BIOL 225 Chapter Notes - Chapter 42: Thoracic Duct, Osmoregulation, Fibrinogen

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19 Apr 2016
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1 diastole muscle is relaxed (0. 4 seconds) atrial and ventricular diastole. Blood from vena cava going into right atrium then continues to right ventricle. 2 atrial systole (systole =contraction), ventricle diastole (0. 1 seconds: ventricular systole, atrial diastole. Some cardiac muscle cells are autorhythmic, meaning they contract and relax repeatedly without any signal from the nervous system. Sa node (natural pacemaker: pacemaker generates wave of signals to contract. Signal spreads across both atria so both contract: av node receives signal received at atria and sends to ventricles (signals are delayed) and signals spread throughout ventricles. Impulses from the sa node first spread rapidly through the walls of the atria, causing both atria to contract in unison. The impulses originating at the sa node reach other autorhythmic cells located in the wall between the left and right atria. These cells form a relay point called the av node. Impulse is delayed here about 0. 1 seconds before spreading to the heart apex.

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