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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
What does fibrillation mean?
loss of coordination of myocardial cells | disconnect = causes fibrillation
26
What are the 2 types of fibrillation?
atrial and ventricular
27
What is atrial fibrillation? What is the treatment?
asymptomatic can lead to stroke | Tx: blood thinners
28
What is ventricular fibrillation? What is the treatment?
ventricles not contracting in unison = cannot pump blood to body = life-threatening | Tx: defibrillators (jump start heart) and pacemakers
29
What is bradycardia?
slow heart rate (under 60bpm)
30
What is tachycardia?
fast heart rate (over 100bpm)
31
What is angina pectoris?
chest pain due to lack of blood flow to the heart
32
What is arrhythmia?
irregular heart rate
33
How does parasympathetic stimulation affect the heart?
hyperpolarizes membrane potential | slows depolarization === slows heart rate
34
How does sympathetic stimulation affect the heart?
depolarizes membrane potential = speed up pacemaker potential = speed up heart rate
35
What is another term for epinephrine?
adrenaline
36
What nerve innervates the heart?
vagus nerve
37
What is the term that is used in ECG denoting where the 3 leads/electrodes are connected on the body?
Einthoven's triangle = right and left arms, left leg
38
What does the P-wave represent?
depolarization of atria
39
What does the QRS complex present?
depolarization of ventricles (ventricles onctract = big force = large part of graph) | small atrial repolarization
40
What does the T-wave represent?
repolarization of ventricle
41
What are the 3 things to look for in an ECG?
heart rate | rhythm is regular | all waves and segment present
42
What does the ECG measure?
the overall change in voltage that the heart is giving out
43
What is the 3rd-degree block in an abnormal ECG?
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
What is atrial fibrillation in an abnormal ECG?
no P-waves | QRS complex = noisy and weird | irregular rhythm
45
What is happening in the heart during atrial fibrillation?
atria not contracting uniformly = blood not flowing into ventricles = cannot pump blood efficiently
46
What is happening in the heart during a 3rd-degree block?
SA node works fine | PF contracts ventricles at own rhythm = every 3 seconds
47
What is ventricular fibrillation in an abnormal ECG?
just a bunch of squiggly waves
48
What is happening in the heart during ventricular fibrillation?
ventricles = no depolarization = no contraction = can't pump blood to body
49
What is a second-degree block on an abnormal ECG?
Some P-waves are irregular and some match up with the PQRST-set
50
What is happening in the heart during a second-degree block?
PF not always firing in sync with SA and AV | heart skips a beat
51
What is the 1st-degree block?
big delay between P-wave and QRS-T bc Sa not functioning effectively = heart rate is slower
52
How is using a 12-lead ECG beneficial?
gives more info | can indicate heart tissue damage and heart attacks
53
Which ANS response (parasympathetic or sympathetic) has a greater influence on the heart?
parasympathetic - constantly slowing it down
54
What receptors are activated in the parasympathetic pathway of the heart?
M2 muscarinic receptors
55
What kind of nerve is the vagus nerve in relation to the heart?
pre-ganglionic
56
What type of neurotransmitter system does the sympathetic pathway use to act on the heart?
cholinergic system
57
Where are epinephrine and norepinephrine released from?
Epi = adrenal gland | sympathetic post-ganglionic neurons
58
Which neurotransmitter (NE or Epi) better binds to beta-1 receptors?
Epi due to structure
59
What is phospholamban?
regulatory protein activated by cAMP
60
What is systole?
contraction of heart muscle | top number
61
What are the 2 types of systole?
atrial and ventricular
62
What is diastole?
heart muscle relaxes, expands due to passive filling of blood | bottom number
63
What is the Frank-Starling Law?
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
What is the end-diastolic volume (EDV)?
volume of blood in the filled chamber as ventricle is relaxing = stretch determines sarcomere length
65
What is stroke volume?
indication of force of contraction
66
What is the end-diastolic volume determined by?
venous return
67
What are 3 ways that contribute to venous return?
skeletal muscle pump | respiratory pump | sympathetic innervation of veins
68
What is the skeletal pump?
constriction of veins due to contraction of skeletal muscles that return blood to the heart
69
What is inotropic effect?
refers to the force of contraction
70
What are inotropic agents? Example of one.
any chemical that affects contractility and its influence is inotropic effect | NE and epi
71
What is a positive inotropic effect?
increase force of contraction | NE and epi
72
What is a negative inotropic effect?
decrease force of contraction
73
What is ejection fraction?
how much volume is being ejected with that one contraction (stroke volume / EDV)
74
What is cardiac output?
output of blood from the heart affected by stroke volume and heart rate
75
What is stroke volume determined by?
force of contraction in ventricles
76
What 2 things influence the force of ventricular contraction?
contractility | EDV
77
What is end diastolic volume vary with?
venous return
78
What is the respiratory pump?
changes in abdominal pressure during breathing
79
What happens as vessels get narrower and narrower?
will decrease on how much blood can go through = increase in pressure
80
Why do arteries have a high amount of elastic tissue and smooth muscles?
to withstand great pressure changes
81
What is the purpose of having less fibrous tissue encapsulating the blood vessels?
increase diffusion of O2 and nutrients as fibrous tissue inhibits this
82
What is the purpose of endothelium on blood vessels?
lines the vessels
83
What is vasoconstriction? Affect from NE?
increase of NE = narrowing of vessel diameter
84
What is vasodilation? Affect from NE?
decrease of NE = widening of vessel diameter
85
What is the function of capillary beds and what feature allows this function?
site of O2 and nutrient exchange | porous
86
What are the 2 types of capillaries?
continuous and fenestral
87
What are continuous capillaries?
continuous with other vessels | leaky junctions = openings where nutrients and O2 can pass
88
What are fenestrated capillaries?
highly porous | for demanding tissues
89
What is transcytosis?
transport of things from one side to another through vesicles | vesicles can form channel-like openings
90
How can BP be artificially controlled?
block beta 1 receptors
91
What are fenestrations?
breaking of endothelial cells allowing nutrients and materials to flow through cells
92
What is blood flow opposed by?
resistance of the system
93
What is needed in order for blood to flow?
pressure gradient from high to low
94
What are the 3 factors that affect resistance in blood flow?
radius and length of blood vessels | viscosity of blood
95
What is the primary determinant of the velocity of blood flow?
the shape of the cross-sectional area of vessels (some are round and others are flat)
96
What branch of the ANS controls most vascular smooth muscle?
sympathetic
97
What type of receptors are on vessels for the ANS input?
alpha-adrenergic receptors

Cell Physiology (13 decks)

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