Lecture Exam 3 HEART
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Why is the heart considered
a double pump?
- 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.
List the four chambers of the heart,
and specify to which circuit they belong to.
- 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
What are the three layers
of the pericardium?
- 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.
Name the three major veins
opening to the right atrium:
- Superior Vena Cava
- Inferior Vena Cava
- Coronary Sinus
Name the two major arteries
leaving the heart:
Pulmonary Artery and Aortic Artery
How is the blood brought
back to the heart from the lungs?
Draw a flow chart of the circulation
through the heart naming all chambers vessels and valves.
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 ->
Describe the structure and function
of atrioventricular and semilunar valves:
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.
What are the pectinate muscles, the cordae tendinae and the papillary muscles?
- 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.
What is the fibrous skeleton and function?
- 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...
What are systole and diastole?
- 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.
What is the conducting system? Describe in detail the strucutres of the conductuve system of the heart and how they
affect heart contraction.
- 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.
What is the influence of the parasympathetic and sympathetic systems on heart rate of contraction?
- 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.
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