Electrical Activity of the Heart Flashcards

1
Q

Why does cardiac muscle have a longer depolarisation time than skeletal muscle?

A

To allow for regulation of the amount of calcium getting into the cell, the calcium released inside the cell and so the strength of contraction

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2
Q

In cardiac muscle what effect does a long refractory period have?

A

Stops the cardiac muscle from exhibiting tetanus

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3
Q

What does cardiac muscle form to allow it to function as a unit?

A

A functional syncytium

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4
Q

What allows the functional syncytium to work?

A

Gap junctions - electrical connections

Desmosomes - physical connections

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5
Q

What is a functional syncytium?

A

A group of cells that are synchronised electrically in an action potential

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6
Q

Why does cardiac muscle have a long refractory period?

A

Because it has a long action potential

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7
Q

What do cardiac muscle cells with unstable resting membrane potentials act as?

A

Pacemakers

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8
Q

In non-pacemaker cells what causes the plateau?

A

Increase in calcium ions inside the cell because of L-type calcium channels
Decrease in potassium ions inside the cell

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9
Q

In non-pacemaker cells what is the initial depolarisation caused by?

A

Increase in sodium ions inside the cell

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10
Q

How is the pacemaker potential generated?

A

Gradual decrease in potassium ions
Early increase in sodium ions
Late increase in calcium ions by t-type channels

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11
Q

What drugs modulate the electrical activity of the heart?

A

Calcium ion channel blockers

Cardiac glycosides

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12
Q

What do calcium ion channel blockers do?

A

Decrease force of contraction

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13
Q

What do cardiac glycosides do?

A

Increase force of contraction

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14
Q

How does temperature effect electrical activity of the heart?

A

Increases it by 10 beats per minute for each degrees increase

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15
Q

What does hyperkalemia do to the heart?

A

Fibrillation and heart block

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16
Q

What does hypokalemia do to the heart?

A

Fibrillation and heart block

17
Q

What does hypercalcemia do to the heart?

A

Increased heart rate and increased force of contraction

18
Q

What does hypocalcemia do to the heart?

A

Decreases heart rate and force of contraction

19
Q

Which part of the special conducting system is the pacemaker?

A

The sinoatrial node

20
Q

Which part of the special conducting system is the delay box?

A

The atrioventricular node

21
Q

What are the purkinje fibres?

A

The rapid conduction system