Lecture 9: The Excitable Heart

Question 1

What is the appearance of electrical /conduction cells?

Answer 1

Pale striated appearance

Question 2

What is the appearance of contractile cells?

Answer 2

Striated appearance

Question 3

What are electrical/conduction cells made of?

Answer 3

Low actin/myosin

Question 4

What are contractile cells made of?

Answer 4

High actin/myosin

Question 5

Where do action potentials propagate in cardiac cells?

Answer 5

Along the surface membrane of electrical and contractile cells

Question 6

Where does depolarisation in the heart start?

Answer 6

The Sinoatrial node

Question 7

What connects the cells of the heart?

Answer 7

Intercalated disks

Question 8

What do gap junctions do?

Answer 8

Allow current flow between adjacent cells

Question 9

What are gap junctions?

Answer 9

Pores with low resistance to ionic current

Question 10

Where are gap junctions found?

Answer 10

Between contractile and electrical/conduction cells

Question 11

What is a functional syncytium?

Answer 11

Many cells functioning as one unit

Question 12

Following the sinoatrial node where does an electrical current go?

Answer 12

Internodal bundles/interatrial bundle

Question 13

Following the internodal bundles where does an electrical current go?

Answer 13

AV node

Question 14

Following the AV node where does an electrical current go?

Answer 14

AV bundle

Question 15

Following the AV bundle where does an electrical current go?

Answer 15

Right/left bundle branches

Question 16

Following the left/right branches where does an electrical current go?

Answer 16

Purkunje fibers

Question 17

What does the AV node do to an electrical impulse?

Answer 17

It briefly pauses it, allowing the atria to finish contracting

Question 18

Why is the wiring of the heart conduction system done in the manner that it is?

Answer 18

To follow the direction of blood flow through the heart

Question 19

What happens corresponding to the P wave during the excitation and the conduction pathway?

Answer 19

Left/right atrium depolarise and signal is arriving at this part of the heart therefore contraction is occurring

Question 20

What happens corresponding to the base line following the P wave during the excitation and the conduction pathway?

Answer 20

Both atria are fully depolarised therefore in full contraction and signal is being held at the AV node

Question 21

What happens corresponding to the QRS complex during the excitation and the conduction pathway?

Answer 21

Atria are repolarising as signal has left whilst AV node allows signal through the septal wall

Question 22

What happens corresponding to the base line following the QRS complex during the excitation and the conduction pathway?

Answer 22

Ventricles are fully depolarised and contracting as signal has moved through purkinje fibres

Question 23

What happens corresponding to the T wave during the excitation and the conduction pathway?

Answer 23

Repolarization of the ventricles begins as blood has been pushed out

Question 24

What happens corresponding to the base line following the T wave during the excitation and the conduction pathway?

Answer 24

Ventricles fully repolarize

Question 25

What does an ECG measure?

Answer 25

Electrical signals in your heart

Question 26

What is depolarisation at the atria shown by on an ECG?

Answer 26

P wave

Question 27

What is full depolarisation of the atria shown by on an ECG?

Answer 27

A base line

Question 28

What is repolarised atria and depolarising ventricles shown by on an ECG?

Answer 28

QRS complex

Question 29

What is full depolarisation of ventricles shown by on an ECG?

Answer 29

A base line

Question 30

What is repolarisation of the ventricles shown by on an ECG?

Answer 30

T wave

Question 31

What does ‘lubb’ reference in heart sounds?

Answer 31

The atrioventricular valves closing

Question 32

What does ‘Dubb’ reference in heart sounds?

Answer 32

The semilunar valves closing