structure with postnatal heart structure:
    • prenatal
    • fetal circulation bypasses collapses lungs
    • fetal blood bypasses the pulmonary circuit
    • foramen ovale: blood goes directly from the R atrium to the left, thru a hole in the interatrial septum
    • ductus ateriosus: most of the blood from the R ventricle is shunted directly into the aorta
    • * lungs only recv a trickle of blood, sufficient to meet metabolic needs

    • postnatal
    • right ventricle pumps all of its blood into the lungs
    • foramen ovale closes and becomes fossa ovalis
    • ductus arteriosus constricts and becomes liagmentum arteriosum
  29. trace the flow of blood thru the prenatal heart:
    • placental (oxygenated) blood from the unbilical vein mixes with fetal blood from the inferior vena cava and returns to the heart
    • blood bypasses the lungs by flowing directly from the right artium thru the foramen ovale into the left atrium
    • blood also bypasses the lungs by flwoing from the pulmonary trunk thru the ductus ateriosus into the aorta
    • the back to the placenta to get oxygented blood again
  30. describe the coronary circulation:
    • a system of blood vessels that serve the heart wall
    • immediately after the aorta leaves the left ventricle it gives off a right and left coronary artery
    • left coronary artery: 2 branches, supplies blood to both ventricles, and left atrium
    • right coronary artery: 2 branches, supplies blood to both ventricles and right atrium
    • cornonary sinus: posterior side of heart, empties blood into the right atrium
  31. trace the blood flow of coronary circulation:
    • aorta
    • coronary arteries
    • capillaries
    • coronary veins
    • coronary sinus
    • right atrium
  32. describe the events of reduced blood flow within the coronary arteries:
    • Plaque or thrombus can block coronary blood flow
    • leads to angina: chest pain
    • myocradial infraction (MI): (heart attack) caused by a fatty deposit or blood clot in a coronary artery, *death of part of myocardium*
    • Cogestive heart failure: weakening cardiac walls and/or disrupted electrial conduction system

    resoultion: ballon angioplasty or coronary bypass
  33. review the special structural characteristics of cardiac muslce tissue:
    • short, thick brached cells
    • one, centrally placed nucleus
    • uses Ca2+ from the SR and the ECF
    • intercalated discs
    • high amouts of mitochondria
    • desmosomes - prevent the contracting cardiocytes from pulling apart
    • gap junctions - ion channel, enable each cardiocyte to electrically stimulate its neighbors
    • aerobic respiration to make ATP
    • no anaerobic fermentation - so no fatigue
  34. describe why the heart is not dependent on the nervous system for rhythm:
    • each peice continues its own rhythmic pulsations, sloitary, isolated cardiac muscle cells pulsate rhymically so caridocytes are said to be autorhythmic
    • *has its own pacemaker, electrical system
  35. describe the functional characteristics of cardiac muscle tissue:
    • autorhythmic cells: pacemaker cells, example - sinoatrial (SA) node, determins heart rate
    • conducting cells: spreads electricl signal, may have pacemaker activity
    • conductile cells: 99% of myocardium, no pacemaker activity
  36. describe the structure of teh electrical conduction system of the heart:
    • *composed of internal pacemaker and nervelike conduction pathways thru the myocaridum
    • sinoatrial (SA) node: right atrium, near the superior vena cava
    • atrioventricular (AV) node: lower end of interatrial septum, near the right AV valve
    • bundle of HIS: leaves AV node
    • bundle branches: left or right, enter interventriulcar septum, descend toward apex
    • purkinje fibers: lower end of bundle branches, spread throughout ventricular myocardium
  37. describe the fxn of the electriacl conduction system"
    • sinoartiral (SA) node: pacemaker- initaiates each heartbeat, determins heart rate
    • atrioventricular (AV) node: electrical gateway to ventricles
    • bundle of HIS: pathways by which signals leave the AV node
    • bundle branches: forks
    • prukinje fibers: distribute the electrical excitation to the ventricles
  38. describe the flow of electrical signals thru the cardiac conduction system:
    • 1. SA node fires
    • 2. excitation spreas through atrial myocardium * atria contract*
    • 3. AV node fires
    • 4. excitiation spreads down AV bundle *fast*
    • 5. purkinje fibers distribute exctiation *ventricles contract*
  39. the normal heartbeat triggered by the SA nodes is called:
    sinus rhythm
  40. any region of spontaneous firing other than the SA node is called:
    ectopic focus
  41. State the normal heart rate, the heart rate from the AV node, and the heart rate from the purkinje fibers when they are acting as an ectopic focus:
    • normal heart rate: 70-80 BPM
    • AV node HR ( nodal rhythm): 40-50 BPM
    • purkinje fibers: 20-40 BPM
  42. any abnormal cardia rhythm is called:
  43. a persistent, resting adult heart rate below 60 BPM is called:
  44. a persistent, resting adult heart rate above 100 BPM is called:
  45. irregular and chaotic action potential propagation, where the heart quivers, and blood is not being pumped, is called:

    • *fatal if not corrected
    • *atrail fibillation vs. ventricular fibillation (only minutes to fix)
  46. Cells of the SA node do not have a stable resting memebrane potential. their memebran potential starts at about -60 mV and drifts upward, showing a gradual depolarization called:
    pacemaker potential

    * results from slow inflow of Na+ w/o compensating outflow of K+
  47. explain the flow of ions underlying each phase of a cardiac pacemaker cell action potential:
    • 1. slow inflow of Na+
    • 2. threshold of -40 mV
    • 3. Ca2+ channels open, Ca2+ flows in
    • 4. rising depolarization, peaks at 0 mV
    • 5. K+ channels open, K+ leaves the cell
    • 6. falling repolarization
    • 7. pacemaker potential starts over again

    • * each depolarization of the SA node sets off one heartbeat
    • *fires every 0.8 seconds, so HR 75 bpm
  48. explain the flow of ions underlying each phase of contractile cell action potential:
    • 1. voltage-gated Na+ channels open
    • 2. Na+ inflow deplarizes the membrane and triggers the opening of still more Na+ channels, creating a postitive feedback cycle and a rapidly rising membrane voltage.
    • 3. Na+ channels close when the cell depolarizes, and the volage peaks at nearly + 30 mV
    • 4. Ca2+ entering through slow Ca2+ channels prolongs depolarization of membrane, creating a plateau. Plateau falls slightly because of some K+ leakage, but most channels remain closed until end of plateau.

    • *cardiocytes contract, sustained contraction necessary for expulsion of blood
    • 5. Ca2+ channels close and Ca2+ is transported out of cell, K+ channels open and rapid K+ outflow returns membrane to its resting potential

    *absolute refractory peroid: prevents wave summation and tetnus, which would stop pumping action of the heart
  49. describe the atrial excitation in electrical conduction of the myocardium:
    • signal travesl thru the atria at about 1 m/s
    • atrial contraction, complete
    • when signal reaches AV node the signal slows down to about 0.05 m/s
    • the delay is essential becuase it gives the ventricles time to fill with blood before they being to contract
  50. describe the ventricular excitation in electrical conduction of the myocardium:
    • signal travels thru the AV bundle and prkinje fibers at a speed of 4 m/s, the fastest in the conduction system
    • consiquently the entire ventricular myocardium deploarizes within 200 ms after the SA node fires, causing the ventricles to contract in near unison
  51. Explain the purpose of an electrocardiogram (ECG/EKG):
    • to provide a comprehensive image of the heart's electrical activity.
    • a composite recording of all action potentials produced by the nodal and myocardial cells- not constructed as a tracing of a single action potential
  52. describe how the P wave segment of teh ECG corresponds to the electrical activity and contraction of the myocardium:
    • produced when a signla from SA node spreads thru atria and depolarizes them
    • *atria contract
    • 1. atria being depolarizing
    • 2. atria depolarization complete
  53. describe how the QRS complex segment of teh ECG corresponds to the electrical activity and contraction of the myocardium:
    • (Q): small downward deflection, delay time, allow for blood flow between atria andn ventricles
    • (R): tall sharp peak, ventricle polarization
    • (S): final downward deflection, ST segment corresponds to the pateau in the myocardial action potential, thus reps. time in which ventricles contract and eject blood
  54. describe how the T wave segment of teh ECG corresponds to the electrical activity and contraction of the myocardium:
    • ventricular repolarization immedialtely before diastole
    • *heart is ready for next cycle
  55. describe the diagnoistic interpretation of abnormal ECGs called nodal rhythm:
    • missing or inverted P waves
    • generated by the AV node in the absences of SA node activity
  56. describe the diagnoistic interpretation of abnormal ECGs called a heart block:
    • two or more P waves per cycle
    • some P waves are not transmitted through the AV node and thus fails to generate QRS complexes
    • extrasystole
  57. describe the diagnoistic interpretation of abnormal ECGs called ventriuclar fibrillation:
    • enlarged Q waves
    • grossly irregular waves of depolarization. typically seen in a myocardial infarction
  58. one complete contraction and relaxation of all four heart chambers is called:
    cardiac cycle
  59. Describe the operations of the AV valves in the heart in terms of gradients and flow:
    • when atrial pressure is greater than ventricular pressure, the AV valves opens and blood flows thru P atria > P ventricles = open
    • when ventricular pressure rises about the atrial pressure, the blood in the ventricles pushes the valve cusps closed P ventricles > P atria = closed
  60. describe the operations of the semilunar valves in the heart in terms of gradients and flow:
    • when the pressure in the ventricles is greater that the pressure in the great arteries, the semilunar valves are forced open and blood is ejected, P ventricles > P artery = open
    • when ventricular pressure is lower than arterial pressure, the aterial blood holdes these valves closed, P artery > P ventricles = closed
  61. describe the ventricular filling (1) phase of the cardiac cycle, including the timing and heart sounds:
    • AV valves open, blood flows into ventricles
    • semilunar valves closed
    • 1st 1/3 is rapid ventricular filling
    • 2nd 1/3 is diastasis, slower filling
    • last 1/3 is atrial systole

    • * each ventricle contains EDV of 130 ml, only 40 ml (30%) is contributed by atrial systole
    • *R atria contracts before L atria b/c it recvs signal from SA node 1st

  62. describe the isovolumetric contraction (2) of the cardiac cycle, including the timing and heart sounds:
    • P in the ventricles rises sharply, and reverses the P gradient b/w atria and ventricles
    • AV valves are closed!
    • heart sound S1 occurs
    • * eventhough ventricles contract, they do not eject blood and there is no change in volume
    • "iso" - same - volume

  63. describe the ventricular ejection (3) phase of the cardiac cycle, including timing and heart sounds:
    • ventricular pressure exceeds aterial (artery) pressure
    • semilunar valves are open
    • AV valves closed
    • blood ejects out of each ventricle
    • ventricles do not expel all the blood, each contains 130 ml EDV, and ejcects about 70 ml called the stroke volume

  64. describe the isovolumetric relaxation (4) phase of the cardia cycle, including timing and heart sounds:
    • AV valves already closed
    • semilunar valves close, heart sound s2 occurs
    • ventricles are not taking in blood b/c all ventricles are closed