Transcript Cardiac
Circulatory system Pressure gradients move blood through the heart and vessels. Pulmonary circulation vs. systemic circulation head and arms aorta (to pulmonary circuit) (from pulmonary circuit) heart other organs diaphragm liver “Double pump” both ventricles pump an equal volume of blood into systemic and pulmonary circuits Higher resistance through the systemic circuit intestines legs Pressure - force exerted by pumped blood on a vessel wall Resistance - opposition to blood flow from friction vena cava Right atrium Tricuspid valve Right ventricle vena cava Right pulmonary artery Left pulmonary artery Pulmonary semilunar valve Right atrium Tricuspid valve Right ventricle Aorta Left pulmonary vein Right pulmonary vein Left atrium Bicuspid valve Left ventricle Aorta Left pulmonary vein Right pulmonary vein Aortic semilunar Left atrium valve Bicuspid valve Left ventricle Valves ensure one-way flow When pressure is greater behind the valve, it opens. When pressure is greater in front of the valve, it closes Leakproof “seams” semilunar valve Shape of the AV valves is maintained by chordae tendineae Right atrium Tricuspid valve Chordae tendineae Papillary muscle contracts with ventricle Septum Right ventricle Ventricular Systole Ventricular Diastole Blood pressure variation Heart myocardium Cardiac muscle fibers are interconnected by intercalated discs. Junctions between cardiac muscle cells Desmosome Gap junction Action potential Intercalated disc Pacemaker activity Slow depolarizations set off action potentials in a cycle Pacemaker cells only! These cells do not contract Cardiac muscle Self-excitable muscles - action potential gradually depolarizes, then repolarizes Spontaneous action potential Pacemaker cell Gap junctions Action potential spread to other cells Gap junctions No gap junctions between atria and ventricles Fibrous insulating tissue prevents AP from directly spreading from atria to ventricles Conduction of contraction Pacemaker locations: SA node AV node Sinoatrial (SA) node Atrioventricular (AV) node Bundle of His Purkinje fibers Bundle of His Purkinje fibers Problems with heart rhythm AV node rhythm is slower - bradycardia Problems with heart rhythm Heart block – a type of bradycardia. Ventricles pump slowly and out of rhythm of atria Ventricular fibrillation Problems with heart rhythm Atrial fibrillation Ventricular fibrillation Action potential in cardiac muscle These are contractile cells not pacemaker cells Plateau phase Threshold potential Long refractory period ensures no summation of twitches Relaxation of cardiac muscles is essential Electrocardiogram Currents from heart spread to body tissues and fluid Sum of all electrical activity spread to electrodes and recorded R T P P Q PR S ST TP interval Cardiac cycle Ventricular and atrial diastole Cardiac cycle Atrial contraction Cardiac cycle Isovolumetric ventricular contraction “Lub” End diastolic volume is in the ventricles Cardiac cycle Ventricular ejection Cardiac cycle Isovolumetric ventricular relaxation “Dub” End systolic volume is in ventricles Heart murmurs Systolic or diastolic murmurs Often due to stenosis or regurgitation at a valve (“whistle” vs. “swish”) Normal heart “lub-dup” Diastolic mitral stenosis “lub-dup-whistle” Diastolic aortic regurgitation “lub-dup-swish” Systolic aortic stenosis “lub-whistle-dup” Systolic tricuspid regurgitation “lub-swish-dup” Diastolic patent ductus arteriosus Sympathetic signals increase stroke volume Extrinsically: conduction speed contraction strength Recall: muscle length and force Frank Starling law Stroke volume (SV) (ml) (intrinsic increase in stroke volume) Optimal length Increase in SV B1 A1 Normal resting length (Cardiac muscle does not normally operate within the descending limb of the length– tension curve.) Increase in EDV End-diastolic volume (EDV) (ml)