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EvelynMallardCardio (Heart function terms (Heart Rate amount of blood…
EvelynMallardCardio
Heart function terms
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End Diastolic Volume-the amount of blood that collects in a ventricle during diastole
EDV is determined by how long a ventricular diastole lasts and by venous pressure
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End Systolic Volume-the volume of bold remaining in a ventricle after it has contracted
The ESV is determined by arterial blood pressure and the force of ventricular contraction
Cardiac Output the amount of blood pumped out by each ventricle in 1 minute (Stroke Volume x Heart Rate)
Electrical Conduction
- Action Potential (AP) enters AV bundle (bundl of HIS)-superior interventricular septum
- AP enters right/left bundle branches-extend through interventricular septum toward apex-
Conduct AP to apex and initiate contraction of cardiac muscle cells in interventricular septum
- Atrioventricular Node (AV)-inferior interatrial septum - impulse delayed @ 0.1 seconds-allows atria to complete contration before ventricls are stimulated
- At apex, bundle branches become subendocardial conducting (aka SCN or Purkinje fibers)-located in walls of ventricles/papillary muscles-conduct AP from apex to remainder of Ventricular myocardium-stimulates contraction of the ventricular myocardium and papillary muscles.
- Begins with the sinoatrial (SA) node-superior right atrial wall
aka pacemaker-generates AP 75 x per minute
stimulate action of the atria
spread through the internodal pathway to AV node
Anatomy of the heart
External structures
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Auricles (left and right)-protruding appendages that extend from the anterior atrial which somewhat increase the atria volume.
Anterior Interventricular sulcus-cradles the anterior interventricular artery, marks the anterior position of the septum separating the right and left ventricles
Coronary sulcus (left and right)- (aka atrioventricular groove, encircles the junction of the atria and ventricles. Houses the coronary artery
Coronary Artery (left and right)-Part of Coronary Circulation - supplies oxygenate blood to the left side of the heart .
Anterior interventricular artery-part of coronary circulation - branch left coronary artery - located in the anterior inter ventricular sulcus
Circumflex Artery-Part of coronary circulation (subdivision of systemic circuit - branch of left coronary artery - curves around the superior part of the left ventricle
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Internal Structures
Atrioventricular valves- one located at each atrioventricular junction-prevent back flow in to the atria when the ventricles contract.
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Chordae tendineae- tiny white collagen chords attached to each AV valve, that anchor the cusps to the papillary muscles.
Papillary Muscles- located in the ventricles of the heart. They attach to the cusps of the AV valves via the chord tendineae ad contract to during ventricular contraction. These muscle contract to hold the AV valves closed during contraction.
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Semilunar valves-guard the bases of the large arteries issuing from the ventricles (aorta and pulmonary trunk) and prevent back flow into the ventricles
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Ventricles-left and right-two inferior chambers- pump that imitates the flow of blood through a circulation pathway. RV - Pulmonary Circuit, LV -Systemic Circuit.
Fossa Ovalus- small shallow depression in the interatrial septum. scar left behind after closure of the foramen oval which was present in the fetal heart to allow blood to bypass the right ventricle and lungs
Interatrial septum-wall-like partition that separates the atria (longitudinally. Prevents oxygenated blood from the lungs from mixing with deoxygenated blood returning from the body
Atria - left and right-two superior chambers of the heart - receive blood form the body/lungs and pass that blood on to the ventricles. RA - from body, LA- from lungs
3 veins empty in to the right atrium: Superior and inferior vena cava, and the coronary sinus
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The Cardiac Cycle-all of the events associated with the flow of blood through the heart during a single heart beat. Atrial systole (contraction) and diastole (relaxation), followed by ventricular systole and diastole
Electrocardiogram (ECG)
A. Ventricular Filling
SA node depolarizes, initiating atrial depolarization (P Wave on an ECG). After atria depolarize, they contract
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P Wave-Electrical activity associated with atrial depolarization - atrial contraction occurs @ 0.1ms after the P wave begins- all heart chambers are relaxed, blood returning to atria and passing through open AV valves into ventricles
B. Ventricular Systole- The electrical impulse generated by the SA nose continues through the intrinsic conduction system until it gets to the subendocardial conducting network (SCN)
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The atrial myocardium repolarizes, atria start to relax (enter diastole)
When the pressure in the ventricles exceed pressure in atria, blood starts to move toward the atria, closing the AV valves -the closure of the AV valves produces the first heart sound.
For about 0.05 sec, both AV and semilunar valves are closed - period of isovolumetric contraction.
Ventricles are still contracting, pressure continues to rise-when it exceeds the pressure in the aorta and pulmonary trunk, the SL valves open, and most of the blood in the ventricles is ejected in to these arteries.
C. Isovolumetric relaxation-the ventricular myocardium begins to depolarize (T wave), after which the ventricles start to relax
as the ventricles relax, ventricular pressure drops
ventricular pressure quickly becomes lower than the pressure in the aorta and pulmonary trunk, causing the blood in these arteries to back flow
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For a short time, all 4 valves are closed, which is why called isovolumetric relaxation stage - the ventricles do not completely empty during ejection - the small amount of blood remaining in the ventricles is the blood that was not ejected during this cycle's ventricular contraction. This volume of blood is called the end systolic volume, or ESV
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Heart Chambes fill when they ar in diastole (relaxed) and empty when they are in systole (contracting).
-right and left happen simultaneously -difference isnlevel of pressure generated
Max - LV - 120 mmHg, RV 23-30 mmHg
-these events always allow the electrical events of the ECG.
-marked by a succession of pressure and blood volume changes in the heart
-pressure and volume changes lead to opening and closing of valves, which regulates the flow of blood through the heart.
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