Stockton College Physiology, Cardiovascular System Chapter 14
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| 2 Types of pump in Cardiovascular system | -Chamber pump: heart rhythmic contraction
-Lg veins in Human leg: blood pushed out vein by surrounding tissue pressure, veins have valves tht prevent backflow
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| How does blood flow from heart? | Blood flows from arteries on left side, thru capillaries in tissues, comes back thru right side of heart via veins thru vena cava
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| How does blood flow thru vessels? | Down pressure gradient from high pressure to low pressure
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| Hydrostatic Pressure | pressure exerted when fluid isn't moving (pressure in our cardio system-even though it's moving and should be "hydraulic pressure"
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| Order of Cardio vessels decreasing blood pressure | Aorta>Arteries>Arterioles>Capillaries>Venules>Veins>Venae cavae
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| Reason to get blood from vein instead of artery? | Blood pressure too high in arteries and much lower in veins
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| Driving Force | Pressure created in ventricles
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| Relationship between volume & pressure | Inverse relationship-as volume of vessel decreases, pressure increases (squeezing on water-filled balloon)
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| What does blood flow depend on? | Positive pressure gradient. Flow goes from high>low pressure. Flow depends on change in pressure. If pressure of 1 area equals pressure of another area, no flow occurs. NEED pressure change to induce flow!
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| Cardiovascular Resistance | Tendency of cardiovascular system to oppose blood flow.
Resistance mainly determined by radius of tube.
R has pos relationship w/ L & n(viscosity) and neg relationship w/ r
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| Relationship of Flow & Resistance | Inverse-As resistance incr, flow decr.
F~Pressure/Resistance
F~1/Resistance
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| Poiseuille's Equation | R~ 1/r(^4)
R~ Ln/r(^4)
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| Impact of radius change on flow & resistance | -Flow inc 16 fold whn radius doubles
-Sm change in radius caused Lg effect on resistance to blood flow
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| Vasoconstriction | decrease in blood vessel volume
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| Vasodilation | increase in blood vessel volume
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| Flow Rate | Volume of blood that passes one point in system per unit time (L/min, mL/min)
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| Velocity | -Distance fixed volume of blood travels in given period of time
-velocity is faster in smaller vessel, but flow rate can be same in Lg/Sm vessel
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| Velocity Equation | V=flow rate/cross section area
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| How Cardiac muscles differ from Skeletal muscles | -Smaller size
-More mitochondria
-have intercalated discs to connect
-T-tubules are larger for more efficiency
-Smaller sarcoplasmic reticulum
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| 2 Components of Intercalated Discs | -Desmosomes
-Gap Junctions
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| Desmosomes | found in intercalated discs: transfer force from cell to cell
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| Gap Junctions | found in intercalated discs: transfer electrical signals rapidly from cell to cell
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| Mitochondria in Cardiac muscle | consume 70-80% of Oxygen delivered in blood (more than 2 times other cells in body)
-reason reduced blood flow due to blockage of coronary artery can be deadly
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| Description of Myocardial Muscle Cells | -branched
-single nucleus
-attached to ea. other by intercalated discs
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| Heart's upward contraction | Spiral arrangement of muscles allows ventricular contraction to squeeze blood upward from apex(bottom) of heart
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| Myocardium | cardiac muscle of heart
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| Pericardium | sac surrounding heart, within sac is thin pericardial fluid tht lubes heart surface
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| What are the 2 types of cardiac muscle cells? | -contractile cells
-autorhythmic cells
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| Contractile cells | cardiac muscle cells tht contract after autorhythmic cells start
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| Autorhythmic cells | pacemakers,synchronize contractile cells to coordinate a heart contraction
-where action potentials originate
-difference from contractile cells-smaller, no organized sarcomeres
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| Importance of Calcium in heart excitation-contraction | Cardiac muscle excitation-contraction coupling includes Calcium-induced Calcium release.
-voltage gated calcium channels open in cell membrane of T-tubules & let calcium enter
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| How can cardiac muscle contraction be graded? | -single muscle fiber can start a graded contraction
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| What is force generated from cardiac cell-cell dependent on? | -Force generated dependent on # of crossbridges (which is determined by how much Ca2+ is bound to troponin, which depends on amt of Ca2+ tht enters cell
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| Role of epinephrine & norepinephrine | regulate amnt of calcium available for contraction
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| What is diff in action potential of cardiac contractile cells from nerve/skeletal muscle action potentials? | -cardiac has longer plateu due to opening of Ca2+ channels & closing of K+ channels
-VERY important to prevent tetanus(state of continued muscular contraction) in heart
-muscles must relax for ventricles to fill up
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| What is the Action potential sequence of events for cardiac contractile cells? | 0-Na+ channels open
1-Na+ channels close
2-Ca2+ channels open; fast K+ channels close
3-Ca2+ channels close; slow K+ channels open
4-Resting Potential
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| What causes unstable membrane potential in autorhythmic cells? | the pacemaker potential-membrane potential never rests due to leaky funny channels
(contain channels diff frm other excitable tissue)
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| Sympathetic vs. Parasympathetic Stimulation | -Sympathetic stim & epinephrine DEPOLARIZE autorhythmic cell & speed up depolarization rate, increasing heart rate
-Parasympathetic stim w/ ACh HYPERPOLARIZES the membrane potential of autorhythmic cell & SLOWS depolarization, decreasing HR
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| How do depolarizations of autorhythmic cells spread to adjacent contractile cells to initiate heart contraction? | Through GAP JUNCTIONS
-Electrical current leaves SA node to auto cells which sends via gap junctions in intercalated discs to contractile cells
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| SA Node | Sinoatrial Node-main pacemaker of heart (grp of autorhythmic cells), set heart's pace since they're the fastest
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| Internodal Pathway | non-contractile autorhythmic cells: connect SA node to AV node
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| Bundle of HIS | passes from AV (atrialventricular) node into septum and divides into right & left branches
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| What is the sequence of heart electrical conduction leading to muscle contraction (pump)? | 1-SA node depolarizes
2-Rapid electric activity from SA to AV via Internodal pathway
3-Depolarization spreads slowly across atria/conduction slows thru AV node
4-Depolarization moves rapidly thry ventricular conducting system to heart apex
5-depolariz
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| What is complete heart block? | -When electrical signalling from atria to ventricles thru AV node is disrupted, resulting in ventricle contracting at diff rate than atria. Can insert pacemaker
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| Electrocardiogram | Record of heart electrical activity due to NaCl being good electrical conductor. usually placed on skin thry Eithoven's Triangle tht encloses heart (both arms & left leg)
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| In ECG, why do downward deflections correspond to periods of depolarization? | Bc it represents multiple action potentials in heart
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| Cardiac Depolarization | Whn cell generates electrical impulse it causes ions to cross cell membrane & causes the action potential, also called depolarization. movement of ions across cell membrane thru Ca2+ channels causes contraction of the cardiac cells/muscle
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| Cardiac Repolarization | the return of the ions to their previous resting state, which corresponds with relaxation of the myocardial muscle
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| Normal Heart Rate Values/ Tachycardia= Brachycardia= | Norm HR= 70-100bpm
Tachycardia=faster HR
Brachycardia="brakes", slower HR
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| Fibrillation | myocardial cells contract in disorganized manner.
Life threatening emergency bc can't get enough blood to brain (treated by electrical shock to heart)
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| Arrhythmia | electrical problems tht arises during generation/conduction of action potentials thru the heart
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| Long QT Syndrome (LQTS) | change in QT interval, can be Genetic or iatrogenic (caused by side effects of certain medications)
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| Diastole | (die/dead=relax) time during cardiac muscle relaxation
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| Systole | (sit up=contract)time during cardiac muscle contraction
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| What are the characteristics of the heart at rest? | -brief moment of relaxed atria & ventricles
-atra filling w/ blood after ventricles completed contraction
-As ventricles relax, valves open to let blood flow downward by gravity from atria to ventricles
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| Complete Cardiac Cycle Events 1-3 | 1-late diastole:all chambers relaxed & ventricles fill
2-Atrial systole: atrial contraction forces sm amt add't blood into ventricles
3-Isovolumetric ventricular contraction: pushes AV valves closed
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| Complete Cardiac Cycle Events 4-5 | 4-Ventricular ejection:as ventricular pressure rises & exceeds ateriole pressure, semilunar valves open and eject blood
5-Isovolumetric ventricular relaxation: as ventricles relax, pressure in ventricles falls&blood flows back thru semilunar valves/close
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| EDV | End Diastole Volume=max amt of blood in ventricles, ~135ml
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| ESV | End Systole Volume=minimum amt blood in ventricles, 1/2 blood volume remains, ~65ml
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| What creates heart sounds? | -1st sound "lub"=happens at isovolumic ventricular contraction from pushing AV valves closed
-2nd sound "dub"= happens at isovolumic ventricular relaxation from closing of semilunar valves after pressure drop in atria & AV valves open
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| Wigger Diagram | summarizes events of cardiac contraction by combined chart of ECG, blood pressure, heart sounds, left ventricular volume throughout all the events
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| Stroke Volume | Amount of blood pumped by 1 ventricle during a contraction
-70ml is average for humans
-can incr up to 100ml during exercise
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| How to calculate stroke volume? | EDV-ESV=Stroke Volume
(Blood vol b4 contraction)-(Blood vol after contraction)
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| What are heart attacks/strokes? | -Heart attack: blood flow is blocked to certain area of heart
-Stroke: Lack of blood supply to brain, causing rapid loss of brain functions
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| Frank Starling Law of the Heart | -Shows relationship bw heart muscle stretch & force generated by heart
-force increases w/ sarcomere length
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| Heart muscle stretch | determined by ventricular end-diastolic volume (ml), more blood=more force=more stretch
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| Heart muscle force | determined by stroke volume (ml)
-muscle force incr w/ sarcomere length, so more blood entering heart= more forceful heart pumps=more stretch
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| What is end diastolic volume determined by? | Venous return: amt blood entering heart from veins
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| How does stretch increase in cardiac muscle? | When add't blood flows into heart, connects to EDV & stroke volume
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| Inotropic effect | -effect from chemical tht increases or decreases contraction force
-ex-norepinephrine, epinephrine, digitalis
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| What is EDV (End Diastolic Volume) determined by? | Venous return tht is affected by:
1.skeletal muscle contraction
2. respirator pump: creates sub-atmospheric pressure in inferior vena cava & helps draw blood
3.sympathetic activity: decreases size of veins, thus more blood flows out of veins into hear
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| Cardiac Output | -Amount of blood pumped per ventricle per unit time (usually same for both ventricles)
-During exercise CO can incr to 30-35ml/min
-CO(cardiac output)=HR x SV (stroke volume)
-Avg CO= 5040ml/min= 72 beats/min x 70ml/beat
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| How is heart rate controlled? | -heart normally under tonic contrl (dial to be turned) by the parasympathetic division
-Reduce activity of parasym to incr HR to 90-100BPM
-Above 100BPM, sympathetic input needed to incr HR
-Both para & sympath influence HR by affecting conduction rate
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