PSIO 202: CARDIOVASCULAR SYSTEM
51 Cards in this Set
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Systemic Circulation
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-carries oxygenated blood from aorta to tissues
-left ventricle ejects blood into aorta
-blood distributed to brain, heart, kidneys, GI system, muscle, and skin
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Pulmonary Circulation
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-right ventricle ejects blood into pulmonary circulation
-carries deoxygenated (venous) blood to the lungs and then back to the heart
- blood leaving pulmonary capillaries (arterial blood) enters left atrium
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Cardiac Output
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amount of blood pumped by the ventricles per unit time
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cardiac output at rest is about
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cardiac output at rest is about
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Atrioventricular Valves
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valves btwn atria and ventricle
-right AV valve- tricuspid
-left AV valve- bicuspid (Mitral)
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Semilunar valves
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btwn left ventricle and aorta and right ventricle and pulmonary trunk
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Aortic Semilunar Valve
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separates left ventricle and aorta
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Pulmonary Semilunar Valve
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separates the right ventricle and the pulmonary trunk
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Chordae Tendinae
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-tendons attached to the AV valve tissue flaps
-attach valve cusps to inner ventricular walls
-prevent prolapse of valves into the atria during ventricular contraction
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Papillary muscles
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regulate tension in the chordae tendinae and contract simultaneously with ventricles
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Semilunar valves are pressure dependent
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they open only when ventricular pressure exceeds the pressure on the other side of the valve
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Coronary Circularion
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blood supply to heart
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Coronary Arteries originating from ascending aorta
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-right coronary artery
-left coronary artery
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Right coronary artery branches into
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-marginal branch
-posterior interventricular brance
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Marginal Branch of right coronary artery
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supplies anterior portions of the right ventricle
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posterior interventricular branch
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supplies posterior portions of both ventricles
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Right coronary artery supplies
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SA node, AV node, parts of the right atrium, the interventricular septum, the right and left ventricle
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left coronary artery supplies
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SA node, parts of left atrium, interventricular septum, ventricles
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left coronary artery branches into
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-circumflex branch
-anterior interventricular branch
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left coronary artery branches into
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left atrium and posterior regions of the left ventricle
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anterior interventricular branch supplies
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anterior portions of both ventricles
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Coronary Circulation: Veins
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-great cardiac
-middle cardiac
both drain into coronary sinus which drains into right atrium
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Trace blood flow through pulmonary and systemic circulation
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deoxygenated blood in veins enters the right atrium through the superior vena cava, inferior vena cava, or coronary sinus--> tricuspid valve --> right ventricle --> pulmonary semilunar valve --> pulmonary arteries (venous blood) --> pulmonary capillaries --> pulmonary veins (arterial bloo…
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Cardiac Muscle consists of
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-branched, striated fibers with one or two centrally located nuclei
-actin and myosin myofibrils
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Gap junctions
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small channels which allow electrical impulses to pass quickly from one cell to the next and spread rapidly through heart muscle
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Gap junctions located
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intercalated discs - lie btwn adjacent muscle cells
also contain desmosomes to hold adjacent cells together
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SA node (the pacemaker)
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-mass of cells in right atrial wall
-spontaneously discharge action potentials at a rate of 100-120+ per min
- autonomic nerves modify the rate of discharge, so that the resting heart rate is about 70 b/min
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sequence of cardiac muscle excitation
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1. depolarization of the SA node, impulses travel down and across both atria causing atrial muscle fiber contraction
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At the AV border
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there is a band of poor conducting fibers to slow the impulse in order to give the atria time to fully empty before the ventricles begin to contract
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AV bundle
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leads to right and left bundle branches which transmit the action potential into the muscle of both ventricles
-sequence of excitation causes lower portions of ventricles to contract first pushing blood upwards
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pacemaker cells are auto-rhythmic
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initiates action potentials spontaneously
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pacemaker potentials
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unstable resting potentials of pacemaker cells
Ca++ influx accounts for the rising phase of the action potential (rather than Na)
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absolute refractory period
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the time when the cell will not respond regardless of the strength of stimulus
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relative refractory period
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the time when the cell will respond only if the stimulus ins suprathreshold
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ventricular Systole
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starts when the AV valves close and the pressure within the ventricles begins o rise as the cardiac muscle fibers are depolarized and contract
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Ventricular Diastole
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starts with ventricular muscle depolarization, leading to a drop in ventricular pressure, and filling of ventricle
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What affects stroke volume
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-aortic (or pulmonary artery) blood pressure or after load
-end-diastolic volume
-contractility
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Afterload
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the ventricles cannot eject blood into the aorta or pulmonary artery until the pressure in the ventricle exceeds the pressure in the vessel
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Preload
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end diastolic volume, the chambers can pump only what is delivered to them.
stroke volume increases with the rate of cardiac filling
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Contractility
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the strength of cardiac muscle contraction
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Active contractility
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change in contractility due to stimulation of the sympathetic nervous input to the heart
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Passive Contractility
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change in contractility due to changes in length of cardiac muscle fibers, "Frank-Starling Mechanism"
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Contro of active contractility
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actions of Norepinephrine or epinepherine increases rate of pacemaker activity and force of cardiac muscle contraction
-action potential invades t tubules and calcium is released from the SR
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Norepinephrine
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increases permeability of cardiac muscle fiber to calcium
increases the number of actin/myosin crossbridges
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cardiac cycle
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all the events associated with one heartbeat
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systole
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the period of ventricular contraction and blood ejection
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diastole
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the period of ventricular relaxation and filling
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Heart rate
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beats / minute
each cardiac cycle takes about 0.8 sec at rest. 75 beats / min
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chronotropic effects
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effects of ANS on heart rate
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ANS activity can be modified by
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circulating hormones, and higher brain structures
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Cardiovascular center of Brain
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located in caudal portion of medulla oblongata
- sympathetic neurons that send nerve fibers to the heart are located here
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PSIO 202: QUIZ 2