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188 Cards in this Set
- Front
- Back
What are the three main muscle types in the heart?
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1. Atrial muscle
2. Ventricular muscle 3. Specialized muscle |
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All muscle cells in the heart are what?
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EXCITABLE!!!!1!11!!!
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What does it mean for muscle cells to be excitable?
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It means they can produce a brief, pulse-like change in their membrane potential and this AP can be conducted all over the heart simultaneously.
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The SA nodal cells have a higher or lower resting potential? Why?
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SA nodal cells have a HIGHER resting potential because of higher K+ conductance.
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TRUE OR FALSE: SA nodal cells spontaneously generate action potentials.
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TRUE!
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Current flow is always taken as which direction?
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Positive ion flow, outward flow being positive.
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What kind of nerves alter the heart rate?
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Autonomic nerves alter the heart rate by affecting the pacemaker potential.
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What kind of stimulation accelerates the heart by increasing the slope of the pacemaker potential?
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Sympathetic stimulation!
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What are T-Type Ca2+ channels?
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They are channels that have tiny conductances that transiently open
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What are L-Type Ca2+ channels?
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They are channels that have large conductances with long-lasting openings.
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Which type of Ca2+ channels contribute the last third of the pacemaker potential?
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T-Type!
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What kind of stimulation slows the heart rate by decreasing the slope of the pacemaker potential?
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Parasympathetic stimulation!
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At phase 0 in the states of the Na+ channel during an action potential, depolarizations open what?
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Depolarizations opens the activation gate, sodium conductance increases, and forms the upstroke.
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At Phase 1 in the states of the Na+ channel during an action potential, what occurs?
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Closure of the inactivation gate decreases sodium conductance and contributes to the notch repolarization
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At Phase 2 in the states of the Na+ channel during an action potential, what occurs?
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Time-dependent closure of the activation gate forms the closed but inactivatable state.
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At Phase 3 in the states of the Na+ channel during an action potential, what occurs?
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Activation gates open upon repolarization and resets the channel to its rest state.
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At Phase 4 in the states of the Na+ channel during an action potential, what occurs?
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Rest: activation gate closed, inactivation gate open (channel is closed but activatable)
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What effect does epinephrine have on the cardiomyocite action potential?
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It elevates the action potential plateau.
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How does the action potential spread in the regions of ventricular cardiomyocytes?
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APs spread passively through the gap junctions between cells.
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What currents are responsible for the upstroke in the ventricular muscle cells?
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Sodium current INTO the cell
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During what part of the action potential do the Na channel inactivation gates close and activation gates open?
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Activation gates are open and inactivation gates are closed during phase 1 (rapid repolarization).
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What is the ECG?
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A record of the electrical activity of the heart that is projected onto the surface of the body where it is measured by surface electrodes.
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The heart muscle fibers act as what?
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Electric dipoles!
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The dipole moment is given as what?
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p=q+d
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What constitutes LEAD I?
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Left arm - right arm
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What constitutes LEAD II?
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Left leg - right arm
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What constitutes LEAD III?
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Left leg - left arm
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I + III = what?
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II
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Is convention - to + or + to -?
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- to +!
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If it is a closed circuit, vector addition should equal what?
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0
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The values of Leads I and III can be used to calculate what?
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The electric dipole moment of the heart!
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Sympathetic stimulation causes what to happen to the membrane channels?
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Phosphorylation which results in depolarizations.
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What is the Effective Refractory Period?
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It corresponds to when an action potential will not have sufficient current to depolarize adjacent cells.
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Cardiologists use ECGs for what 4 things?
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1.Excitation of the pacemakers
2. Spread of activation from one region to another 3. Pathways by which wave of activation spreads 4. Basis of the action potential |
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What is Kirchhoff’s lead law of voltage?
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Lead I + Lead III = Lead II
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What causes the P-wave?
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Atrial depolarization
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What causes the QRS complex?
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Ventricular depolarization
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What causes the T wave?
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Repolarization of the subepicardium before the subendocardium.
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What is the epicardium?
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The epicardium is the layer of cells on the outer surface of the heart
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What is the endocardium?
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The endocardium is the layer of cells lining the inner surface of the heart facing the blood.
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What is subepicardium?
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Subepicardium is a layer of cells adjacent to the epicardium layer.
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What is Subendocardium?
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Subendocardium is a layer of cells adjacent to the endocardium layer.
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The largest depolarization in the heart defines what?
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The MEAN electrical axis
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What are the 4 assumptions with Einthoven's triangle?
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1. hearts electrical activity can be represented as single dipole
2. heart is small compared to field (so heart is considered the center) 3. Thorax is a homogeneous conductor 4. Thorax is a sphere |
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What are 4 major differences between cardiac muscle and skeletal muscle?
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1. Cardiac muscle fiber is smaller
2. Cardiac muscle have less nuclei 3. Cardiac muscle fibers often branch 4. Cardiac muscle has intercalated disks |
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Intercalated disks contain what three things?
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1. Gap junctions
2. adherens junction 3. Desmosomes |
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TRUE OR FALSE: The strength of cardiac muscle contraction is regulated by recruitment and summation.
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FALSE. Strength is NOT regulated.
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In cardiac muscle, why are all cardiomyocytes activated for each heart beat?
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Because the cells are electrically coupled: there is 100% recruitment at all times.
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Why is it not possible to stimulate the cardiomyocytes for a second time during the heart beat?
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Because the APs are so long.
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What controls the actomyosin cross-bridge cycling?
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Cytoplasmic Ca2+ concentrations
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At low calcium concentrations, what is happening to the force or ATPase activity?
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There is NO force or ATPase activity.
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At high calcium concentrations, what is happening to the force and ATPase activity?
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Force and ATPase activity is at its maximum
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At steady state, force is proportional to what?
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Proportional to the size of the Ca transient
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When frequency increases, the next beat is stronger or weaker?
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Weaker!
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Why is the next beat after frequency increase weaker?
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It is weaker because the RyR2 (ryanodine receptor 2) release channels are recovering from inactivation
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In regards to the positive staircase, at the new steady-state, is force still proportional to the Ca transient?
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Yes!
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What are Ryanodine Receptors?
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They form Ca channels across the SR membrane
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Ca entry through what triggers SR Ca release?
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Ca entry through the DHPR (dihydropyridine receptors) triggers SR Ca release.
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The size of the sarcolemma Ca trigger and the amount of Ca stored in the SR determines what?
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The size of the Ca transient!
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Reuptake of Ca by the SR and sarcolemma extrusion of Ca cause what?
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Relaxation!
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Mitochondria can take up Ca through what mechanism?
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Electrophoretic uniport
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What regulates Cardiac Contractility?
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1. size of the Ca transient
2. Sensitivity of the myofilaments to a given Ca transient |
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Sympathetic stimulation increases force by doing what?
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Increasing the Ca transient!
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What does the stretch of cardiac muscle do at short sarcomere lengths?
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Stretch increases force by removing interfering overlap of the myofilaments and by increasing the Ca sensitivity.
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The degree of filling of the heart strongly influences what?
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Its force in contraction!
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What happens if the heart overfills?
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The active force would decrease and there would be no way to empty the heart!
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Stretching increases what?
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Stretching increases the fraction of active cross-bridges at any given Ca concentration.
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The Ca transient can be altered by what 4 things?
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1. Changing ECF Ca concentration
2. Altering Na-Ca exchange across membrane 3. increasing the heart rate 4. regulatory phosphorylation |
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Cardiac muscle normally operates on which limb of the length-tension curve?
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Ascending limb!
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What is Cardiac Output?
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Average flow into the aorta. CO = SV X heart rate
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Stroke volume is determined by what 3 things?
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1. Preload
2. Aterload 3. Contractility |
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What is the preload?
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Central venous pressure. It is the pressure load prior to contraction of the heart
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What is the hearts contractility?
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Its ability to produce force at any given stretch.
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What is the afterload?
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The afterload is the arterial pressure after contraction has begun.
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The integral of the pressure-volume loop is what?
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The Pressure-Volume Work!
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Of the Pressure-Volume Loop, what is A (the lower left corner) on the graph (left ventricular pressure vs left ventricular volume)?
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A is when the mitral valve opens when atrial pressure exceeds intraventricular pressure
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Of the Pressure-Volume Loop, what is B (the lower right corner) on the graph (left ventricular pressure vs left ventricular volume)?
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B is when the mitral valve closes when contraction begins and pressure rises above atrial pressure
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Of the Pressure-Volume Loop, what is C (the upper right corner) on the graph (left ventricular pressure vs left ventricular volume)?
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C is when aortic valve opens when intraventricular pressure exceeds diastolic arterial pressure
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Of the Pressure-Volume Loop, what is D (top middle between E and C) on the graph (left ventricular pressure vs left ventricular volume)?
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D is the ejection of stroke volume of blood
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Of the Pressure-Volume Loop, what is E (the high left corner) on the graph (left ventricular pressure vs left ventricular volume)?
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Aortic valve closes when intraventricular pressure falls below arterial pressure
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The total mechanical energy is the sum of what three energies?
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1. Kinetic
2. Potential 3. Gravitational |
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What are the units of cardiac output?
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Liters per minute.
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What 5 things does Stroke Volume depends on?
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1. heart size
2. contractility 3. duration of contraction 4. preload 5. afterload |
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What does the Frank-Starling Law of the Heart state?
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States that increasing right arterial pressure increases the stroke volume of both ventricles.
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What happens if the preload increases?
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Increasing the preload increases the stroke volume!
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What happens if the afterload is increased?
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Increasing the afterload DECREASES the stroke volume!
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What does the Ventricular Function curve show?
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It shows the cardiac output of the heart when it is pumping against a constant arterial resistance and when HR when right atrial pressure is varied.
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Sympathetic stimulation shifts isovolumetric systolic curve where?
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Shifts the curve up and to the left!
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What does Fick's Principle estimate?
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It estimates cardiac output from O2 consumption!'
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What is the simple mass balance equation that estimates the input and output of oxygen?
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Qa[O2]a + Qo2 = Qv[O2]v
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Positive ionotropic agents do what?
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Increase cardiac contractility by shifting isovolumetric systolic curve up and to the left
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What are the 4 functions of the vascular system?
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1. Transforms pulsatile flow from the heart to more continuous flow (arteries)
2. Distributes the cardiac output to the tissues (arterioles) 3. Exchanges materials with the tissue (capillaries) 4. Provides a volume reservoir (veins) |
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What is Lateral Pressure?
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Lateral pressure is pressure perpendicular to the flow
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What is End Pressure?
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Pressure that is same direction as flow.
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Is compliance greater or lower in the veins than the arteries?
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Compliance of veins is MUCH greater than compliance of arteries.
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What does high compliance mean?
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Stretches easily
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Low compliance means what?
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Means that adding small volumes markedly increases the pressure.
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What is Systolic Pressure?
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Highest pressure point in the artery
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What is the Diastolic Pressure?
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Lowest pressure point in the artery
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What is the Dicrotic notch/incisura?
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Brief rise in pressure during its fall in diastole that uccurs when the aortic valve snaps shut
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What is Pulse Pressure?
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It is the difference between systolic and diastolic pressure (normally 40 mmHg)
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When does Pulse Pressure increase?
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Increases with stroke volume and decreases in arterial compliance
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What causes the arterial pressure pulse?
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The hearts ejection of blood into the arterial tree
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Diastolic pressure plus one-third pulse estimates what?
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Estimates the mean arterial pressure!
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What is the first Korotkoff Sound?
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Corresponds to the point where cuff pressure is *just* lower than systolic pressure.
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What does it mean when Korotkoff sounds disappear?
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Disappearance corresponds to the point where cuff pressure is *just* lower than diastolic pressure.
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What is Reynold's number?
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Reynold's number is the point at which turbulent flow begins.
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What are capillaries?
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Capillaries are the smallest blood vessel that has walls that consist of a single layer of endothelial cells
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What are the 6 conditions required for Poiseuille's law to be valid?
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1. Fluid is newtonian
2. Flow is laminar 3. No slippage at the vascular wall 4. Flow is steady 5. Tube is cylindrical 6. Walls of the tube are rigid |
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What is the formula for Reynold's number?
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Re = 2r(average velocity)density/viscosity
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Blood pressure can be measured with what?
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sphygmomanometer
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What are the three types of Capillaries in order of abundance?
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1. Continuous
2. Fenestrated 3. Discontinuous |
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Where are Continuous capillaries located?
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Muscle, skin, lungs, fat, connective tissues and nervous tissue.
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Where are Fenestrated capillaries located?
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Kidneys, intestinal mucosa, exocrine glands, body of the eye.
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Where are Discontinuous capillaries located?
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Liver
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Capillary exchange occurs through what three mechanisms?
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1. Passive diffusion
2. Bulk flow of fluid 3. Transcytosis |
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What channel specifically allow water to pass through?
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Aquaporins
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At low flow, the diffusional transfer of solute is called what?
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Flow limited
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Where is gradient highest?
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At high flows
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To increase diffusional transfer, physiological systems can do what 3 things?
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1. Increase blood flow
2. increase the gradient for diffusion 3. increase the effective area for diffusion |
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What is Solute Extraction?
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Fraction of arteriolar that would be transferred across the capillary wall if the interstitial fluid concentration were 0. IT IS DEMENSIONLESS.
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What is the Colloid Osmotic Pressure?
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Pressure when solutes have the same concentration on both sides of the capillary makes no net osmotic pressure.
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What are the 3 functions of the Lymphatic System?
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1. Preservation of the circulatory volume
2. Absorption of nutrients 3. Defense against bacterial and viral invasion |
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Osmotic pressure only varies where?
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In interstitial fluid!
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What is Lymphedema?
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A severe accumulation of massive amounts of protein-rich fluid in the tissues.
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What are chylomicrons?
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Chylomicrons are tiny globules of fat being transported by the lymph vessels.
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What is Extrinsic Propulsion?
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Propulsion caused by tissue movements and muscle activity
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What is Intrinsic Propulsion?
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Propulsion caused by rhythmic contractions of lymphatic smooth muscle.
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Lymph must be pumped along the lymphatics by what two main mechanisms?
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Extrinsic and Intrinsic propulsion
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Lymph vessels posses what to ensure unidirectional flow from the tissues to circulation?
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VALVES!
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What decreases capillary pressure?
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Vasoconstriction!
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How does the body react to hemorrage?
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By vasoconstriction mediated by the sympathetic nerves
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What is vasoconstriction?
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Constriction of the arteries and arterioles
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What is venoconstriction?
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Constriction of the veins
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Increasing the arterial resistance does what to the capillary pressure towards the venous pressure?
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Lowers the capillary pressure
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Vascular smooth muscle contracts by the activation of what?
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Myosin Light Chain Kinase!
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What does MLCK do?
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Myosin Light Chain Kinase phosphorylates regulatory light changes on myosin and activates contraction.
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What does MLCP do?
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Myosin Light Chane Phosphatase dephosphorylates myosin light chains and turns off contraction.
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What is the outermost layer of the artery?
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Tunica adventitia
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What is the middle layer of the artery?
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Tunica media
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What is the innermost in the artery?
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Tunic intima
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What is Electromechanical coupling?
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It involves the depolarization of the smooth muscle cell to open voltage gated Ca channels to allow influx of Ca.
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Increased Ca concentration helps bind to what to activate the MLCK?
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Calcium binds to calmodulin to activate MLCK.
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What is Pharmacomechanical coupling?
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Chemical signals (like norepinephrine) bind to receptors in the sarcolemma and activate signaling that eventually raises Ca concentration.
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What is Ca Sensitization?
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It is the increasing of myosin phosphorylation by inhibition of MLCP.
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What 4 things make up the Intrinsic Control of Blood Vessel caliber?
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1. Myogenic response
2. Endothelial secretion (NO, protacyclin, endothelin) 3. Metabolic control (adenosine, acid pH, K+) 4. Local paracrine secretion (epinephrine) |
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Which nervous system predominately controls the vascular system?
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Sympathetic nervous system
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What is metabolic hyperemia or functional hyperemia?
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It is the increase of blood flow to regions of the brain when it is altered
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What does Vasopressin (ADH - anti-diuretic hormone) do?
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It constricts blood vessels
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What does angiotensin II do?
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It constricts blood vessels, induces thirst, and releases ADH and aldosterone.
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What 3 things increase renin release?
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1. Renal sympathetic nerves
2. decreased distal tubular na+ 3. Decreased afferent arteriolar pressure |
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Atrail Natriuretic Peptide opposes what system?
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Renin-Angiotensin-aldosterone system (RAA)
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What does Perfusion of tissues mean?
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Means the blood flow through the tissue
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What is the Total Peripheral Resistance?
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It is the resistance of all arteries, arterioles, capillaries, venules, and veins that supply the tissues of the body.
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What is the Mean Systemic Pressure?
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It is the pressure that would be measured at all points in the systemic circulation if all inputs and outputs were stopped and pressure was the same everywhere.
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What is the Stressed volume?
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It is the added amount of blood needed to bring the pressure from 0 to the mean systemic pressure
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What is the Unstressed volume?
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It is the volume of blood that just fills the circulatory system with no pressure.
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Vasoconstriction does what to the TPR?
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Increases the resistance!
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What does transfusion do for the value of the cardiac function curve and the atrial pressure?
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Transfusion (addition of blood) will increase both the atrial pressure and cardiac output.
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The Frank-Starling Law ofthe heart indicates that the increased filling pressure of the right heart results from what?
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Increased cardiac input
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What is the flow through the systemic circulation?
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Q(veins) = Afterload - preload/total peripheral resistance
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Venoconstriction does what to the mean systemic pressure?
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Venoconstriction increases the mean systemic pressure!
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In the vascular function curve, what does the knee represent?
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The knee represents flow being 0 and the right atrial pressure is the mean systemic pressure.
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At low right atrium pressures (below 0), what happens?
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Veins collapse due to their lower luminal prussere
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Is the mean systemic pressure affected by changes in the TPR?
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NO.
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What is Hemorrhage?
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Is the loss of blood from the cardiovascular system.
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Strenous exercise has what 4 major effects on the cardiovascular system?
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1. Increased heart rate
2. Increased cardiac contractility 3. Vasoconstriction and vasodilation 4. Venoconstriction |
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Where does vasodilation occur during exercise?
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The muscles!
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Where does vasoconstriction occur during exercise?
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In blood beds that are inessential to the immediate muscles being used.
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What purpose does venoconstriction have during exercise?
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It shifts the point at which the circulatory system fills with blood.
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Arterial pressure is regulated by what three things?
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1. cardiac contractility
2. vascular smooth muscle contractility 3. blood volume |
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What .3 mechanisms regulate arterial pressure?
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1. Neurogenic mechanisms (fast)
2. Hormonal mechanisms (minutes to hours) 3. Intrinsic mechanisms (days to weeks) |
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What receptors sense blood pressure?
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Baroreceptors in the carotid sinus and aortic arch sense blood pressure!
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Which baroreceptors are more numerous?
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Unmyelinated baroreceptor C fibers
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What are Unmyelinated baroreceptor C fibers?
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They are receptors with low conduction velocities but higher thresholds
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At normal blood pressure, how many Baroreceptor C fibers are activated?
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1/4
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What is the Dynamic response?
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A rapid burst of impulses
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What are Baroreceptor A fibers?
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They are large diameter, myelinated receptors that activate at normal blood pressures and at pressures slightly above normal.
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Reduced sympathetic output to the vasculature causes what two things?
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Causes vasodilation and a fall in the total peripheral resistance
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What accelerates the heart faster than sympathetic stimulation?
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Parasympathetic withdrawal!
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Sympathetic stimulation of the heart is through what?
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The rostral Ventrolateral medulla
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What influences the heart rate?
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Inspiration of air!
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When blood pressure is high, the baroreceptor responds with how many impulses?
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4
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When blood pressure is low, the baroreceptor responds with how many impulses?
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3
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ADH and RAA shift the renal Function curve where?
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To the right!
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ANP shifts the Renal Function Curve where?
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To the left!
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What is the Respiratory Sinus Arrhythmia?
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It is the effect where inspiration inhibits parasympathetic tone which accelerates the heart rate.
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What secretes ADH?
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The posterior pituitary gland in response to hypovolemia
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