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CVT Apex > CV A&P: APs, DO2, Flow > Flashcards

CV A&P: APs, DO2, Flow Flashcards

1
Q

Ventricular myocytes
RMP vs TP

A
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2
Q

How does K & Ca affect RMP & TP?

A

↑K = ↑RMP

↑Ca = ↑TP

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3
Q

the wave of depolarization is facilitated by

A

gap junctions

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4
Q

Ventricular myocytes have (less/equal/more) mitochondria than skeletal.

A

more

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5
Q

automaticity vs excitability

A

Automaticity: generate AP spontaneously

Excitability: respond to an electrical stimulus by depolarizing and firing an AP

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6
Q

How do K levels affect signal propigation?

A

↓K = (-) RMP = resist depolarization

↑K = (+) RMP = easier depolarization
to an extent! severe hyperK can block depolarization

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7
Q

In excitable tissue, the primary job of the sodium-potassium ATPase

A

restore the ionic balance towards RMP

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8
Q

cardiac myocyte O2 consumption at rest

A

8-10 ml/O2/100g/min

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9
Q

What makes cardiac muscle similar and different to neural and skeletal tissue?

A
  • like neurons: can generate a RMP & propagate an AP
  • skeletal: have actin & myosin contractile elements
  • unique: intercalated disc junctions = fxnl synctium, gap jxns, more mitochondria
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10
Q

no net ion movement

A

equilibrium potential

charges inside = charges outside

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11
Q
A
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12
Q

conductance

A

ability to transmit electrical current

open ion channels increase it, while closed ones decrease it

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13
Q

The 4 “-tropies”

A
  1. Inotropy: myocardial contraction force
  2. Chronotropy: heart rate
  3. Dromotropy: conduction velocity (velocity = distance / time)
  4. Lustropy: rate of myocardial relaxation
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14
Q

RMP is determined by 3 things:

A
  1. Chemical force (concentration gradient)
  2. Electrostatic counterforce
  3. Sodium/potassium ATPase
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15
Q

T/F:
At rest, nerve cells continuously lose positive charge.

A

True
continuously leaks K+

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16
Q

T/F:
A cell can only depolarize from Na+ influx.

A

False
Ca influx also works

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17
Q

Which part of the cycle is the “all or nothing” phenomenon

A

depolarization

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18
Q

T/F:
In excitable tissue, an AP reults in depolarization.

A

FALSE
depolarization results in an action potential
(so long as TP is achieved)

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19
Q

When does the cell repolarize?

A

When K leaves or Cl enters

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20
Q

T/F:
After repolarization, the cell typically hyperpolarizes for a very short time.

A

True

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21
Q

T/F:
A hyperpolarized cell can be depolarized.

A

True
more difficult tho

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22
Q

the 2 actions of the Na/K/ATPase

A
  1. removes Na that entersed during depolarization.
  2. returns K that left during repolarization
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23
Q

the positive inotrope that inhibits Na/K/ATPase

A

Digoxin

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24
Q

Severe hypoK makes MRP more negative, so its harder to depolarize. How does severe hyperK have the same effect?

A

severe hyperK inactivates Na channels (remain closed-inactive state)

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25
Q

When is hyperK purposely induced? Why?

A
  • Potassium containing cardioplegia solution used during cardiopulmonary bypass arrests the heart in diastole.
  • This prevents repolarization & locks the Na channels in their closed-inactive state.
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26
Q

How do Ca levels affect conductivity?

A
  • HypoCa = TP more (-) = depolarize easily
  • HyperCa = TP more (+) = resist depolarization

K will have the opposite effect on ease of depolarization

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27
Q

How does IV calcium reduce the risk of dysrhythmias in hyperkalemia ?

A

increases the gap between RMP and TP

hyperK increases RMP = more depo
more Ca increases TP = less depo

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28
Q

Which phase of the ventricular action potential is associated with the
GREATEST calcium conductance?

A

2

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29
Q

What gives myocytes time to contract?

A

their AP has a plateau phase which prolongs depolarization

(unlike neurons)

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30
Q

These structures do not have a plateau phase

A

SA & AV nodes

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31
Q

Which parts of the EKG correspond to each AP phase?

A
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32
Q

Which current is responsible for spontaneous phase four depolarization in
the SA node?

A

The funny current (I-f)

the primary determinant of the pacemaker’s intrinsic heart rate.

AKA it sets the rate of spontaneous phase four depolarization in the SA node.

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33
Q

The order of the cardiac conduction system

A

SA Node → Internodal Tracts → AV Node → Bundle of His → Left & Right Bundle Branches → Purkinje Fibers

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34
Q

The heart rate is determined by

A

intrinsic firing rate of the SA node

(its rate of phase 4 spontaneous depolarization) & autonomic tone

35
Q

Disease or hypoxia of the SA node impairs its function as the dominant pacemaker. In this situation, which cells takeover?

A

next highest rate of **spontaneous phase 4 depolarization **

36
Q

Volatile anesthetics depress the automaticity of the SA node, which explains why these drugs can cause…

A

junctional rhythm

37
Q

The SA and AV node action potential consists of 3 phases:

A
  • Phase 4 = Spontaneous depolarization: Nat in (I-f) and then Ca in (T-type)
  • Phase 0 = Depolarization: Ca in (L-type)
  • Phase 3 = Repolarization: K+

No phase 1 or 2!

38
Q

Physiologically, we can increase the heart rate by…
(2)

A
  1. increasing the rate of phase 4 spontaneous depolarization
    and/or
  2. bringing RMP and TP closer together
38
Q

Name the internodal tracts

39
Q

The SA node has a (lower/higher) RMP than a myocyte

40
Q

The AV node has a slower intrinsic firing rate than a myocyte, as evidenced by…

A

lower phase 4 slope

41
Q

The SA node’s membrane is leaky to

42
Q

I-f current is activated by

A

HYPERpolarization

43
Q

Intrinsic firing rates of the conductive tissues

44
Q

… of the SA node determines the intrinsic heart rate.

A

The rate of spontaneous phase 4 depolarization

45
Q

T/F:
All the cells in the myocardium are capable of automaticity (self-generating an action potential).

A

True
each cell type has its own intrinsic rate of spontaneous depolarization

46
Q

What determines how frequently the heart depolarizes?

A

The cells with the fastest rate of depolarization

47
Q

The ANS modulates HR. Which structures of the SNS and PNS control heart rate?

A
  • PNS: right vagus innervates the SA & left vagus innervates the AV
  • SNS: Cardiac accelerator fibers (1-T4)
48
Q

We can alter the heart rate by manipulating three variables:

A
  1. The rate of spontaneous phase 4 depolarization
  2. Threshold potential
  3. Resting membrane potential
49
Q

How do we manipulate phase 4 spont. depo, RMP & TP to increase HR?

A
  1. Increase slope of phase 4 depo
  2. slope constant, but TP more negative
  3. slope constant, but RMP more positive
50
Q

Which NTs and receptors of the SNS & PNS affect HR?

A

SNS:
Norepi @ B1 increases HR by increasing Na & Ca conductance, increasing phase 4 slope

PNS:
ACh @ M2 slows HR by** increasing K conductance & hyperpolarizing** the SA node (↓ RMP & phase 4 slope)

51
Q

CaO2, DO2, VO2, and CvO2
for a 70 kg adult

A
  • CaO2: Arterial oxygen content = 20 mL/O2/dL
  • DO2: Oxygen delivery = 1,000 mL/min
  • VO2: Oxygen consumption = 250 mL/min
  • CvO2: Venous oxygen content = 15 mL/dL
52
Q

CaO2

A

oxygen content

g of O2/dL of arterial blood

53
Q

DO2

A

delivery

O2 carried in blood and how fast its delivered to tissues

54
Q

EO2

A

extraction ratio (by tissues)

whole body = 25%

55
Q

VO2

A

consumption (by tissues)

56
Q

CvO2

A

venous oxygen content

15 ml/dL

57
Q
A
  • brackets = O2 carrying capacity (CaO2)
  • 10 is a conversion factor that corrects Hgb g/dL and CO L/min

Example: If CO = 5 L/min and CaO2 = 20 mL/dL, then DO2 = 1,000 mL 02/min.

58
Q

If CO = 5 L/min and CaO2 = 20 mL/dL, then DO2 = ___

A

1,000 mL O2/min

59
Q

External respiration

A
  1. Ventilation
  2. Distribution
  3. Diffusion
  4. Perfusion
60
Q

if PaO2 = 100mmHg, what is SaO2?

61
Q

CO NR

62
Q

CO= HR x SV
What makes up SV?

A
  1. preload
  2. afterload
  3. contractility
63
Q

What makes up interal respiration?

A

EO2 (extraction)
VO2 (consumption)

64
Q

PvO2 & SvO2 NR

A

PvO2 = 40 mmHg
SvO2 = 75%

65
Q

DO2 comprises of these 2 concepts

A
  1. amount of oxygen in blood
  2. speed of delivery to tissue
66
Q

Most oxygen is bound to Hgb, while a small amount is dissolved in the blood. The dissolved oxygen follows this law

A

gas dissolved in a solution = Henry’s law

at a constant temperature, the amount of gas that dissolves in solution is directly proportional to the partial pressure of that gas

67
Q

factors for
Hgb’s O2 carrying capacity
&
O2 dissolved in blood

68
Q

2 Laws that can describe flow

A

Ohm’s

Poiseuille’s (uses Ohm’s, adds vessel diameter, viscosity and tube length)

69
Q

Ohm’s Law

70
Q

How does changing the radius increase flow?

71
Q

Vascular resistance is primarily determined by

A

the radius of the arterioles

Small changes in vessel diameter can yield profound effects on tissue blood flow.

72
Q

Reynolds’ number (Re)

A

predict if the flow is laminar or turbulent

  • Re < 2,000: mostly laminar
  • Re = 2,000 - 4,000: transitional flow
  • Re > 4,000: mostly turbulent
73
Q

vibrations
murmur vs. bruit

A

murmur = valvular Dz
bruit = carotid stenosis

74
Q

Blood viscosity is directly proportional to ___ and inversely proportional to ___.

A

hematocrit

body temperature

When giving PRBCs, we improve flow by diluting w/ NS & warming device

75
Q

Ohms equation as it applies to HD

76
Q

Calculating MAP using CO & SVR

77
Q

Poiseuille’s Law

78
Q

How to determine increase in flow from radius

79
Q

laminar
vs.
turbulent
vs.
transitional

A
  • Laminar: parallel path thru tube
  • Turbulent: non-linear & will create eddies
  • Transitional: laminar along walls & turbulent in center
80
Q

Which flow loses energy? and to what?

A

turbulent

to heat & vibration

81
Q

Viscosity is the result of

A

friction from intermolecular forces as a fluid passes through a tube

82
Q

Blood viscosity is determined by ….. & inversely r/t ….

A

hematocrit & body T

temperature
(↓T = ↑viscosity ➡️ ↑ resistance)

CVT Apex (12 decks)

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