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W/Physiology > Topic list 2 > Flashcards

Topic list 2 Flashcards

1
Q

AP duration in myocytes

A

t= 200-400ms

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2
Q

AP conduction velocity in myocytes

A

v= 1m/s

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3
Q

What is the cardiac vector?

A

The vector sum of all cardiac electrical activity at any moment

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4
Q

Usual duration of PR/PQ interval

A

0.12-0.2 seconds

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5
Q

Usual duration of QRS interval

A

0.06-0.1 seconds

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6
Q

Usual amplitude of QRS interval

A

0.5-2mV

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7
Q

Usual duration of QT interval

A

0.36-0.4 seconds

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8
Q

What is the electrical axis of the heart?

A

It is the mean direction of the action potentials traveling through the ventricles during ventricular depolarization

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9
Q

How does unipolar recording work?

A

Two limbs are connected through electrical resistances to the negative terminal and the third limb is connected to the positive terminal

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10
Q

What is the isoelectric method for finding the electrical axis of the heart? (2)

A
  • find the lead where QRS is isoelectric (usually III or aVL) and find the perpendicular to that : it’s the electrical axis
  • In the perpendicular, look at R + or - to determine the direction of the axis
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11
Q

What is the EDV value?

A

About 130-140mL

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12
Q

What is the ESV value?

A

About 60mL

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13
Q

What is the ejection fraction?

A

SV/EDV

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14
Q

What is the usual range for the ejection fraction?

A

0.5

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15
Q

What is the usual max dp/dt?

A

1000-1200 mmHg/s

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16
Q

What are cardiac glycosides?

A

drugs that inhibit the Na+/K+ ATPase on the outer cell surface

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17
Q

What is the value of CO at resting conditions?

A

5600mL/min

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18
Q

What happens under steady-state conditions to CO?

A

It must then be equal to venous return

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19
Q

What is the CI?

A

it is a haemodynamic parameter that related the cardiac output from the left ventricle in one minute to the body surface area.

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20
Q

What is TPR?

A

total peripheral resistance : the ratio of the arteriovenous pressure difference to the flow through the entire systemic circulation (essentially CO)

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21
Q

What are the 3 ways of increasing preload?

A
  • Increasing EDV
  • Increasing filling time
  • Frank Starling law
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22
Q

What are the 3 ways of increasing venous return?

A
  • muscular milking
  • by breathing (respiratory pump due to lower thoracic pressure than abdominal),
  • sympathetic system stimulation : NE stimulates muscle constriction.
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23
Q

What is the Frank Starling law?

A

When you increase the stretch of the heart, it allows for more cross-bridges to be active. So greater stretch means greater force of contraction.

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24
Q

What is the afterload?

A

The amount of resistance to overcome for the left ventricle to eject blood into the aorta

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25
Q

What are 3 ways to increase the afterload?

A
  • increasing peripheral resistance, which increases the pressure in the aorta
  • if there’s sclerotic sections, blockage
  • high blood pressure
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26
Q

What does the ESPVR describe?

A

The maximum pressure that can be developped by the left ventricle at any given volume

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27
Q

What are 4 things that affect contractility that get phosphorylated by PKA when NE/E binds to the B1 AR?

A
  • L type VDCC
  • Troponin I
  • Phospholamban (PLB)
  • Ryanodine receptor
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28
Q

What are the 3 techniques for determining CO?

A
  • Fick’s principle
  • Dilution technique
  • Thermodilution technique
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29
Q

What are the 4 parts of microcirculation?

A
  • Terminal arterioles
  • Metarterioles
  • Capillaries
  • Venules
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30
Q

What are the 4 types of capillaries?

A
  • Fenestrated
  • Tight
  • Continuous
  • Sinusoidal
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31
Q

What keeps the RBCs from touching the endothelial wall at all times?

A

The glycocalyx inner covering of the capillary endothelium

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32
Q

What is the Bayliss effect?

A

The intrinsic capability of a body part to maintain a constant blood flow despite changes in perfusion pressure

33
Q

What are the 3 types of mechanisms responsible for autoregulation?

A
  • Metabolic
  • Myogenic
  • Endothelial
34
Q

Which 6 metabolites can cause functional hyperemia?

A
  • adenosine
  • CO2
  • K+
  • H+
  • Lactate
  • Pi
35
Q

What is nitric oxide synthesized from?

A

arginin and O2 by no synthase

36
Q

What is the frequency for SA node?

A

100

37
Q

What is the frequency for AV and bundle of His?

A

40-60

38
Q

What is the frequency for bundle branches / purkinje?

A

20-40 (so low it can’t even pump properly)

39
Q

What is the special property of the pacemaker cells?

A

Automaticity : they spontaneously depolarize and generate an AP

40
Q

Which channel is involved for If current?

A

HCN4 (hyperpolarization activated cyclic nucleotide gated)

41
Q

What activates this HCN4? (2)

A
  • Hyperpolarization < -50 mV

- increase in cAMP

42
Q

What activates T-VDCC channel?

A

Reaching the -55mV threshold

43
Q

What drug can inhibit the If?

A

ivabradine

44
Q

What can inhibit the T channels?

A

verapamil

45
Q

What channel does IK1 use?

A

inwardly rectifying K channel (IRKC)

46
Q

What is IKTO?

A

Transient outwards potassium current

47
Q

What drug can inactivate the gNa?

A

lidocaine

48
Q

Which drug can inactivate L-type VDCC?

A

dihydropopiridine

49
Q

At what potential does early repolarization happen?

A

20mV

50
Q

What are the 3 main causes of functional hyperemia in the heart?

A
  • Adenosine
  • O2
  • K+
51
Q

What are the causes for releasing adenosine in functional hyperemia? (2)

A
  • insufficient coronary blood flow

- fall in myocardial pO2

52
Q

What are the 4 ways of affecting short term local control of circulation?

A
  • Myogenic mechanism (Bayliss)
  • Metabolic mechanism (Bayliss)
  • Shear stress effect
  • Humoral regulation
53
Q

What is the effect of decreased pO2 / increased pCO2 in the parenchyma? (3)

A

Decreased pH
Decreased adenosine
Increased lactate

54
Q

What is the effect of decreased pO2 / increased pCO2 in the smooth muscle cell? (2)

A

Decreased ATP

Increased K+ (hyperpolarization)

55
Q

What is the effect of decreased pH on the SMC?

A

Increased K+ (bc channels work well ig) int he cell, so decreased Em, so harder to make it contract

56
Q

What is the effect of NO?

A

Activates soluble guanylyl cyclase in VSMCs to increase cGMP, which will cause vasodilation by decreasing myofilaments affinity to Ca2+

57
Q

What are the end products of the cascade triggered by Renin? (3)

A

Angiotensin II, ADH, aldosterone

58
Q

How much lymph is produced per hour?

A

120mL/hour

59
Q

How much lymph is filtrated per day?

A

20L/day

60
Q

How much lymph is reabsorbed per day?

A

16-18L /day

61
Q

How much of the total blood volume do the veins contain?

A

About 65% of the total blood volume

62
Q

What are the 3 main differences between the slow and fast response AP?

A
  1. value of RMP
  2. nodal tissue: resting pot keeps changing
  3. Myocardial AP is longer than nodal and both are longer than neuronal
63
Q

What are the 5 ion currents involved in the generation of AP?

A
  1. Funny current (Na)
  2. Ica,t
  3. Ica,L
  4. Ik
  5. Ik, ach (inward rectifying)
64
Q

Which channel is involved for If current?

A

HCN4 (hyper polarization activated cyclic nucleotide gated)

65
Q

What activates HCN4? (2)

A
  • Hyperpolarization under -50mV

- cAMP

66
Q

What activates T-VDCC channel?

A

-50mV potential threshold

67
Q

What drug can inhibit the If?

A

Ivabradine

68
Q

What can inhibit the T channels?

A

verapramil

69
Q

Which drug increases HR?

A

Atropine

70
Q

What is inotropy?

A

Any effect that tries to increase contractility of the heart

71
Q

What 4 things is contractility dependent on?

A

preload, nervous system, hormones, ions

72
Q

What is the typical flow in a capillary when 1/4th are open?

A

About 8pL/s

73
Q

What is compliance?

A

The ability to distand / increase in volume with an increase in transmural pressure

74
Q

Which receptor does adenosine bind to in the heart?

A

gi coupled A1 receptor

75
Q

What are the 3 major endothelial vasoactive substances?

A

endothelin, NO, prostacyclin

76
Q

What are the 2 stages of formation of CSF?

A

ultrafiltration of plasma and secretion into the ventricles

77
Q

What are the 4 types of capillaries?

A
  • Continuous capillaries
  • Fenestrated capillaries
  • Sinusoidal capillaries
  • Tight capillaries
78
Q

What are the 3 types of forces that participate in venous return?

A
  • Vis a tergo
  • Vis a latere
  • Vis a fronte
79
Q

Which type of innervation is dominant in regulation of venal blood flow?

A

sympathetic innervation by releasing catecholamines

W/Physiology (31 decks)

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