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Stack #123144
Cardiac Physiology II
Question | Answer |
---|---|
Heart Wall - 3 layers | Epicardium: This serous membrane of smooth outer surface of heart Myocardium: Middle layer composed of cardiac muscle cell and responsibility for heart contracting Endocardium: Smooth inner surface of heart chambers |
Regulation of the Heart | Intrinsic regulation: Results from normal functional characteristics, not on neural or hormonal regulation Extrinsic regulation: Involves neural and hormonal control Parasympathetic + sympathetic stimulation |
Extrinsic Regulation | Parasympathetic stimulation Supplied by vagus nerve, decreases heart rate, acetylcholine secreted Sympathetic stimulation Supplied by cardiac nerves, increases heart rate and force of contraction, epinephrine and norepinephrine released |
Pacemaker Regulation | Once the pacemaker cells reach threshold, the magnitude and duration of the AP is always the same. In order to change the frequency, the time between APs must vary. The interval can only be changed in two ways. The rate of depolarization can be changed |
Heart Homeostasis | -Effect of BP Baroreceptors monitor BP =Effect of pH, co2,o2 Chemoreceptors monitor -Effect of extracellular ion conc Increase or decrease in extracellular K+ decreases heart rate -Effect of body temp HR increases when body temp inc HR dec when.. |
Mean Arteriole Pressure Average blood pressure in aorta MAP=CO x PR PR is total resistance against which blood must be pumped | CO is amount of blood pumped by heart per minute CO=SV x HR SV: Stroke volume of blood pumped during each heart beat HR: Heart rate or number of times heart beats per minute Cardiac reserve: Difference between CO at rest and maximum CO |
Cardiac Arrhythmias | Tachycardia: HR in excess of 100bpm Bradycardia: HR less than 60 bpm Sinus arrhythmia: HR varies 5% during resp cycle + up to 30% during deep respiration Premature atrial contractions: Occasional shortened intervals btwn 1 contraction |