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Cardiovascular System > Regulation of Stroke Volume > Flashcards

Regulation of Stroke Volume Flashcards

1
Q

Control of heart rate is

A

Neural

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2
Q

Regulation of stroke volume depends on

A

Preload
Afterload
Neural
Pathological

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3
Q

Describe the increase of heart rate (5)

A
  1. Sympathetic system releases noradrenaline
  2. Adrenaline from adrenal medulla
  3. Both act on B1 receptors on sinoatrial node
  4. Increases slope of the pacemaker potential
  5. Increases heart rate= tachycardia
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4
Q

What does increasing the slope of the pacemaker mean?

A

The cell gets the threshold sooner

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5
Q

Describe the decrease of heart rate

A
  1. Vagus release Ach
  2. Acts on muscarinic receptors on sinoatrial node
  3. Hyperpolarises cells and decreases slope of pacemaker potential
  4. Decreases heart rate = bradycardia
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6
Q

Stroke volume

A

The volume of blood in ml ejected from each ventricle due to the contraction of the heart

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7
Q

What does Starling’s law state

A

The energy of contraction is proportional to the initial length of cardiac muscle fibre

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8
Q

The more stretched the cardiac muscle fibre is

A

the higher the calcium sensitivity of the myofibrils, causing a greater number of actin-myosin cross-bridges to form within the muscle fibres

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9
Q

Pre load is affected by what

A

End Diastolic Volume

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10
Q

Increased venous return means (2)

A

Increased EDV

Increased stroke volume

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11
Q

Decreased venous return means (2)

A

Decreased EDV

Decreased stroke volume

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12
Q

What is pre load

A

The load applied to muscles before it contracts

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13
Q

What is after load

A

The load against which the muscle tries to contract

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14
Q

Aortic pressure is affected by

A

How much blood is pushed into the aorta (Cardiac output)

How easy it is for the blood to get out of the aorta (TPR)

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15
Q

What happens if the TPR increases

A

The aortic pressure increases
Ventricles will have to work harder to build pressure to open valve
Less energy for ejecting blood- SV decreases

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16
Q

What is afterload set by

A

The arterial pressure against which the blood is expelled which is dependent on the TPR

17
Q

If the TPR increases what happens to the stroke volume

A

It will go down

18
Q

Neural regulation to increase stroke volume (5)

A
  1. Sympathetic nerves release noradrenaline
  2. Plus circulating adrenaline from adrenal medulla
  3. Both act on B1 receptors on myocytes
  4. Increase contractility
  5. Stronger but shorter contractions
19
Q

Inotropic

A

Strength of contraction

20
Q

Contractility

A

How many calcium cells released

21
Q

Neural regulation to decrease stroke volume

A

Parasympathetic has little effect as vagus does not innervate the ventricular muscle

22
Q

Hypercalcemia effect on SV

A

Shifts curve up and left (Increased SV, reduced EDV- filling phase it cut short)

23
Q

Hypocalcemia effect on SV

A

Shifts curve down and right (decreased SV, more time for filling EDV increases)

24
Q

Ischaemia effect on SV

A

Shifts curve down and right (lower SV, more filling time)

25
Q

Barbiturates

A

Shifts curve down and right

26
Q

How does the heart compensate for a reduced pumping ability (3)

A

Works around a bigger EDV
Lowe ejection fraction
Reduced exercise capacity

27
Q

Control of CO- HR increases (2)

A

via decreased vagal tone

Increased sympathetic tone

28
Q

Control of CO- Contractility increases (2)

A

via increased sympathetic tone

alters inotropic state and shortens systole (more time for filling and increase stroke volume)

29
Q

Control of CO- venous return increases

A 
Via venoconstruction (alpha 1) and skeletal respiratory pumps
Maintains preload
30
Q

Control of CO- TPR falls (2)

A

due to arteriolar dilation in muscle, skin and heart

Reduces afterload

Cardiovascular System (42 decks)

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