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ANSC 3080 > Midterm 1 - Cardiac Function and Control > Flashcards

Midterm 1 - Cardiac Function and Control Flashcards

1
Q

what are the 2 types of muscle cells that compose the myocardium

A

contractile cells
auto rhythmic cells

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2
Q

what percentage of cells in myocardium physically contract

A

99%

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3
Q

what is require for contraction

A

action potential

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4
Q

what are autorhythmic cells

A

modified non-contractile cells

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5
Q

where are autorhytmic cells

A

concentrated in specific regions of the heart

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6
Q

what do autorhytmic cells do

A

spontaneously generate action potential - pacemaker

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7
Q

what are gap junctions

A

water-filled pores that form open connections between adjacent cells

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8
Q

what do gap junctions allow

A

for ion to move freely from one cell to another - electrical activity can pass from cell to cell

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9
Q

what do the gap junctions have no need for

A

no need for synapse - allow AP to jump rapidly through cells

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10
Q

what is the electrical conduction system generated by

A

pacemaker cells - auto rhythmic

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11
Q

what is the Sino-Atrial (SA) node

A

the command centre (determine heart contraction)

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12
Q

what does the SA node do

A

rhythmical self excitation

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13
Q

what is the difference between SA and AV nodes

A

AV nodes have slower pace, therefore under SA control

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14
Q

do both AV and SA nodes have auto rhythmic activity

A

yes

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15
Q

what is AV node a gateway for

A

electrical conduction between atria and ventricle

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16
Q

what does the bundle of His and Purkinje fibers help

A

to quickly propagate electrical activity from the AV node to the rest of the ventricles

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17
Q

what is the role of the electrical system

A

maintain appropriate heart rate
coordinate contraction of atria and ventricles
coordinate contraction of each chamber

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18
Q

what is the clinical relevance of the electrical system

A

use ECG to determine heart rhythm
problems with conduction - abnormal rhythm (arrhythmia)

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19
Q

during contraction, where do APs from auto rhythmic cells propagate to

A

the contractile cells

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20
Q

what is responsible for muscle contraction

A

action potentials in contractile cells

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21
Q

due to the gap junction, what can the heart be considered

A

a functional syncytium

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22
Q

do to the gap junction, what rule does contraction follow

A

all or none rule

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23
Q

how does the action potential of contractile cells differ from auto rhythmic

A

stable resting membrane potential (no drift)

24
Q

how does the action potential of contractile cells differ from skeletal muscle AP

A

duration
length of refractory period

25
Q

duration of skeletal muscle AP

A

very short, milliseconds

26
Q

duration of contractile muscle AP

A

long, 100s of milliseconds

27
Q

does skeletal muscle have a shorter or longer refractory period than cardiac muscle

A

shorter

28
Q

what is the effect of the sympathetic nervous system

A

stimulates heart rate
increases contractile force
reduces the contraction time

29
Q

how does the SNS stimulate the heart rate

A

stimulates the firing of the SA node and the velocity of the AV node conduction (shorter delay)

30
Q

how does the SNS increase contraction force

A

increase release of Ca2+ from sarcoplasmic store, which increases strength

31
Q

how does the SNS reduce contraction time

A

increases speed of Ca2+ transport (reduces plateau length)

32
Q

what is present in all cardiac cells associated with SNS

A

actions mediated by epinephrine/norepinephrine on B-adrenegic receptors

33
Q

effect of the parasympathetic nervous system (vagus nerve)

A

decreases heart rate

34
Q

how does the PSNS decrease heart rate

A

reduce SA node firing and decreases the velocity of the AV node conduction (longer delay)

35
Q

what occurs in auto rhythmic cells due to PSNS

A

actions mediated by binding of acetylcholine on muscarinic receptors - increase in K+ permeability and hyper polarization increase time required to reach the AP threshold

36
Q

where is the current conducted from heart cells firing AP simultaneously

A

through body fluid to skin

37
Q

what does an ECG do

A

measure heart membrane potential throughout cardiac cycle

38
Q

what do electrodes do in ECG

A

they are placed at different location on skin to read progression of the electric current wave

39
Q

how many waves does a standard ECG have

A

3

40
Q

what are the 3 waves of an ECG

A

P wave
QRS wave
T wave

41
Q

what does the P wave on an ECG show

A

depolarization of atria

42
Q

what does the QRS wave show on ECG

A

depolarization of the ventricles

43
Q

what does the T wave on an ECG show

A

depolarization of the ventricles

44
Q

what is the base-apex lead configuration

A

one lead on left chest, second lead over the neck in jugular groove

45
Q

what does the shape of an ECG depend on

A

where electrodes are placed

46
Q

2 uses of an ECG

A

assessment of heart rate and rhythm
detection of abnormalities

47
Q

how does an ECG measure heart rate

A

measure intervals between cycles

48
Q

how does an ECG measure contraction force

A

measure amplitude of waves

49
Q

how does an ECG measure rhythm

A

measure intervals between each waves

50
Q

how does an ECG detect abnormalities

A

by measuring heart rate under resting conditions
rhythm

51
Q

what is bradycardia

A

slower rate

52
Q

what is tachycardia

A

faster rate

53
Q

what are problems with rate generally associated with

A

the SA node… pacemaker is an artificial SA node

54
Q

how does an ECG detect rhythm

A

abnorally long P-Q interval
ectopic beats (extrasystole)

55
Q

what does an abnormally long P-Q interval mean

A

AV conduction problem

56
Q

what do ectopic beats (extrasystole) mean

A

action potential generated independently of the SA node which results in ventricular extracontraction

ANSC 3080 (21 decks)

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