The Heart Flashcards
Heart location
In the mediastinum
Middle of the chest, tilted over to left
Pericardium
The heart is enclosed and held in place by the pericardium
Consists of outer fibrous pericardium and an inner serous pericardium
Pericardium: Serous Pericardium
Has two layer
- visceral
- pariteal
Layers of the heart wall
3 layers
Epicardium ( composed of cardiac muscle) , Myocardium- biggest, all muscle
Endocardium- epithelial tissue, lines inside of the heart
Right atrium
Receives blood from the superior and inferior vena cava and the coronary sinus
Blood passes from right to left atrium through the tricuspid valve
Chambers of the heart
Include two upper atria and two lower ventricles
On the surface of the heart are the auricles ( small pouches on the anterior surface that increase the capacity of each atrium ) and sulci ( grooves that contain blood vessels and fat and separate the chambers )
Right ventricle
Receives blood from the right atrium and sends blood to the pulmonary trunk via the pulmonary semilunar valve
Left atrium
Receives blood from the pulmonary veins
Blood passes from the left atrium to the left ventricle through the bicuspid valve
Left ventricle
Forms the apex of the heart
Blood passes from the left ventricle through the aortic semilunar valve into the aorta
Wall is much thicker than that of the right ventricle
Flow of blood
Right Atrium- Left Ventricle-Pulmonary Trunk -Lungs-Pulmonary Veins-LA-down LV-through AV- Atrium - pumped around to body-returns via vena cava
Coronary circulation
The flow of blood through many vessels. Delivers oxygenated blood and nutrients to and removes carbon dioxide and wastes from the myocardium
Coronary veins
Deoxygenated blood returns to the right atrium primarily via the coronary sinus
Removes carbon dioxide and wastes from the myocardium
4 types of electircal activity in the heart
Pacemaker potential
Atrial action potential
Ventricular action potential
Electrocardiogram
Conduction system
- Sino Atrial Node fires aka SA node
- AtrioVentricular node fires
- Excitement spreads down AV bundles
- Right and Left bundle branches
- Purkinje Fibers
Cardiac muscle cells
Self-exitable, therefore autorythmic
- Repeatedly generate spontaneous action potentials that then trigger heart contractions
- They form the conduction system, the route for propagating action potential through the heart muscle
Phase of the action potentials
AP is of long duration, varying from 100-250 ms for the structures above
Action potential in a ventricular fiber
Characterized by a rapid dpolarization, plateau and repolarization
EKG
Electrocardiogram, a recording of the electrical changes that accompany each heart beat
Helps to determine if the conduction pathway is abnormal
Action Potential Propagation through the heart
- Depolarization of atrial contractile fibers produces P wave
- Atrial systole ( contraction )
- Depolarization of ventricular contractile fibers produces QRS complex
- Ventricular systole ( contraction )
- Depolarization of ventricular contractile fibers, , begins at apex, produces T wave
- Ventricular diastole ( relaxation ) depolarization is complete
ATP production in cardiac muscle
Cardiac muscle generates ATP via anaerobic cellular respiration and creatine phosphate
The cardiac cycle
One cycle consists of the contraction (systole) and relaxation (distole) of both atria, rapidly followed by the systole and diastole of both ventricles
Electrical events, pressure changes, heart sounds, volume changes, mechanical events
Electrical events
PRQST
1.P
4.R & Q : aka Atrial systole 0.1 seconds long
8.S & T : Ventricular systole 0.3 seconds long
After T its Relaxation Period 0.4 seconds long
8 steps in the cardiac cycle
Steps 1-3 only
Begins : relaxed. ventricles 70% filled
- Atrial systole begins: atrial contractions begin and rising pressure forces open the right and left AV valves. no venous flow into atria but little back flow either
- Atria eject blood into ventricles: filling ventricles
- Atrial systole ends : ventricles contusion maximum volume+ end-diastolic volume, which is normally about 130 ml
8 steps in the cardiac cycle
Steps 4-5
- Ventricular systole begins: Av valves close as P vent quickly exceeds Patria, pressure in ventricles continue to rise and all values closed aka isovolumetric ventricular contraction
- Ventricular ejection: When pressure in ventricles exceeds atrial pressure in great vessels, semilunar valves forced open. Blood flows into pulmonary and aortic trunks
Stroke volume now at 80ml. Percent of end-diastolic volume that is ejected is around 60%
8 steps in the cardiac cycle
Steps 6-7
- Ventricular pressure falls near end of systole: back flow from vessel drinks closes semilunar valves, ventricles contain end-systolic volume; about 40% or 50ml. Aortic elastic recoil causes dicrotic notch
- Ventricular diastole: starts at 370msec
Ventricular pressure is still higher then atrial pressure, all heart valves are now closed, the ventricles relax and this all lasts for remaining 430msec of cycles plus 100msec of the next cycle
Cardiac outout
The volume of blood ejected from the left or right ventricle into the aorta or pulmonary trunk each minute
Stroke volume
The amount of blood pumped out of the ventricle in one beat
Regulation of stroke volume
Three factors regulate it
- Preload: the degree of stretch in the heart before it contracts
- Contractility:the forcefulness of contraction of individual ventricular muscle fibers
- Afterload: The pressure that must be exceeded if ejection of blood from the ventricles is to occur
Regulation of Heart Rate
Several factors
- Autonomic Nervous System
- Hormones
- Ions
- Age
- Gender
- Physical fitness
- Temperature
Exercise and the Heart
Regular Aerobic exercises can
- Increase cardiac output
- Increase HDL
- Decrease triglycerides
- Improve lung function
- Decrease blood pressure
- Assist in weight control
Pericardial Cavity
Potential space filled with pericardial fluid that reduces friction between the two membranes
Myocardial thickness and functions
The thickness of myocardium of the four chambers varies according to the function of each chamber
The atria walls are thin because they deliver blood to the ventricles
Ventricle walls are thicker bc they pump blood greater distances
Right ventricle walls are thinner then left bc they pump blood into the lungs which are nearby and offer very little resistance to blood flow
Left ventricle walls are thicker bc they pump blood through the body where the resistance to blood flow is greater
Fibrous skeleton of heart
Forms the foundation for which the heart valves attach, serves as points of insertion for cardiac muscle bundles, prevents overstitching of the valves as blood passes through them and acts as an electrical insulator that prevents direct spread of action potentials from the atria to the ventricles
Atrioventricular valves
Prevent blood flow from the ventricles back into the atria
Prevented by contraction of papillary muscles tightening the chord tendinae
Operations of the semilunar valves
Allow ejection of the blood from the heart into arteries but prevents back flow of blood into the ventricles
Open when press in the ventricles exceed the pressure in the arteries
Systemic and Pulmonary Circulations
Left side of the heart is the pump for systemic circulation, pump oxygenated blood from the lungs into the body
Right side of the heart is the pump for pulmonary circulation, receives deoxygenated blood from the body and sends it to the lungs for oxygenation
Coronary Arteries
Principal arteries, branching from the ascending aorta and carrying oxygenated blood are the right and left coronary arteries
Development of the heart
The heart develops from the mesoderm before the end of the third weeks of gestation
The endothelial tubes develop into the four chambered heart and great vessels of the heart
Development of the heart
The heart develops from the mesoderm before the end of the third weeks of gestation
The endothelial tubes develop into the four chambered heart and great vessels of the heart
