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october exam > cardiac > Flashcards

cardiac Flashcards

(88 cards)

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1
Q

properties of cardiac muscle

A

-have properties of both skeletal and neural tissue
-when presented with electrial stimulus, cardiac myocytes contract in a coordinated way contributing to pumping mechanism of the heart

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2
Q

automaticity

A

ability to generate an AP spontaneously. cardiac conduction cells (SA node) display this when they set the HR

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3
Q

excitability

A

ability to respond to an electrical stimulus by depoloraizing and firing AP

cardiac cells are excitable b/c they can respond (depolarize) when presented with an electrical stimulus

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4
Q

conductance

A

the ability to transmit electrical current

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5
Q

can ions pass through cell membrane

A

no- they are charged

ion needs an open channel to cross from one side of the membrane to the other

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6
Q

what does open channel vs closed channel do

A

open channel- increases conductance of the ion

closed channel- reduces conductance of the ion

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7
Q

chronotropy is in reference to

A

HR

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8
Q

dromotropy

A

describes conduction velocity through the heart

(velocity= distance/ time)

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9
Q

lusitropy

A

describes rate of myocardial relaxation during diastole

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10
Q

RMP

A

electrical potential across a cell membrane at rest

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11
Q

what determine RMP (3 things)

A

chemical force (chemical gradient), electrostatic counterforce, na/k atpase

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12
Q

at rest nerve cell continious leaks __

A

k (loses pos charges)

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13
Q

what is primary determinant of RMP

A

K

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14
Q

decreased vs increased K

A

decreased K = rmp becomes more neg- cells more resistance to depolarization
increased K= rmp becomes more pos- cells depolarize more easily

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15
Q

threshold potential

A

voltage change that must occur to iniate depolorarization

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16
Q

what is the prime determinent of threshold potential

A

serum ca

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17
Q

decreased vs increased ca

A

decreased ca= tp becomes more neg

increased ca= tp becomes more pos

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18
Q

depolarization

A

movement of a cells membrane potential to a more pos value (less of a charge difference between inside and outside of the cell)

a cell depolorizes when na or ca enters the cell

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19
Q

can depolorization be stopped

A

no depolorization is all or none- once it begins it cannot be stopped

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20
Q

ability of a cell to depolarize is determined by the difference of

A

rmp and TP

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21
Q

when RMP is closer to TP..

A

earier to depolarize

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22
Q

when RMP is further from TP

A

harder to depolarize

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23
Q

repolarization

A

return of cells membrane potential to more neg value after depolarization

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24
Q

cell repolarizes when ___ or ___

A

k leaves cell or cl enters cell

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25
during the refractory period can the cell depolarize
cell is resistance to depolarization- this is b/c RMP is further from TP
26
hyperpolarization
movement of cells membrane potential to a more neg value beyond baseline RMP
27
when does hyperpolarization happen
after repolarization cell typically hyperpolarizes for short time
28
in excitable tissue what restores the ionic balance towards RMP
na- k atpase restores ionic balance
29
what is the purpose of na- k atpase
- removes na that entered the cell during depolarization -returns k that has left the cell during repolarization
30
for every 3 na ions it removes, it brings __ k ions into the cell
2
31
does na- k atpase turn on and off
always on!!
32
is na- k atpase active
active! - needs atp- duh
33
how is na- k atpase inhibited
inhibited by digoxin
34
what happens with severe hyperkalemia
serum k very high- inactives na channels (they arrest in their closed inactive state) ex: K+ in cardioplegia solution arrests the heart in diastole during CPB, K concentration does not allow the cells to repolarize)
35
decreased serum ca
TP becomes more neg cells depolarize more easily
36
36
hypercalcemia
tp increases cells more resistant to depolarization ex: IV calcium is given to reduce risk of dysrthyhmias in pt with hyperkalemia (increase gap between RMP and TP)
37
unlike neurons, cardiac myocytes AP have
a plateua phase where depolarization is prolonged. this gives cardiac myocytes time to contract, so the heart has enough time to eject stroke volume
38
what nodes do not have a plateau phase
SA and AV node
39
5 phases of cardiac AP
phase 0= depolarization: Na in phase 1= inital repolarization: Cl in and K out phase 2= plateau: ca in and k out phase 3= repolarization: K out phase 4= maintence of transmembrane potential: k out and na/k atpase function
40
41
how does conduction move
sa- intenodal tracts- av- bundle of his- L and R bundle branches- purkinje fibers
42
sa node action potential characteristics
3 phases (phase 1 or phase 2) rmp is higher na/ k atpase re-establishes na and k gradients after repolarization
43
what cells in myocardium are capable of automaticity
all cells! but they all have a diff rate of spontaneous depolraization
44
at rest which autonomic tone takes over
pns>sns
45
pns tone uses what nerves
vagus nerve (CN 10)
46
what nodes to the R and L vagus nerve innervate
R innervates SA L innervates AV
47
sns tone comes from what nerves
cardiac accelerator fibers (t1-t4)
48
what is the intrinsic firing rate of SA
70-80 (faster in denervated heart)
49
what is the intrinsic firing rate of AV node
40-60
50
what is the inrinsic firing rate of purkine fibers
15-40
51
what 3 ways can you alter the HR
1. rate of spontaneous phase 4 depolarization 2. threshold potential 3. resting membrane potential
52
what situations (slope changes) increase HR
1. slope of phase 4 depol increases 2. slope of phase 4 depol remains constant but TP becomes more neg 3. slope of phase 4 deol remains constant but RMP becomes less neg- shortens distance between RMP and TP so cells reach threshold faster
53
what catecholamine and receptor increases HR by sns tone
NE stimulates B1 - increases HR by increasing na and ca conductance - increasing slope of phase 4 (steeper slope)
54
what receptor slows HR (pns activation)
acetacholine stimulates m2 receptor- increases k conductance and hyperpolarizes SA node decrease RMP and reduces slope of spontaneous phase 4 depolariazation (less steep slope)
55
look into oxygen delivery equation
dont know
56
what does cao2 tell us
oxygen content in the blood- how many grams of o2 is in decileter of arterial blood most o2 is bound to hgb- small amount is dissolved
57
what law does the amount of gas dissolved in a solution follow
henrys law- at a constant temp the amount of gas that dissolves in a solution is directly proportional to partial pressure of that gas
58
whats ohms law
forms the basis for understanding hemodynamics map=( co x svr)/ 80 + cvp
59
poiseullies law
an adaptation of ohms law- incorporates vessel diameter, viscosity and tube length look up formula
60
flow describes
movement of liquid, electrict or air per unit time
61
what is the greatest impact on flow
altering radius of tube- raises radius to 4th power
62
vascular resistance is primarily determined by
radius of arterioles- small changes in vessel diameter can yield big impacts on tissue blood flow
63
what is reyonlds number used for
can be used to predict if the flow will be laminar or turbulent
64
what are the numbers to determine reynolds number
re < 2,000 predicts that flow will be mostly laminar re >4000 predicts that flow will be mostly turbulent re= 2,000- 4,000 suggests transitional flow
65
whats the issue with turbulent flow
a lot of energy is lost to heat and vibration
66
vibrations occuring with turbulent flow can produce
a murmur (valvular ht disease) or bruit (carotid stenosis)`
67
viscosity
result of friction from intermolecular forces as fluid passes through a tube. blood viscosity is determined by hct and body temp
68
viscosity is inversely proportional to
temp. a cooler temp increases viscosity and resistance
69
how does viscosity relate to administering rbcs
can improve flow- can dilute the unit with normal saline (decreased hct) by running it through fluid warmer (inc temp)
70
CO
hr x sv 5-6 L/min
71
CI
co/ bsa 2.8-4.2 L/min
72
sv
edv- esv 50-110 ml/beat
73
sv index
sv/ bsa 30-65 ml/beats per min2
74
ejection fraction
edv- esv / edv x 100 60-70%
75
normal map
70-110
76
pulse pressure
sbp-dbp 40
77
svr
map- cvp/ co x 80 800-1500 dynes x sec x cm5 to do svr index just replace co with ci
78
pvr
mpap - paop / co x 80 150-250 dynes x sec x cm5
79
sarcomere
the functional unit of contractile tissue in the heart. the amount of tension that each sarcomere can generate is directly r/t the number of cross brides that can be formed before contraction
80
the greater the tension the ___ the force of contraction
greater- up to a point!
81
preload
ventricular wall tension at end of diastole (just before contraction often interchangable with ventricular end diastolic volume
82
what curve tells reltionship between ventricular volume and ventricular output
frank starling
83
is contractility dependent on PL and AL
no inc PL= inc force of contraction (starlings law) not the same as increased contractility! contractility is the ability of myocardial sarcomeres to perform work (shorten and produce force)
84
atrial kick contributes to __ % of CO
20-30
85
when would you be reliant on atrial kick
a non compliant stiff ventricle
86
conditions associated with reduced myocardial compliance
myocardial hypertrophy, HF with pEF, fibrosis, aging more likely to see lower CO, cardiac rhythm disturbances, afib, junctional rhythm
87

october exam (12 decks)

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