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118 Cards in this Set
- Front
- Back
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How do cardiac myocytes differ from skeletal muscle fibers?
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T-tubule system is diad, not triad
T-tubule system found at Z line rather than A-I junction Myocytes have hormonal granules Terminal cisternae and SR not as well developed |
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Which bands shorten during sarcomere contraction?
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H and I bands (HI!)
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How do nodal myocytes differ from cardiac myocytes?
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Have gap junctions but not intercalated disks
Thin, irregular in shape Fewer striations Irregular branching Arranged haphazardly on stroma with collagenous and elastic fibers |
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Which layer of the heart is the AV node found?
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Subendocardial layer
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What are the histological features of Purkinje cells?
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Larger than cardiac myocytes
Connected by intercalated disks Contain lots of glycogen (paler in appearance) |
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What types of cells are found in the bundle branches?
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P cells
Purkinje cells Transitional cells |
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What makes up the cardiac skeleton?
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Annuli fibrosi
Trigonum fibrosi Septum membraneceum |
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What is the tricuspid valve (location)?
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Right atrioventricular valve
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What is the mitral valve? (location)
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Left atrioventricular valve
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Name the two semilunar valves.
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Aortic valve and pulmonary valve
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In what layer of blood vessels are the nervi vascularis and vasa vasorum found?
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Tunica adventitia
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What are the components of the tunica intima?
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Endothelium
Basal lamina Subendothelium |
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How do you distinguish between a small artery and an arteriole?
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Tunica media in arteriole has 1-2 layers
Tunica media in small artery ahd 6-8 layers |
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Pericytes can be found in what type of blood vessel?
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Continuous capillaries
Post-capillary venules |
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What are the three types of capillaries?
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Continuous
Fenestrated Sinusoidal (discontinuous) |
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Where are continuous capillaries usually found?
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Muscle
Lung CNS Connective tissue |
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Where are CLOSED fenestrated capillaries usually found?
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Kidney
Endocrine glands Intestinal tract |
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Where are sinusoidal (discontinuous) capillaries found?
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Liver
Spleen Bone |
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What are zonula occludens?
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Tight junctions
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What is a unique feature of large veins that is not found in other veins?
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Bundles of smooth muscle in the tunica adventitia
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How big in diameter are small veins?
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1-2 mm
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How big in diameter are medium sized veins?
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2-9 mm
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The epicardium also makes up what layer of the pericardium?
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Visceral layer
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The epicardium is made up of what two components?
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Serous cells (simple squamous epithelium)
Subepicardial layer |
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What does the subepicardial layer consist of?
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Adipose tissue
Connective tissue, nerves, veins, ganglia |
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What does cardionatrin do?
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Increases excretion of water and sodium
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What does cardiodilatin do?
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Lowers BP by causing vasodilation
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What three structures are found within an intercalated disk?
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Macula adherens
Fascia adherens Gap junctions |
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What type of epithelium is found in the epicardium?
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Simple squamous epithelium
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What type of epithelium makes up the endocardium?
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Single layer of squamous epithelium
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What types of cells make up the SA node?
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P cells
Transitional myocardial cell |
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What are the characteristics of P cells?
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Smaller than cardiac myocytes
Have fewer and more scattered myofilaments Connected to other nodal cells by gap junctions |
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What does the annuli fibrosi surround?
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Atrioventricular openings
Base of aorta Base of pulmonary artery |
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What is the cardiac skeleton composed of?
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Dense connective tissue--collagen, chondroid
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What kind of tissue makes up the tunica adventitia?
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Collagenous and elastic
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What do pericytes do?
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Can give rise to endothelial cells or vascular smooth muscle cells
Involved in hemangiopericytoma |
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What layers form capillaries?
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Simple squamous endothelium and basal lamina
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What is the importance of postcapillary venules?
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Important for vascular permeability
Preferential site for leukocyte emigration |
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Maximal active tension occurs at what sarcomere length?
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2.2 microns
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Name some classic symptoms of heart disease.
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Dyspnea
Syncope Fatigue Chest pain Palpitations |
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What is the role of titin?
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Tether myosin to Z line
Provide elasticity to myocyte |
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How much of the volume of cardiomyocytes is contractile proteins and mitochondria, respectively?
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50%
25% |
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What protein removes calcium in order to allow the cardiac myocytes to relax?
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Sarcoendoplasmic reticulum calcium ATP-ase
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Where are calcium ions stored in the sarcoendoplasmic reticulum?
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Calsequestrin
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What inhibits SERCA?
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Phospholamban
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What is preload?
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The initial muscle length of fibers prior to contraction; heart in resting state
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What is afterload?
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The pressure myocardial fibers must contract against
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The Starling Law applies to preload or after load?
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Preload
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Name some factors that can attribute to afterload.
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Aortic valve resistance
Systemic vascular resistance Arterial BP Myocardial wall tension |
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What three factors contribute to contractibility?
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Force
Speed Efficiency |
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What phenomena can show increase in contractibility?
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Bowditch Effect (Treppe)
Rest potentiation Post extrasystolic potentiation |
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What is the role of desmosomes in the intercalated disks?
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Prevents separation of myocytes during contraction
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Where are OPEN fenestrated capillaries usually found?
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Renal glomeruli
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What is the Bowditch (Treppe) effect?
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Increase in frequency of contraction will increase force of contraction until very fast contraction frequencies encountered
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What is one explanation for the Bowditch effect?
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Increased efficiency of SERCA and calcium induced calcium release
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In what tracing is the dicrotic notch or incissura seen?
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Aortic pressure tracing
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Why does the dicrotic notch or incissura occur?
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During closure of aortic valve, small bit of blood must flow backward to fill the valve leaflets
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What is the stroke volume?
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The amount of blood that is ejected into the aorta
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Increase in venous return increases the preload or afterload?
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Preload
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Increase in arterial pressure increases the preload or afterload?
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Afterload
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What does the ejection fraction estimate?
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Contractility of cardiac muscle
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What is normal ejection fraction?
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55-70%
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What does the A wave correspond to?
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Active diastole
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What does the E wave correspond to?
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Early phase of diastole
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What is resting tension proportional to?
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Resting sarcomere length
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How is active tension related to resting and total tension?
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Active tension=total-resting
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What is the mechanism of catecholamines on phospholamban?
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Interact with beta receptors-->activate G protein-->increase in cAMP-->phosphorylate phospholamban-->SERCA not inhibited-->increase in contractibility
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What is concentric hypertrophy?
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Thickening of organ (ie ventricle) without overall enlargement
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What is eccentric hypertrophy?
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Growth of organ in size and volume (ie. ventricle)
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Which ion channel goes through several non-conducting states before it opens?
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Voltage dependent POTASSIUM channels
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Which ion channel is quickly inactivated due to a peptide ball?
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Voltage dependent SODIUM channels
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What is the role of magnesium and polyamines in Phase 2 of ventricular action potential?
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Blocks leak type potassium channels to inactivate
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Where is titin found?
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Myocyte-extends from Z line to M line
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What is the pulmonary capillary wedge pressure an indirect measure of?
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Left atrial pressure
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What is the equilibrium potential of potassium in the cardiac muscle?
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-90 mV
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What is the equilibrium potential of sodium in the cardiac muscle?
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+60 mV
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How does the resting membrane potential of ventricles differ from that of the SA node?
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RMP in ventricle is stable and due to dominance of potassium leak channels
RMP in SA node is dynamic and more positive. More sodium than potassium leak channels and depolarizing state due to T-type Ca channels |
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What occurs in phase 0 (rapid depolarization) of the ventricles?
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Activation of voltage activated sodium channels and L-type calcium channels
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What type of potassium channel (rapid or slow) is seen in phase 1 of ventricle action potential?
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Rapid A-type potassium channel (activates and inactivates quickly)
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What occurs in phase 2 of ventricle action potential?
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Potassium leak channels blocked by polyamines and magnesium
Residual sodium leak channels L-type calcium channels for contraction Sodium-calcium exchanger |
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What occurs in p hase 3 of ventricle action potential?
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Activation of delayed potassium voltage and time dependent potassium channels
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How does depolarization differ in ventricles and SA node?
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Ventricles--due to voltage dependent sodium channels
SA node--due to voltage activated L-type calcium channels |
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How does repolarization differ in ventricles and SA node in terms of speed?
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SA node repolarization occurs stronger and quicker
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Why do epicardial myocytes have a more pronounced phase 1 (repolarization) than endocardial myocytes?
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More type A-potassium channels in epicardial myocytes--more repolarization
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Leads I, II and aVF is associated with what wall of the heart?
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Inferior wall
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Leads 1, aVL, V5 and V6 are associated with what wall of the heart?
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Lateral wall
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Leads V1-V4 are associated with what wall of the heart?
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Anterior wall
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Each large box on an ECG is how many seconds?
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0.04 seconds
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In which lead is the P wave a negative deflection?
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aVR
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Which lead has the largest amplitude P wave?
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Lead II
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What is a QS wave?
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Monophasic negative deflection-no positive R wave
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Is the Q wave positive or negative?
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Negative
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You can find a net negative QRS voltage in what lead?
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aVR (occasionally V1, V2, V3)
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What is a normal range for QRS interval?
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0.05-0.08 seconds (2 little boxes)
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Why is a prolonged QT interval a worrisome finding?
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Indicates patient is at higher risk of cardiac arrest and sudden cardiac death
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What is the normal range for the QT interval?
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Depends on patient's heart rate
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The ST segment refers to what phase of the action potential?
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Plateau phase
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Deflections of ST segment away from the baseline can be indicators of what?
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Ischemia or myocardial injury (ie MI)
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What parameters define ST segment deviation in frontal plane leads?
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At least 1mm in 2+ adjacent frontal plane leads
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What parameters define ST segment deviation in precordial leads?
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At least 2mm in 2+ adjacent precordial leads
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What makes a pathologic Q wave?
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Width of at least 40msec (one box)
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What are the four criteria for normal sinus rhythm?
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Every P wave followed by QRS
Every QRS is preceded by a P wave In one lead, all P waves should look the same P wave is positive in lead II and negative in lead aVR |
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What are the ECG hallmarks of atrial fibrillation?
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Lack of P waves and irregularly irregular rhythm
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What are the ECG hallmarks of ventricular fibrillation?
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No identifiable P, QRS or T waves
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What do you see in an ECG of patient with ventricular tachycardia?
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Three or more consecutive VPCs at rate greater than 100 beats/min
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What is a Torsade de Pointes?
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Form of polymorphic ventricular tachycardia
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What is an AV block?
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Delay or block of conduction of wave of depolarization from atria to ventricles
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What is seen in a First Degree AV block?
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All P waves are followed by QRS but PR interval is prolonged
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What is seen in a Second degree AV block?
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Some P waves produce a QRS complex and some don't
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What is seen in a third degree AV block?
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None of P waves conducted to ventricles---QRS complexes dependent on pacemaker somewhere below Bundle of His
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True or false: You can exclude the diagnosis of ACS with a normal ECG.
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False
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How do you exclude a diagnosis of ACS?
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Serial ECGs and serial troponin levels over several hours
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What is the role of the His Bundle-Purkinje system?
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To spread depolarization through ventricles faster than from one myocyte to another
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List three types of acute coronary syndromes
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Unstable angina pectoris
NSTEMI STEM |
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What are some ECG changes seen with acute myocardial infarction?
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Hyperacute T waves
Pathologic Q waves T wave inversion ST segment elevation or depression |
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When the SA node is serving as the natural pacemaker, the patient is said to be in _____.
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Sinus rhythm
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What do you see in an ECG of a patient with atrial premature contraction?
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Early arrival, abnormal, sometimes inverted P wave
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A bizarre QRS complex with prolonged QRS interval and ST segment and T wave sloping in opposite direction of QRS is seen in what condition?
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Ventricular premature contraction
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