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157 Cards in this Set
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Cardio physio
Describe the properties of arteries: (2) |
1. thick-walled
2. extensive elastic tissue and smooth muscle |
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Cardio physio
What is the blood volume in the arteries called? |
Stressed volume
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Cardio physio
Q: What does HTN do to the wall to lumen ratio of arteries? |
Increases it through hypertrophy of the arteries
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Cardio physio
Q: Across which vessels is there the largest decrease in pressure? |
Arterioles
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Cardio physio
Where is the site of highest resistance in the cardiovascular system? |
Arterioles
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Cardio physio
Q: What vessels have the highest wall:lumen ration? |
Arterioles, they are thick-walled and have a high cross sectional area.
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Cardio physio
Describe how arteriolar resistance is regulated by the autonomic nervous system? |
Autonomic nervous system regulation:
1. alpha 1 adrenergic receptors are found in the arterioles of the skin, splanchnic, and renal circulations. 2. Beta 2 receptors are found on arterioles of skeletal muscle. |
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Cardio physio
What vessels have the largest total cross-sectional and surface area? |
Capillaries
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Cardio physio
Describe the wall thickness in capillaries: |
Capillaries are thin-walled
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Cardio physio
Q: In hemorrhage it is most important to constrict what vessels to maintain systemic filling pressure? |
Veins
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Cardio physio
What autonomic regulation to veins have? |
They have alpha 1 adrenergic receptors
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Cardio physio
Describe the wall thickness of veins? |
They are thin walled
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Cardio physio
What is the blood volume contained in the veins called? |
Unstressed volume
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Cardio physio
What three structures are in the carotid sheath? |
1. internal jugular vein (lateral)
2. common carotid artery (medial) 3. Vagus nerve (posterior) |
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Cardio physio
Describe the velocity of blood flow: (formula) |
V = blood flow (Q) / cross-sectional area (A)
Velocity is directly proportional to blood flow and inversely proportional to the cross-sectional area at any level of the cardiovascular system. |
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Cardio physio
Q: Where is velocity higher - the aorta or the sum of all of the capillaries? |
Aorta. As we need it to be because the lower velocity of blood flow in the capillaries optimizes conditions for exchange of substances across the capillary wall
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Cardio physio
Q: What is the formula for blood flow? |
Pressure = CO x resistance
(ABC's: P=QR) *Blood flow is inversely proportional to the resistance of the blood vessels. |
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Cardio physio
Describe the relationship between resistance and radius? |
The resistance is inversely proportional to the fourth power of the vessel radius. For ex, if the blood vessel radius decreases by a factor of 2, then resistance increases by a factor of 16 and blood flow decreases by a factor of 16.
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Cardio physio
VIP What happens if an artery is added in parallel? |
If an artery is added in parallel, the total resistance DECREASES since each artery in parallel receives a fraction of the total blood flow. And each parallel artery receives a fraction of the total blood flow.
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Cardio physio
How is resistance related to visocity? And what does visocity depend on? |
Resistance is equal (roughly) to: viscosity x length / radius
Visocity depends on hematocrit. So it increases in polycythemia, hyperproteinemic states (multiple myeloma), and hereditary spherocytosis. |
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Cardio physio
Q: A women donates a kidney what happens to her total peripheral resistance? |
Her total peripheral resistance will increase because she is removing a parallel resistance. there is one less pathway for blood to get to from the aorta to the vena cava so it is harder for blood to get there = increase resistance.
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Cardio physio:
What is Reynold's number? |
It is a number that predicts whether blood flow will be laminar or turbulent. When it is increased, there is a greater tendency for turbulence, which causes bruits.
"Reynold's water park: the higher the slide (higher #) = increase level of danger (bruits) |
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Cardio physio
What does a decrease in visocity (anemia) do to Reynolds number? What does an increase in blood velocity (narrowing of vessel) do to Reynold's number? |
Decrease in viscosity = increases Reynold's number
Increase in blood velocity = increase in Reynold's number |
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Cardio physio
What does compliance of blood vessels refer to? How is compliance related to elastance? |
Compliance describes the distensibility of blood vessels.
Compliance is inversely related to elastance. The greater the amount of elastic tissue in the blood vessel, the higher the elastance and the lower the compliance. |
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Cardio physio
In which is compliance greater: veins or arteries? |
Veins
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Cardio physio
Where does the largest decrease in pressure occur? |
Across the arterioles because they are the site of highest resistance.
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Cardio physio
What are the normal pressures of the heart? |
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Heart pressures: |
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Cardio physio
Q: If a catheter deflated measures a pressure of 25/8 and when its inflated it measures 7 mmHg and is nonpulsatile, what has it measured? |
When the balloon is deflated the catheter measures simply the pulmonary a. pressure and when it is inflated it is wedged in a small branch of the pulm. artery. The balloon obstructs all blood flow to the vessels distal to the pt of obstruction so they have no flow. So you can think of these distal vessels as extensions of the catheter and thus measure left atrial pressure.
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Cardio physio
Is arterial pressure constant throughout the cardiac cycle? |
No it is pulsatile
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Cardio physio
What is diastolic pressure and when is it measured? |
It is the lowest arterial pressure during the cardiac cycle, measured when the heart is relaxed and blood is returning to the heart via veins.
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Cardio physio
What is the pulse pressure? What determines the pulse pressure? |
Pulse pressure: the difference between systolic and diastolic pressures.
The most important determinant of pulse pressure is stroke volume. As blood is ejected from the L ventricle, systolic pressure increases because of the low capacitance of arteries. Because diastolic pressure remains unchanged during ventricular systole, the pulse pressure increases to the same extent as systolic pressure. |
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Cardio physio
Q: What does aging do to pulse pressure? |
Aging causes a decrease in capacitance/compliance (stiffer arteries) = increase in pulse pressure.
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Cardio physio
What is mean arterial pressure? |
Mean arterial pressure is an average arterial pressure with respect to time and is calculated as diastolic pressure + 1/3 of pulse pressure.
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Cardio physio
What happens to your mean arterial pressure as you age? |
It increases
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Cardio physio
Q: what is the Fick equation of O2 consumption? (had two questions on this) |
O2 consumption = CO x (arterial O2 content - venous O2 content)
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Cardio physio
What does the P wave represent in EKG? PR interval? QRS? QT? ST? T wave? |
P wave: atrial depol (does not include atrial repol - buried within the QRS complex)
PR interval: varies with conduction velocity through the atrioventricular node. QRS: depolarization of the ventricles QT interval: from q wave to end of t wave. Represents all things ventricular (depol and repol) ST segment: from end of s wave to beginning of T. Represents period when ventricles are depolarized (completely). T wave: represents ventricular repolarization. |
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Cardio physio
Torsades des pointes |
Ventricular tachycardia characterized by shifting sinusoidal waveforms on ECG. Can progress to V-fib.
Anything that prolongs the PT interval can predispose to torsades des pointes. |
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Cardio physio
Wolff-Parkinson-White syndrome |
Accessory conduction prathway from atria to ventricles (bundle of kent), bypassing the AV node.
As a result, ventricles begin to partially depolarize earlier, giving rise to delta waves on ECG. May result in reentry current leading to supraventricular tachycardia. |
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Cardio physio
In a myocardial action potential, what does inward and outward current do? What is the function of the Na/K ATPase? |
Inward: depolarizes membrane
Outward: hyperpolarizes Na/K ATPase: maintains ionic gradient across cell membrane. |
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Cardio physio
Where are action potential of the longest duration? |
In purkinjie fibers
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Cardio physio
What are the phases of the non-nodal action potentials? |
phase 0: caused by transcient increase in Na conductance. This increase results in an inward Na current that depolarizes the membrane. (Na goes in)
Phase 1: there is a decrease in Na inward current and K ions move out (favored by both chemical and electrical gradients) Phase 2: caused by transcient increase in Ca conductane which causes an inward Ca current as well as the continued outward K current (stable) Phase 3: repolarization. Ca conductance decreases and K conductance increases - increased K causes hyperpolarization Phase 4: resting membrane potential. Period where inward and outward currents are equal and membrane potential approaches the K equilibrium potential. |
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Cardio physio
Q: When does the maximal ventricular Na conduction occur on an EKG? |
Max ventricular conduction occurs during the ORS interval. THe shape of the ORS is determined by the spread of the combined (phase O) depolarization of the ventricles.
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Cardio physio
What is the normal pacemaker of the heart? |
SA node
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Cardio physio
Describe the resting potential of the SA node? |
Unstable
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Cardio physio
What does phase 4 of the SA node AP represent? |
Automaticity
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Cardio physio
In which node is the intrinsic rate of phase 4 depolarization the fastest? Slowest? |
In the SA node (slowed in His-purkinjie)
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Cardio physio
What are the phases of SA node AP's? |
Phase 0: the upstroke caused by inward Ca current.
Phase 3: repolarization caused by an outward K current Phase 4: slow diastolic depolarization determined by HR. It is caused by an increase in Na conductance which results in an increase in Na conductance causing an inward If (funny) current. |
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Cardio physio
What do catacholamines and Acetylcholine do to slope of phase 4 of nodal conduction? |
Catecholamines: increases slope (increases HR)
Acetylcholine: decreases slope (decreases HR) |
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Cardio physio
What causes repolarization in both types of AP's? |
Outward K current
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Cardio physio
What is conduction velocity? |
Conduction velocity: the time required for excitation to spread throughout cardiac tissue. It depends on the size of the inward current during the upstroke of the AP (the larger the inward current, the higher the conduction velocity).
Velocity is the fastest in the Purkinjie system and slowest in the AV node (seen as PR interval on ECG) allowing time for ventricular filling before contraction. |
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Cardio physio
What is the absolute refractory period? |
ARP: begins with upstroke of AP and ends after plateau.
Time during which NO AP can be initiated regardless of how much inward current is supplied. |
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Cardio physio
What is the effective refractory period? |
ERP: longer than ARP
Period during which a conducted AP cannot be elicited. |
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Cardio physio
What is a relative refractory period? |
RRP: period immediately after the ARP when repolarization is almost complete.
AP can be elicited but more than the usual inward current is required. |
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Cardio physio
What are chromotrophic effects? |
Chromoctrophic effects are things that produce changes in firing rate of SA node thus changing the HR.
"Chrome of a gun - fire a gun" = firing rate |
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Cardio physio
What are dromotrophic effects? |
Dromotrophic effects are ones that change the conduction velocity in the AV node.
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Cardio physio
What are negative dromotrophic effects? |
Neg Dromotrophic effects: decreases conduction velocity through the AV node, slowing conduction of action potential from the atria to the ventricles increasing the PR interval (because it acts on AV node).
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Cardio physio
Describe the parasympathetic innervation of the SA node, atria, and AV node: |
SA node, atria, and AV node all hae parasympathetic vagal innervation but the ventricles don't. They use the neurotransmitter acetylcholine (acts on muscarinic receptors).
Acetylocholine produces negative chronotropic (decreasing HR by decreasing If) --and-- Negative dromotrophic effects (decreasing inward Ca current) causes an increase in the PR interval (increase in time to fill AV node full of Ca before AV node can conduct to ventricles; this fine for the ventricles because they filling while they wait) |
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Cardio physio
What are the sympatheic effects on nodes? |
NE is the neurotransmitter working at beta 1 receptors.
It produces postive chronotrophic effects (increased If/Na = increased rate of phase 4 depolarization = increased HR) -and- Positive dromotrophic effects which increases Ca current = decreased PR interval = decreases ventricular filling time. |
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Cardio physio
What does the starling curve tell us about what happens when we have an increase in end-diastolic volume. |
Starling curve:
Increases in end-diastolic volume cause an increase in ventricular fiber length, which produces an increase in developed tension. |
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Cardio physio
What does the starling curve tell us about an increase in venous return? |
Increase venous return = increase ventricular filling = increase length of cardiac muscle fiber = increase force of ventricular contraction = increase CO.
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Cardio physio
What are three causes of an increase in contractility? |
1. catecholamines
2. digitalis 3. sympathetic stimulation (causes an increase in catecholamine NE --> increase HR and increased inward Ca current) ie exercise |
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Cardio physio
What two things decrease contractility? |
1. pharmacolic depressants
2. loss of myocardium (MI) |
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Cardio physio
Q: When is the most oxygen delivered to the left ventricle via the coronary circulation? |
The vast majority of O2 is delivered to ventricles during isovolumetric contraction (left ventricle is filled with blood from the left atrium and ventricular pressure is increasing but volume of ventricle is constant, though muscle length is not, since aortic valve is still closed)
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Cardio physio
Describe the period of ventricular ejection: |
This begins when aortic valve opens which occurs when left ventricular pressure exceeds pressure in the aorta. Blood is ejected into aorta (stroke volume).
This period spans the width of the P/V loop so you can measure SV by the width of the curve. Peak systolic pressure is the highest point on this line. This line ends with aortic valve closing whish is synonymous with the dicrotic notch or pulse pressure. |
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Cardio physio
At the beginning of what part of the cardiac cycle does systole begin? |
Systole begins at the start of isovolumetric contraction (right lower corner) when mitral valve closes.
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Cardio physio
During what stage in the cardiac cycle is the atrial filling? |
Atrial filling occurs during isovolumetric relaxation (left most vertical line). Therefore the amount of preload can be determined by the height of this line.
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Cardio physio
How is an increase in afterload represented on a cardiac cycle loop? |
Increase in afterload: lengthening of the isovolumetric contraction line (right most vertical line) as well as a shortening of the ventricular ejection line (decrease in SV) and shortening of the ventricular filling line (increased ESV)
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Cardio physio
When does ventricular filling occur? |
After isovolumetric relaxation. Once the left ventriclar pressure decreases to less than atrial pressure, the mitral valve opens and filling of the ventricle begins. (lower horizontal line) This period ends with mitral valve closure.
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Cardio physio
Q: What point along the pressure-volume curve represents diastolic pressure? What is it commonly mistaken for? |
Diastolic pressure = point aortic valve opens (end of isometric contraction) because this marks the beginning of the period of ejection which is equal to diastolic pressure.
Diastolic pressure is commonly mistaken for the point of aortic valve closure (pt of dicrotic notch on the pulse pressure). |
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Cardio physio
What point on the cardiac cycle P/V loop does S1 and S2 occur? |
S1: beginning of isovolumetric contraction (lower right corner)
S2: end of ventricular ejectin, aortic valve closure (upper left corner) |
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Cardio physio
How is increased preload represented on the PV loop? |
Increased preload = increased EDV = increased venous return = increased SV = increased width of the pressure-volume loop.
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Cardio physio
How is an increased afterload represented on the PV loop? |
Increased afterload = increase in aortic pressure = decrease in SV = decreased width of PV loop = increase in end-systolic volume (line
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Cardio physio
How is increaesd contractility represented in the PV loop? |
Ventricle develops greater tension than usual during systole = increased stroke volume = decrease in end-systolic volume (vertical line to the left is more leftward than normal)
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Cardio physio
What determines venous return? |
Total peripheral resistance determines venous return.
An increase in TPR = decrease in venous return to heart. |
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Cardio physio
What do positive inotrophic agents do to heart? |
Positive inotrophic agents increase contractility and increase CO = decrease in right atrial and ventricular pressure(because more blood is ejected from the heart on each beat).
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Cardio physio
According to the venous return curve what happens when there is an increase in blood volume? |
Increase in bld vol = increase in mean systemic pressure (pt of intersection on x axis) = shifting of venous return curve to the right = Both CO and right atrial pressure (x axis) are increased.
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Cardio physio
According to the venous return curve what happens when there is a decrease in venous compliance? |
Same as increase in bld vol
Decrease in venous capacitance = decrease venous pools = increase amount of bld in circulation = increase in mean systemic pressure (pt of intersection on x axis) = shifting of venous return curve to the right = Both CO and right atrial pressure (x axis) are increased. |
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Cardio physio
According to the venous return curve what happens when there is decrease in blood volume (hemorrhage)? |
Decrease in bld volume = decrease of mean systemic pressure (pt of intersection on x axis) = shift venous curve to the left = both CO and right atrial pressure would decrease.
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Cardio physio
Q: Pt with a knife wound into the L subclavian causing a large subclavian arteriovenous fistula. What will happen to this patients CO, HR, SV, and diastolic pressure? |
Arteriovenous fistula = increase CO = increase HR and SV
And because its a fistula = the diastolic pressure can decrease because blood can rapidly exist the fistula. |
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Cardiac physio
What does an increase in TPR do to the CO curve that lines with the venous return curve? Decrease TPR? |
Increase in TPR: (same as negative inotrophy effects) = decrease in CO (increased aortic pressure)
-and- Decrease in venous return (more blood is retained in arterial side) Decreased TPR = opposite Increase in shift of the CO curve (caused by a decrease in aortic pressure) = increase CO and increased venous return. In both: RIGHT ATRIAL PRESSURE IS UNCHANGED. |
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Cardiac physio
Q: formula for CO? |
CO = SV x HR
(decrease HR = more time for ventricles to fill) |
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Cardiac physio
What 4 things increase myocardial O2 demand? |
1. increase in afterload (increased diastolic BP)
2. increase in contractility (more contractions) 3. increase in HR 4. increase heart size (more m. to feed) |
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Cardiac physio
What is the formula for mean arterial pressure? |
Mean arterial pressure = CO x TPR
= 2/3 diastolic pres + 1/3 systolic pres |
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Cardiac physio
What is pulse pressure roughly equal to? |
Pulse pressure is roughly equal to stroke volume.
Pulse pressure = systolic - diastole |
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Cardiac physio
What happens to CO during exercise? |
Initially, during exercise, CO increases as a result of an increase in SV. After prolonged exercise, CO increases as a result of an increase in HR.
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Cardiac physio
What happens to CO if HR is too high? |
If HR is too high = diastolic filling decreases = CO decreases
ex. ventricular tachycardia |
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Cardiac physio
What is ejection fraction? Formula? |
Ejection fraction: an index of ventricular contractility (normally around 55%)
EF = SV/EDV = EDV-ESV / EDV (amount of blood ejected/amt left over) x 100 |
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Cardiac physio
What three general things affect stroke volume? |
SV CAP
Stroke volume is effected by contractility, afterload, and preload. |
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Cardiac physio
Seven specific instances where there is an increase in SV and contractility? |
Increase in stroke volume and contractility:
1. Catecholamines (increase activity of Ca pump in SR) 2. increase in intracellular Ca 3. decrease in extracellular Ca 4. digitalis (increase in intracellular Na, resulting in increase in Ca) 5. pregnancy (increase volume) 6. anxiety (symp increase in preload) 7. exercise (increase preload) |
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Cardiac physio
Five specific instances where there is decrease in stroke volume and contractility: |
Decrease in contractility and sv:
1. beta 1 blockade 2. heart failure 3. acidosis 4. hypoxia/hypercapnia 5. Ca channel blockers (can't get Ca into cause a contraction) |
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Cardiac physio
What is atrial systole? (4) |
Atrial systole:
1. comes after P wave 2. contributes to ventricular filling 3. increase in atrial pressure (venous pressure) caused by atrial systole is a wave 4. filling of ventricle by atrial systole can cause the fourth heart sound (problem with compliance) |
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Cardiac physio
What happens in isovolumetric contraction? (3) |
1. Rightward most verticle line - ventricular pressure just became great than atrial pressure so the mitral/tricuspid valves close (S1) and ventricle starts contracting (increasing pressure). Ends with pressure increase so high to open aortic valve.
2. begins after the onset of QRS (since atrial repolarization is blurred in QRS). 3. No blood leaves ventricle at this time |
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Cardiac physio
What happens in rapid ejection? (6) |
1. First half of Ventricular (systolic) ejection.
2. Ventricular pressure is at maximum value during this phase. 3. At the very end of this perid the t-wave starts (thus the onset of the t-wave marks the end of both ventricular contraction and rapid ventricular ejection) 4. Most of stroke volume is ejected in this phase 5. Right ventricular contraction causes the tricuspid valve to bulge into the atrium = C wave 6. atrial filling begins |
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Cardiac physio
What happens in reduced ventricular ejection? |
1. Second half of ventricular ejection (top horizontal line)
2. ejection continues but is slower 3. ventricular pressure begins to decrease 4. aortic pressure also decreases 5. atrial filling continues 6. t wave runs throughout (ventricular repolarization) |
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Cardiac physio
What happens during isovolumetric ventricular relaxation? (7) |
1. Same as in cardiac cycle, left most vertical line.
2. begins at end of t wave 3. begins when aortic valve closes (followed closely by closure of the pulmonic valve) = S2 (inspiration causes splitting of second heart sound. 4. Ventricular pressure decreases rapidly because the ventricles are now relaxed 5. The "blip" in aortic pressure tracing occurs after closure of the aortic valve (dicrotic notch) 6. At end, ventricular pressure becomes less than atrial pressure = mitral valve opens. 7. V wave occurs from increased atrial pressure due to filling against a closed tricuspid valve. |
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Cardiac physio
What is a dicrotic notch? |
A small downward deflection in arterial pulse or pressure contour immediately following the closure of the semilunar valves (aortic/pulmonic).
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Cardiac physio
What happens during rapid ventricular filling? |
1. First half of ventricular filling (bottom horizontal line)
2. mitral valve opens in beginning and ventricular filling from the atrium begins 3. aortic pressures continue to decrease because blood continues to run off into the smaller arteries 4. rapid flow of blood from the atria into the ventricles causes the third heart sound, which is normal in children but not in adults. |
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Cardiac physio
What happens during reduced ventricular filling (diastasis)? |
1. Reduced ventricular filling is the second half of ventricular filling (lower horz line)
2. it is the longest phase in the cardiac cycle 3. time given to this phase is dependant on HR (increase HR = decrease time). |
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Cardiac physio
Why doesn't coronary arteries deliver O2 to left ventricle during the ventricular relaxation instead of isovolumetric contraction? |
Because isovolumetric relaxation can vary in time and be shorter than isovolumetric contraction.
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Cardiac physio
Splitting in: Pulmonic stenosis |
Expiration: nl
Inspiration: wide (P2 later than nL) |
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Cardiac physio
Splitting in: ASD |
Expiration: wide (P2 later)
Inspiration: wide (P2 later) "fixed wide splitting" |
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Cardiac physio
Splitting in: Aortic stenosis |
Expiration: P2 closes before A2 and is widely split
Inspiration: P2 closes beofre A2 but is closer together. |
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Cardiac physio
What is preload? |
Preload: EDV
It increases slightly with exercise, with increasing blood volume (transfusion) and excitement (sympathetics). |
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Cardiac physio
What is afterload? |
Afterload = diastolic arterial pressure (proportional to peripheral resistance)
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Cardiac physio
What do venous dilators like nitroglycerin do to preload? |
Nitroglycerin decreases preload.
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Cardiac physio
What is preload equivalent to? |
Preload is equivalent to end-diastolic volume which is related to right atrial pressure. When venous return increases, end-diastolic volume increases, and stretches or lengthens the ventricular muscle fibers (see Starling relationship).
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Cardiac physio
When is velocity of contraction maximal? What causes it to decrease? |
Velocity of contraction is maximal when the afterload is zero.
Velocity is decreased by increases in afterload. |
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Cardiac physio
Describe the regulation of arterial pressure when there is a decrease in mean arterial pressure? |
Decrease in MAP = medullary vasomotor center senses this and decreases baroreceptor firing = increases sympathetic activity (and decreases parasymp) = beta 1 causes and increase in HR and contractility to increase CO; alpha 1 causes venoconstriction (increase CO)and vasocontriction (increase TPR)
-and- A decrease in MAP = JGA senses this = increase renin-angiotensin = increase in angiotensin II (increase TPR) and increase in aldosterone (in bld vol=increase CO) This results in an increase of MAP |
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Cardiac physio
Receptors along the aortic arch transmit via what nerve to where? What does it respond to? |
Aortic arch transmits via the vagus nerve to medulla.
These only respond to an increase in BP. |
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Cardiac physio
Receptors along the carotid sinus transmit via what nerve to where? What does it respond to? |
Carotid sinus transmits via the glossopharnygeal nerve to the medulla. This responds to a decrease and increase in BP!
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Cardiac physio
Where is the most common location of baroreceptors? |
Bifucation of the common carotid arteries.
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Cardiac physio
How does body respond to hemorrhage? |
Hemorrhage = hypotension = decrease stretch = decrease afferent baroreceptors firing = increase efferent sympathetic firing and decrease efferent parasymp stimulation = vasoconstriction, increase HR, increase contractility, increase BP
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Cardiac physio
How does carotid massage work? |
Increase pressure on carotid artery = increase stretch = decrease efferent sympathetic firing = decrease HR
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Cardiac physio
VIP VIP Q: Animal has a nerve stimulation of the glossopharyngeal and vagus nerve. What will happen? |
Bradycardia and hypotension
Reason: Glosso (9) and Vagus (10) afferent info to the medulla from the carotid sinus and aortic arch baroreceptors, recpectfully. The firing rate of these neurons increases with increasing BP. So artificial stimulation makes it look like an increase in BP = baroreceptor reflex = decrease symp tone and increase parasymp tone = bradycardia and hypotension. |
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Cardiac physio
VIP VIP Q: Remove pts glossopharyngeal nerve (9) and vagus (10), what are the immediate changes? |
Tachycardia and hypertension
The firing rate of these neurons increases with increasing BP. Therefore severing the nerves sends the medulla false signs that pt has suddenly lost all BP = increase sympathetic = tachycardia and hypertension. |
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Cardiac physio
What are the steps of the renin-angiotensin system: |
Renin-angiotensin
1. decrease in renal perfusion causes the juxtaglomerular cells of the afferent arteriole to secrete renin 2. renin converts angiotensinogen to angiotensin I in plasma 3. ACE converts angiotensin I to II, primarily in lungs. |
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Cardiac physio
What do ACE inhibitors do? |
ACE inhibitors like captopril block the conversion of angiotensin I to II and so they decrease blood pressure.
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Cardiac physio
What are the four functions of angiotensin II |
1. potent vasoconstriction (this increases GFR -> increase reabsorption of Na and HCO3)
2. release of aldosterone from the adrenal cortex 3. release of ADH from posterior pituitary 4. stimulates hypothalamus to increase thirst |
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Cardiac physio
Describe the Cushing response to cerebral ischemia: |
In response to cerebral ischemia => increases in intracranial pressure cause compression of the cerebral blood vessels, leading to cerebral ischemia and increased cerebral pCO2 --> vasomotor center causes an increase in sympathetic outflow to heart and blood vessels --> profound INCREASE in arterial pressure.
Also this causes constriction of peripheral vessels (increase in TPR). |
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Cardiac physio
Where are chemoreceptors of carotid and aortic bodies located? |
Chemoreceptors: located near the bifurcation of the common carotid arteris and along aortic arch.
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Cardiac physio
What is preload equivalent to? |
Preload is equivalent to end-diastolic volume which is related to right atrial pressure. When venous return increases, end-diastolic volume increases, and stretches or lengthens the ventricular muscle fibers (see Starling relationship).
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Cardiac physio
When is velocity of contraction maximal? What causes it to decrease? |
Velocity of contraction is maximal when the afterload is zero.
Velocity is decreased by increases in afterload. |
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Cardiac physio
Describe the regulation of arterial pressure when there is a decrease in mean arterial pressure? |
Decrease in MAP = medullary vasomotor center senses this and decreases baroreceptor firing = increases sympathetic activity (and decreases parasymp) = beta 1 causes and increase in HR and contractility to increase CO; alpha 1 causes venoconstriction (increase CO)and vasocontriction (increase TPR)
-and- A decrease in MAP = JGA senses this = increase renin-angiotensin = increase in angiotensin II (increase TPR) and increase in aldosterone (in bld vol=increase CO) This results in an increase of MAP |
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Cardiac physio
Receptors along the aortic arch transmit via what nerve to where? What does it respond to? |
Aortic arch transmits via the vagus nerve to medulla.
These only respond to an increase in BP. |
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Cardiac physio
Receptors along the carotid sinus transmit via what nerve to where? What does it respond to? |
Carotid sinus transmits via the glossopharnygeal nerve to the medulla. This responds to a decrease and increase in BP!
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Cardiac physio
Where is the most common location of baroreceptors? |
Bifucation of the common carotid arteries.
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Cardiac physio
How does body respond to hemorrhage? |
Hemorrhage = hypotension = decrease stretch = decrease afferent baroreceptors firing = increase efferent sympathetic firing and decrease efferent parasymp stimulation = vasoconstriction, increase HR, increase contractility, increase BP
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Cardiac physio
How does carotid massage work? |
Increase pressure on carotid artery = increase stretch = decrease efferent sympathetic firing = decrease HR
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Cardiac physio
VIP VIP Q: Animal has a nerve stimulation of the glossopharyngeal and vagus nerve. What will happen? |
Bradycardia and hypotension
Reason: Glosso (9) and Vagus (10) afferent info to the medulla from the carotid sinus and aortic arch baroreceptors, recpectfully. The firing rate of these neurons increases with increasing BP. So artificial stimulation makes it look like an increase in BP = baroreceptor reflex = decrease symp tone and increase parasymp tone = bradycardia and hypotension. |
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Cardiac physio
VIP VIP Q: Remove pts glossopharyngeal nerve (9) and vagus (10), what are the immediate changes? |
Tachycardia and hypertension
The firing rate of these neurons increases with increasing BP. Therefore severing the nerves sends the medulla false signs that pt has suddenly lost all BP = increase sympathetic = tachycardia and hypertension. |
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Cardiac physio
What are the steps of the renin-angiotensin system: |
Renin-angiotensin
1. decrease in renal perfusion causes the juxtaglomerular cells of the afferent arteriole to secrete renin 2. renin converts angiotensinogen to angiotensin I in plasma 3. ACE converts angiotensin I to II, primarily in lungs. |
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Cardiac physio
What do ACE inhibitors do? |
ACE inhibitors like captopril block the conversion of angiotensin I to II and so they decrease blood pressure.
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Cardiac physio
What are the four functions of angiotensin II |
1. potent vasoconstriction (this increases GFR -> increase reabsorption of Na and HCO3)
2. release of aldosterone from the adrenal cortex 3. release of ADH from posterior pituitary 4. stimulates hypothalamus to increase thirst |
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Cardiac physio
Describe the Cushing response to cerebral ischemia: |
In response to cerebral ischemia => increases in intracranial pressure cause compression of the cerebral blood vessels, leading to cerebral ischemia and increased cerebral pCO2 --> vasomotor center causes an increase in sympathetic outflow to heart and blood vessels --> profound INCREASE in arterial pressure.
Also this causes constriction of peripheral vessels (increase in TPR). |
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Cardiac physio
Where are chemoreceptors of carotid and aortic bodies located? |
Chemoreceptors: located near the bifurcation of the common carotid arteris and along aortic arch.
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Cardiac physio
What are the chemoreceptors sensitive to? |
Chemoreceptors are very sensitive to decreases in partial pressure of oxygen.
Decreases in pO2 activate vasomotor centers that produce vasoconstriction, and increase in TPR, and increase in arterial pressure. |
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Cardiac physio
When is ADH (vasopressin) secreted? |
It is secreted in response to an increase in plasma osmolarity and decreased blood volume. It binds to receptors on principal cells, causing an increase number of water channels and increase water reabsorption.
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Cardiac physio
What does Atrial natriuretic peptide do? |
ANP: works on kidney
1. It is released from the atria in response to an increase in atrial pressure. 2. It causes relaxation of vascular smooth muscle, dilation of arterioles, and decreased TPR. 3. It also causes increased excretion of Na and water by the kidney (increased GFR) which reduces blood volume. 4. it inhibits renin secretion |
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Cardiac physio
What organ gets the largest share of systemic CO? |
Liver
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Cardiac physio
What organ gets the highest blood flow per gram of tissue? |
Kidney
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Cardiac physio
What organ has the largest arteriovenous O2 difference? |
Heart (an increase in O2 demand is met by increase in coronary blood flow, not by an increase extraction of O2)
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Cardiac physio
What does an increase in capillary hydrostatic pressure do? What causes this to increase? |
Pc = pushes stuff out of capillary (favoring filtration).
It is determined by arterial and venous pressures and resistances. So, and increase in BP increases Pc. |
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Cardiac physio
What is does capillary oncotic pressure do? What causes it to decrease/increase? |
Capillary oncotic: wants to keep stuff in the capillaries. So, a decrease in protein concentration of the blood (liver/kidney problems) will incourage filtration out of the capillary. And an increase (dehydration) will oppose filtration.
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Cardiac physio
What is interstitial oncotic pressure? What causes this to increase? |
Intersitial oncotic pressure is something that attracts fluid into the interstium and out of the capillary. It is dependant on protein concentration of the interstitial fluid so in inadaquate lymphatic function there will be an increase in interstitial oncotic pressure.
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Cardiac physio
What is edema and what causes it (4)? |
Edema:
excess fluid outflow into the interstitium caused by: 1. increase in capillary hydrostatic pressure (heart failure) 2. decrease in plasma proteins; decrease in capillary oncotic pres (nephrotic, liver failure) 3. increase in capillary permeability; increase in hydraulic conductance (Kf)(toxins, infections, burns) 4. increase in interstitial fluid colloid osmotic pressure; increase in interstitial oncotic pressure (lymphatic blockage) |
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Cardiac physio
Factors in autoregulation: Heart |
Local metabolites: O2, adenosine, NO
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Cardiac physio
Factors in autoregulation: Brain |
Local metabolites: CO2 (pH)
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Cardiac physio
Factors in autoregulation: Kidneys |
Myogenic and tubuloglomerular feedback
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Cardiac physio
Factors in autoregulation: Lungs |
Hypoxia causes vasoconstriction!!!
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Cardiac physio
Factors in autoregulation: Skeletal muscle |
Local metabolites: lactate, adenosine, K+
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Cardiac physio
Factors in autoregulation: Skin |
Sympathetic stimulation is the most important mechanism - temperature control.
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Cardiac physio
Explain active and reactive hyperemia of the heart: |
Increases in myocardial contractility are accompanied by an increased demand for O2. To meet this demand, compensatory vasodilation of coronary vessels occurs so both blood flow and O2 delivery to the contracting heart muscle increases (active).
During systole, mechanical compression of the coronary vessels reduces blood flow. After the period of occulsion, blood flow increases to repay the O2 debt (reactive) |
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Cardiac physio
Describe the sympathetic innervation of skeletal muscle during autoregulation: |
Symp innervation is controlled by local metabolic factors. There are both alpha 1 (vasoconstriction) and beta 2 (vasodilation) receptors on the bld vessels in the skeletal muscle. Blood flow hear exhibits autoregulation and active and reactive hyperemia.
During exercise when demand is high, local metabolites are dominant (pure sympathetic control is used when muscles are at rest). Local vasodilators (lactate, adenosine, and K) cause reactive hyperemia after exercise causes a compression of arteries and decrease of blood flow. |
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Cardiac physio
What is the prinicipal function of cutaneous sympathetic nerves? |
Temperture regulation.
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Cardiac physio
What happens when standing? |
Increase HR
Decrease SV Decrease CO Decrease BP (initally, then corrects) Increase in TPR Decrease in central venous pressure |
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Cardiac physio
Q: What happens when a person suddenly stands? |
The BP in the brain and upper body tends to fall = strong sympathetic discharge to get BP back to nL = increase HR, increase conduction velocity, and increase myocardial contractility.
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Cardiac physio
Q: What happens when exercising? |
Increase HR
Increase SV INcrease CO Increase art pressure Increase pulse pressure Decrease TPR Increase AV O2 difference (muscles just use more O2 than can be delivered) Increase arterial diameter Decreased O2 conc Increased metabolite conc. |
