Cardiovascular System Part 2 Circulation Heart Anatomy Contraction Blood Pressure Cardiac Action Potentials EKG

Circulation Pulmonary Circuit: Systemic Circuit: R. atrium R. ventricle Pulmonary arteries Lung capillaries Pulmonary veins Systemic Circuit: L. atrium L. ventricle Aorta Systemic arteries Organ & tissue capillaries Systemic veins Vena cavas

Circulation Atherosclerosis= cholesterol and lipid buildup on and in the walls of vessels. Increased thickening  increased pressure  thickening  decreased elasticity potential clotting

Circulation Aneurysm= swelling or dilation of aorta or other blood vessels May lead to rupture May be caused by: Aging breakdown of elastic fibers Atheroscleosis Genetic disorders Infection

Heart Anatomy Myocardium= cardiac muscle tissue Pericardium= tough fibrous sac around the heart

Heart Anatomy

Heart Anatomy

Contraction Heartbeat= one cardiac cycle; one contraction/ relaxation Systole= contraction Diastole= relaxation Contraction of a chamber causes an increase in pressure that opens the valve to the next chamber. “Lub-Dub” sound produced by the closing of AV and semilunar valves respectively.

Blood Pressure Blood pressure= pressure exerted by the blood against the vessel walls Normal = 120/80 120: systolic pressure; highest pressure 80: diastolic pressure; lowest pressure Hypertension= high blood pressure  increased resistance to flow  enlargement and weakening of heart

Blood Pressure

Cardiac Action Potentials Self-excitatory pacemaker cells= Spontaneously produce action potentials Intercalated discs= Bridge plasma membranes between 2 cardiac cells Offer almost a spontaneous contraction of many cardiac cells at once

Cardiac Action Potentials Pacemakers: Sinoatrial (SA) node: initiates atrial contraction Sends signal from location in the R. atrium through the left atrium Atrioventricular (AV) node: Located in the septum When SA signal is received at AV node there is a slow response The AV node sends the signal down the purkinje fibers Ventricles contract

Cardiac Action Potentials

EKG (aka ECG) Electrocardiogram Evaluates electrical events in the heart Reads a potential difference between electrodes on the skin Measures change in ECF currents, not in individual cells

EKG (aka ECG) P-wave= atrial depolarization QRS-complex= ventricular depolarization (w/atrial repolarization) T-wave= ventricular repolarization

EKG (aka ECG) Little to no summation in cardiac muscle: No tetanic contraction Refractory period: Time after excitation when cells can not reach action potential Allows for ventricular filling Caused by the slow inactivation of sodium channels

EKG (aka ECG) Arrhythmia= Irregular heart rhythms Pacemakers irregular Detectable by EKGs Ex) Bradychardia – fewer beats/min than average Tachychardia – many more beats/min than average Ventricular fibrillation – haphazard contractions

EKG (aka ECG) More arrythmias: http://www. rnceus. com/course_frame