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Cell Physiology > Lectures 14-15 > Flashcards

Lectures 14-15 Flashcards

1
Q

What are myocardial autorhythmic cells?

A

can generate their own APs without external input | ensures heart is beating

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2
Q

What is pacemaker potential?

A

unstable membrane potential starting at -60mV | no resting membrane potential

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3
Q

What is the cardiac action potential?

A

the pacemaker potential | no resting membrane potential, always fluctuating

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4
Q

What causes autorhythmic cells to be auto-rhythmic?

A

HCN channels

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5
Q

What does HCN channel stand for?

A

Hyperpolarization-activated Cyclic Nucleotide-gated channels

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6
Q

What are HCN channels?

A

(only in heart) | permeable to Na+/K+ and similar to those voltage-gated channels | 6-segments, S4 = charged | 2nd messengers bind to HCN = modulate activity, activate cAMP

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7
Q

What activates HCN channels?

A

hyperpolarization

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8
Q

How does HCN get activated via hyperpolarization?

A

when intracellular charge becomes negative &raquo_space;> activates and opens HCN &raquo_space;> allows influx of Na+ &raquo_space;> depolarization = AP

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9
Q

What are 2 cyclic nucleotides?

A

cAMP and cGMP

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10
Q

What are the funny currents (If)?

A

the current generated by HCN

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11
Q

What ion drives cardiac AP?

A

calcium (mostly) (na+ = just depolarizes)

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12
Q

What membrane potential is needed to activate HCN channels?

A

-40mV or below

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13
Q

What will an HCN blocker drug cause?

A

inhibits heart cells to propagate another pacemaker potential

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14
Q

What are the 3 main areas where auto-rhythmic cells are found within the heart? Order them from fastest to slowest and indicate intrinsic capacity.

A

sinoatrial (SA) node = 1s | atrioventricular (AV) node = 2s | Purkinje fibers = 3s

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15
Q

Which node initiates the autorhythmic activity and dictates the heartbeat?

A

SA node

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16
Q

What do the AV node and Purkinje fibers act as? How?

A

fail-safe systems | will generate pacemaker potential if SA node fails

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17
Q

What happens if the SA node doesn’t work?

A

AV node generates rhythm but at a slower pace than SA node bc intrinsic capacity = 2s

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18
Q

How do the AV node and Purkinje fibers beat at the pace of the SA node if they have their own rhythm?

A

all are connected and because SA is faster and first, it will send its AP down to the other 2 = make them beat with SA

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19
Q

What autorhythmic cells surround the ventricles?

A

AV bundle (bundle of His)

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20
Q

When does one need a pacemaker?

A

if ventricular pace is too slow

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21
Q

Why does the conduction of AP slow down as it moves through the AV node (AV delay)? What is the purpose for this?

A

the delay is that AV node passes the signal through the Purkinje fibers 1st before contracting ventricles | allows the ventricles to fill with blood

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22
Q

What would happen to the conduction if the AV node malfunctioned and could no longer depolarize?

A

SA and PF = not connected &raquo_space;> SA fires every 1s = atrium contracts every second === PF fires every 3s = ventricles contract every 3s &raquo_space;> ventricles are getting filled 3x more due to atrial contraction per 1 ventricular contraction

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23
Q

Which group of autorhythmic cells contracts the atria?

A

SA node

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24
Q

What will the individual experience due to AV node malfunction?

A

dizziness due to O2 not being delivered at the appropriate time

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25
Q

What does fibrillation mean?

A

loss of coordination of myocardial cells | disconnect = causes fibrillation

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26
Q

What are the 2 types of fibrillation?

A

atrial and ventricular

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27
Q

What is atrial fibrillation? What is the treatment?

A

asymptomatic can lead to stroke | Tx: blood thinners

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28
Q

What is ventricular fibrillation? What is the treatment?

A

ventricles not contracting in unison = cannot pump blood to body = life-threatening | Tx: defibrillators (jump start heart) and pacemakers

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29
Q

What is bradycardia?

A

slow heart rate (under 60bpm)

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30
Q

What is tachycardia?

A

fast heart rate (over 100bpm)

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31
Q

What is angina pectoris?

A

chest pain due to lack of blood flow to the heart

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32
Q

What is arrhythmia?

A

irregular heart rate

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33
Q

How does parasympathetic stimulation affect the heart?

A

hyperpolarizes membrane potential | slows depolarization === slows heart rate

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34
Q

How does sympathetic stimulation affect the heart?

A

depolarizes membrane potential = speed up pacemaker potential = speed up heart rate

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35
Q

What is another term for epinephrine?

A

adrenaline

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36
Q

What nerve innervates the heart?

A

vagus nerve

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37
Q

What is the term that is used in ECG denoting where the 3 leads/electrodes are connected on the body?

A

Einthoven’s triangle = right and left arms, left leg

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38
Q

What does the P-wave represent?

A

depolarization of atria

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39
Q

What does the QRS complex present?

A

depolarization of ventricles (ventricles onctract = big force = large part of graph) | small atrial repolarization

40
Q

What does the T-wave represent?

A

repolarization of ventricle

41
Q

What are the 3 things to look for in an ECG?

A

heart rate | rhythm is regular | all waves and segment present

42
Q

What does the ECG measure?

A

the overall change in voltage that the heart is giving out

43
Q

What is the 3rd-degree block in an abnormal ECG?

A

complete disconnect of the SA and AV nodes from the PF | regular 1s P-waves = SA works fine | QRS complex not following P-waves = happening at PF rhythm pace due to disconnect

44
Q

What is atrial fibrillation in an abnormal ECG?

A

no P-waves | QRS complex = noisy and weird | irregular rhythm

45
Q

What is happening in the heart during atrial fibrillation?

A

atria not contracting uniformly = blood not flowing into ventricles = cannot pump blood efficiently

46
Q

What is happening in the heart during a 3rd-degree block?

A

SA node works fine | PF contracts ventricles at own rhythm = every 3 seconds

47
Q

What is ventricular fibrillation in an abnormal ECG?

A

just a bunch of squiggly waves

48
Q

What is happening in the heart during ventricular fibrillation?

A

ventricles = no depolarization = no contraction = can’t pump blood to body

49
Q

What is a second-degree block on an abnormal ECG?

A

Some P-waves are irregular and some match up with the PQRST-set

50
Q

What is happening in the heart during a second-degree block?

A

PF not always firing in sync with SA and AV | heart skips a beat

51
Q

What is the 1st-degree block?

A

big delay between P-wave and QRS-T bc Sa not functioning effectively = heart rate is slower

52
Q

How is using a 12-lead ECG beneficial?

A

gives more info | can indicate heart tissue damage and heart attacks

53
Q

Which ANS response (parasympathetic or sympathetic) has a greater influence on the heart?

A

parasympathetic - constantly slowing it down

54
Q

What receptors are activated in the parasympathetic pathway of the heart?

A

M2 muscarinic receptors

55
Q

What kind of nerve is the vagus nerve in relation to the heart?

A

pre-ganglionic

56
Q

What type of neurotransmitter system does the sympathetic pathway use to act on the heart?

A

cholinergic system

57
Q

Where are epinephrine and norepinephrine released from?

A

Epi = adrenal gland | sympathetic post-ganglionic neurons

58
Q

Which neurotransmitter (NE or Epi) better binds to beta-1 receptors?

A

Epi due to structure

59
Q

What is phospholamban?

A

regulatory protein activated by cAMP

60
Q

What is systole?

A

contraction of heart muscle | top number

61
Q

What are the 2 types of systole?

A

atrial and ventricular

62
Q

What is diastole?

A

heart muscle relaxes, expands due to passive filling of blood | bottom number

63
Q

What is the Frank-Starling Law?

A

relationship between the stretch of heart muscle and the force generated when the heart muscle contracts | force generated will push certain amount of blood

64
Q

What is the end-diastolic volume (EDV)?

A

volume of blood in the filled chamber as ventricle is relaxing = stretch determines sarcomere length

65
Q

What is stroke volume?

A

indication of force of contraction

66
Q

What is the end-diastolic volume determined by?

A

venous return

67
Q

What are 3 ways that contribute to venous return?

A

skeletal muscle pump | respiratory pump | sympathetic innervation of veins

68
Q

What is the skeletal pump?

A

constriction of veins due to contraction of skeletal muscles that return blood to the heart

69
Q

What is inotropic effect?

A

refers to the force of contraction

70
Q

What are inotropic agents? Example of one.

A

any chemical that affects contractility and its influence is inotropic effect | NE and epi

71
Q

What is a positive inotropic effect?

A

increase force of contraction | NE and epi

72
Q

What is a negative inotropic effect?

A

decrease force of contraction

73
Q

What is ejection fraction?

A

how much volume is being ejected with that one contraction (stroke volume / EDV)

74
Q

What is cardiac output?

A

output of blood from the heart affected by stroke volume and heart rate

75
Q

What is stroke volume determined by?

A

force of contraction in ventricles

76
Q

What 2 things influence the force of ventricular contraction?

A

contractility | EDV

77
Q

What is end diastolic volume vary with?

A

venous return

78
Q

What is the respiratory pump?

A

changes in abdominal pressure during breathing

79
Q

What happens as vessels get narrower and narrower?

A

will decrease on how much blood can go through = increase in pressure

80
Q

Why do arteries have a high amount of elastic tissue and smooth muscles?

A

to withstand great pressure changes

81
Q

What is the purpose of having less fibrous tissue encapsulating the blood vessels?

A

increase diffusion of O2 and nutrients as fibrous tissue inhibits this

82
Q

What is the purpose of endothelium on blood vessels?

A

lines the vessels

83
Q

What is vasoconstriction? Affect from NE?

A

increase of NE = narrowing of vessel diameter

84
Q

What is vasodilation? Affect from NE?

A

decrease of NE = widening of vessel diameter

85
Q

What is the function of capillary beds and what feature allows this function?

A

site of O2 and nutrient exchange | porous

86
Q

What are the 2 types of capillaries?

A

continuous and fenestral

87
Q

What are continuous capillaries?

A

continuous with other vessels | leaky junctions = openings where nutrients and O2 can pass

88
Q

What are fenestrated capillaries?

A

highly porous | for demanding tissues

89
Q

What is transcytosis?

A

transport of things from one side to another through vesicles | vesicles can form channel-like openings

90
Q

How can BP be artificially controlled?

A

block beta 1 receptors

91
Q

What are fenestrations?

A

breaking of endothelial cells allowing nutrients and materials to flow through cells

92
Q

What is blood flow opposed by?

A

resistance of the system

93
Q

What is needed in order for blood to flow?

A

pressure gradient from high to low

94
Q

What are the 3 factors that affect resistance in blood flow?

A

radius and length of blood vessels | viscosity of blood

95
Q

What is the primary determinant of the velocity of blood flow?

A

the shape of the cross-sectional area of vessels (some are round and others are flat)

96
Q

What branch of the ANS controls most vascular smooth muscle?

A

sympathetic

97
Q

What type of receptors are on vessels for the ANS input?

A

alpha-adrenergic receptors

Cell Physiology (13 decks)

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