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BMS 752 (Medical Physiology) > Unit II > Flashcards

Unit II Flashcards

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USMLE® Step 1 flashcards
1
Q

why is O2 important to the heart

A

because it is less able to function by anything other than oxidative phosphorylation

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2
Q

what is the firing rate range of the SA node?

AV node?

A

60-120

40

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3
Q

two examples of conduction defects that would cause arrhythmias

A

heart block

bundle branch block

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4
Q

functional hyperemia

A

activly increasing blood flow to metabolically active heart cell tissues

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5
Q

describe the effect of G protein subunit ßy (parasympathetic)

what happens to heart rate

A

G protein subunit ßy binds to KAch channels

potassium influx increases

membrane is hyper polarized

pacemaker potential is more negative

heart rate will decrease

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6
Q

what protein regulates SERCA activity

A

phosopholamban

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7
Q

how can you determine ventricle wall compliance from a PV loop

A

the diastolic compliance curve (lower line) will have a steeper slope

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8
Q

describe the process of calculating HR by RR interval

A

measure the interval of time between R waves

divide 60s by the RR time

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9
Q

T/F changing the filling (venous) pressure of the system alters stroke volume by increase LVESV

A

false, on LVEDV will be changed with an increase in venous pressure

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10
Q

what is the distance blood must move to loss 1mmHg of pressure

A

13.6 mm

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11
Q

poiseuille law

A

Q = (pi x deltaP x r^4)/8nL

n is viscosity

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12
Q

what are three conductive causes of arrhythmias

A

delayed after polarizations

conductions defects

circuit re-entry

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13
Q

why is parasympathetic stimulation a non factor in humans

A

because very few vagal pathways reach the heart

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14
Q

positive inotropic effect

what type of drugs would cause this

A

increased contractility of the heart

Beta adrenergic agonists

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15
Q

why does the AV node have the lowest conduction velocity

A

small cell diameter and few gap junctions

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16
Q

MAP equation

A

MAP = Cardiac output x total peripheral resistance

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17
Q

how can EF% be determined using a PV loop

A

dividing the width of the loop (stroke volume) by the volume when the aortic valve closes (LVESV)

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18
Q

how does digitalis (digoxin) produce greater contractility in the heart

A

it increases intracellular Na concentration, decreasing the activty of the Ca/Na exchanger and increasing the amount of intracellular calcium

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19
Q

what is the limiting factor in determining how much O2 the heart gets

why

A

the amount of blood flow

because whatever oxygen is present in blood will be taken up by the cells

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20
Q

MAP formula

A

diastolic pressure + 1/3 pulse pressure

or

TPR x CO

or

Ps+Pd/3

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21
Q

what percent of O2 in the blood is extracted by heart muscle on the first pass

A

70-80%

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22
Q

is an ECG an action potential?

elaborate

A

no

ECG reflects the cumulative effect of action potentials at skin level

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23
Q

how does the maximum of the pacemaker potential effect firing rate

A

the more negative the pacemaker potential is, the slower the firing rate will be

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24
Q

what is the function of leads V1-6 on ECG

A

to observe the deoplarization wave in the frontal plane from a particular area of the heart

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25
Q

what would happen to HR if the SA node were nonfunctional due to injury

A

the AV node would take over and produce a HR around 40bpm

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26
Q

formula for parallel resistnace

A

1/R = 1/R1 + 1/R2 + 1/R3

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27
Q

what three factors determine the conduction velocity of pacemaker APs

A

diameter of fibers (decrease viscosity)

number of gap junctions (increase conductance)

rate of slow depolarization (increased slope)

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28
Q

what causes a change in slope during phase 4 of a pacemaker AP

what will happen in each instance?

A

sympathetic/parasympathetic nerve stimulation

sym: slope increases and causes higher firing frequency
para: slope decreases = lower firing frequency

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29
Q

what are the assumptions of Poiseuille’s Law

C L N R S H

A

cylindrical tubes with aconstant diameter and length longer than the radius

laminar, not turblulent flow

newtonion flow

rigid walls

steady, non-pulsatile flow

horizontal flow with no gravitational effects

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30
Q

what is the difference between hydorstatic pressure in arteries and veins in the brain

at the heart

at the legs

why are they different

A

80

100

100

because at the head veins are losing pressure because of gravity, and at the feet they are gaining pressure

arterial pressure makes up the difference

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31
Q

Laplace Law for a sphere

A

tension in the ventricular wall is equal to the pressure multiplied by the radius divided by the width of the ventricle

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32
Q

what are the two key elements of excitation-contraction coupling

A

structure

CICR

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33
Q

T/F the right arm is always a positive lead in ECG

A

false, it is always negative

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34
Q

what should a normal sinus rhythm look like on ECG

A

positive P waves in the leads I and II indicate rhythm from the SA node

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35
Q

what are the three phases of a pacemaker cell

A

Phase 4 (slow depolarization)

Phase 0 (upstroke)

Phase 3 (repolarization)

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36
Q

two intrinsic mechanisms that regulate coronary blood flow

A

myogenic response to arterial pressure

local metabolic control

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37
Q

how is RMP maintained

A

Na/K pump keeps and restores membrane to RMP

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38
Q

normal vs impaired EF%

A

55-65%

= 40%

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39
Q

incisura

A

the point on a ventricular pressure graph where the aortic valve closes, indicated by a small increase in pressure followed by a stedy decline

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40
Q

at what point on an ECG would correspond with AV node firing

A

halfway through the P wave into the PR segment

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41
Q

what happens to coronary blood flow to the left ventricle during systole?

why?

what happens in the right ventricle

A

it decreases

the pressure of the contraction increases the pressure on coronary vessels

the right coronay blood flow has less pressure so the effect is less dramatic

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42
Q

what is this?

define the variables

A

a pressure time graph of the left ventricle

A diastolic filling

M1 mitral valve closes

B isovolumic contraction

A1 aortic valve opens

C ejection

A2 aortic valve closes

D isovolumic relaxation

M2 mitral valve opens

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43
Q

heart block/bundle branch block

A

failure of the AV node to conduct from the atria to the ventricles

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44
Q

why does the AV node make the heart vulnerable

A

damage to the AV node will cause a loss of conduction to the ventricles

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45
Q

driving force behind absorption

A

plasma colloid osmotic pressure

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46
Q

what is the “LUB” sound

what is the “DUB” sound

A

mitral and tricupsid valve closure

aortic and pulmonic valve closure

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47
Q

what is the function of phospholamban in response to sympathetic beta receptor stimulation

A

phosphorylation by cAMP will disassociated phospholamband from SERCA to allow calcium to be removed from the cytoplasm

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48
Q

what would a long PR segement indicate

A

slow AV conduction

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49
Q

what part of the cardiac conduction system has the slow conduction velocity?

the fastest?

A

the AV node

purkinje fibers

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50
Q

where is V3

A

midway between V4 and V2

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51
Q

what would be considered right axis deviation?

what would cause this

A

heart axis shift to between 90 and 180 degrees

left bundle branch block, right ventricular hypertrophy

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52
Q

where is V1

A

4th intercostal space to the right of the sternum

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53
Q

darcys law

A

flow = pressure gradiant/resistance

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54
Q

lymphpatic filling pressure formula

A

Pressure in tissue - Pressure in lymph

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55
Q

what two parts of the ECG should be isoelectric

A

PR segement and ST segment

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56
Q

what are the three main parts of an ECG wave

A

P wave

QRS complex

T wave

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57
Q

why can’t you appreciate atrial repolarization on a normal ECG

A

because it is masked by the QRS

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58
Q

what is the direction of aVL

A

from the heart towards the legs

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59
Q

T/F the heart is the only place where each muscle fiber has a capillary

A

true

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60
Q

what current is at work in phase 3 of a pacemaker cell

A

IKv1.1

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61
Q

what is the supranormal period?

when does it occur?

A

a period where cells can be restimulated and threshold is lower than normal

only during phase 4

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62
Q

what is different that allows contraction during relative refractory period

A

during the relative refractory period some Na inactivation gates are open a second AP is possible

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63
Q

what is SERCA

what does it do

A

sarco/endoplasmic reticulum calcium ATPase

pulls calcium from the cytoplasm at the expense of ATP while the muscle is at rest

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64
Q

what effect will sympathetic stimulation have on ions in cardiac pacemaker cells

what will be in end result

A

increase of Ca and Na influx

increase the rate of depolarization (faster heart rate), slope (increased contractility), cardiac output

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65
Q

three parts of diastole

A

isovolumic relaxation

passive ventricular filling

atrial systole

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66
Q

how much will increasing vessel radius increase flow (Q)

A

by x^4

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67
Q

what would be considered a left axis devation?

what would cause that

A

a heart vector that is from 0 to -90 degrees

left ventricular hypertropy or inferior MI

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68
Q

automaticity

A

the ability of cardiac pacemaker cells to produce their own APs

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69
Q

where are fenestrated capillaries found

A

places that need to secrete largeer particiles

GI, exocrine, renal, choroid

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70
Q

what counteracts high venous pressure in the legs when upright

A

the calf muscle pump

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71
Q

what determines venoconstriction

A

sympathetic tone

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72
Q

which part of the cardiac cycle is longer?

as HR increases, which part get shorter?

A

diastole

diastole

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73
Q

why does pulse pressure increase with age?

Mean BP?

A

atherosclerosis of large vessels

high vascular resistnace

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74
Q

two systolic murmurs

A

aortic valve stenosis

mitral or tricuspid valve incompetance

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75
Q

shear rate

what will this cause

A

increase the force running parallel to the vessel wall

the synthesis and release of NO2

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76
Q

how long does the absolute refractory period last in a cardiac myocyte AP

what are three advantages of this

A

almost as long as the twitch does

  1. no summation of APs
  2. no tetanus
  3. allows for filling
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77
Q

what is the effect of digitalis on the heart

A

it increases contractility

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78
Q

compliance formula

A

compliance = (deltaV)/delta P

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79
Q

what are two common causes of heart block

A

ischemic heart disease

valve fibrosis

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80
Q

what is the difference in duration of AP between cardiac myocytes and pacemaker cells

A

cardiac myocytes are fast, pacemaker cells are slow

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81
Q

what reynold number would indicate turbulent flow?

laminar flow?

A

>3000, turbulent

<2000, laminar

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82
Q

what is the standard paper speed of an ECG

A

25mm/sec

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83
Q

what is stroke volume

how do you calculate it

A

the volume of blood ejected each beat

SV = EDV-ESV

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84
Q

reflectivity coefficient

relevant fnumbers associated

A

the probability that particlesin blood will reflect off vessel walls

theta = 1, the vesselis not permeable

theta < 1, the vessel wall is freely passing

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85
Q

what determines the shape of veins

what is the result of venosconstrition

A

th pressure and level of vessel constriction

decrease blood reserve, send blood back to the heart

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86
Q

what happens when calcium is released from the sarcoplasmic reticulum in cardiac myocytes

BE SPECIFIC

A

calcium enters the L type calcium channel

it binds with ryanodine receptors on the SR

calcium induces calcium release from the SR

calcium binds to troponin C on tropomyson

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87
Q

what features of the heart allow for high O2 extraction rate in the heart

A

low PO2 and high myoglobin content aloow for rapid uptake

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88
Q

T/F a larger muscle will produce greater voltage and larger ECG waveform

A

true

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89
Q

what structures are depolarizing during the PR segment

A

AV node

Bundle of His

Bundle branches

Purkinje fibers

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90
Q

what currents are at work in Phase 4 of a pacemaker cell

A

IF

ICaT

IKv1.1

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91
Q

T/F coronary blood flow is directly correlated to blood pressure

A

false, coronary blood flow is largely independent of blood pressure flucuations

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92
Q

filtration

A

movement of solute out of blood via hydrostatic pressure

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93
Q

myocardial stunning

A

the loss of function due to an ischemia that can be reversible if reperfused

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94
Q

trigger calcium

A

calcium that enters the cell through a calcium channel that bings to ryanodine receptors and triggers CICR

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95
Q

which is more susceptible to ischemia during systole, epicardium or endocardium

why

A

endo

because the coronary vessels in this area are compressed almost to zero in this area

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96
Q

how should HR be calculated of ECG when the heart rate is constant

A

R-R distance

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97
Q

what is the relationship between turbulence and viscosity

A

increasing viscosity will increas turbulence

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98
Q

how can stroke volume be evaluated from a PV loop

A

SV = the width of the loop

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99
Q

what generates a myogenic reponse to regulate coronary blood flow

A

stretch receptors in smooth muscle

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100
Q

what are the functions of cAMP in regards to contractility of the heart

A

it stimulates L type calcium channels to increase Ca influx

phosphorylation of phospholamban to increase SERCA activilty

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101
Q

what is the function of desmosomes in intercalated discs

A

they hold the cells together

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102
Q

laminar flow

A

flow that is linear down the vessel, with the fluid near the center moving fastest and that near the edge of the lumen moving slower

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103
Q

what would a steeper diastolic compliance curve on a PV loop indicate

A

a decreased level of compliance indicated by less volume filling at a given pressure and preload

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104
Q

what is ejection fraction indicative of

A

the effectiveness of ventricular ejection

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105
Q

describe the path of blood through the heart

A

vena cava

right atrium

tricuspid valve

right ventricle

pulmonary semilunar valve

pulmonary artery

lungs

pulmonary vein

left atria

mitral valve

left ventricle

aortic valve

aorta

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106
Q

how long after cardiac ischemia will cells begin to die

A

20-40mins

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107
Q

what happens to velocity when the cross sectional area of a vessel is increased

decreased?

A

increased area will cause a decrease in velocty

decreased area increases velocity

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108
Q

what determines MAP

A

cardiac output

total peripheral resistance

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109
Q

what is a condition that would cause decreased compliance in the left ventricle?

the aorta?

what would cause an increase?

A

myocardial infarction

HTN

nothing

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110
Q

what intrinsic factors control function hyperemia of the coronar vessels

A

local metabolic control

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111
Q

T/F the resistance to blood flow can be measured directly

A

false, it is measured by R = (deltaP)/Q

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4
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112
Q

how do velocity, diameter, and density relate to turbulence

A

increasing any of these factors will increase turbulence

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113
Q

what happens to flow when it reaches critical velosity

A

it becomes turbulent and it takes significantly more force to increase flow

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114
Q

increased vascular tone will result in what

A

a constriction of coronary vessels to increase resistance and decrease blood flow

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115
Q

why does intracellular calcium increased contractility

A

more calcium means there are more Ca bound to troponin which will allow for more myosin binding sites

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116
Q

what is quick way to estimate HR on ECG if the rate is regular

A

1 space between R waves is 300bpm

2 = 150

3 = 100

4 = 75

5 = 60

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117
Q

what are the four areas of auscultation over the heart

A

aortic

pulmonic

tricuspid

mitral

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118
Q

what limbs are used in lead III?

what is the direction of the wave

A

left arm and lower limb

down and to the right

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119
Q

two special structure found in intercalated disks

A

desmosomes and gap junctions

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120
Q

how is flow related to the length of the tube

A

longer tube = less flow

121
Q

two locations of nodal cells in the heart

BE SPECIFIC

A

SA node (right atria)

AV node (inferior posterior section of the intratrial septum)

122
Q

what will be the effect of increasing afterload on a PV Loop

what is the result

A

it will move the point of aortic valve closing to the right due to higher pressure required with less volume ejected

decreased stroke volume

123
Q

PR interval

A

the length between the begining of the P wave to the Q wave

124
Q

what is the pattern of heart damage when the coronary arterial pressure falls below 40mmHg

A

the epicardium is less injured, the endocardium is more widespread and severely injured

125
Q

what causes ventricular fibrillation to persist

A

re-entry of AP into the circuit, causing repeating circus pathways

126
Q

how are cardiac pacemaker cells able to produce a slow depolarization

A

they have an unstable resting membrane potential

127
Q

what is the physiological and clinical significance of delayed AV conduction

A

optimal ventricalr filling during atrial contraction

128
Q

where are discontinous capillaries found

A

places that need to get rid of or absorb large particles

liver, spleen, bone marrow

129
Q

basal tone

A

the amount of vasoconstriction at rest

130
Q

how long is an AP delayed at the AV node

A

0.1 second

131
Q

what is the difference between contractility and Frank-Starlings law

A

contractility is intrinsic and Ca dependant

Frank-Starling is dependent on preload, not calcium

132
Q

what are the four phases of the ventricular cycle

A

filling

isovolumic contraction

ejection

isovolumic relatxation

133
Q

PR segement

A

isoelectric portion of the ECG between the end of the P wave and the start of the QRS

134
Q

what would happen if the purkinje fibers began to fire at a rate of 140bpm even with a functional SA and AV node

A

the whole heart will be driven by the faster rate

135
Q

what is the function of the bundle of his, bundle branches, and purkinje fibers

A

ventricular excitation

136
Q

how can Laplace Law be manipulated to find pressure

A

P = (w/r)(T)

137
Q

at what point will increasing blood pressure stop increasing coronary blood flow

A

150 mmHg

138
Q

what current is at work in phase 0 of a pacemaker cell

A

ICaL

139
Q

what is this?

define the variables

A

a pressure volume loop

A diastolic filling

M1 mitral valve closes

B isovolumic contraction

A1 aortic valve opens

C ejection

A2 aortic valve closes

D isovolumic relaxation

M2 mitral valve opens

140
Q

what is the effect of neural control on coronary blood flow

what is the secondary effect of this

A

sympathetic stimulation causes a transient, weak, alpha constriction

metabolic demand is increased, which causes vasodilation and increase in blood flow

141
Q

what recordings are included on a 12 lead ECG

A

I, II, III

aVR, aVL, aVF

V1-6

142
Q

Frank-Starlings law

A

increased ventricular filling (preload) will increase tension in the heart muscle and increase contraction force

143
Q

two causes of incresaed pulse pressure

A

exercise

decreased compliance

144
Q

two examples of delayed after polarization

A

ectopic beats

PVCs

145
Q

describe the process that produces Phase 2 (plateau)

A

L type calcium channels open at threshold (-50mV)

calcium enters the cell

creates a slow inward current

146
Q

when the heart is stimulated by a metabolic and neural factor, which wins out

A

metabolic

147
Q

EDV vs ESV

A

EDV: the amount of blood in heart during ventricular filling

ESV: the amount of blood remaining in the heart after a contraction

148
Q

what causes the absolute refractory period

A

the closing of Na inactivation gates

149
Q

what percent of ATP used in the heart is for contraction?

SR pumps?

A

60-70%

30-40%

150
Q

which part of the autonomic nervous system dominates HR variability

A

parasympathetic

151
Q

a patient presents with an HR +200bpm

why would this need to be treated immediately

A

because over 180bpm increasing HR causes a decrease, not an increase in CO

152
Q

what current is at work in Phase 1 of a cardiac myocyte AP

A

Ito (IKv1.4)

153
Q

what is the function of a ryanodine receptor

A

binds with calcium to allow for the release of calcium from the SR

154
Q

describe the pathway of sympathetic stimulation on pacemaker cells up to PKA

A

Norepinephrine is release from the adrenal medulla

NE binds to beta 2 adrenergic receptor

B2 receptor releases G protein

alpha subunit activates adenylate cyclase

adenylate cyclase releases protein kinase A

155
Q

how is resistance effected by size of the artery

A

large arteries have little resistance, small arteries have a lot of resistance

156
Q

what current is at work in Phase 3 of a cardiac myocyte AP

A

IKv1.1

157
Q

what are three conditions related to turbulence

A

anemia (low viscosity)

atherosclerosis (turbid flow is more difficult to move)

aneurysms (larger diameter causes turbid flow)

158
Q

ejection fraction

A

the amount of blood ejected from the left ventricle each beat

159
Q

where is V2

A

fourth intercostal space at the left sternal border

160
Q

what is the effect of norepinephrine on the coronary vessels

A

it increases intracellular calcium to increase tension

161
Q

what starts a ventricular fibrillation

A

R on T firing

162
Q

what is the effect of hypoxia on the coronary vessels

A

vasodilation

163
Q

what determine the total energy of a vessel

how does this relate to the amount of pressure

A

the pressure + the kinetic energy

a larger veseel will have a lower velocity and high pressure

a smaller vessel will have a high velocity but produce low pressure

164
Q

what substances provide local metabolic control to coronary blood flow

K A N A C O

A

K+

ATP

NO

Adenosine

CO2

O2

165
Q

compensatory pause

what is the function

A

a prolonged isoelectric period following an ectopic beat and the resumption of sinus

allows the heart to reset

166
Q

T/F compliance always goes up in the heart

A

false it always go down

167
Q

water flux

A

Jv = LpS[Pc-Pi] - theta(pic - pii)

Lp = hydrostatic pressure

S = surface area

Pc = hydrostatic pressure in capillaries

Pi = hydrostatic pressure in interstitium

Theta: reflection coefficient

pic and pii =oncotic pressure in side and outside capillaries

168
Q

T/F there is no parasympathetic innervation to the heart vessels

A

true

169
Q

reactive hyperemia

A

a significant increase in blood flow into a tissue after ischemia has been relieved

170
Q

how is flow related to pressure gradient

A

greater pressure, greater flow

171
Q

what current is at work in Phase 4 of a cardiac myocyte AP

A

IKir

172
Q

the movement of what two ions is balanced during phase 2

A

potassium intitally decreases in conductance, then increases as the AP transitions to phase 3

calcium increases in conductance then slowly decreases

173
Q

three CNS symptoms caused by tetrotoxin

A

muscle weakness

numbness

coma

174
Q

three examples of conditions that might cause a murmur

A

high blood flow through a valve in pregnancy

systemic disease such as anemia

valvular heart disease

175
Q

what happens to blood flow through vessels with progressively smaller radii

A

the resistance to flow for the whole segment is the sum off all the resitances, so increased resistance at the end of the vessel increases resistance for the whole

176
Q

what are three general symptoms of tetrotoxin poisoning

A

GI distress

CNS

Cardiovascular

177
Q

what is the RMP of a cardiac myocyte

A

-90mV

178
Q

what is the relationship between MAP and pulse pressure

A

as MAP increases, pulse pressure increases

179
Q

what are the 5 phases of a cardiac myocyte AP

A

Phase 4 (resting)

Phase 0 (upstroke)

Phase 1 (Early Repolarization)

Phase 2 (Plateau)

Phase 3 (final repolarization)

180
Q

explain the hydraulic filter of the arterial blood flow

A

the aorta expands to hold blood from the left ventricle so that blood flows at a constant pressure, not in pulses

181
Q

contractility

A

the intrinisic contractile force of the heart a given preload and afterload

182
Q

what forms ECG recordings

A

the electrical signals formed by action potentials in the heart

183
Q

why can turbulence be good?

A

it ensures mixing of blood

provides heart sounds

184
Q

three types of capillaries

A

continous

fenestrated

discontinuous

185
Q

what properties allow veins to store blood

A

thin

collapsable

high compliance

186
Q

where is 2/3 of blood kept in the body

what is the clincial significance

A

in the veins as a blood reserve

blood in veins can refill arteries if there is a hemorrhage

187
Q

describe the pathway of parasympathetic stimulation on HR (up to G protein release)

A

acetylcholine binds to muscarinic receptors

M receptors release G protein

G protein subunits beta and gamma induce intracellular response

188
Q

if you hear systolic murmur over the 5th intercostal space at the midclavicular line, what would be the expected cause

what if it were at the 5th sternal intercostal space

A

mitral valve incompetance

tricuspid valve incompetence

189
Q

two phases of the cardiac cycle

A

systole

diastole

190
Q

afterload

A

the force that opposes ventricular shortening against aortic pressure

191
Q

on a standard ECG what are the units on the x axis? y axis?

A

x axis = .04seconds per division

y axis = .1mV per division

192
Q

what six things can be evaluated looking at a PV loop

A
  • stroke volume
  • cardiac output
  • ejection fraction
  • contracility
  • ventricular wall compliance
  • ventricular preload an afterload
193
Q

T/F the slowest functional pacemaker dominates the heart

A

fast, the fastest pacemaker does

194
Q

what does SERCA do

A

uses ATP to pump calcium back into the SR afer a contraction to allow the muscle to relax

195
Q

why do the purkinje fibers have the highest conduction velocity

A

large diameter and many gap junctions

196
Q

what is necessary for cardiac muscle relaxation

A

a decrease in intracellular calcium concentration

197
Q

what part of an ECG would correspond with SA node firing

A

the isoelectric period prior to the P wave

198
Q

define the phrase “the heart is a syncytium”

A

it works as a unit

199
Q

what is the driving force behind the movement of blood during the cardiac cycle

A

pressure

200
Q

what would happen if the AV node were knocked out but the SA was still firing

A

the SA node AP would not be able to reach the purkinje fibers so the fibers would produce a HR of around 30

201
Q

R on T firing

A

ectopic APs that occur during the “vulnerable period” of the late T wave

202
Q

what is the function of phospholamban at rest

describe the sympathetic interaction between phospholamban and SERCA

A

at rest phospholamban inhibits SERCA

stimulation of beta adrenergic receptors releases cAMP

cAMP phosphorylates phospholamban

phosphorylation allows SERCA to function

203
Q

which pacemaker node in the heart produces impulses at the highest frequency

A

the SA node

204
Q

three cardiovascular symptoms caused by tetrotoxin

A

decreased cardiac output

hypotension

bradycardia

205
Q

what happens during circuit re-entry that causes arrhythmia

A

conduction from the ventricle is looped around to cause an abnormal conduction and stimulation pattern

206
Q

what is the systemic resistance to blood flow

A

20mmhg/L/min

207
Q

T/F contractility is dependent on preload and afterload

A

false, it is an intrinsic capability of the heart dependent on calcium

208
Q

how should HR be calculated if the HR varies

A

count the number of RR intervals in 10 seconds and multiply by 6

209
Q

what type of murmur would be heard with aortic valve incompetance

A

diastolic murmur over the 2nd right intercostal space

210
Q

where is V6

A

at the midaxillary line at the 5th intercostal space

211
Q

Laplace Law formula

A

T = (P x r)/w

212
Q

what are two factors that determine the fire frequency of pacemaker cells

A

the rate of depolarization in phase 4

the maxium pacemaker potential

213
Q

hydrostatic pressure

formula

A

the pressure exerted by a fluid on its container

Hp = height x density x gravity

214
Q

what is an example of atissue with parallel vessels

A

lungs

215
Q

what effect would increased contractility have on a PV loop

what would be the result

A

the systolic pressure curve would sift to the upper left, indicating a higher pressure per volume

increasing stroke volume

216
Q

negative inotropic effect

what would cause this

A

decreased contractility

beta blockers

217
Q

turbulent flow

A

flow that creates whirls due movement faster than critical velocity

218
Q

what current is at work in Phase 0 of a cardiac myocyte AP

A

INa

219
Q

how does tonic stimulation apply to pacemaker cells

A

the parasympathetic nervous system displays tonicity by constantly having a inhibitory effect on heartrate

220
Q

when is pressure the highest in the ventricles and aorta

A

during ventricular systole

221
Q

what is effect of compliance on end systolic volume?

end diastolic volume?

A

no effect

decreased volume

222
Q

what is a normal ejection fraction

what would it mean if EF were low

A

+50%

lower values indicate heart failure

223
Q

scalar ECG

A

a recording of the potential differences between two points on the body surface

224
Q

what two limbs are used in lead II?

what is the direction of the wave

A

right arm and a leg

from the right arm down to the leg

225
Q

what is the general process of calcium induced calcium release CICR

A

Calcium enters the the cell during phase two, triggering the release of calcium from the SR and producing a contraction

226
Q

what is this and what is it used for

A

the nerst equation used to determine the Ex for a particular ion

227
Q

at what pressure will blood flow to the endocardium be attenuated

A

40mmHg

228
Q

what are the leads that should be placed for an ECG

A

right/left arm and leg

V1-6

229
Q

what is the average presure in arterial blood flow

venous

flow rate

A

100mmhg

0

5L/min

230
Q

what two limbs are used in lead I?

what is the direction of the force?

A

right and left arms

from right to left

231
Q

what electrical event does the QRS complex represent

A

ventricular depolarization

232
Q

if you hear a systolic murmur over the 2nd right sternal intercostal space, what would this most likely be

A

aortic vale stenosis

233
Q

what are the two advantages of the plateau period for cardiac function

A

maintenance of force generation (long contraction)

creation of a long absolute refractory period (allows for filling)

234
Q

what two structures are most important to EC coupling

A

T tubules

sarcoplasmic reticulum

235
Q

what electrical event does the P wave represent

A

atrial depolarization

236
Q

what are the functions of protein kinase A in pacemaker cells

what is the result

A

increasing Na conductance to allow If

phosphorylation of T-type calcium channels to increase Ca conductance and allow ICat

increase pacemaker potential

237
Q

define the variables

A
  1. mitral valve opens
  2. diastolic filling
  3. mitral valve closes
  4. isovolumic contraction
  5. aortic valve opens
  6. ejection
  7. aortic valve closes
  8. isovolumic relaxation
  9. stroke volume
238
Q

what are the Dipolar leads in ECG?

why are they called that

A

Leads I-III

because there will always be two leads, one will be more negative to reflect the passing of an AP wave

239
Q

where is V4

A

the midclavicular line at the 5th intercostal space

240
Q

two parts of systole

A

isovolumic contraction

ejection

241
Q

where is the aortic area of ausculation?

pulmonic?

mitral?

tricuspid?

A

2nd right intercostal space

2nd left intercostal space

5th intercostal space at the sternm

5th intercostal space at the mid clavicle

242
Q

what electrical event does the T wave represent

A

ventricular repolarization

243
Q

what is pulse pressure dependant on

A

stroke volume and arterial compliance

244
Q

in general, what is measured by a pressure/volume loop

A

the efficiency and work performed by the heart

245
Q

what is the function of the AV node

A

delays ventricular excitiation to ensure filling

246
Q

a standard paper speed, what are the x and y axes

A

x is time

y is voltage

247
Q

four large cardiac vessels

A

right coronary

left coronary

left circumflex

left anterior descending

248
Q

Describe the calcium signalling process

A

Ca enters the cell

trigger calcium binds to ryanodine triggering CICR

depolarization and muscle contraction

repolarization through calcium sequestering by SERCA

249
Q

transmural pressure

A

the difference in pressure placed on the intraventricular septum by the ventricles

250
Q

what is cardiac output

how do you calculate it

A

the total volume of blood ejected from the heart each minute

CO = SV x HR

251
Q

einthovens triangle

A

an imaginary triangle formed by the upper and lower limbs along with the pelvis used to measure the amplitude and direction of cardiac APs at the skin

252
Q

reynolds number equation

A

Re = VDp/n

253
Q

how can you determine the contractility of the heart from a PV loop

A

the systolic pressure (upper) line will have an increased slope with increased contractility

254
Q

what happens during diastole to compensate for compression of coronary vessels to the endocardium during systole

A

blood flow is greater than average, so that the average amount of blood flow ist he same

255
Q

pulse pressure formula

A

pulse pressure = systolic - diastolic

or

pp = stoke volume/arterila compliance

256
Q

velocity equation for a blood vessle

A

Velocity = Flow(Q)/vessel cross section(A)

257
Q

where is V5

A

at the anterior axillary line in the 5th intercostal space

258
Q

describe the process of calculating heart rate using R-R interval

A

measure the distance in mm between consecutive R waves

divide the paper length in 60s (1500mm) by the RR length

259
Q

what is the direction of aVL

A

from the heart to the left arm

260
Q

what would be the effect of increased preload on a PV loop

what would be the result

A

it would increase the LVEDV, increasing the amount of tension in the wall and increasing contraction force

increased stroke volume

261
Q

what are two factors that generate RMP

A

unequal distribution of ions (Gibbs donnan)

relative permeability of ions (conductance)

262
Q

why do cardiac myocytes have a lot of mitochondira

A

they function mainly on aerobic metabolism

263
Q

what is the function of phospholamban at rest

A

inhibition of SERCA

264
Q

heart cells are particularly vulnerable to arrhythmias at what point in the cardiac cycle

A

the phase 4 supranormal period

265
Q

how do SNS and PsNS differ in terms of onset of effect after stimulus and decay of effect when the stimulus is with drawn

A

SNS: slow onset, slow decay

PsNS: fast onset, fast decay

266
Q

what are the two extrinsic regulators of coronary blood flow

A

sympathetic control

hormone regulation

267
Q

describe the effect of G protein subunit Gαi on pacemaker cells

A

cAMP is decreased, causing a decrease in PKA

If, ICaL, IKv1.1 all decrease

slope/rate of depolarization are decreased

268
Q

what would be effect of decreased compliance on a PV loop

what is the result

A

decreased compliance would require more pressure with less filling, resulting in a steeper diastolic loop

decreased stroke volume

269
Q

three GI symptoms caused by tetrotoxin

A

nausea, vomitting, cramping

270
Q

what is the benefit of parallel vessels rather than vessels in series

A

one vessel with high resistance does not compromise blood flow through the rest of the vessels

271
Q

what is the direction of aVR

A

from the heart toward the right arm

272
Q

what is the clinical relevance of having a high number of capillaries in the heart

A

it allows for the minimum possible distance to intracellular mitochondria

273
Q

how can cardiac output be evaulated on a PV loop

A

CO = SV x HR

274
Q

ST segment

A

the isoelectric portion between the end of QRS and the start of the T wave

275
Q

what will an ECG look like with heart block

A

normally firing P waves from the SA node with missing QRS complexes

276
Q

whatis ST segment depression/T wave inversion indicative of

A

signs of previous ischemia

277
Q

four arterial pressures

A

systolic

diastolic

pulse

MAP

278
Q

where are continous capillaries found

A

cells with relatively or variable metabolic need

CNS, Lung, Skin, msucle

279
Q

what are the three augmented unipolar leads

A

aVL, aVR, aVF

280
Q

how can a cardiac AP be considred a wave

A

there is a wavefront of depolarized cells followed by hyperpolarizing cellls

281
Q

how does coronary blood flow regulate heart function

A

sympathetic stimulation of the coronary vessels can increase cardiac metabolic rate

removing the stimulus will decrease metabolism

282
Q

what is the end result of parasympathetic stimulation on pacemaker cells

A

decreased pacemaker potential and rate of depolarization, leading to a slower HR

283
Q

myogenic reponse

A

increasing transmural pressure will cause constriction of coronary vessels

decreasing will cause dilation

284
Q

what is ficks principle used for?

what is the equation

A

to determine CO by the amount of O2 consumed divided by the difference of arterial and venous PO2

CO = (VO2)/(Cpv - Cpa) *high minus low

285
Q

compliance formula

A

change in volume/change in pressure

286
Q

describe the path of an action potential through the heart

A

SA node

internodal pathways

AV node

bundle of His

bundle branches

purkinje fibers

287
Q

tetradotoxin

A

a volrage gated channel blocker derived from the venom of a puffer fish

288
Q

how does SERCA allow for enhanced contractility

A

increased SERCA activation will increase the amount of Ca in the SR and allow for a greater release, whch will trigger a stronger contraction

289
Q

what is the function of gap junctions in an intercalated disc

A

allow direct transport between cells

290
Q

what would a high slope on a pressure/time graph indicate

A

increased contractility

291
Q

what current is at work in Phase 2 of a cardiac myocyte AP

A

ICaL

IKv1.4

IKv1.1

292
Q

T/F increasing contractility would affect LVEDV

A

false

293
Q

oncotic pressure

A

the pressure driving fluid into blood due to protein content

294
Q

what is the formula for EF

A

SV/EDV

295
Q

what point on a pressure/volume loop indicate LVEDV and LVESV

A

mitral valve closing

aortic valve close

296
Q

what is the primary determinant of coronary blood flow

A

intrinsic mechanisms

297
Q

ryanodine receptors

A

receptors on the SR of muscle cells that are triggered by calcium to release calcium into the cytoplasm

298
Q

what intrinsic factors control flow autoregulation and reactive hyperemia in coronary vessels

A

myogenic response and local metabolic control

BMS 752 (Medical Physiology) (13 decks)

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