Notes in Week 1 EKG

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Published	02/18/2025	Action potentials in the heart are usually initiated in the {{c1::SA node}}, which serves as the {{c2::pacemaker}}
Published	02/18/2025	Action potentials spread from the SA node to the {{c1::AV}} node and right/left {{c1::atria}}, simultaneously
Published	02/18/2025	From the AV node, the myocardial action potential enters the {{c1::bundle of His}}
Published	02/18/2025	From the bundle of His, the myocardial action potential enters the {{c1::Purkinje fibers}} and ultimately the ventricles
Published	02/18/2025	The resting membrane potential of cardiac cells and neurons is determined primarily by {{c1::potassium (K+)}} ions
Published	02/18/2025	In a cardiac cell, the conductance to K+ at rest is {{c1::high::high/low}}
Published	02/18/2025	Phase {{c1::0}} of the myocardial action potential is characterized by rapid {{c2::upstroke/depolarization}}
Published	02/18/2025	Phase 0 of the myocardial action potential is caused by opening of voltage-gated {{c1::Na+}} channels
Published	02/18/2025	Phase {{c1::1}} of the myocardial action potential is characterized by {{c2::initial repolarization}}
Published	02/18/2025	Phase 1 of the myocardial action potential is caused by inactivation of voltage-gated {{c1::Na+}} channels and opening of voltage-gated {{c1::K+}} cha…
Published	02/18/2025	Phase {{c1::2}} of the myocardial action potential is characterized by {{c2::plateau}}
Published	02/18/2025	Phase 2 of the myocardial action potential (plateau) is caused by a balance of {{c1::K+}} efflux and {{c1::Ca2+}} influx through voltage-gated channel…
Published	02/18/2025	The calcium channels that open during the plateau phase (myocardial action potential) are {{c1::L}}-type channels
Published	02/18/2025	The influx of calcium during the plateau phase of a myocardial action potential triggers release of Ca2+ from the {{c1::sarcoplasmic reticulum}}, caus…
Published	02/18/2025	Phase {{c1::3}} of the myocardial action potential is characterized by {{c2::rapid repolarization}}
Published	02/18/2025	Phase 3 of the myocardial action potential is caused by massive efflux of {{c1::K+}} and closure of voltage-gated {{c1::Ca2+}} channels
Published	02/18/2025	Phase {{c1::4}} of the myocardial action potential is characterized by a return to {{c2::resting membrane potential}}
Published	02/18/2025	What type of action potential occurs in the ventricles, atria, and Purkinje system?{{c1::Myocardial action potentials (phase 0 through phase 4)}}
Published	02/18/2025	Phase {{c1::0}} of the SA node action potential is characterized by {{c2::upstroke}}
Published	02/18/2025	Phase 0 of the SA node action potential is caused by opening of voltage-gated {{c1::Ca2+}} channels
Published	02/18/2025	How does the rate of upstroke in an SA node action potential compare to that of a myocardial action potential?{{c1::SA node is slower}}
Published	02/18/2025	What types of calcium channels exist in the SA node?{{c1::L-type (primary) and T-type::2}}
Published	02/18/2025	What phases of the myocardial action potential are not present in an SA node action potential?{{c1::Phase 1 & 2 (initial repolarization & plat…
Published	02/18/2025	Phase {{c1::3}} of the SA node action potential is characterized by {{c2::repolarization}}
Published	02/18/2025	Phase 3 of the SA node action potential is caused by activation of {{c1::K+}} channels and inactivation of {{c1::Ca2+}} channels
Published	02/18/2025	Phase {{c2::4}} of the SA node action potential is characterized by {{c1::slow depolarization}}
Published	02/18/2025	The rate of phase {{c1::4}} in the SA node action potential cycle determines {{c2::heart rate}}
Published	02/18/2025	Which phase in the SA node accounts for its pacemaker activity and automaticity?{{c1::Phase 4 (slow depolarization)}}
Published	02/18/2025	Phase 4 of the SA node action potential is caused by a slow, mixed Na+/K+ inward current via {{c1::If ("funny")}} channels
Published	02/18/2025	What cell types are considered latent pacemakers of the heart?{{c1::Cells of the AV node}}{{c1::Bundle of His}}{{c1::Purkinje fibers}}
Published	02/18/2025	{{c1::Conduction velocity}} is the speed at which action potentials are propagated within the tissue
Published	02/18/2025	Where in the heart is conduction velocity the slowest?{{c1::AV node}}
Published	02/18/2025	Where in the heart is conduction velocity the fastest?{{c1::Purkinje fibers}}
Published	02/18/2025	Conduction velocity depends on the {{c1::size (magnitude)}} of the inward current during the upstroke of an action potential
Published	02/18/2025	{{c1::Excitability}} is the ability of cardiac cells to initiate action potentials in response to inward, depolarizing current
Published	02/18/2025	The {{c1::absolute}} refractory period refers to the period in which no action potential can be initiated
Published	02/18/2025	In cardiac cells, the absolute refractory period begins with the {{c1::upstroke}} and ends after the {{c2::plateau}}
Published	02/18/2025	The {{c1::effective}} refractory period refers to the period in which a(n) {{c2::conductive}} action potential cannot be generated
Published	02/18/2025	The {{c1::relative}} refractory period refers to the period in which a second action potential is possible, but requires a greater-than-normal stimulu…
Published	02/18/2025	The effects of the autonomic nervous system on heart rate are called {{c1::chronotropic}} effects
Published	02/18/2025	A negative chronotropic effect {{c1::decreases}} heart rate
Published	02/18/2025	A positive chronotropic effect {{c1::increases}} heart rate
Published	02/18/2025	Through what receptor does the sympathetic nervous system increase heart rate?{{c1::β1 adrenergic receptor}}
Published	02/18/2025	Activation of β1 receptors in the SA node produces an increase in {{c1::funny current (If)}} channel activity, which increases the rate of phase 4 dep…
Published	02/18/2025	Through what receptor does the parasympathetic nervous system decrease heart rate?{{c1::M2 muscarinic receptor::specific}}
Published	02/18/2025	Activation of M2 receptors in the SA node produces a decrease in {{c1::funny current (If)}} channel activity, which decreases the rate of phase 4…
Published	02/18/2025	The effects of the autonomic nervous system on conduction velocity are called {{c1::dromotropic}} effects
Published	02/18/2025	A negative dromotropic effect {{c1::decreases}} conduction velocity through the AV node
Published	02/18/2025	A positive dromotropic effect {{c1::increases}} conduction velocity through the AV node
Published	02/18/2025	What is the result of sympathetic stimulation on conduction velocity?{{c1::Increased}}
Published	02/18/2025	What is the result of parasympathetic stimulation on conduction velocity?{{c1::Decreased}}
Published	02/18/2025	A(n) {{c2::negative}} dromotropic effect increases the {{c1::PR}} interval on an ECG
Published	02/18/2025	A(n) {{c2::positive}} dromotropic effect decreases the {{c1::PR}} interval on an ECG
Published	02/18/2025	The {{c1::P wave}} on ECG represents {{c2::atrial depolarization}}
Published	02/18/2025	Atrial repolarization is not seen on an ECG because it is masked by the {{c1::QRS complex}}
Published	02/18/2025	The duration of the P wave correlates with the {{c1::conduction velocity}} through the atria
Published	02/18/2025	The {{c1::PR interval}} on ECG is the time from the initial depolarization of the atria to the initial depolarization of the ventricles
Published	02/18/2025	The PR interval on ECG depends on the conduction velocity through the {{c1::AV node}}
Published	02/18/2025	The {{c1::QRS complex}} on ECG represents {{c2::ventricular depolarization}}
Published	02/18/2025	The {{c2::T wave}} on ECG represents {{c1::ventricular repolarization}}
Published	02/18/2025	T-wave inversion may indicate recent {{c1::myocardial infarction (MI)}}
Published	02/18/2025	The {{c1::QT interval}} on ECG represents the entire period of ventricular depolarization, contraction, and repolarization
Published	02/18/2025	The {{c1::ST segment}} on ECG is an isoelectric period (horizontal line) when the ventricles are depolarized
Published	02/18/2025	The {{c1::J point}} on ECG is the junction between the end of QRS complex and start of ST segment
Published	02/18/2025	Which pacemaker in the heart has the fastest rate?{{c1::SA node (hence why it is dominant)}}
Published	02/18/2025	The {{c1::left}} bundle branch of the bundle of His divides into anterior and posterior {{c2::fascicles}}
Published	02/18/2025	The {{c1::AV}} node is located in the posteroinferior part of the interatrial septum
Published	02/18/2025	Slowed conduction through the AV node normally causes a(n) {{c1::100}}-msec delay, allowing time for ventricular filling
Published	02/18/2025	The {{c1::sarcomere}} is the contractile unit of the myocardial cell
Published	02/18/2025	What part of a myocardial cell is responsible for carrying action potentials into the cell interior?{{c1::T tubules}}
Published	02/18/2025	What part of a myocardial cell is the site of storage and release of Ca2+ for excitation-contraction coupling?{{c1::Sarcoplasmic reticulum (SR)}}
Published	02/18/2025	During the plateau of a myocardial action potential, Ca2+ enters the cell through {{c1::dihydropyridine}} receptors (L-type Ca2+ channels)
Published	02/18/2025	Entry of Ca2+ into the myocardial cell during the myocardial action potential triggers further release of Ca2+ through {{c1::ryanodine}} receptors (Ca…
Published	02/18/2025	In the myocardial cell, high intracellular Ca2+ binds to {{c1::troponin C}}, causing {{c2::tropomyosin}} to move out of the way, which allows actin an…
Published	02/18/2025	The magnitude of the tension that develops during myocardial excitation-contraction coupling is proportional to levels of intracellular {{c1::Ca2+}}
Published	02/18/2025	Relaxation of a myocardial cell occurs when:- Ca2+ is reaccumulated in the sarcoplasmic reticulum by the action of {{c1::Ca2+ ATPase (SERCA)}}- Ca2+ …
Published	02/18/2025	{{c1::Gap junctions}} are low-resistance paths between cardiac cells that allow for rapid electrical spread of action potentials
Published	02/18/2025	Contractility, or {{c1::inotropy}}, is the intrinsic ability of myocardial cells to develop force at a given muscle length
Published	02/18/2025	A positive inotropic effect {{c1::increases}} heart contractility
Published	02/18/2025	A negative inotropic effect {{c1::decreases}} heart contractility
Published	02/18/2025	Cardiac contractility increases with increased intracellular {{c1::Ca2+}} concentration
Published	02/18/2025	Sympathetic stimulation increases myocardial contractility via {{c1::β1}} receptors
Published	02/18/2025	Sympathetic stimulation increases the activity of {{c2::Ca2+ ATPase (SERCA)}} via phosphorylation/inhibition of {{c1::phospholamban}}
Published	02/18/2025	Parasympathetic stimulation decreases {{c2::atrial}} contractility via {{c1::M2}} receptors
Published	02/18/2025	What effect does increased heart rate have on cardiac contractility?{{c1::Increased contractility (to an extent)}}
Published	02/18/2025	What effect does decreased heart rate have on cardiac contractility?{{c1::Decreased contractility}}
Published	02/18/2025	Cardiac contractility increases with {{c1::decreased}} extracellular Na+
Published	02/18/2025	What effect do cardiac glycosides (e.g., digoxin) have on intracellular Na+ concentration?{{c1::Increased}}
Published	02/18/2025	Increased intracellular [Na+] in cardiac myocytes causes decreased activity of the {{c1::Na+ / Ca2+ (NCX)}} exchanger
Published	02/18/2025	Decreased activity of the Na+/Ca2+ exchanger (NCX) (e.g., due to cardiac glycosides) causes {{c1::increased}} intracellular Ca2+ concen…
Published	02/18/2025	The velocity of shortening of cardiac muscle is maximal when afterload is {{c1::zero}}
Published	02/18/2025	The velocity of shortening of cardiac muscle {{c1::decreases}} as afterload increases
Published	02/18/2025	The {{c1::SA}} node is located in the wall of the right atrium near the orifice of the superior vena cava
Published	02/18/2025	What is the effect of β1-blockade on contractility (and SV)? {{c1::Decreased contractility}}
Published	02/18/2025	What is the effect of acidosis on contractility (and SV)?{{c1::Decreased contractility}}
Published	02/18/2025	What is the effect of hypoxia (low O2) and hypercapnia (high CO2) on contractility (and SV)?{{c1::Decreased}}
Published	02/18/2025	What is the effect of dilated cardiomyopathy on contractility?{{c1::Decreased (systolic dysfunction)}}
Published	02/18/2025	Patients who have been hit by lightning will present with a characteristic {{c1::Lichtenberg figure}} skin finding
Published	02/18/2025	While lightning injuries are rare, the most common cause of death is a(n) {{c1::arrhythmia}}
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