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Medsci142 > Cardiac Cycle and Output > Flashcards

Cardiac Cycle and Output Flashcards

1
Q

What are the 5 Stages of the Cardiac Cycle?

A
  1. Ventricular Filling
  2. Atrial Contraction
  3. Isometric Ventricular Contraction (Systole)
  4. Ventricular Ejection
  5. Isometric Ventricular Relaxation
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2
Q

During Ventricular Filling, to What Percentage does the ventricle Fill To?

A

80%

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3
Q

During Ventricular Filling, does the Pressure Within The Ventricle have to be Greater Or Lesser than the Pressure Within The Atrium

A

Lesser

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4
Q

During Atrial Contraction, what Percentage of the Ventricular Volume is Pumped Into The Ventricle?

A

The remaining 20% left over from ventricular filling

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5
Q

Atrial Contraction is Triggered by…

A

SA node firing

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6
Q

During Isovolumetric Ventricular Contraction, what happens to the Bicuspid/Mitral and Tricuspid valves?

A

They are pushed closed

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7
Q

During Isovolumetric Ventricular Contraction, will the semilunar valves open?

A

No, because the pressure within the ventricle is still rising to the same level as arterial pressure

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8
Q

During Isovolumetric Ventricular Contraction, are any Valves open?

A

No

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9
Q

During Ventricular Ejection, does the Ventricle still keep contracting?

A

Yes

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10
Q

During Ventricular Ejection, does the Pressure Within The Ventricle have to be Greater Or Lesser than the Arterial Pressure?

A

Greater

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11
Q

During Isovolumetric Ventricular Relaxation, does blood Enter The Ventricle?

A

No

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12
Q

What is the Formula for Cardiac Output?

A

CO = Heart Rate (How Fast) x Stroke Volume (How Much Blood)

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13
Q

What is a Normal Cardiac Output at Rest?

A

4-7 Litres per Minute

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14
Q

What is the Average Resting Stroke Volume?

A

70ml

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15
Q

What is the Formula for Cardiac Reserve?

A

Cardiac Reserve = COMax - CORest

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16
Q

What 3 Factors regulate Stroke Volume?

A

Preload, Contractility and Afterload

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17
Q

What is Preload?

A

The Stretch on the heart before it contracts

18
Q

What is Contractility?

A

The forcefulness of contraction in the heart

19
Q

What is Afterload?

A

The pressure that the ventricle has to work against during ventricular ejection (arterial pressure)

20
Q

What is the Frank-Starling Law Of The Heart?

A

The more blood goes in, the more blood goes out

21
Q

What is an example of a Positive Inotrophic Agent?

22
Q

What is an example of a Negative Inotrophic Agent?

23
Q

When does the First Heart Sound Occur?

A

During isometric ventricullar contraction (Systole) as the blood experiences turbulence against the closed Mitral/Bicuspid and Tricuspid valves

24
Q

When does the Second Heart Sound Occur?

A

During isometric ventricular relaxation as the blood experiences turbulence against the closed pulmonary and aortic valves

25
Q

What causes Depolarisation in a Ventricular Contractile Fibre during an Action Potential?

A

Rapid opening of voltage-gated fast Na+ channels causing rapid influx of Na+

26
Q

What causes the Plateu in a Cardiac Action Potential?

A

The influx of Ca2+ as slow voltage-gated Ca2+ channels open and the outflux of K+ as some K+ open

27
Q

What causes Repolarisation in a Ventricular Contractile Fibre during an Action Potential?

A

The closing of Ca2+ channels and the K+ outflow when more voltage-gated K+ channels open

28
Q

What does an ECG measure?

A

The sum of all the electrical activity in the heart

29
Q

What does the P Wave indicate?

A

Atrial depolarisation

30
Q

What is the QRS Complex?

A

Onset of ventricular depolarisation

31
Q

What is the T Wave?

A

Ventricular repolarisation

32
Q

What inputs into the Cardiovascular Centre in the Medulla?

A

Higher Brain Centres (Cerebral Cortex, Limbic System, Hypothalamus)
Proprioreceptors (Monitoring joint movement)
Baroreceptors (Monitoring Blood Pressure)
Chemoreceptors (Monitoring Blood Acidity, CO2 and O2)

33
Q

Vagus Nerves are Sympathetic or Parasympathetic? What do they do to the Heart?

A

Parasympathetic, Decreases heart rate

34
Q

Is the Vagus Nerve always Active?

A

Yes, just to different degrees depending on demand

35
Q

Cardiac Accelerator Nerves are Sympathetic or Parasympathetic? What do they do to the Heart?

A

Sympathetic, Increases heart rate and contractility

36
Q

Vasomotor Nerves are Sympathetic or Parasympathetic? What do they do to Blood Vessels?

A

Sympathetic, Cause vasoconstriction

37
Q

On the Heart, Parasympathetic Nerves use what Neurotransmitter?

A

Acetylcholine

38
Q

On the Heart, Sympathetic Nerves use what Neurotransmitter?

A

Noradrenaline/Norepinephrine

39
Q

How do BaroreceptorsmeasureBlood Pressure?

A

By measuring stretch in the blood vessels

40
Q

Where are Baroreceptors found?

A

In the carotid sinus and the arch of the aorta. Cardiopulmonary Baroreceptors found in the major veins of the heart and in the lungs

Medsci142 (11 decks)

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