Chapter 18 - The Heart Flashcards
Function of the Heart
To pump blood. It provides the pressure responsible for moving the blood through the vessels, and then filtering into the capillaries where the tissue fluid bathes the cells.
Anatomy of the Heart
A hollow organ, which consists of 4 chambers. A dual pump. Two sides, a left and a right that each pumps into two distinct pathways, the systemic and the pulmonary pathways.
Size and Shape of the Heart
Cone-shaped with a pointed end called the apex and a broad section called the base. About the size of a clenched fist, and angled towards the left.
Location of the Heart
Lies in a space between the lungs called the mediastinum. The base of the heart lies behind the sternum and the apex points to the left.
Pericardium
A double layer membrane that surround the heart.
- Parietal layer: tough fibrous membrane, outer layer.
- Visceral layer (epicardium): inner layer, a delicate serous layer that adheres to the heart muscle.
Pericardial Cavity
Space between the two membranes, filled with pericardial fluid which reduces friction when the heart is beating
Atria
Left and right. The two upper chambers, each one empties into the lower chambers, the ventricles.
Ventricles
Left and right. The lower chambers, they pump blood out into the two circuits.
Wall structure of the Heart
3 layers. The endocardium, the myocardium, and the epicardium.
Endocardium
The inner lining of the heart. Consists of a single layer of squamous epithelia. Its continuous with the epithelium that lines the remainder of the circulatory system. It fold over and with connective tissue makes up the valves of the heart.
Myocardium
This is the muscle layer. The thickest of the three layers. It’s very thin in the atria, and thicker in the ventricles. The right ventricle has three layers of muscle, while the left ventricle has four layers.
Epicardium
The thin serous membrane which adheres to the myocardium. Also called the pericardium.
Heart Vavles
Regulate the flow of the blood through the heart.
Atrioventricular Valves
Regulate flow from the atria to the ventricles, one on each side of the heart. When blood flows into the atria, the pressure of the incoming blood forces the blood open, when the ventricles begin to contract, the pressure causes the valves to swing shut.
Tricuspid Valve
Three flaps, located between the right atria and the right ventricle.
Bicuspid Valve
Mitral. Two flaps, is separates the left atria from the left ventricle.
Semilunar Valves
These separate the arteries from the ventricles. They prevent the back flow of blood from the arteries into the ventricles during ventricular relaxation.
Pulmonary Semilunar Valve
Separates the right ventricle from the pulmonary trunk
Aortic Semilunar Valve
Separates the left ventricle from the aorta
Path of blood through the heart
sup&inf vena cava and coronary sinus —> right atrium —> tricuspid valve —> right ventricle —>pulmonary semilunar valve —> pulmonary trunk —> pulmonary rt&lft arteries —> lungs —> pulmonary veins —> left atrium —> bicuspid valve —> left ventricle —> aortic semilunar valve —> aorta —> system
Coronary Circulation
Cardiac muscle is very metabolically active, and requires a constant supply of blood for nourishment. It is supplied by the right and left coronary arteries.
Cellular Organization of Heart Cells
Cardiac muscle is made of branching, striated cells separated by tone another by intercalated discs. They have 2 types of membrane junctions desmosomes and gap junctions.
All or None Response
Because the AP moves across every cell, it contracts with the maximum force with every contraction.
Resting Membrane Potential
-90 mv
SA node
A special set of cells located in the wall of the right atrium that always depolarize first. This is where the heartbeat originates, the pacemaker.
AV node
Located just above the ventricles.
Conduction in the Heart
SA node –> atrial myocardium –> AV node –> Bundle of His –> left and right bundles –> Purkinje fibers –> ventricular myocardium
ECG
Electrocardiogram. Measure of the electrical activity of the heart.
Systole
Contraction of the heart. Blood is being expelled from the heart
Diastole
Relaxation of the heart, blood is filling up the heart.
Isovolumetric Contraction
The ventricles contract, pressure inside exceeds that of the atria and the AV valves close. The semilunar valves are not yet open. The pressure in the ventricles increases dramatically and quickly.
Ventricular Ejection
As soon as the pressure in the ventricles exceeds that of the pulmonary trunk or the aorta, the semilunar valves open and blood rushes through.
Isovolumetric Relaxation
The period of time when all valves are closed during diastole.
Heart Sounds
Lub-dub. The lub is due to the closing of the AV valves. The dub is due to the closing of the semilunar valves.
Cardiac Output
The amount of blood pumped by one ventricle per minute. It is equal to the heart rate times the stoke volume.
Cardiac Reserve
the difference between the cardiac output at rest and the maximum cardiac output.
Positively Chronotropic Regulation
Factors that increase heart rate
Negatively Chronotropic Regulation
Factors that decrease heart rate
Nervous Cardiac Controls
Most immediate and important mechanisms for altering heart rate. Cardiac control center, efferent pathways, and afferent pathway.
Hormonal Controls
Epinephrine and norepinephrine are released by the adrenal medulla, will increase the pacemaker cell activity.
End Diastolic Volume , EDV
Th amount of blood in the ventricle at the end of diastole.
End Systolic Volume ESV
The amount of blood left in the ventricles at the end of systole.
Stroke Volume
Equal to EDV minus ESV. Can be controlled by altering venous return, the amount of blood returning to the heart in veins per unit of time.
Starling’s Law of the Heart
Within it’s limits, the heart will pump out all of the blood it receives. Output should equal input.
Contractility
The amount of force produced during a contraction independent of the preload. The most important factor in altering ESV and therefore stroke volume.
Heart Attack
Coronary artery has been blocked, blood is topped from flowing to a certain part of the heart. That part is either damaged, or it dies. Myocardium may form scar tissue.
Fibrillation
Condition which frequently follows a heart attack. It need to be corrected. Different part of the ventricles are contracting at different rates.
Defibrillation
Reversal of fibrillation. May use a powerful electric current through the heart, which completely depolarizes all the cells and starts it over anew.
Congestive Heart Failure
Occurs when the pump begins to fail. The pump is no longer pumping all of the blood that it receives, it starts to pool in the heart.
Pulmonary Edema
If the left side of the heart fails. Blood backs up in the pulmonary circulation. Fluid begins to build up in the lungs.
Peripheral Edema
If the right side of the heart fails. Blood backs up in the systemic system. Swelling may occur in the feet and ankles.
Angina Pectoris
Pain in the chest and left arm. Usually due to a blockage in one of the coronary arteries.
Risk Factors for Heart Disease
High blood cholesterol, high blood pressure, smoking, obesity, lack of exercise, diabetes mellitus, and genetics.
Partial Heart Block
The depolarization wave is delayed at the AV node. So the atria might need to try 2, 3, or 4 times to get a signal to the ventricles. Resulting in a 2:1, 3:1, or 4:1 block.
Complete Block
No impulse at all is going to get through to the ventricles. The ventricles will attempt to make themselves beat.
Preventricular Contraction
An extra beat of the ventricles.
Heart Murmur
A squishy sound which can be heard during the normal heart sounds. Due to the valves not closing completely.
