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Cardiovascular system > The Cardiac Cycle - L4 > Flashcards

The Cardiac Cycle - L4 Flashcards

1
Q

What is the cardiac cycle?

A

All the events associated with the flow of blood through the heart during a single complete heartbeat

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2
Q

How long is the cardiac cycle is the heart rate is 65bpm?

A

approx 0.92 sec

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3
Q

What is 1 heart beat divided into?

A

2 Sequential phases: systole and diastole

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4
Q

What is systole?

A

Period of cardiac contraction and emptying
Often an implied time of ejection, despite period of isovolumetric contraction

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5
Q

What does systole vary on? What is it at 65bpm and 200bpm?

A

The length varies depending on what the heart rate: 0.3 sec @ 65bpm, 0.16 sec @ 200bpm

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6
Q

What happens at a higher heart rate to systole? What happens to calcium?

A

Myocardium contracts & repolarises faster at high HR (increased Calcium return to SR)

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7
Q

Systole is often an implied time of x?, despite x?

A

Often an implied time of ejection, despite period of isovolumetric contraction

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8
Q

What is diastole?

A

Period of cardiac relaxation
Often an implied time of refilling, despite period of isovolumetric relaxation

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9
Q

What does diastole vary with? @65bpm?@200bpm?

A

The length varies with varying heart rate
0.62sec @65bpm; 0.14sec @200bpm

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10
Q

Action of valves control?

A

Cardiac cycle

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11
Q

When do the AV valves open - the bicuspid/tricuspid valves??

A

open when pressure in atria is greater then those in the ventricles
when pressure gets greater in ventricles than in atria then the AV valves close

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12
Q

When do the semilunar valves open and close?

A

semilunar valves open when pressure in ventricles is greater then the pressure in the arteries and the semilunar valves close when the pressure in the arteries is greater then the pressure in the ventricles

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13
Q

Mechanical phases of cardiac cycle step:

A
  1. Late diastole: both sets of chambers are relaxed and
    ventricles fill passively.
  2. Atrial systole: atrial contraction forces a small amount of additional blood into ventricles.
  3. Isovolumic ventricular contraction: first phase of
    ventricular contraction pushes AV valves closed but does not create enough pressure to open semilunar valves. 0.05 sec
  4. Ventricular ejection: as ventricular pressure rises and exceeds pressure in the arteries, the semilunar valves
    open and blood is ejected.
  5. Isovolumic ventricular relaxation: as ventricles relax, pressure in ventricles falls, blood flows back into cups of semilunar valves and snaps them closed.
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14
Q

What does cardiac cycle begin and end with?

A

Begins with a ventricular diastole and ends with a ventricular diastole

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15
Q

Heart sounds - what is S1:”lub”?
What is S2: “dup”?

A

S1 – “lub” (AV valve closure)
S2 – “dup” (semilunar valve closure)

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16
Q

With diastole it is often an implied time of x, despite x?

A

Often an implied time of refilling, despite period of isovolumetric relaxation

17
Q

The sequence of events which may overlap are?

A

Atrial diastole -> ventricular diastole -> atrial systole -> ventricular systole

18
Q

What is the action of the valves?

A

They open passively due to pressure gradients

19
Q

EDV?

A

End diastolic volume = volume of blood in ventricle at end of diastole
130mL

20
Q

ESV?

A

End systolic volume = volume of blood in ventricle at end of systole
70mL

21
Q

SV?

A

Stroke volume = volume of blood ejected from ventricle in each cycle

SV = EDV-ESV
SV = 130-70 = 60mL in this case

22
Q

What is the ejection fraction?

A

% EDV ejected with each stroke: ranges from 50-75%

23
Q

What is ejection fraction useful for?

A

A good index of ventricular function

24
Q

Wiggers’ Diagram main events: 6

A
  1. Atrial systole
  2. Isovolumic ventricular contraction
  3. Ventricular systole
  4. Early ventricular diastole
  5. Late ventricular systole
  6. Atrial systole again

1,2,3 make up QRS complex
4,5 cardiac cycle

25
Q

cardiac cycle - one complete heartbeat

A

STEP 1 OF CARDIAC CYCLE

both atria and ventricles are filling passively: overlap

atria are passively filling from pulmonary veins from the lungs with oxygenated lungs and passively filling from the systemic return from the superior and inferior vena cava into right atria here, the AV valves are open as pressure is greater in atria then ventricles and blood fills ventricles

ventricles are filling passively

26
Q

STEP 2 OF CARDIAC CYCLE: MECHANICAL PHASES

A

Atria have a systolic contraction to complete ventricular refilling
to force remaining blood in through valves and then the valves close
AV valves close

27
Q

STEP 3

A

When AV valves close, just before we have the ventricular contraction where we have ejection of stroke volume that is when we have the period of the isovulimic ventricular contraction: AV closed here as pressure in ventricles is greater then what is in atria.
The ventricles are depolarising and they are getting ready to contract , the pressure is building, starting to contract but not forcefully enough to open semi lunar valves
All the valves are closed at this point - no blood entering or leaving
The volume remains the same but pressure is increasing, it is contracting.
Lasts 0.05 of a second

28
Q

STEP 4 of cardiac cycle - mechanical phase

A

Systole has began, Ventricles are contracting, and now fully depolarised
Ventricular ejection occurs - ventricular pressure rises and exceeds the pressure in aorta and pulmonary artery, semi lunar valves open and blood leaves heart through these ventricles. The stroke volume occurs

29
Q

Step 5 of cardiac cycle - mechanical phase?

A

Isovolumic ventricular relaxation
Ventricles has been ejected and now ventricles stop contracting and pressure reduces in ventricles and pressure within aorta and pulmonary arteries increases and causes closing of semi lunar valves. All the valves in heart are closed
When ventricles contract only 1/2 of blood is ejected, so some volume of blood left in ventricles
The volume is same but pressure is reducing
Ventricles are repolarising and getting ready to refill and begin the whole cycle again

30
Q
  1. P wave?
  2. QRS?
  3. ST?
  4. T wave?
  5. TP?
A
  1. Atria depolarising, threshold has been reached
  2. Atria contracting and sending blood into ventricles and ventricles getting ready to contract and depolarises
  3. Ventricles are contracting and ejecting its contents
  4. Repolarisation of ventricle
  5. Ventricular diastolic, they are refilling
31
Q

Isovolumic ventricular contraction happens at end of?

A

Isovolumic ventricular contraction happens at end atrial systole just before ventricular starts to do complete ventricle contraction

32
Q

What is the dicrotic notch?

A

The end of systole and the beginning of diastole in these arteries.

33
Q

EXAM Q - write about wiggers diagram, talk your way through each step: ECG, mechanical phase of cardiac cycle etc

A

Cardiovascular system (13 decks)

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