Mairead - The Heart - values and forces Flashcards

1
Q

What is the cardiac cycle

A

The period between the start of one heartbeat and the start of the next

Alternating cycles of contraction and relaxation

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2
Q

What is systole

A

The period of contraction (emptying)

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3
Q

What is diastole

A

The period of relaxation (and filling)

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4
Q

What is cardiodynamics

A

The movements and forces generated during cardiac contraction

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5
Q

What is EDV?

A

End diastolic volume

The volume of blood in the ventricles at the end of atrial contraction/systole

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6
Q

What is ESV

A

End systolic volume

The volume of blood in the ventricle at the end of ventricular systole

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7
Q

What is SV

A

Stroke volume

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8
Q

What is the equation for stroke volume?

A

Sv = EDV - ESV

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9
Q

What is ejection fraction?

A

The % of EDV that becomes the SV

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10
Q

What is cardiac output

A

The amount of blood flow in the circulation

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11
Q

What is the equation for CO?

A

Cardiac output = SV X HR

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12
Q

What is the equation for blood flow?

A

Pressure/resistance

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13
Q

How might SV be changed?

A

By increasing venous return

By altering the force of contraction of the heart

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14
Q

How can heart rate be changed?

A

It can be increased/decreased by changing the pacemaker excitability

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15
Q

How might heart rate by altered?

A

By autonomic innervation

By hormones

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16
Q

How can cardiac output by altered?

A

Changed in heart rate or stroke volume

17
Q

What determines EDV?

A

Venous return

Filling time

18
Q

What is filling time

A

The duration of ventricle diastole: this depends on heart rate

19
Q

What is venous return

A

The rate of blood flow during ventricular diastole (filling)

20
Q

What affects venous return

A

CO

Blood volume

Peripheral circulation (vasoconstriction/vasodilation)

Skeletal muscle activity

Respiratory pump

Hormones

21
Q

What factors affect end systolic volume?

A

Preload
Contractility of the ventricles
Afterload

22
Q

What is preload
(5)

A

The degree of stretching of the ventricle prior to contraction

This is produced by blood returning from the veins

This affects muscle tension

There is a physiological range of preload

Optimum preload is with a degree of stretch so that greater tension can develop when the ventricles contract

23
Q

What two factors cause preload to vary?

A

Posture
Exercise

24
Q

What is Frank starling Principle/ Starling’s Law of the heart

A

Within physiological limits the heart pumps out all the blood pumped into it

More in = more out

25
What is contractility?
The amount of force produced during a contraction at a given preload
26
What is contractility determined by?
ANS Hormones Extracellular ions
27
How is contractility affected by ANS and hormones?
They have an ionotrophic effect on Ca++
28
What is a positive ionotrophic effect? (2)
Where there is an increase in Ca++ entry during contraction This increases the force and duration of contraction
29
What is negative ionotrophic effect?
Where the Ca++ entry is blocked
30
What is afterload
The amount of tension the contracting ventricles must generate to open the semilunar valves
31
What affects afterload and how?
High aortic pressure will increase the time of isovolumetric contraction and decrease the time of emptying
32
What are two causes of high pressure?
Blood vessel constriction Circulatory blockage