Lecture 7 - The Excitable Heart

Question 1

Electrical cells:

1. What percentage
2. Appearance?
3. Examples

Contractile cells:

1. What percentage?
2. Appearance?
3. Example

Answer 1

-

Question 2

Action potentials propagate along the _____ ______ of what?

What’re the 4 bullet points?

1. Intrinsic depolarisation….
2. Where does the impulse spread?
3. In contractile cells: ?
4. How does it spread?

Answer 2

Surface membrane of electrical and contractile cells

Question 3

What connects cardiac cells of heart?

What are gap junctions?

Answer 3

-

Question 4

Gap junctions spreading the impulse

1. Along……
2. Between….
3. Between……

This

1. Increases…..
2. Causes…..(special name)

Answer 4

-

Question 5

Electrical wiring of the heart - 6 parts

Answer 5

Go to the slides for this and understand the story

Question 6

Excitation and the conduction pathway

1. Q____
2. ____ pulse
3. Complete _____ depolarisation
4. ____ pulse
5. ____ repolarisation and _____ depolarisation
6. Start of ventricular _____
7. Complete ______ repolarisation

Answer 6

1. Quiescence = nothing happening, heart full of blood and ready to initiate beat
2. SAN pulse - excitation of intra- and inter-atrial conduction pathway. Start of atrial depolarisation (some change in shape)
3. Complete atrial depolarisation (electrical signal moved all the way through atria)
4. AVN pulse = excitation of AV bundle and Purkinje fibres. Walls depolarise (vent start to contract) and atria starting to repolarise
5. Atrial repolarisation and ventricular depolarisation. Atria full relaxed and vent fully contracted (isovolumetric vent contract and ejection)
6. Start of ventricular repolarisation (isovolumetric vent relaxation)
7. Complete ventricular relaxation (so back to 1.)

Question 7

ECG

1. What does the P wave denote?
2. QRS complex?
3. T wave?
4. PR/PQ interval?
5. QT interval?
6. RR interval?

Answer 7

1. P = SAN pulse, atrial depolarisation (end of this wave = they fully depolarised)
2. QRS = ventricular contraction (movement of signal down septum etc bigger spike because walls are larger than atria). Here the atria are repolarising but it’s obscured because vent’s deplo signal very big
3. T wave = ventricular repolarisation
4. PR/PQ = indication of the conduction time through the AV node
5. QT = estimate of the time the ventricles are contracting
6. RR = time between heartbeats