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Heart is two pumps in one: Right side – pulmonary circulation Left side – systemic circulation Heart → Arteries → Arterioles → Capillaries → Venules→ Veins → Heart Artery – any vessel that carries blood AWAY from the heart. Vein – any vessel that carries blood TOWARD the heart.
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Heart is two pumps in one: Right side – pulmonary circulation Left side – systemic circulation Heart→ Arteries → Arterioles → Capillaries → Venules→ Veins → Heart Artery – any vessel that carries blood AWAY from the heart. Vein – any vessel that carries blood TOWARD the heart
Parietal pericardium: outer fibrous layer inner serous layer Pericardial cavity Visceral pericardium Pericarditis
Heart Wall • Layers (superficial to deep): • Epicardium – serous membrane • Myocardium – muscle layer • Endocardium – continuous throughout circulatory system
Magic School Bus https://www.youtube.com/watch?v=c7ulsNQzDxE https://www.youtube.com/watch?v=xDPpTVR3Q34
Cardiac Muscle: involuntary, striated Intercalated discs: gap junctions functional syncytium desmosomes – “spot welds”
Ventricular Geometry LV RV
Common Disorders Ischemia – reduced blood flow Hypoxia – reduced oxygen supply Angina pectoris – “strangled chest” referred pain Myocardial infarction – death of an area of tissue due to interrupted blood flow (“Heart attack”) Congestive heart failure – heart is unable to supply bloodflow to body Fibrillation – uncoordinated, unsynchronized beating of heart, no net bloodflow
Cardiac cycle • One complete heart beat: • Systole (contraction) and • Diastole (relaxation) of both ventricles • Remember: Blood pressure = systole/diastole ≈ 120/80 normal average
“Heart beat” • http://www.youtube.com/watch?v=ZlB-915CfCg • http://www.youtube.com/watch?v=7eFn8Cgcx8g • http://www.youtube.com/watch?v=NYB-rJZQt4w&feature=fvw
- Know http://www.youtube.com/watch?v=12_nJamoyTk
Cardiac Muscle Contraction http://www.youtube.com/watch?v=IjU81a5TjZs; http://www.dnatube.com/video/317/Beating-Heart-Cell; http://www.youtube.com/watch?v=55tAIOcBg3w&feature=related; http://www.youtube.com/watch?v=_gbGA5il4Sg • Heart muscle: • Is stimulated by nerves and is self-excitable (automaticity) • Contracts as a unit • Has a long (250 ms) absolute refractory period • Cardiac muscle contraction is similar to skeletal muscle contraction
Heart Physiology: Intrinsic Conduction • Autorhythmic cells: • Initiate action potentials • Have unstable resting potentials called pacemaker potentials • Use calcium influx (rather than sodium) for rising phase of the action potential http://www.youtube.com/watch?v=Lhl897Mz-h8&feature=related; http://www.interactivephysiology.com/demo/systems/buildframes.html?cardio/actnpot/01
Heart Physiology: Sequence of Excitation - know • Sinoatrial (SA) node generates impulses about 75 times/minute • Atrioventricular (AV) node delays the impulse approximately 0.1 second • Impulse passes from atria to ventricles via the atrioventricular bundle (bundle of His) http://www.smm.org/heart/heart/pumping.htm; http://depts.washington.edu/physdx/heart/demo.html
Heart Physiology: Sequence of Excitation - know • AV bundle splits into two pathways in the interventricular septum (bundle branches) • Bundle branches carry the impulse toward the apex of the heart • Purkinje fibers carry the impulse to the heart apex and ventricular walls
Extrinsic Innervation of the Heart - know • Heart is stimulated by the sympathetic cardioacceleratory center • Heart is inhibited by the parasympathetic cardioinhibitory center
Electrocardiography • Electrical activity is recorded by electrocardiogram (ECG) • P wave corresponds to depolarization of SA node • QRS complex corresponds to ventricular depolarization • T wave corresponds to ventricular repolarization • Atrial repolarization record is masked by the larger QRS complex http://www.youtube.com/watch?v=lYMSkGXFoN4&feature=related
Electrocardiography (EKG) http://www.youtube.com/watch?v=ew6Jp74vaN4
AED https://www.youtube.com/watch?v=ZRVFvtoLkRM
Heart Murmurs – abnormal sounds caused by the flow of blood. Mitral stenosis (abnormal narrowing) Mitral valve prolapse (turns “inside out”)
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Conduction system of the heart Sinoatrial (SA) node – “pacemaker’ → Atrioventricular (AV) node → Atrioventricular (AV) Bundle - Bundle of His→ Purkinje fibers – conduction myofibers Ectopic pacemaker = implanted device that uses electrical impulses to reproduce or regulate the rhythms of the heart
ECG (or EKG) • An electrocardiogram (ECG / EKG) is an electrical recording of the heart and is used in the investigation of heart disease. • Normal adult 12-lead ECG: