Lecture 9 Heart Physiology

Question 1

Electrical cells of heart

Answer 1

1%
Pale striated appearance
Low actin and Myosin

Question 2

Contractile cells of heart

Answer 2

99%
Striated appearance
High actin and Myosin

Question 3

Action potentials spread (propagate) along the..

Answer 3

Surface membrane of electrical and contractile cells.

Question 4

Where does depolarization start?

Answer 4

sinoatrial node (SAN). This signal spreads to neighbouring cells.

Question 5

In a contractile cell:

Answer 5

increased cytosolic Ca2+ level, X-bridge attachment and contraction

Question 6

What connects cardiac cells together?

Answer 6

Intercalated disks and gap junctions.

Question 7

Intercalated discs connect

Answer 7

most cells of the heart.

Question 8

Gap Junctions consists of

Answer 8

Pores with low resistance to ionic current.

Allows current flow between adjacent cells.

Connect electrical cells
Connect contraction cells
Connect electrical cells and contraction cells

Question 9

why don/t Contractile cells communicate the signal quickly?

Answer 9

High actin and myosin

Question 10

Functional syncytium

Answer 10

Individual cells work as a unit.

communicate using gap junctions

Question 11

SA node (sinoatrial)

Answer 11

where signal begins to tell the heart to beat (contract)

sits above right atrium

Question 12

where does the SA node signal go?

Answer 12

3 directions
right atrium
left atrium
AV node

Question 13

Right atrium receives signal from SA node to..

Answer 13

contract

Question 14

Left atrium receives signal from SA node to..

Answer 14

contract

Question 15

Why and How does the SA node signal get to the left atrium?

Answer 15

Both atriums have to contract simultaneously

Goes across the interatrial bundle

Question 16

How does the SA node get to the AV node?

Answer 16

through internodal bundles

Question 17

Internodal bundles

Answer 17

Connects the SA (sinoatrial) node and AV (atrioventricular) node

Question 18

AV node (atrioventricular)
(what it does, where does the signal go)

Answer 18

Between right atrium and right ventricle

Collects signal from SA node and holds signal (pause)

Paused signal is passed to the AV bundle

Question 19

Why does the AV node have to hold the signal from SA node?

Answer 19

both the atria need to contract first before the ventricles contract.

No pause will result in contraction of atrium and ventricles at same time and blood will be pushed all around the place in the heart.

Question 20

AV bundle
(what it does, where does the signal go?)

Answer 20

Runs through the centre wall of heart ( septum)

Branches into 2 different directions to the left and right side of heart.

Purkinje fibres

Question 21

Purkinje fibres

Answer 21

Brings signal back up through the ventricular wall

Signal is sent to contractile cells along the wall which causes ventricles to contract.

Question 22

Why do the purkinje fibres bring the signal back up through the ventricular wall?

Answer 22

Get the maximum amount of blood from the ventricle.

Question 23

Excitation and conduction pathway

Answer 23

Quiescence

P wave (1st phase)

P - R interval

QRS complex (3rd phase)

R - T interval

T wave (5th phase)

Straight period after T wave (6th phase)

Question 24

Quiescence

Answer 24

straight line no electrical signal

heart is filling with blood

Ready to contract

Question 25

P wave (1st phase)

Answer 25

SA node fires Left and right atria is depolarizing

Question 26

P - R interval Straight period in between P wave and QRS complex (2nd phase)

Answer 26

Atria fully depolarized (and contracting) Signal finished AV node is holding the signal not allowing anything else to depolarize

Question 27

QRS complex (3rd phase)

Answer 27

signal from AV node released Repolarization of Atria Depolarization of ventricles

Question 28

R - T interval Straight period between QRS complex and T wave (4th phase)

Answer 28

Ventricles fully depolarized | Atria fully repolarized

Question 29

T wave (5th phase)

Answer 29

Repolarization of ventricles

Question 30

Straight period after T wave (6th phase)

Answer 30

Ventricles fully repolarized Ready to go back to quiescence

Question 31

2 heart sound

Answer 31

lubb (1st) Dupp (2nd) associated with snapping shut valves

Question 32

ECG

Answer 32

electrocardiogram. pressure in atria, ventricles, aorta.

Question 33

Initiate contraction

Answer 33

SA node fires Sends an electrical signal Depolarizion of right and left atrium (contraction) P wave

Question 34

Atrial Systole (contraction) phase

Answer 34

P wave Both atria contract AV valves open Semilunar valves close (aortic and pulmonary) AV node holds signal Increase atrial pressure Increase ventricular volume

Question 35

Isovolumetric ventricular contraction phase

Answer 35

QRS complex AV valves close Semilunar valves close (aortic and pulmonary) Blood volume of ventricles remain same Increase Ventricular pressure Atria repolarizes Ventricles depolarize

Question 36

Ejection phase

Answer 36

Between QRS complex and T wave Semilunar valves burst open (aortic and pulmonary) Pressure pushes blood from ventricles into the Aorta and Pulmonary artery Pressure in ventricles still continue to increase Aorta pressure increases

Question 37

Isovolumetric ventricular relaxation phase

Answer 37

T wave AV valves close Semilunar valves close ventricles repolarize Pressure in ventricles decrease (steep) Blood volume in ventricles constant

Question 38

Quiescence phase

Answer 38

Period after T wave AV valves open Passively refill ventricles with blood Blood volume in ventricles increase Pressure in ventricles low Ready for next heart beat