Conducting A Heart Beat

Question 1

The heart is ….

Answer 1

Myogenic, no neural control, beats independently

Question 2

Where does contraction begin?

Answer 2

SAN (60-80 bpm, autorythmic sinus pattern)

Wall of right atrium (grooves or right oricle)

Question 3

Where do impulses go after SAN?

Answer 3

Impulses sent across both atria via Bacchman bundles

Question 4

What happens after bacchman bundles?

Answer 4

AVN (between atria & ventricles)

Delayed 0.1s, till ventricles fill

Question 5

What happens to the conduction speed to the AVN and why?

Answer 5

Decrease in conduction speed as
Less gap junctions
Small fiber diameter

Question 6

What happens after the AVN?

Answer 6

Impulses sent to the Bundle of His

From right and left ventricles to apex of heart

Question 7

What happens after the Bundle of His?

Answer 7

Purkinje fibres (fastest conduction)
Walls of ventricles (lateral parts)

Question 8

What is all conduction carried out by?

Answer 8

Nodal cells

Question 9

What are nodal cells?

Answer 9

Electrical signal carriers of the heart

As opposed to contractile cells - myocardial cells

Question 10

What does the heart contract as?

Answer 10

One unit, a functional syncytium