The Heart Chapt. 9 Heart Muscle; The Heart as a Pump and Function of - - PowerPoint PPT Presentation
The Heart Chapt. 9 Heart Muscle; The Heart as a Pump and Function of the Heart Valve By: Dr. Foadoddini Department of Physiology & Pharmacology Birjand University of Medical Sciences Dr. Foadoddini Dr. Foadoddini Electrical Activity
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By: Dr. Foadoddini
Department of Physiology & Pharmacology Birjand University of Medical Sciences
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– They are selective – A given ion may have several different channel
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Gradient:
– Digitalis inhibit Na‐K pump – [Ca]o = 2×10‐3 and [Ca]i = 10‐7 – 10‐5 M – Na‐Ca Exchanger can operate in either direction (depend upon the membrane potential) – Decreased Na‐K ATPase activity increase intracellular Na and Ca
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Intercalated disck Functional Syncytium
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The long ERP prevent the heart developing sustained, tetanic contraction
These potentials are so called ‘Fast Response’ action potential because of rapid phase 0 depolarization
↑IK (Delayed rectifier) ↓IK (Inward rectifier)
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In non-pacemaker cells
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One way path Passive opening/closing Diameter diffferences Cordae tendineae
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Volume-pressure curves as heart work
Area under curve as cardiac external work
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1. ABC: Ventricular Diastole 2. CD: Isovolumic contraction. 3. DF: Ventricular Systole 4. DE: Ejection (Rapid and reduced ejection) 5. FA: Isovolumic relaxation 6. ABC: Filling phase (Rapid filling and diastases) Atrial systole
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End-diastolic pressure
Venous return/Atrial pressure
CO
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Frank-Starling mechanism
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Arterial pressure
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– They are in SA and AV node – They do not have a true resting potential – Fast Na channels are inactivated – They induces Overdrive suppression
↑IK (Delayed rectifier) T-type Ca current
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Stokes-Aadams syndrome (after A-V block)
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influences are dominant over sympathetic (vagal tone)
= Dromotropy
Neuronal mechanisms that alter pace-maker activity
Normal range = 100 to 110 beats/min 60 beats/min to over 200 beats/min
Ventricular escape
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