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Physiology of human organ systems > cardiovascular system > Flashcards

cardiovascular system Flashcards

1
Q

What is Darcy’s law?

A

Flow rate = pressure change/ resistance

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2
Q

What is a cardiac functional synctium?

A

Group of cells interlinked physically and electrically with multiple nuclei, that act as one fibre.

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3
Q

What forms physical connections between cardiac cells?

A

Desosomes.

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4
Q

What forms electrical connections between cells?

A

Gap junctions.

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5
Q

Can cardiac muscle produce tetanic contractions?

A

No.

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6
Q

Why can cardiac cells not produce tetanic contractions?

A

They have a long refractory period; the cell takes a while to repolarise. This results in a longer time between each contraction and means tetanic contracture is not possible.

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7
Q

What allows sino-atrial cells to act as pacemakers?

A

They have no plateau segment, because as soon as the cell repolarises to its resting potential, this activates the cyclic calcium channels which allow for a slow depolarisation.

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8
Q

How fast does SAN pacemaker potential travel?

A

0.5m/s

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9
Q

Which structure delays the AVN ap to 0.05m/s

A

annulus fibrosus.

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10
Q

Where does the action potential travel fastest?

A

The bundle of His and Purkinje fibres.

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11
Q

What is the first sound on a phonocardiogram?

A

AV valve closure.

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12
Q

What is the second sound on a phonocardiogram?

A

Semilunar valve closure.

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13
Q

What is the third sound on a phonocardiogram?

A

Passive refilling of chambers.

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14
Q

What is the fourth sound on a phonocardiogram?

A

Active refilling of chambers.

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15
Q

What might be the cause of a systolic heart murmur?

A

Semilunar valve stenosis or AV valve regurgitation.

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16
Q

What might be the cause of a diastolic heart murmur?

A

AV valve stenosis or semilunar valve regurgitation.

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17
Q

What might be the cause of a continuous murmur?

A

Septal defect.

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18
Q

What do adrenaline and noradrenaline act on?

A

They bind to beta receptors on pacemaker cells. They increase the permeability of the slow-release calcium channel, causing them to reach the threshold earlier. This increase heart rate.

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19
Q

Which nerve decreases heart rate?

A

The vagus nerve secretes acetylcholine, which binds to muscarinic receptors and slows down the heart rate.

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20
Q

What is frank-starlings’ law?

A

Energy of heart contraction is directly proportional to the initial length of the muscle fibres.

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21
Q

What is the preload?

A

The passive muscle tension caused by the passive force of the blood in a chamber.

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22
Q

What is the afterload?

A

The force required for the muscle fibres to overcome preload and eject the blood.

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23
Q

What might affect the preload?

A

The venous return.

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24
Q

What might affect the afterload?

A

The total peripheral resistance of the arteries/arterioles (these are the resistance vessels)

25
Q

Is the vagus nerve sympathetic or parasympathetic?

A

Parasympathetic.

26
Q

What is cardiac output?

A

Heart rate x stroke volume.

27
Q

Explain how to measure systolic blood pressure using the korotkoff method.

A

Inflate a cuff until no sound can be heard after the occlusion. Slowly release the cuff pressure a sound can be heard. This is the systolic pressure.

28
Q

Explain how to measure diastolic pressure using the korotkoff method.

A

Reduce the cuff pressure from the measured systolic pressure until the turbulent sound can no longer be heard. This is the diastolic pressure.

29
Q

How does gravity affect blood circulation and the heart?

A

The veins are distensible, meaning they can expand and pool more blood when they are lower in the body and subject to stronger forces. The result is that venous return is reduced.

30
Q

How can reduced venous return result in postural hypertension?

A

Reduced venous return reduces preload and end-diastolic volume and reduced cardiac output. This can result in a sudden drop in mean arterial blood pressure.

31
Q

How can gravity help measure central venous return?

A

Veins above the heart can collapse in response to reduced forces. This can be interpreted to yield a central venous pressure.

32
Q

What are the three ways in which the body can increase venous return?

A

Skeletal muscle pump
Respiratory pump
Venomotor tone

33
Q

How does venomotor increase VR?

A

Smooth muscle in the veins can contract and push the blood along, in a similar way to arteries.

34
Q

How can the respiratory pump increase VR?

A

Inspiring increase the thoracic pressure, which forces blood back to the heart and thus pull more blood back to the heart.

35
Q

How can skeletal muscle pump increase VR?

A

The skeletal muscle can massage the blood back up to the heart via its normal action.

36
Q

When is the skeletal muscle pump particularly important and present?

A

During exercise.

37
Q

What are continuous capillaries and where might they be found?

A

They are capillaries with tight junctions between them and no pores at all. They are the blood capillaries that form the blood brain barrier.

38
Q

What are discontinuous capillaries?

A

Capillaries with large pores that allow for mass fluid exchange.

39
Q

Explain how bulk flow pushes certain contents out of the blood stream.

A

Hydrostatic pressure is high and oncotic pressure low. The high fluid pressure forces solute out, into the interstitial fluid.

40
Q

Explain how bulk flow pulls content into the blood stream.

A

As the hydrostatic pressure pushes content out, it decreases in volume and pressure which increases the oncotic (osmotic) pressure because plasma proteins haven’t left the blood stream.

41
Q

How much of the interstitial fluid is reabsorbed by the lymphatic system?

A

15%

42
Q

What happens when the blind ended lymph vessels become blocked?

A

They accumulate lymph and form an oedema.

43
Q

What is the equation for mean arterial pressure?

A

MAP= cardiac output x total peripheral resistance

44
Q

In the process active metabolic hyperaemia, what do the endothelial cells detect?

A

Metabolite concentrations

45
Q

What do endothelial cells do when they detect an increased metabolite concetration?

A

Secrete EDRF paracrine signal to cause arterioles to relax and increase blood flow.

46
Q

What must match the rate of metabolite production?

A

The perfusion.

47
Q

What is flow/pressure autoregulation?

A

When metabolite concentration decrease is detected, it can indicate a drop in MAP and therefore, the cells constrict to increase the pressure.

48
Q

When might reactive hyperaemia occur?

A

When a blood vessel occlusion causes a build-up of metabolites.

49
Q

When the body is injured, where does a dendrite of c-fibre nociceptors go?

A

They stimulate mast cells to release histamine, which induces arterioles to dilate in the region.

50
Q

Where is the parasympathetic control of circulation?

A

There isn’t any for the majority- exceptions are gonads and salivary glands.

51
Q

What do adrenaline and noradrenaline bind to?

A

In the periphery, they bind to alpha 1 and induce arteriolar constriction.
In skeletal and cardiac muscle, they bind to beta 2 receptors and cause dilation

52
Q

Why are coronary vessel receptors particularly sensitive to hyperaemia?

A

The contraction of the heart causes the coronary vessels to occlude. This means the heart muscle does not receive blood during systole, at the peak pressure.

53
Q

Which nerve are the carotid sinus baroreceptors innervated by?

A

The glossopharyngeal nerve.

54
Q

Where can the cardiovascular centre be found?

A

The medulla.

55
Q

What is the initial step in the valsalva manoeuvre?

A

Forced expiration but with the glottis closed.

56
Q

What does the valsalva manoeuvre cause?

A

An increased intrathoracic pressure.

57
Q

What does an increased intrathoracic pressure cause?

A

It causes a reduction on venous return and therefore filling pressure. This results in a drop in MAP.

58
Q

What does the body do in response to a sharp drop in MAP?

A

The baroreflex kicks in and increases the blood pressure and venous return.

59
Q

When the valsalva manoeuvre is stopped, what happens?

A

The blood pressure very suddenly increases

Physiology of human organ systems (5 decks)

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