Cardiovascular system function and blood Flashcards

1
Q

What is the proportion of contractile cells and pacemaker cells in the heart?

A
Contractile - 99%
Pacemaker activity (auto rhythmic cells) - 1%
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2
Q

Where are the SA nodes located and what is special about them? (2)

A

They are located in the right atrial wall near the vena cava opening

Cells in the SA node fire the fastest - generate heart beat
Do not have a resting potential

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3
Q

Describe the action potential of a SA node cell graph: (3)

A

Never a flat line - always moving
Constant movement of ions
Refractory period

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4
Q

What is different about the ventricular cells? (2)

A

No pacemaker potential

Cells remain at rest until excited from the pacemaker

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5
Q

What are the 3 phases of ventricular cells:

A

Rapid depolarisation - Na+ influx
Plateau phase - Ca2+ influx (refractory period)
Depolarisation - K+ efflux

Graph looks like a n shape

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6
Q

Describe cardiac excitation: (4)

A
  • APs generated at SA node
  • Rapid excitation through both atria
  • Excitation reaches AV node where conduction is SLOW (atria can contract and empty blood in Ventricles)
  • Excitation spreads rapidly down the bundle of His and Purkinje fibres to allow simultaneous activation of ventricular cells
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7
Q

What parts of the heart rate can we see from a trace? (3)

A

P wave - atrial depolarisation
QRS - ventricular depolarisation
T wave - ventricular repolarisation

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8
Q

What factors effect stroke volume? (3)

A
  1. End diastolic volume
  2. Aortic pressure (stiffness, peripheral resistance, blood volume)
  3. Contractility
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9
Q

What is the cardiac output equation?

A

Cardiac output = stroke volume x heart rate

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10
Q

What are the heart rate factors that effect cardiac output? (3)

A

Pacemaker cells
Noradrenaline - increase HR
ACh - decrease HR

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11
Q

What factors effect heart rate? (3)

A

Pacemaker (SA node)
Conduction (AV node)

Noradrenaline, adrenaline and ACh all effect them too

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12
Q

What its the standard cardiac output, stroke volume, and heart rate in a person at rest?

A

Cardiac output = 5L/min (x4 at exercise)
Stroke volume = 70ml/beat (x2 at exercise)
Heart rate = 70beats/min (x3 at exercise)

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13
Q

What is the equation for Flow (cardiac output)?

A

Mean BP/Peripheral resistance

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14
Q

What are the stroke volume factors that effect cardiac output? (3)

A

Preload
Afterload
Contractility (noradrenaline) - increase

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15
Q

Factors effecting peripheral resistance:

A

Changes in vessel radius have the greatest influence on resistance - vasoconstriction and vasodilation

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16
Q

What 3 factors monitor blood pressure:

A

Effector mechanisms - ANS
Pressure sensors - baroreceptors
Central integration - CNS Cv centres

17
Q

What are the effects of noradrenaline on A1 and B1 and B2 receptors?

A

A1 - vasoconstriction
B2 - vasodilation
B1 - increase HR

18
Q

What happens when blood pressure falls? (4)

A

Baroreceptors sense it
CNS input
Increase sympathetic drive to heart
HR increased therefore BP increase