L9 - Electrical Activity of the Heart Flashcards Preview

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Flashcards in L9 - Electrical Activity of the Heart Deck (50)
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1

What three type of cells is the electrical activity spread by

Nodal cells
Conducting cells
Muscle cells

2

What type of structures conduct the electrical activity

Electrical synapses

3

Describe the overview of the process of excitation in the heart

Initiation at the SA node
Conduction to the atrioventricular node and then to the AV ring
Conduction to the left atria via brachmans bundle (interatrial tract)
Passage through thebundle of His
Purkinje system distributes to the ventricular muscle cells

4

The SA node acts as a

Pacemaker

5

What is another word for the interatrial tract

Brachmans bundle

6

Describe the location of the SA node

Posterior aspect
Junction superior vena cava and right atrium

7

What is the function of the interatrial tract

Spreads the depolarisation from the right atrium to the left atrium

8

Describe the location of the AV node

Posterior aspect - right side inter atrial septum

9

What are the three subzones of the AV node

AV N NV

10

What is the function of the AV node delay

To allow the atrial contraction to finish

11

What is the function of the AV node refractory period

Prevent excess ventricular contraction

12

What happens to the AV refractoriness as heart rate increases

It increase

13

Subnodal conduction leads to

Spetal activation - depolarisation of the septa

14

What can be said about the contraction of the heart

Spiral muscle contraction evoking a torsion

15

Process of depolarisation in the heart

Depolarise the atria
Depolarise in interventricular septum
Depolarisation of the anteroseptal region of the myocardium toward the apex
Ventricles now depolarised
Posterior portion of the base of the left ventricle now depolarised
Depolarisation of the bulk of the ventricular myocardium from the endocardium to the myocardium

16

Which three types of cells fire action potentials with plateau phases

Purkinje fibres
Atrial and ventricular muscle cells

17

Two properties of pacemaker cells

Automaticity
Rhythmicity

18

What is the primary pacemaker cells of the heart

SA node

19

What other cells are able to act as pacemakers

AV node
Purkinje cells

20

What is the rising phase of a pacemaker cells Vm leading to action potential firing

Prepotential

21

What is responsible for the prepotential

Decreased K efflux and increased cation influx

22

What current produces the prepotential

If

23

Describe the If current

Hypepolarisation induced, inactive when +ve

24

When is the If inactive

When +ve

25

What induces IF

Hyperpolarisation

26

What is the action potential of a pacemaker cell generated by

Fast Ca influx

27

What is repolarisation of the pacemaker cell caused by

Increased K efflux

28

What three regualtory mechanisms affect the pacemaker cell action potential

Innervation
Temperature
Other pacemaker cells

29

How do vagal fibres affect the pacemaker cells

Parasympathetic
Hyperpolarisation of the pacemaker cells and decrease slope of the pre potential

30

How does sympathetic stimulation affect the pacemaker cells

Increased prepotential slope and increased firing rate (threshold is reached much faster)