Lecture 9 Heart Physiology Flashcards

1
Q

Electrical cells of heart

A

1%
Pale striated appearance
Low actin and Myosin

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2
Q

Contractile cells of heart

A

99%
Striated appearance
High actin and Myosin

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3
Q

Action potentials spread (propagate) along the..

A

Surface membrane of electrical and contractile cells.

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4
Q

Where does depolarization start?

A

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

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5
Q

In a contractile cell:

A

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

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6
Q

What connects cardiac cells together?

A

Intercalated disks and gap junctions.

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7
Q

Intercalated discs connect

A

most cells of the heart.

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8
Q

Gap Junctions consists of

A

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

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9
Q

why don/t Contractile cells communicate the signal quickly?

A

High actin and myosin

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10
Q

Functional syncytium

A

Individual cells work as a unit.

communicate using gap junctions

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11
Q

SA node (sinoatrial)

A

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

sits above right atrium

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12
Q

where does the SA node signal go?

A

3 directions
right atrium
left atrium
AV node

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13
Q

Right atrium receives signal from SA node to..

A

contract

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14
Q

Left atrium receives signal from SA node to..

A

contract

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15
Q

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

A

Both atriums have to contract simultaneously

Goes across the interatrial bundle

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16
Q

How does the SA node get to the AV node?

A

through internodal bundles

17
Q

Internodal bundles

A

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

18
Q
AV node (atrioventricular)
(what it does, where does the signal go)
A

Between right atrium and right ventricle

Collects signal from SA node and holds signal (pause)

Paused signal is passed to the AV bundle

19
Q

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

A

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.

20
Q
AV bundle
(what it does, where does the signal go?)
A

Runs through the centre wall of heart ( septum)

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

Purkinje fibres

21
Q

Purkinje fibres

A

Brings signal back up through the ventricular wall

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

22
Q

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

A

Get the maximum amount of blood from the ventricle.

23
Q

Excitation and conduction pathway

A

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)

24
Q

Quiescence

A

straight line no electrical signal

heart is filling with blood

Ready to contract

25
Q

P wave (1st phase)

A

SA node fires

Left and right atria is depolarizing

26
Q

P - R interval

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

A

Atria fully depolarized (and contracting)

Signal finished

AV node is holding the signal not allowing anything else to depolarize

27
Q

QRS complex (3rd phase)

A

signal from AV node released

Repolarization of Atria

Depolarization of ventricles

28
Q

R - T interval

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

A

Ventricles fully depolarized

Atria fully repolarized

29
Q

T wave (5th phase)

A

Repolarization of ventricles

30
Q

Straight period after T wave (6th phase)

A

Ventricles fully repolarized

Ready to go back to quiescence

31
Q

2 heart sound

A

lubb (1st)
Dupp (2nd)

associated with snapping shut valves

32
Q

ECG

A

electrocardiogram.

pressure in atria, ventricles, aorta.

33
Q

Initiate contraction

A

SA node fires Sends an electrical signal

Depolarizion of right and left atrium (contraction)

P wave

34
Q

Atrial Systole (contraction) phase

A

P wave

Both atria contract

AV valves open

Semilunar valves close (aortic and pulmonary)

AV node holds signal

Increase atrial pressure

Increase ventricular volume

35
Q

Isovolumetric ventricular contraction phase

A

QRS complex

AV valves close

Semilunar valves close (aortic and pulmonary)

Blood volume of ventricles remain same

Increase Ventricular pressure

Atria repolarizes
Ventricles depolarize

36
Q

Ejection phase

A

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

37
Q

Isovolumetric ventricular relaxation phase

A

T wave

AV valves close

Semilunar valves close

ventricles repolarize

Pressure in ventricles decrease (steep)

Blood volume in ventricles constant

38
Q

Quiescence phase

A

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