The Cardiovascular System Chapter 11

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): 1.Epicardium – serous membrane 2.Myocardium – muscle layer 3.Endocardium – continuous throughout circulatory system

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” 915CfCghttp:// 915CfCg x8ghttp:// x8g rJZQt4w&feature=fvwhttp:// rJZQt4w&feature=fvw

Know sequence of cardiac cycle

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Cardiac Muscle Contraction - know 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 System - know 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 actnpot/01 actnpot/01

Pacemaker and Action Potentials of the Heart - know

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)

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

Heart Physiology: Sequence of Excitation - know

Heart Excitation Related to ECG - know

Extrinsic Innervation of the Heart - know Heart is stimulated by the sympathetic cardioaccelerator y center Heart is inhibited by the parasympathetic cardioinhibitory center

Electrocardiography - know 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

Electrocardiography (EKG) outube.com/ watch?v=ew 6Jp74vaN4

Heart Murmurs – abnormal sounds caused by the flow of blood. Mitral stenosis (abnormal narrowing) Mitral valve prolapse (turns “inside out”)

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

Ectopic pacemaker

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:

Abnormally slow heartbeat

Abnormally fast heartbeat

Regulation of Heart Rate Sympathetic N.S. increases heart rate and force of contraction through increased epinephrine secretion Parasympathetic N.S. decreases heart rate and force of contraction through the vagus nerve. Sends continuous impulses. Secretes acetylcholine

Other factors that influence heart rate Temperature Ion concentration K + and Ca + + Hormones Hypoxia, acidosis and alkalosis slow heart Age Gender Physical fitness

Fetal Circulation Obtains oxygen and nutrients from maternal circulation Two arteries off internal iliac arteries run through umbilical cord Umbilical vein returns oxygenated blood Several shunts in fetal circulation:

Ductus venosus – bypasses fetal liver and dumps blood from umbilical vein into inferior vena cava. Foramen ovale – hole in atrial septum, blood passes from right atrium to left atrium, bypassing the developing lungs Ductus arteriosus – connects pulmonary artery with aorta If does not close – patent ductus arteriosus – get mixing of venous and arterial blood.