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1 Chapter 18 Class Notes B BSC2086 Spring 2011 (Slide 2) Depolarization of the Heart is ____________________ and ____________________. About ___% of Cardiac Cells have automaticity or _____________________, which means they are ____________________. Autorhythmic Cells initiate Depolarization of __________________ and the _______________________ cells as well. (Slide 3) Autorhythmic Cells stimulate and pace the ________________________________ of the Heart. Gap Junctions between Heart cells ensure the ________________________________________. Depolarization of the Heart cell has a long ______________________________ period (cannot be excited for _________ ms). (Slide 4) The bulk of heart muscle (________%) is made of __________________ Muscle Fibers that are responsible for the Heart’s _________________ activity. (Slide 5) Similar to skeletal muscle, ________________________ opens voltage-gated __________channels in the cardiac muscle sarcolemma membrane, which causes a _____________________________________ from_________ mV to __________mV. (Slide 6) The ____________________wave in _______________________ causes the Sacrcoplasmic Reticulum to release _________ cations into the cytosol. Ca2+ provides the signal (via troponin binding) for _______________________________________. This couples ______________________ to _____________________________ (i.e., through sliding of myofilaments). (Slide 7) The Depolarization wave also opens ______________________channels in the Sarcolemma. Ca2+ influx from slow channels liberates bursts of Ca2+ , and the resulting _________________________ prolongs the _______________________ phase (causes a plateau). 2 Plateau 2 3 1 Tension development (contraction) Tension (g) Membrane potential (mV) Action potential Absolute refractory period Time (ms) 1 Depolarization is due to Na+ influx through fast voltage-gated Na+ channels. A positive feedback cycle rapidly opens many Na+ channels, reversing the membrane potential. Channel inactivation ends this phase. 2 Plateau phase is due to Ca2+ influx through slow Ca2+ channels. This keeps the cell depolarized because few K+ channels are open. 3 Repolarization is due to Ca2+ channels inactivating and K+ channels opening. This allows K+ efflux, which brings the membrane potential back to its resting voltage. Figure 18.12 Copyright © 2010 Pearson Education, Inc. (Slide 9) ________________________________________ coupling occurs as Ca2+ binds to troponin and sliding of the filaments begins. Duration of the Action Potential and the Contractile Phase is much ____________in __________________muscle than in ______________ muscle. _______________________ results from ___________________ of Ca2+ channels and _________________ of voltage-gated K+ channels. (Slide 10) The _____________________________________________ is a network of _____________________________ (and non- contractile) cells that initiate and distribute impulses to coordinate the ____________________________ and _______________________ of the Heart. (Slide 11) _____________________________ have unstable resting potentials called _______________________ potentials due to open ____________________ channels. Autorhythmic Cells __________________________________ towards threshold potential, and at threshold potential, ___________ channels open. (Slide 12) Explosive ____________ influx produces the rising phase of the ___________________________________. _______________ , not Na+ is responsible for the Action Potential of Autorhythmic Cells . Repolarization results from _____________________ of Ca2+ channels and ____________________ of voltage-gated K+ channels. 3 (Slide 14) The Autorhythmic Cells form an ________________________ system that distributes the action potential throughout the heart, and it includes the ____________ and __________________ ______________, __________________________________ (= Bundle of His), _____ Bundle ___________________, and _____________________________. (Slide 15) The ___________________________ (pacemaker) generates impulses about ______________ times/minute (____________________ rhythm), and depolarizes _____________________ than any other part of the myocardium. (Slide 16) The ______________________ node, has smaller diameter fibers; fewer gap junctions, and _____________ impulses approximately 0.1 second; the AV depolarizes _______________ times per minute in absence of SA node input. (Slide 17) Atrioventricular (AV) __________________, also called the _________________________ is the ______________ connection between the Atria and Ventricles. (Slide 18) The ________________ and ___________________ Bundle _________________ are ____________ pathways in the ____________________________ Septum that carry electrical impulses toward the Apex of the Heart. (Slide 19) The _____________________ fibers complete the pathway into ________________ and ____________________ walls. The AV ________________ and ________________ fibers depolarize only __________________ times per minute in absence of AV node input. 4 Superior vena cava Right atrium 1 The Sinoatrial (SA) node (pacemaker) generates impulses. Internodal pathway 2 The impulses pause (0.1 s) at the Atrioventricular (AV) node. 3 The atrioventricular (AV) bundle connects the atria to the ventricles. 4 The bundle branches conduct the impulses through the interventricular septum. 5 The Purkinje fibers depolarize the contractile cells of both ventricles. Left atrium Purkinje fibers Interventricular septum (a) Anatomy of the intrinsic conduction system showing the sequence of electrical excitation Copyright © 2010 Pearson Education, Inc. Figure 18.14a Please describe 3 results of defects of the Intrinsic Conduction system (slide #21): (Slide 22) Defective SA node may result in these 2 things: (Slide 22) Defective AV node may result in these 2 things: (Slides 23-24) The heartbeat is modified by the _________________________ nervous system. Cardiac heartbeat regulation centers are located in the __________________________________. The cardio-acceleratory (increases heartbeat) center innervates SA and AV nodes, heart muscle, and coronary arteries through ___________________________________. Cardio-inhibitory (decreases heartbeat) center inhibits SA and AV nodes through ______________________ Fibers in the ___________________ Nerves. (Slide 26) An electrocardiogram (ECG or EKG): a composite of all the ______________________________ generated by nodal and contractile heart cells at a given time. 5 (Slide 27) Please name and describe the 3 major electrical waves of the heart: Please draw and label the 4 types of EKGs shown in Slide 37: What are the 2 heart sounds and please describe them (Slide #38). (Slide 39) What is a heart murmur and when does it occur? What kind of sound does a stenotic valve make (slide # 40)? 6 Please describe the Events of the Cardiac Cycle (slides #42 – 46). Lub sound At QRS wave = Ventricular Depolarization Aortic pressure Increases after QRS wave Dup sound At T wave = Atrial Repolarization Copyright © 2010 Pearson Education, Inc. 7 Copyright © 2010 Pearson Education, Inc. (Slide 49) What is Cardiac Output and how is it calculated? What is the Cardiac Output at rest? While maximally exercising? (Slide 51) Stroke Volume (SV) = End Diastolic Volume (EDV) – End Systolic Volume (ESV). What are 3 main factors affecting Stroke Volume? The Frank-Starling law of the heart means that __________________ increases heart efficiency (slide #53, not 52). 8 (Slide 54) What 2 general things increase heart contractility? (Slide #56) The ______________________________ system exerts the most important extrinsic control over heart. Sympathetic nerves release _______________________ (NE) at Heart synapses. NE binding to B1adrenergic receptor initiates a ________________ second messenger system, that increases ______________ intracellular levels, and increases Ventricular _________________________________ and the Heart’s __________________________________. Extracellular fluid Norepinephrine Adenylate cyclase b 1-Adrenergic receptor Ca2+ ATP is converted to cAMP G protein (Gs) GDP Ca2+ channel Cytoplasm Phosphorylates aplasma membrane Ca2+ channels, increasing extracellular Ca2+ entry Inactive protein Active kinase A protein Phosphorylates SR Ca2+ channels, kinase A increasing intracellular Ca2+ Phosphorylates SR Ca2+ c b release pumps, speeding Ca2+ Enhanced 2+ removal2+and relaxation Ca Ca actin-myosin Troponin binds Ca2+ uptake interaction to pump SR Ca2+ channel Sarcoplasmic I Increased Cardiac reticulum (SR) muscle Force and Velocity Copyright © 2010 Pearson Education, Inc. Figure 18.21 (Slide 58) Afterload is the ___________________________________ pressure that the ventricles must overcome to eject blood. ______________________________ increases the Afterload, and results in ____________________ End Systolic Volume and _______________ total Stroke Volume. 9 (Slide 59) Positive chronotropic factors ______________________ heart rate. Negative chronotropic factors __________________ heart rate (Slide #60) The Sympathetic nervous system is activated by emotional or physical stressors, leading to the release of _________________________ which causes the pacemaker to fire _____________________________. (Slide #61) The ________________________________ Nervous system opposes Sympathetic effects. ______________________________ hyperpolarizes pacemaker cells by opening K+ channels. The Heart at rest exhibits “______________________” as ______________________ input is dominant, which ____________________ the heart during rest. (Slide #64) __________________________ from adrenal medulla enhances heart rate and contractility, and _________________ increases heart rate and enhances the effects of norepinephrine and epinephrine. ____________________________ is abnormally fast heart rate (>____________ bpm), and if persistent, may lead to ________________________. (Slide 67) Bradycardia: heart rate slower than __________ bpm. Name 4 causes of congestive heart failure (slide #68):