Cardiac Action Potentials Flashcards
(107 cards)
1
Q
the heart is an _ controlled pump
A
electronically
2
Q
what is autorhythmicity
A
beating rhythmically without external stimuli
3
Q
where does excitation originate
A
pacemaker cells in the SA NODE
4
Q
what do pacemaker cells do
A
initiate heart beat
5
Q
where is the SA node located
A
upper right atrium close to superior vena cava entrance
6
Q
what is sinus rhythm
A
when the heart is controlled by SA node
7
Q
cells in SA node generate regular _ _ potentials
A
spontaneous pacemaker
8
Q
do SA node cells have a stable resting membrane potential
A
no
9
Q
pacemaker potential is
A
slow drift towards AP spontaneously
10
Q
once the Vm reaches the threshold what happens
A
an AP in generated
11
Q
pacemaker potential is a slow _
A
depolarisation
12
Q
depolarisation occurs due to a _ in K+ _
A
decrease, efflux
13
Q
depolarisation occurs due to an _ of Na+
A
influx
14
Q
depolarisation occurs due to an _ of Ca2+
A
influx
15
Q
depolarisation is
a. more negative to positive
b. more positive to negative
A
more negative to more positive
16
Q
during depolarisation what type of channel allows an influx of Ca2+
A
T-type Ca2+ channels
17
Q
if a cell retains more positive charges it moves towards
a. hyperpolarisation
b. depolarisation
A
depolarisation
18
Q
phase 0 is the
A
rising phase
19
Q
phase 0 is caused by activation of what type of channels
A
L-type Ca2+ channels
20
Q
L-type Ca2+ channels are
a. long-lasting
b. short-lasting
A
long-lasting
21
Q
once L-type Ca2+ channels open during depolarisation what occurs
a. Ca2+ efflux
b. Ca2+ influx
A
Ca2+ influx
22
Q
repolarisation (falling phase) is caused by which two things
A
L-type Ca2+ inactivation
K+ channels activation
23
Q
activation of K+ channels during repolarisation results in
a. K+ efflux
b. K+ influx
A
K+ efflux
24
Q
excitation starts at the
A
SA node
25
excitation spreads across the atria by
cell-to-cell conduction
26
excitation goes from the SA node to the
AV node
27
excitation at the AV node is
delayed
28
why is excitation delayed at the AV node
to allow atria to finish contraction before ventricles contract
29
after reaching the AV node where does excitation spread next
bundle of His (L+R)
30
after the bundle of His where does excitation spread next
purkinje fibres
31
after purkinje fibres where does excitation spread next
into the ventricles
32
excitation spreads from the purkinje fibres to the ventricles via
cell to cell interactions
33
excitation spreads
a. slowly
b. quickly
quickly
34
what allows cell-to-cell interactions
gap junctions
35
what two structures make up the intercalated disk
desmosomes, gap junctions
36
what is the AV node
small bundle of specialised cardiac cells
37
where is the AV node located
right atrium base, above junction of atria and ventricles
38
the AV node is the only point of contact between what
atria and ventricles
39
```
the AV node has _ _
a. small cells
b.big cells
and a _ conduction velocity
a. fast
b.slow
```
small cells
| slow
40
excitation spreads from the SA node to the AV node mainly through _ _ but also via some _ _
gap junctions
| internodal pathways
41
in the ventricular muscles excitation is spread through ...
cell-to-cell conduction
42
in contractile muscle cells what is the resting membrane potential
-90mV
43
what causes the rising phase of AP
a fast Na+ influx
44
the rising phase of AP is
a. hyperpolarisation
b. depolarisation
depolarisation
45
phase 0 is the
rising phase
46
phase 1 is
early repolarisation
47
phase 2 is the
plateau phase
48
phase 3 is
final repolarisation
49
phase 4 is the
resting phase
50
```
during phase 0 the Vm _ reverses
a. rapidly
b. slowly
to _ mV
a. +40
b. +20
c. -20
d. -40
```
rapidly
| +20
51
in phase 0 the Vm becomes more _
a. positive
b. negative
positive
52
in phase 1 the Vm becomes more _
a. positive
b. negative
negative
53
in phase 2 there is a _ influx
a. positive
b. negative
positive
54
in phase 3 the Vm becomes more _
a. positive
b. negative
negative
55
what 3 phases are present on intracellular AP
0, 3, 4
56
what happens during the plateau phase
the membrane potential is maintained at its peak for a few hundred milliseconds
57
the plateau phase is unique to contractile cardiac cells, true or false
true
58
what is the plateau phase mainly due to
influx of Ca2+
59
during plateau what type of channels do Ca2+ ions come in through
L-type
60
what two things is the falling phase of AP due to
inactivation of Ca2+ channels (efflux)
| activation of K+ channels (efflux)
61
what is a normal heart rate
60-100bpm
62
bradycardia is a heart rate of
under 60 bpm
63
tachycardia is a heart rate of
over 100 bpm
64
heart rate is mainly influenced by the _ _ system
autonomic nervous
65
sympathetic stimulation _ heart rate
a. increases
b. decreases
decreases
66
parasympathetic stimulation _ heart rate
a. increases
b. decreases
increases
67
changes in heart rate usually involve _ action of sympathetic and parasympathetics
reciprocal
68
what does vagal tone mean
the continuous influence of the vagus nerve on the SA node under resting conditions
69
the vagus nerve is part of the _ nerve supple
a. sympathetic
b. parasympathetic
parasympathetic
70
vagus nerve supplies _ and _ _
SA and AV node
71
what is the vagus nerves neurotransmitter
acetyl choline
72
what receptors do acetyl choline act through
muscarinic M2
73
what is a competitive inhibitor of acetyl choline
atropine
74
when the vagus is stimulated what happens in the cell
takes the cell longer to hyperpolarise and reach the threshold
75
what happens to the drift in a cell when the vagus is stimuated
it becomes slower
76
the gradient of the pacemaker potential slope _ and so to does the _ _
a. increases
b. decreases
decreases
| AP frequency
77
what is a negative chronotropic effect
when something causes the heart rate to decrease
78
cardiac sympathetic nerves supply the _ and _ _ and _
SA and AV nodes
| myocardium
79
sympathetic stimulation _ heart rate and _ AV nodal delay
increases
| decreases
80
what is a positive inotropic effect
an increased force of contraction
81
sympathetic stimulation causes an increase _ _ _
force of contraction
82
what is the neurotransmitter of sympathetic stimulation
noradrenaline
83
what receptors does noradrenaline act through
beta1 adrenoreceptors
84
due to sympathetic stimulation the gradient of the pacemaker potential _
a. increases
b. decreases
increases
85
what is positive chronotropic effects
increase in heart rate
86
noradrenaline causes the AP frequency to _
a. increase
b. decrease
increase
87
acetyl choline causes the AP frequency to _
a. increase
b. decrease
decrease
88
sympathetic stimulation causes the slope of pacemaker potential to
a. increase
b. decrease
increase
89
parasympathetic stimulation causes the slope of pacemaker potential to
a. increase
b. decrease
decrease
90
sympathetic stimulation causes heart rate to
a. increase
b. decrease
increase
91
parasympathetic stimulation causes heart rate to
a. increase
b. decrease
decrease
92
sympathetic stimulation causes the pacemaker cells K+ efflux to
a. increase
b. decrease
decrease
93
parasympathetic stimulation causes pacemaker cells K+ efflux to
a. increase
b. decrease
increase
94
sympathetic stimulation causes the pacemaker cell Na+ and Ca2+ influx to
a. increase
b. decrease
increase
95
parasympathetic stimulation causes pacemaker cell Na+ and Ca2+ to
a. increase
b. decrease
decrease
96
sympathetic stimulation causes the AV nodal delay to
a. increase
b. decrease
decrease
97
parasympathetic stimulation causes AV nodal delay to
a. increase
b. decrease
increase
98
what are the two types of AP in the heart
fast response
| slow response
99
Na+ always _ a cell via a channel
a. enters
b. exits
enters
100
K+ always _ a cell via a channel
a. enters
b. exits
exits
101
Ca2+ always _ a cell via a channel
a. enters
b. exits
enters
102
Na+ entering the cell causes _
a. depolarisation
b. polarisation
depolarisation
103
K+ leaving the cell causes _
a. depolarisation
b. polarisation
polarisation
104
Ca2+ entering the cell causes _
a. depolarisation
b. polarisation
depolarisation
105
what does length of cardiac muscle stop
heart beating too quickly
106
where does a fast response AP occur (3)
atrial and ventricular muscles
| purkinje fibres
107
where does a slow response AP occur (2)
SA node, AV node
