Cardiovascular system 6

Question 1

What is a defining physical feature electrical (conduction) cells

Answer 1

‘Pale’ striated appearance - due to low actin and myosin

Question 2

Why is there less actin and myosin in electrical cells

Answer 2

Electrical signal is conducted using Ca2+ molecules - the same signal used to activate contraction. In the absence of this a signal can travel

Question 3

How does the signal get conducted

Answer 3

Depolarisation starts at sinoatrial node and spreads to neighbouring cells (Both conduction and contractile)

Question 4

How does the signal spread

Answer 4

Through intercalated disks

Question 5

What are intercalated disks

Answer 5

Connect most cells of the heart.

Contain gap junctions - pores with low resistance to ionic current (especially calcium)

Question 6

What is a syncytium

Answer 6

A cytoplasmic mass containing several nuclei, formed by fusion of cells.

Question 7

What is Quiescence

Answer 7

When nothing is electrically happening in the heart - Passive filling is occurring

Question 8

What are the three waves of an ECG

Answer 8

P wave
QRS complex
T wave

Question 9

What does and ECG measure

Answer 9

The electrical change within the heart (depolarising and repolarising)

Question 10

What happens during the P wave

Answer 10

Atria depolarise (Initiated by SA node)

Question 11

What happens after the P wave

Answer 11

The atria is fully depolarised - there is no change and it will be a straight line

Question 12

What happens during the QRS complex

Answer 12

The atria start to repolarise at the same time as the ventricles start to depolarise

Question 13

What happens after the QRS complex

Answer 13

The atria are fully repolarised and the ventricles are fully depolarised. There is no change and it will be a straight line

Question 14

What happens during the T wave

Answer 14

Ventricles start to repolarise - stating at apex

Question 15

What happens after the T wave

Answer 15

The ventricles are fully repolarised and there is a straight line

Question 16

What is the sinoatrial (SA node)

Answer 16

The pacemaker - Small bundle of cells that tell the heart when to beat

Question 17

What are the paths the conduction pathway takes from the SA node

Answer 17

Internodal bundles - Takes to AV node

Interatrial bundle - Takes to left atrium to start contraction

Question 18

What does the Atrioventricular (AV node) do

Answer 18

Receives signal from SA node and puts a hold on it - this is so the atria can contract before the ventricles

Question 19

What are the paths the conduction pathway takes from the AV node

Answer 19

Once atria are relaxing sends message into the AV bundle to the bundle branches - gets carried down the interventricular septum to the apex of the heart

Question 20

What is the final step in the conduction pathway

Answer 20

Purkinje fibres connect to all contractile cells receive the message and start contraction from the apex of the heart

Question 21

Why does contraction start at the apex of the heart

Answer 21

To try and squeeze out as much blood from the ventricles as possible (think of tube of toothpaste)