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Cardiac Rehabilitation > Lecture 4 - Cardiac Physiology > Flashcards

Lecture 4 - Cardiac Physiology Flashcards

1
Q

What is the significance of the plateau during an action potential in a cardiac myocyte?

A

To ensure another contraction doesn’t occur when one is already happening, this will ensure efficient flow and circulation.

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2
Q

What would be the consequences of no refractory period in a cardiac AP?

A

Contraction strength will be weak therefore filling and flow will be compromised.

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3
Q

What are the function of the T-Tubules?

A

Ensure the spread of AP so that electrical current spreads evenly throughout the cell and they are all synchronized.

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4
Q

What are L-Type Channels?

A

Allow calcium to pass into the cell.

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5
Q

What is Calcium Induced Calcium Release?

A

Calcium which then causes the SR to release more calcium for contraction

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6
Q

Whys is the SR is close to the sarcomere?

A

To ensure efficient calcium regulation

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7
Q

Why is it important to get calcium out of the heart?

A

Because the heart needs to be able to relax and this can happen only when the amount of calcium decreases.

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8
Q

What two pathways take calcium out of the cell?

A

SERCA and NCX

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9
Q

Which pathway is preferred to take calcium out of the cell?

A

SERCA - when there is problems with this one the NCX pathway is used. (this one is slower)

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10
Q

Describe the 8 steps of calcium processing for contraction

A
  1. AP enters cell through gap junctions
  2. AP travels along plasma membrane and T-Tubule
  3. L Type channels allow Calcium to move in
  4. This calcium then induces the SR to release more calcium (CICR)
  5. Calcium binds to troponin exposing myosin binding sites
  6. Crossbridges form and contraction occurs
  7. Active transportation of Calcium back into SR (via SERCA) or into the ECF (via NCX)
  8. Tropomyosin blocks myosin binding sites and the muscle relaxes
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11
Q

What are the 7 steps on the top of the Wiggers Diagram?

A

Cardiac Cycle

  1. Atrial Contraction
  2. Isovolumetric Contraction
  3. Early Ejection Phase
  4. Late Ejection Phase
  5. Isovolumetric Relaxation
  6. Early Filling
  7. Late Filling
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12
Q

What direction does the heart move in the longitudinal fibre direction?

A

The base moves towards the apex.

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13
Q

Describe the twist mechanism of the left ventricle

A

Moves like wringing a towel. Base moves in one direction while the Apex moves another, the base stays and the apex twists and moves upwards toward the base

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14
Q

How does the twisting mechanism of the heart promote recoil?

A

The twisting mechanism stores alot of kinetic energy in titin, this causes recoil during diastole. (Like pressing a spring down)

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15
Q

What factors affect HR?

A

Autonomic Innervation

Hormones

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16
Q

What factors affect SV?

A

Venous Return + Filling time = Preload
Autonomic Innervation + Hormones = Contractility
Vasodilation and Vasoconstriction = Afterload

17
Q

What does inotropy mean?

A

The amount of force of contraction

18
Q

What does lusitropy mean?

A

The amount of relaxation

19
Q

What do the x and y co-ordinates represent on the Starling Curve?

A 
Y = Contractile Energy
X = Fibre Length
20
Q

What are some factors of blood flow resistance?

A
  • Pressure differences between the ends of the vessels
  • Blood viscosity
  • Length of vessel
  • Radius of vessel
21
Q

What is stroke volume?

A

Amount of blood ejected from the ventricles

22
Q

How do you calculate stroke volume?

A

By subtracting the amount of blood that is left in the ventricles after contraction (ESV) from the amount of blood which filled the ventricles at the end of ventricular filling (EDV)
SV = EDV-ESV (ml)

23
Q

What does the pressure-volume loop represent?

A

The relationship between ventricular pressure and volume throughout the cardiac cycle

24
Q

Describe how venous return is increased during exercise

A

By the skeletal muscle pump and vasoconstriction

25
Q

What is Cardiac Output?

A

Amount of blood pumped by each ventricle per minute. (l/min)

26
Q

What does the cardiac output represent?

A

BF for the entire CVS

Reflects the ability of the heart to meet the bodys need for BF

27
Q

What happens to CO during exercise?

A

Increases to meet the needs of the skeletal muscle for increased blood flow

28
Q

SV vs CO

A 
SV = amount of blood pumped with each beat
CO = amount of blood pumped per minute
29
Q

What three factors affect SV?

A
  • Preload
  • Afterload
  • Contractility
30
Q

What is the Frank Starling law of the heart?

A

An increased stretch of the heart enhances the contraction of the heart therefore more blood is ejected.

31
Q

Why is the FS law important?

A

Provides an intrinsic mechanism to equalise CO between the R and L ventricles

Cardiac Rehabilitation (4 decks)

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