Lecture Exam 3 HEART

• The heart is a double pump because it pumps blood through 2 separate circuits of blood vessels:
• 1. The pumonary circuit: Carries blood to and from the gas exchange surfaces of the lungs
• 2. The systemic circuit: Carries blood to and from the rest of the body.

• 1. Right Atrium: collects blood from the systemic circuit
• 2. Right Ventricle pumps blood to the pulmonary circuit
• 3. Left Atrium collects blood from the pulmonary circuit
• 4. Left Ventricle pumps blood to the systemic circuit

• 1. Fibrous Pericardium - Outer layer. Strong layer of dense fibrous CT. Keeps the heart in place and prevents the heart form overfilling.
• 2. Parietal Layer of the Serous Pericardium - Double layered sac between the fibrous pericardium and the heart.
• 3. Visceral Pericardium - The space between the 2 layers. Contains a small amount of lubricating pericardial fluid.

• Superior Vena Cava
• Inferior Vena Cava
• Coronary Sinus

Pulmonary Artery and Aortic Artery

Pulmonary Veins

Superior / Inferior Vena Cava -> Right Atrium -> Tricuspid Valve -> Right Ventricle -> Pulmonary Semilunar Valve -> Pulmonary Artery -> Lungs -> Pulmonary Veins -> Left Atrium -> Mitral Valve -> Left Ventricle -> Aortic Semilunar Valve -> Aorta -> Body ->

Atrioventricular Valves (AV) between the atria and the ventricles are controlled by the chordae tendinae and papillary muscles. When the ventricles contract, the pressure of the blood swings teh cusps together, closing the valves to the atria. At the same time, the papillary muscles tense the chordae tendineae and prevent the vales from swinging into the atria.

Semilunar Valves prevent backflow from the pulmonary trunk and aorta into the vetnricles. Semilunar valves have no muscular support; the 3 cusps of the valve support each other like a tripod.

• Pectinate Muscles: Prominent muscular ridges on the anterior atrial wall.
• Chordae Tendineae: Connective tissue fibers that originate at the papillary muscles of the right ventricle and prevent the AV valve from opening backward.
• Papillary Muscles: Located in the ventricles of the heart. Contract to prevent inversion or prolapse of these valves.

• The fibrous skeleton surrounds the valves between the atria and ventricles.
• 1). supports valves
• 2). anchors vessels
• 3). provides electrical insulation to separate the atrial mass from the ventricular mass
• 4). anchors cardiac muscle fibers...

• Systole describes the congraction of a heart chamber during the heartbeat.
• Diastole is the time when the heart chamber is relaxing and filling with blood.

• 1. The Sinoatrial (SA) Node: "Pacemaker" cells. In posterior wall of right atrium.
• 2. The Atrioventricular (AV) Node: In the floor of the right atrium. Receives impulse from the SA Node. Delays the impulse.
• 3. The AV Bundle: In the septum. Carries impulse to the left and right bundle branches which conduct to Purkinje Fibers.
• 4. The Purkinje Fibers: Distribute impulse through ventricles - atrial contraction is completed. Ventricular contraction begins at the apex and continues up into the ventricular walls.

• Parasympathetic: Decreases heart rate
• Sympathetic: Increases heart rate

• Sympathetic neurons cause pacemaker cells to generate action potentials
• more frequently, and thus increase heart rate. In contrast,
• parasympathetic neurons have the opposite effect; they cause a decrease
• in the frequency of action potentials generated by peacemaker cells, and
• thus decrease heart rate. The heart simultaneously receives both
• sympathetic and parasympathetic signals in a "push-pull" manner.
• Increases in one are accompanied by decreases in the other.