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Cardiovascular Physiology > Force generation > Flashcards

Force generation Flashcards

1
Q

What are the striations in the cardiac muscle caused by?

A

Regular arrangement of contractile proteins- the alternating of action and myosin.

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2
Q

What are gap junctions?

A

Protein channels that form low electrical communication pathways between neighbouring monocytes.

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3
Q

What do the intercalated discs contain?

A

Desmosomes

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4
Q

What do the desmosomes do?

A

Provide mechanical adhesion between neighbouring cells and spread tension from one cell to the next.

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5
Q

What do muscle fibres contain?

A

Myofibrils

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6
Q

What are myofibrils?

A

Contractile unit of the heart

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7
Q

What protein filaments are contained in myofibrils?

A

Actin (thin and light)

Myosin (dark and thick)

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8
Q

What are myosin and actin arranged in?

A

Sarcomeres

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9
Q

What is a sarcomere?

A

Functional unit of the heart

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10
Q

What causes muscle tension?

A

The sliding of action and myosin

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11
Q

What is force generation dependent on?

A

ATP interaction between actin and myosin.

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12
Q

What must be present before interaction?

A

Calcium.

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13
Q

What does calcium do to allow myosin to bind to actin?

A

Bonds to troponin which causes the troponin tropomysin complex to slide away exposing the myosin binding site on the actin.

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14
Q

Where is calcium stored?

A

In the lateral sacs of the sacroplasmic reticulum.

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15
Q

What is required for calcium to be released from the lateral sacs?

A

Extra cellular calcium.

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16
Q

In the plateau phase how does calcium enter the cardiac muscle cell?

A

Through l type Ca channels.

17
Q

What is intrinsic mechanisms?

A

Within the heart muscle itself

18
Q

What are extrinsic mechanisms?

A

Nervous and hormonal control

19
Q

What is the refectory period?

A

The period following an action potential in which it is not possible to produce another action potential.

20
Q

What is the importance of the refractory period?

A

It is protective of the heart, preventing the generation of tetanic contractions in the cardiac muscle.

21
Q

What is the stroke volume?

A

The volume of blood ejected by each ventricle per heart beat.

22
Q

How is the SV regulates?

A

By intrinsic and extrinsic mechanisms.

23
Q

How are changes in the SV brought about?

A

By changes in the diastolic length of the myocardial fibres. The more the heart is stretched the greater the SV.

24
Q

What does the end diastolic volume determine?

A

The cardiac preload and it’s determined by the venous return to the heart.

25
Q

What does the frank-Starling mechanism state?

A

The greater the End Diastolic Volume the greater the SV.

26
Q

What else does stretching the heart muscle achieve?

A

It increases the affinity of troponin for Ca.

27
Q

What is the preload?

A

The amount of blood lodged into the heart before contraction.

28
Q

What is the afterload?

A

The resistance into which the heart is pumping. Extra load imposed after contraction.

29
Q

What is the sympathetic neurotransmitter?

A

Noradrenaline

30
Q

What does sympathetic stimulation of the ventricular muscle achieve?

A

Increases force of contraction (positive inotropic effect).

31
Q

What is a positive inotropic effect?

A

Increasing the rate of contraction.

32
Q

On a graph of ventricular contraction, where would a positive inotropic effect lie?

A

To the left.

33
Q

On a graph of ventricular contraction, where would a negative inatropic effect lie?

A

To the right.

34
Q

What effect does adrenaline and noradrenaline have on the heart?

A

Both a inotropic and chronotropic effect.

35
Q

What is the cardiac output?

A

The volume of blood pumped by each ventricle per minute.

36
Q

How do you calculate the cardiac output?

A

CO=SV x HR

37
Q

What is the resting CO in a normal adult?

A

5 litres a minute.

38
Q

How is the CO regulated?

A

By regulated the SV (intrinsic and extrinsic) and by regulating the HR (sympathetic and parasympathetic)

Cardiovascular Physiology (5 decks)

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