Lecture 8 – Electrical activity and mechanical events of the cardiac cycle Flashcards Preview

1060 Human form and function > Lecture 8 – Electrical activity and mechanical events of the cardiac cycle > Flashcards

Flashcards in Lecture 8 – Electrical activity and mechanical events of the cardiac cycle Deck (13):
1

Name the cardiac pacemakers from fastest to slowest

Sinus-atrial (SA) node

Atrio-ventricular (AV) node

His bundle

Purkinje fibres

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2

What is another name for the pacemaker current?

funny current

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3

Is the conduction from the to AV fast or slow?

The conduction is via the atrial muscle and it's slow

4

Is conduction through the AV node fast or slow? reason??

The conduction is slow 'AV pause'

• This allows atrial filling to occur before passing on the electrical impulse

• It also prevents transmission of high rates from the atria

5

Is the conduction through the ventricular ‘conduction system’ fast or slow? reason ?

It's fast. It allows the apex to contract before the base

6

What is an ECG?

An electrocardiogram (ECG) is a medical test that detects cardiac (heart) abnormalities by measuring the electrical activity generated by the heart as it contracts. The machine that records the patient's ECG is called an electrocardiograph.

7

PQRST?

P: atrial depolarisation

Q: depolarisation of the septum(towards the atria)

R: Depolarisation of the ventricles (towards the apex)

S: Depolarisation of the ventricles (towards the atria)

T: Repolarisation of the ventricles (towards the endocardium)

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8

How many valves are there and what are they called?

4 Aortic Valve (semilunar) Tricuspid valve (right AV) Pulmonary valve (semilunar) Mitral valve (Bicuspid/Left AV)

9

The cardiac conduction system?

Conduction from SA to AV nodes is via the atrial muscle and is slow

Conduction through the AV node is slow – ‘AV pause’ 

- this allows atrial filling to occur before passing on the electrical impulse

- it also prevents transmission of high rates from the atria 

Conduction through the ventrcular ‘conduction system’ is fast 

This allows the apex to contract before the ‘base’ 

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10

explain Pressure-Volume (P-V) Loops 

and label the diagram

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11

Explain the cardiac cycle (step 1 and 2)

1. left atrial pressure higher than LV pressure

Mitral valve opens

Blood flows into LV 

 

2. Left atrium contracts

- gives atria kick

 

 

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12

Explain the cardiac cycle (steps 3, 4 5 and 6)

3. Left ventricle contracts 

4. Left ventricular 100 pressure rises 

‘Isovolumic’ contraction 

5. Aortic valve opens when ventricular pressure exceeds aortic pressure 

6.Ventricular ejection 

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13

Explain the cardiac cycle (steps 7, 8, 9 and 10)

7. End-systolic pressure falls 

8. LV pressure falls below 100 aortic pressure and aortic valve shuts 80 

9. Period of isovolumic relaxation 

10. LV pressure falls below atrial pressure and mitral valve opens and ventricle refills 

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