cardiac physiology Flashcards

1
Q

is the resting membrane potential negative or positive

A

negative

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2
Q

what functional response does an action potential cause

A

nerve impulse or muscle contraction

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3
Q

what is an action potential generated by

A

rapid changes in electrochemical gradients across the cell membrane like movement of ions

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4
Q

what is the movement of ions in and out of the cell controlled by

A

specific ion channels embedded in the membrane

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5
Q

name the 3 ions involved in membrane potential

A

K+, Na+, Ca2+

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6
Q

what is depolarisation

A

membrane potential gets less negative

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7
Q

what is depolarisation in muscles

A

membrane potential goes positive

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8
Q

what is repolarisation

A

potential returns to negative resting potential

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9
Q

what is hyperpolarisation

A

membrane potential becomes more negative than resting potential

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10
Q

how to detect and monitor action potentials generated by myocytes

A

electrocardiogram (ECG)

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11
Q

what is excitation-contraction coupling and how is it achieved

A

-process which an electrical action potential leads to cardiac muscle cells contracting

-achieved by converting a chemical signal into mechanical energy via contractile proteins

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12
Q

what is contraction of actin and myosin filaments dependent on

A

calcium signalling

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13
Q

what do gap junctions do

A

link cytoplasm of neighbouring cells and enable rapid passage of ions/small molecules

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14
Q

structural features of myocardium that help membrane potential changes

A

intercalated discs- tight interactions, electrical coupling, branched to extend interconnections, single nucleus, lots of mitochondria

synchronised contractions- ensures cardiomyocytes work together, syncytium cardiac muscle

gap junctions- enable rapid passage of ions/small molecules

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15
Q

how do intercalated discs facilitate membrane potential changes

A

enable tight interactions and help electrical coupling, branched fibres to extend interconnections, single nucleus, abundance of mitochondria

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16
Q

describe the pathway of intrinsic waves of excitation

A

SA node to AV node to myocytes to bundle of His and purkinje fibres

16
Q

which node is also called the cardiac pacemaker

A

sinoatrial node

16
Q

what does the AV node do after receiving signals from the SA node

A

passes signals to bundle of His, depolarises both ventricles, branches out

16
Q

how does the sinoatrial node cause an action potential

A

excites the right atrium then the left atrium then the atrioventricular node

16
Q

autorhythmic cells are also called

A

pacemaker cells

16
Q

what controls sinoatrial activity

A

autonomic nervous system signals

16
Q

what does the influx of K+ cause

A

repolarisation

16
Q

what does the influx of CA2+ cause

A

depolarisation of SAN

16
Q

what does the influx of Na+ cause

A

depolarisation of cardiomyocytes

16
Q

describe the action potential in autorhythmic/pacemaker cells

A

-no external stimulation to initiate action potential, undergoes spontaneous depolarisation when threshold is met

1.slow depolarisation caused by Na+ leaving cell faster than K+ through If channels

2.CA2+ channels open as membrane approaches threshold, causes more rapid depolarisation

3.K+ channels open causing efflux of K+ and membrane repolarises

17
Q

describe the general shape of the graph of action potential of pacemaker cells and list the stages

A

slow depolarisation, action potential, repolarisation
graph-see notes

17
Q

what does efflux mean

A

movement out of cell

17
Q

describe the action potential of cardiomyocytes (contractile system)

A

resting phase- resting potential (-90mV) due to constant leak of K+, sodium and calcium channels closed

depolarisation- NA+ channels open and ions enter, depolarises inside cell (cell gets more positive inside), causes action potential

early repolarisation- cell is slightly positive, outward flow of K+ returns transmembrane potential to 0

plateau phase- K+ leave cell via delayed rectifier K+ channels, CA2+ go in cell, electrically balanced, tmp maintained at a plateau below 0 mV (refractory period)

repolarisation- CA2+ channels inactivated (no more going in cell), more K+ leaving cell so cell gets more negative

17
Q

describe the general shape of the graph of action potential of cardiomyocytes and list the stages

A

resting, depolarisation, early repolarisation, plateau, repolarisation

graph- see notes

18
Q
A