How does the heart function? Control of the heart

The heart muscle The heart is made of cardiac muscle It is involuntary and controlled by the medulla oblongata The intercalated discs help cardiac cells contract uniformly

Action Potentials Like other types of muscle, cardiac cells respond to nerve impulses Changes in Na+, K+, and Ca+ (electrolytes) are essential for the cardiac cells to respond to the nerve signals Unlike skeletal muscle cells, which respond within 2ms, cardiac cells take 200 to 500 ms to respond

Autorhythmicity The sinoatrial (SA)node stimulates the heart cells to contract The SA node is made of specialized cardiac cells It is the “Pacemaker” of the heart because it generates action potentials that cause the heart to beat

The Conducting System of the Heart 1. Action potentials start in the SA node 2. The impulse travels across the walls of the atrium to the AV (Atrioventricular) node and the atria contract 3. The AV node passes the impulse to contract to the ventricles 4. The ventricles contract after a delay of about.11 seconds Why do you think there is a delay before the ventricles contract? So the atria can finish passing the blood to the ventricles

The AV Bundle The AV node forms the AV bundle, a collection of modified cardiac fibers, that extend into the interventricular septum and beyond The AV bundle leads to smaller Purkinje fibers which extend throughout the apex and ventricular walls The Purkinje Fibers are specialized to spread the contract impulse very rapidly

What is an EKG??? EKG (ECG) stands for electrocardiogram EKG’s show the sum of all the heart’s action potentials EKG can show abnormal heart rates and rhythms, blockages, and damage to parts of the heart, possibly caused by “heart attacks.” It is easy to perform and painless for the patient

Systole and Diastole Systole: Occurs when the ventricles are actively contracting The AV valves are closed Semi-lunar valves are open The atria are relaxed

Diastole: Occurs when the atria are actively contracting The AV valves are open The semi-lunar valves are closed The ventricles are relaxed

Disorders of the heart... When a coronary blood vessel becomes blocked, heart tissue can die from lack of oxygen in minutes This region of dead tissue is called an infarct A “heart attack” is technically a myocardial infarction If recognized and treated early, the heart tissue may suffer little or no permanent damage

=n8P3n6GKBSY =n8P3n6GKBSY

Causes of Coronary Artery Disease

Treatments for Occlusions (Blockages): Angioplasty: a balloon is inserted into blocked arteries and inflated, flattening the plaques Stent: a small coil device placed in a vessel after angioplasty Coronary Bypass: healthy blood vessels taken from other parts of the body “bypass” or go around the obstruction.

Cardiac Arrhythmias (Abnormal Rhythms) Tachycardia: elevated heart rate, beats > 100/min Bradycardia: slow heart rate, beats <60/min Atrial Fibrillation: atria quiver or flutter instead of making strong regular contractions N1tcH_07GYk N1tcH_07GYk v=w57gIV3ZLBE v=w57gIV3ZLBE oMZ1E oMZ1E