exam_2_20150304202951 Flashcards
What is the purpose of the pericardium?
it is a fibroserous sac that encloses the heart and protects it from friction
What is the pressure in the Right and Left atria normally?
Right 4-8 mmHgLeft 4-12 mmHg
Which of the ventricles has lower pressure?
The RV is lower pressure 25/8LF is high pressure 90-130
How many semilunar cusps does the pulmonary and aortic valves have?
aortic=3 valve cuspspulmonic=3 semilunar cusps
What is the purpose of the chord tendineae?
tendinous attachments from papillary mm to tricuspid and mitral valves that helps to prevent eversion of valves into the atria during systole
What do sacromeres contain?
actin and myosin
What are the thick and thin filaments of a muscle called?
Actin=thinMyosin=thick
What do troponin and tropomysin regulate?
they regulate the cross bridging of actin and myosin
What is the sarcolemma, sarcoplasma, T tubules and sarcoplasmic reticulum?
sarcolemma=membrane that surrounds the myocytesarcoplasma=intracellular fluid which contains super abundance of mitochondriat-tubles=transmit action potential rapidly from sarcolemma to all myofibrils inside the fiber to citrate all the myofibril of one fiber simultaneouslysarcoplasmic reticulum=stores calcium ions
What is the purpose of intercalated discs?
they enable electrical impulses to spread quickly in a continuous cell to cell fashion
What supplies the heart with blood?
left anterior descending arteryleft circumflex arteryright coronary artery
75% of coronary perfusion is during…
diastole
What happens to the smaller blood vessels during contractions and how does the heart receive O2 during contractions?
the vessels are compressed during systole decreasing blood flow and oxygen is supplied by myoglobin (a protein in muscle that stores O2 and releases it in hypoxia during the period of systolic compression)
There is one capillary per…
fiber
What is the normal oxygen extraction?
70-75%
Formular for MAP
(2D+S)/3
How to calculate pulse pressure?
BP 136/84Pulse Pressure: 136-84=52
What is Laplace’s Law?
T=P x r/WT=tension of vessel wall that opposes the distending pressure inside the vesselP=intraluminal pressureR=vessel radiusW=wall thicknessinternal pressure expands the easel until it is balanced by wall tensionthe larger the radius, the greater the tension needed to balance a particular pressurewall tension is inversely related to wall thickness (the thicker the vessel wall the lower the tension)walls hypertrophy to reduce wall stress
How do you calculate cardiac output?
CO= HRxSVSV=preload, afterload, and contractility
What is the Frank-Starling Curve?
increase preload stretches fibers causing more forceful contraction->increased SV->increased COmyocardial fibers reach a point of stretch beyond which it cannot contract and SV and CO decrease
What are the factors of stroke volume (SV)?
preload: streching force that acts on cardiac muscle before contraction (diastole)afterload: resistance that must be overcome by ventricles in order to open semilunar valves and propel bloodcontractility: the hearts contractile forceincrease in contractility is caused by SNS, inotropic drugs, increase in cytoplasmic Ca
Normal ejection fraction (EF)…
60-70%percentage of preload volume ejected from the LV per beat
Extrinsic Control of HR
Vagus nerve (PNS)superior, middle, and inferior cardiac nerves (SNS) increase contractile force by facilitating influx of Ca into myocytes Norepinephrine Alpha adrenergic Beta adrenergic (B1) Epinephrine beta adrenergic B1 beta adrenergic B2
What are the effects of the B1 beta adrenergic receptor sites?
effected by norepinephrine and epinephrineincrease SA node discharge increase HR
What is the effect of the alpha adrenergic receptor sites?
effected by norepinephrinevasoconstriction
What is the effect of B2 adrenergic receptor sites?
effected by epinephrinecauses vasodilation
Intrinsic Controle of HR
central: thalamus/hypothalamus, diencephalon, cerebral cortexrelfex: baroreceptors, arterial chemoreceptors, bainbridge reflex, respiratory reflex
positive inotrophic means…
increased force of myocardial contraction
Action potential Fast response (ventricular and atrial myocytes)Phase 0
rapid Na=depolarization 20-30 mV
Action potential Fast response (ventricular and atrial myocytes)Phase 1
closing of Na channels=slight repolarization
Action potential Fast response(ventricular and atrial myocytes)Phase 2
influx of ca and some Na influx, efflux K=plateau
Action potential Fast response(ventricular and atrial myocytes)Phase 3
inactivation of Ca channels; heaviest K efflux=repolarization to RMP
Action potential Fast response(ventricular and atrial myocytes)Phase 4
rest
When is there absolute refractory during cardiac cycle?
phases 1,2, and part of 3 the cell cannot be depolarized again
When is there relative refractory period?
phase 3 and continues to phase 4 when the cell may be able to depolarize again
Action potential Slow response(pacemaker cells)Phase 0
slo Ca and Na influx for initial depolarization +20mV
Action potential Slow response(pacemaker cells)Phase 2-3
gradual efflux of K with drop off of Na and Ca currents depolarized to “R” MP
Action potential Slow response(pacemaker cells)Phase 4
spontaneous decreasing K efflux allos depolarization to threshold
What does the P wave signify?
spread of excitation over the atria
What does the QRS wave signify?
spread of excitation over the ventricles
What does the T wave signify?
spread of depolarization over the ventricles
Process of Excitation-Contraction Coupling
action potential is conducted from cell to cell through intercalated discsaction potential is spread into the interior of the cell via T tubulesCa begins to enter cell and the beginning of Ca influx triggers more Ca from the sarcoplasmic reticulum via Ca channelsCa binds to protein troponinthe Ca-torponin complex interacts with tropomyosin to unblock active sites between the actin and myosin filaments=>allows cross bridgingat end of systole, Ca influx ceases and sarcoplasmic reticulum is no longer stimulated to release Casarcoplasmic reticulum avidly takes up Ca via an ATP-energized Ca pumpCa binding to troponin stops and this stops the tropomyosin to again block the sites for interaction between the actin and myosin filaments*Relaxation occurs
What is the effect of Ca on the force of action potentials in the cardiac myocytes?
the greater the amount of Ca in the cytoplasm the greater the force and the lesser amount of Ca in the cytoplasm the lesser the degree of force
What blocks the site of interaction between the actin and myosin filaments in the cardiac myocyte?
tropomyosin
What causes the tropomyosin (attached to actin filament) to expose the binding site for myosin?
Ca*Ca binds to troponin C which causes the tropomyosin to expose the actin binding site and ATP is split to allow energy for myosin to then bind to actin
What are the causes of Congenital heart disease?
it occurs in 1% of live birthsetiology: unknown 90% Rubella, genetic (chromosome 13, 15, 18, 21, 22), Turner syndrome, abnormalities in transcription factors
What are the types of congenital heart disease?
- left to right shunts: blood flow from the L to R and eventually causes pulmonary HTN, atrial septal defects, ventricular septal defects, parent ductus arteriosus 2. R to L shunt: cause unO2 blood from R to L and will cause cyanosis at or near time of birth: Tetralogy of Fallot, transposition of the great arteries3. obstructive lesions: pulmonic valve stenosis, aortic valve stenosis or atresia, coarctation of the aorta
What type of arrhythmia is caused by depolarization during the relative refractory period (i.e. late phase 3 or phase 4)?
tachycardia
How does myocardial ischemia cause arrythmias?
can cause tachycardia because it alters the action potential of myocardial cells because it disrupts the Na/K pump*major reason for PVC’s or V tach that initiate ventricular fibrillation
What is reentry phenomena?
occurs when a propagator impulse fails to die out after normal activation of the heart and persists to re-excite the heart after the refractory period as ended; responsible for Afib, flutter, AV reentry, extra nodal bypass tract, Vtach
Sudden cardiac death
V fib (heart quivers; no cardiac output)Asystole
Etiology of CAD
- athersclerotic most common 2. valvular disease, myocardial hypertrophy and aortic dissection3. coronary spasm: circulating adrenergic agonist, locally released platelet contents, impaired secretion of endothelial cell relaxing factors (nitric oxide) relative to contracting factors (endothelin)4. thrombus5. hypotension, increased HR, congenital abnormalities, vasculitis, vegetative emboli6. increased demand by HTN, increased HR, increased blood volume, LVH, thyrotoxicosis
Three types of coronary syndromes:
angina, MI, sudden cardiac death
types of angina
Stable Angina: no cell necrosis, no usually associated with plaque disruption, pain short 3 to no more than 30 minutes, relieved by rest or nitroUnstable Angina: sudden change in plaque morphology or increased stenosis, pain that occurs with progressively increasing frequency, more prolonged in durationVariant Angina: coronary artery spasm, occurs at rest,
how does a thrombus form from plaque fissuring or stenosis?
fissuring: exposure of plaque to sub endothelial collagen and necrotic plaque contents cause formation of thrombus with variable thrombotic occlusion stenosis: increased stenosis from size of plaque increasing
Patho of MI
- coronary artery occlusion from thrombosis plaque fissuing/erosion; primary prolonged vasospasm; emboli; hypotension superimposed on an unchanged obstruction; decreased O2 carrying capacity of blood
MI Response Times
within 20 minutes potentially reversibleafter 20-40 minutes irreversible myocyte injury within 3-6 hours the extent is largely complete
What irreversible damage by MI is non-Q wave?
subendocardial: limited to inner 1/3-1/2 of ventricular wallthe subendocardium is the least well perfused resin and left ventricular myocardial pressure is greatest near the endocardium
What is intramural refer to in MI?
within the wall, the term intramural refers to microinfarcts
What irreversible damage by MI is represented by Q wave?
transmural: full thickness
What are types of repercussion in the cases of MI?
- thrombolysis, CABG, angioplasty* decreases area of injury and reverses ischemiamay also injure cells and increase apoptosis because O2 utilization by cell is impaired, O2 being delivered to cell from ROS and this causes damage as it draws leukocytes even after flow as been restored may leave cells poorly contractile for a few hours up to 1-2 days because of hypoxi and inflammation caused by hypoxia causes release of myocardial depressant factors that is derived from combined release of TNFa and IL-1
What is the usual location of MI?
40-50% are LAD (left anterior descending) artery
What are the markers for MI?
- creatine kinase (CK) specifically the myocardial isoform CK-MB2. troponin 1 and troponin T: after MI both are detectable within 2-4 hrs with levels peaking at 48 hr and persist for 7-10 days (***more reliable to dx MI because last so long)
What causes the systemic response during MI?
release of catecholamines and angiotensin II *anxious, fearful, weak, cold, clammy skin, acute confusion, stroke for 85+; hypo or hyper BP
Some causes of Acute Coronary Syndrome…
aka Sudden cardiac deathCADnonatherosclerotic cardiac diseases like hypertrophic cardiomyopathy*congenital abnormalitiesPatho: most often caused by lethal arrhythmia triggered by electrical irritability of myocardial cells not part of the conduction system
What is the etiology of LVSD?
- volume overload: regurgitant valves; high-output states (anemia, hyperthyroidism)2. pressure overload: systemic HTN; outflow obstruction (aortic stenosis, asymmetric septal hypertrophy)3. myocyte ischemia/loss of muscle: MI form CAD; connective tissue disease (SLE)4. loss of contractility: myocarditis; poisons (alcohol, cobalt, doxorubicin); infections (viral or bacterial); genetic mutations of cellular architecture or sacromere proteins5. restricted filling: mitral stenosis; pericardial disease (constrictive pericarditis, pericardial tamponade); infiltrative diseases (amyloidosis)
What causes diastolic dysfunction?
it is the inability for the ventricle to relax and fill with blood*diseases that decrease relaxation, decrease elastic recoil or increase stiffness of the ventricle *(left ventricle hypertrophy, myocardial fibrosis, deposition of amyloid, constrictive pericarditis)=> restrict filling
What causes right sided heart failure?
left sided heart failureright ventricular infarctionpulmonary disease including Cor Pulmonalecongenital heart disease*pulmonic or tricuspid valvular disease
How does heart failure trigger the SNS?
increased release of catecholamines= norep and epi to compensate for decreased CO=this causes increased HR and BP and cardiac contractility but causes increased work and O2 demand and can cause arrhythmias
How does heart failure trigger vasopressin secretion?
vasopressin release leads to vasoconstriction and reabsorption of water in the renal tubules to compensate for decreased CO=this increases the preload (LVEDP)= increases stretch=increases forcible contraction (Frank Starling Relationship)=and increases CO = but if it causes too much stretch it will result in decreased CO because actin and myosin will not connect effectively and can result in pulmonary edema which reduces oxygen supply and leads to myocellular hypoxia
How does heart failure activate the renin-angiotensin-aldosterone system?
reduced renal blood pressure triggers this system=aldosterone secretion leads to sodium and water reabsorption in the renal tubules=incresaed preload (LVEDP)=increased stretch=increased forcible contraction=increased CO= but will lead to too much stretch because the myosin and actin do not connect effectively which will cause decreased CO and lead to pulmonary edema and reduced oxygen supply and myocellular hypoxia
How does heart failure activate angiotensin II?
reduced blood flow triggers the renin-angiotensin-aldosterone system which results in renin stimulating the production of angiotensin II and angiotensin II stimulates production of aldosterone which leads to Na reabsorption and K excretionangiotensin II results in smooth muscle vasoconstrictionthis results in increased after load= inhibits NO release-stimulates fibroblasts proliferation
How does heart failure trigger release of atrial natruretic peptide (ANP) and brain natruretic peptide (BNP)?
these are stored in granules in atrial and ventricular cytoplasm*ANP is secreted from atrium and BNP is secreted from ventricle when stretched they inhibit secretion of renin, aldosterone and relax smooth muscle and inhibit Na and water absorptionserum BNP or precursor pro-BNP is used to monitor progression of HF
ANP is secreted from…
atriums
BNP is secreted from…
ventricles
What is the result of increased myocardial stretch?
results cells stretching, increased protein synthesis and number of sarcomeres and mitochondria increased size of myocyte with new sarcomeres increase wall thickness and or the lengthwise addition of new sarcomeres enlarge chamberthis will result in a larger distance between the capillaries which will alter the delivery of Ca=this will interfere with contractility, lead to ischemia of cells and trigger apoptosis *continued stress on the muscle will cause altered gene expression and re-expression of embryonic forms of myosin and troponin will occur and result in inability to contract normally
How does endothelin effect the heart during myocardial hypertrophy?
there is injury to the endothelial and this releases endothelin which causes vasoconstriction=decrease O2 supply
What happens when the myocyte is injured during myocardial hypertrophy?
injury to myocyte results in inflammatory response=cytokine release (TNFa and IL1TNFa promotes cardiac hypertrophy and apoptosisInterleukins promote cardiac remodeling and eventually induces contractile dysfunctionthis stimulates deposition of fibrous tissue and interstitial collagen which will cause chambers to be stiffapoptosis will result in decreased myocytes and increased work/stress on the remainder cells that will ultimately contribute to myocardial contractile failure
The similarities and differences of left sided HF and right sided HF manifestations:
- left sided HF: activates SNS(^HR)decreased COpulmonary congestion (dyspnea, orthopnea, crackles/wheezes, S3 and S4 sounds, displaced lateral apical pulse)increased BNP, LVhypertrophy, decreased EF2. right sided HF:poor EFJVDperipheral edemaascitieshepatomegaly, splenomegaly (from congestion)