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Physiology > Cardiology Lectures 1-3 : The Cardiac Cycle > Flashcards

Cardiology Lectures 1-3 : The Cardiac Cycle Flashcards

1
Q

What electrically couples the cardiac mycocytes?

A

Gap junctions

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2
Q

What provides the mechanical adhesion between the adjacent cardiac cells?

A

Desmosomes

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3
Q

What is the thin filament in the heart myofibrils calles?

A

Actin

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4
Q

What is the thick filament of the heart myofibrils called?

A

Myocin

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5
Q

How are actin and myocin arranges in myfibrils

A

As sacromeres

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6
Q

How is muscle tension in the heart produced?

A

Sliding of actin and myosin filaments

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7
Q

What two things are required for muscle contraction in the heart?

A

ATP and calcium

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8
Q

True or False: ATP is required for muscle relaxation.

A

True

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9
Q

Why is calcium required?

A

Switches on the cross bridge formation

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10
Q

What is the importance of having a long refractory period?

A

Prevents tetanic contraction

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11
Q

What is a refractory peroid?

A

Peroid following an action potential in which it is not possible to produce another action potential

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12
Q

What is stroke volume?

A

The volume of blood ejected by each ventricle per heart beat

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13
Q

What is the end diastolic volume?

A

The volume of blood withn each ventricle at the end of diastole

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14
Q

What determines the end diastolic volume?

A

the venous return to the heart

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15
Q

What is afterload?

A

The resistance the heart is pumping into

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16
Q

What is the preload?

A

How much blood is loaded in the heart before contraction

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17
Q

What is the consequence to the heart of chronically increased afterload?

A

Ventricular hypertrophy

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18
Q

What effect on the heart in cAMP mediated?

A

The increased inotropic affect of sympathetic stimulation to the heart

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19
Q

What effect do parasympathetic nerves have on heart contractility?

A

LIttle effect- little innervation by the vagus

Vagus stimulates rate not force

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20
Q

What is the cardiac output?

A

The volume of blood pumped by each ventricle of the heart per minute

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21
Q

What is the resting CO in a healthy adult typically?

A

5 litres ( 70 x 70ml= 4900ml)

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22
Q

What is meant by autorhythmicity of the heart?

A

The electrical signals which control the heart are generated within the hear itself

23
Q

Where does excitiation originate?

A

Sino-atrial node

24
Q

What happens during the funny current?

A

Decrease in efflux of K

Slow Na influx

25
Q

What happens during the rising phase of the pacemaker AP?

A

Calcium influx

26
Q

What happens during the falling phase of the pacemaker action potential?

27
Q

What is resting membrane potential?

28
Q

What happens during phase 0 of the ventricular muscle AP?

A

Fast influx of Na

29
Q

What happens during phase 1?

A

Slow K efflux

Closure of Na channels

30
Q

What happens during phase 2

31
Q

What happens during phase 3

A

K efflux

closure of Ca channels

32
Q

What is phase 4

A

resting membrane

33
Q

Which phase is known as the plateau phase?

34
Q

Which nerve dominates the rhythmic control of the heart under resting conditions?

A

Vagus

parasympathetic

35
Q

What effect does the vagal tone have on the heart

A

slows its intrinsic rate

36
Q

How does vagal stimulation slow the heart

A

Increases AV nodal delay

37
Q

What is receptor does the parasympathetic stimulation act on?

38
Q

What is the affect of atropine?

A

Speeds up the heart

39
Q

Define the cardiac cycle.

A

All the events that occur from the beginning of one heart beat to the beginning of the next.

40
Q

Name the stages of the cardiac cycle

A 
Passive filling
Atrial contraction
Isovolumetric contraction
Ventricular ejection
Isovolumetric relaxation
41
Q

What is the pressure in the atria and ventricles during passive filling

A

Close to zero

42
Q

Are the AV valves open or closed in passive filling?

43
Q

When do the AV valves shut?

A

When the ventricular pressure exceed atrial pressure ie ventricles begin to contract

44
Q

What is isovolumetric contraction

A

Contraction of the ventricles when both the Av valves and pulmonary/aortic valves are shut - thus there is no change in volume

45
Q

When do the aortic/pulmonary valves open?

A

When the ventricular pressure exceeds aortic/pulmonary pressure

46
Q

When do the aortic/pulmonary valves shut?

A

When the ventricular pressure falls below the aortic/pulmonary pressure

47
Q

What does the valve vibrtion when the aortic valve shuts produce?

A

Dicrotic notch in the aortic pressure wave

48
Q

What is isovolumentric relaxation?

A

The ventricles are relaxing but both sets of valves are shut so there is no change in volume

49
Q

When do the Av valves open again?

A

When ventricular pressure is lower than atrial pressure

50
Q

What is S1?

A

The closure of the AV valves

51
Q

What is S2?

A

The closure of the aortic and pulmonary valves

52
Q

What does S1 mean?

A

The beginning of systole

53
Q

What does S2 mean?

A

The beginning of diastole

Physiology (17 decks)

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