Chapter 13 continued

Chapter 13 continued - Chapter 13 continued _ Begin Exam 3...

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Chapter 13 continued ________________________________________________________________________________ Begin Exam 3 Electrocardiogram – a prolonged QRS complex may result from damage to the AV bundle fibers Role of Hormones on Heart Epinephrine and Norepi Increased contractibility by increasing [Ca++] within the cardiac muscle fiber. Properties similar to skeletal muscle T tubules Sarcoplasmic reticulum calcium storage Troponin-tropomysin regulation Properties similar to smooth muscle Gap junctions Extracellular calcium Look at the diff of excitation in skeletal muscle compared to cardiac in (Fig 13.13) What doesn’t this have? A neuron, no motor-end plates Recording the Electrical Activity of the Heart with an Electrocardiogram Non-invasive technique Used to test for clinical abnormalities in conduction of electrical activity in the heart Body = conductor Currents in body can spread to surface (ECG, EMG, EEG) Standard ECG Trace (13.15b-know how to read) P wave: atrial depolarization QRS complex: ventricular depolarization T wave: ventricular repolarization PQ segment: AV nodal delay QT segment: ventricular systole TQ interval: ventricular diastole (only time the heart rests) ECG and Ventricular Action Potential (Fig 13.15) ** (a) Ventricular action potential recorded from a single contractile cell in the ventrical (single cell) (b) ECG surface recording of the summed electrical activity of all cells (all act as a whole) Arrhythmias Detected on ECG Arrhythmias: Abnormal heart rhythms. Flutter: extremely rapid rates of excitation and contraction of atria or ventricles. Just happens sometimes. Not usually a problem. Fibrillation: major problem Contractions of different groups of myocardial cells occur at different times Coordination of pumping impossible 1
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(Can’t pump the blood out of the heart, not good) Abnormal Heart Rates (Fig 13.16) “Sinus rhythm” = rhythm generated by SA node Abnormal Heart Rates: Ventricular fibrillation – rapid, uncoordinated depolarization of ventricles. Tachycardia - fast Bradycardia - slow (heart rate slows when your face is under water because you body thinks that you are drowning. It slows to conserve oxygen) Extrasystole: Extra contraction (Fig 13.16) PAC = premature atrial contraction PVC = premature ventricular contraction Ischemia Blood supply to the heart is stopped (Fig 13.31). something has blocked coronary arteries Cells become O 2 starved Can’t make ATP to pump Ca ++ out of the cytoplasm Produce lactic acid (H + ) ↑ in H + ++ close gap junctions in damaged cells isolating them Large areas of ischemia heart attack When myocardial cells die, they release enzymes which serve as markers
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This note was uploaded on 09/22/2009 for the course BIOL 2160 taught by Professor Kt during the Spring '08 term at LSU.

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Chapter 13 continued - Chapter 13 continued _ Begin Exam 3...

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