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Physiology Year 1 > Cardiovascular > Flashcards

Cardiovascular Flashcards

1
Q

Why do we need a CVS?

A

Pump blood through lungs & carry oxygen, Transport nutrients to muscles & organs, Circulates hormones & immune mediators, Connection to lymphatic system, Human Reproduction, Temperature Regulation

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2
Q

Fick’s Law (of Diffusion)

A

The time needed to diffuse a given distance is proportional to the square of the distance. t ∝ d²

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3
Q

Deoxygenated Blood Circulation

A

Blood returns to the heart, from the veins, via the right atrium and is pumped through the lungs by the right ventricle.

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4
Q

Oxygenated Blood Circulation

A

Blood returns to the heart, from the lungs, via the left atrium and is pumped through the body by the left ventricle.

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5
Q

Pulmonary Circuit

A

The pathway of deoxygenated blood through the heart, to the lungs.

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6
Q

Systemic Circuit

A

The pathway of oxygenated blood, out from the heart, towards the rest of the body.

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7
Q

Vein

A

A blood vessel that carries blood to the heart, from other parts of the body.

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8
Q

Artery

A

A thick blood vessel that carries blood from the heart to other parts of the body.

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9
Q

Systole

A

The contraction or period of contraction, of the heart, in which blood is forced into the aorta and pulmonary artery.

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10
Q

Diastole

A

The phase in which the heart relaxes, between contractions; specifically the period when two ventricles are dilated, by the blood flowing into them.

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11
Q

What drives blood flow?

A

Output of blood at high pressure creates a pressure difference with the distant blood vessels. The Pressure difference drives blood flow.

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12
Q

Typical Resting Blood Pressure

A

120/80 mmHg

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13
Q

Cardiac Output

A

The volume of blood expelled/ejected by either ventricle of the heart, per unit of time (per min). (usually refers to the left ventricle output)
Cardiac Output = Heart Rate x Stroke Volume

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14
Q

Maximum Heart Rate

A

220 - Age

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15
Q

How do you control blood flow?

A

Controlling the resistance of the vessels gives some control of blood flow.

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16
Q

Blood Flow

A

Blood flow = (Pa - Pv) / Resistance (increased resistance = lower blood flow)

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17
Q

Blood flow is…

A

1) Proportional to pressure across blood vessel

2) Inversely proportional to resistance of blood vessel

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18
Q

Difference in pressure of the Systemic and Pulmonary Systems

A

High pressure for systemic circulation, to pump blood around the body. Low pressure for the pulmonary circulation system to allow gas exchange.

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19
Q

4 main functional groups of blood vessels

A

Arteries, Arterioles, Veins & Venules, Capillaries

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20
Q

Arteries

A

Elastic vessels: Accommodate stroke volume convert ejection into continuous flow

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21
Q

Arterioles

A

Resistance vessels: Control arterial BP and regulate local blood flow

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22
Q

Veins & Venules

A

Capacitance Vessels: Control filling pressure of the heart and provide a reservoir of blood

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23
Q

Capillaries

A

Exchange Vessels: Nutrient Delivery to cells tissue water and lymph formation removal of metabolic waste

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24
Q

Clinical Significance of Cardiac Output

A

Myocardium (muscular tissue of the heart) & brain are relatively under perfused. This creates potential clinical problems e.g. Angina, MI, stroke triggered by relatively moderate fall in perfusion. Cardiac Output and blood flow needs to be carefully controlled.

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25
Q

Where is the main drop of pressure in the pressure profile of circulation?

A

Arterioles, just before the capillaries. This drop in pressure and then the continuous fall in pressure creates a pressure difference. That is what actually drives the flow.

26
Q

Why does blood slow down in capillaries?

A

The total cross-sectional area increases, due to the increase in the number of capillaries. This slows down the blood, because the flow is the same, therefore, the velocity will be inversely proportional to the total cross-sectional area.

27
Q

How do you calculate blood velocity?

A

blood flow / TOTAL cross-sectional area

28
Q

What is the advantage of blood flow being slower in capillaries?

A

It allows gaseous/nutrient exchange to occur.

29
Q

Where is the greatest volume of blood located, when distributed?

A

Systematic Veins and venules serve as a reservoir, holding 65% of volume.

30
Q

Structure of Blood Vessel Walls

A

Sympathetic nerves in the tunica adventitia release noradrenaline, which stimulates α1 receptors leading to vasoconstriction.

Endothelium releases nitric oxide which relaxes the vessels leading to vasoconstriction.

31
Q

Sinoatrial Node

A

A group of cells located in the wall of the right atrium.
Ability to spontaneously produce an action potential, that travels through the heart vis the electrical conduction system. Sets the rhythm of the heart and so it is known as the heart’s natural pacemaker. The rate of action potential production (and therefore the heart rate) is influenced by nerves that supply it.

32
Q

Atrioventricular Node

A

Part of the electrical conduction system of the heart. Electrically connects the right atrium and the right ventricle, delaying impulses that atria have time to eject their blood into ventricles before ventricular contraction.

33
Q

What is the resting potential of the cell?

A

Resting negative voltage in the cell interior, as compared to the cell exterior. It ranges from -40mV to -80mV.

34
Q

Depolarisation

A

The reduction of the membrane’s resting potential, so that it becomes more positive and less negative.

35
Q

Repolarisation

A

A change to the membrane’s potential, after depolarisation, so that it returns to its resting potential.

36
Q

P wave

A

Atrial depolarisation and contraction

37
Q

PR Segment

A

AV Nodal delay

38
Q

QRS Complex

A

Ventricular depolarisation contraction (atria repolarising simultaneously)

39
Q

ST Segment

A

Ventricles contracting and emptying

40
Q

T Wave

A

Ventricular Repolarisation

41
Q

TP interval

A

Ventricles are relaxing and filling

42
Q

Cardiac Diastole

A

All chambers are relaxed and blood flows into the heart

43
Q

Atrial Systole, Ventricular Diastole

A

Atria Contract, pushing blood into relaxed ventricles.

44
Q

Ventricular Systole, Atrial Diastole

A

After the atria relax, ventricles contract, pushing blood out of the heart.

45
Q

Lub

A

Closure of tricuspid/mitral valves at the beginning of the ventricular systole

46
Q

Dub

A

Closure of aortic/pulmonary valves (semilunar valves) at end of ventricular systole

47
Q

Blood Flow Equation

A

Blood Flow (CO) = Blood Pressure/ Total Peripheral Resistance

48
Q

Heart Rate & Contractility

A

SA Node pacemaker also sympathetic and parasympathetic nerves control heart rate. The strength of the contraction is due to sympathetic nerves and circulating adrenaline increasing intracellular calcium.

49
Q

Preload

A

Stretching of heart at rest, increases stroke volume, due to Starling’s Law

50
Q

Afterload

A

Opposes ejection, reduces stroke volume, due to Laplace’s Law

51
Q

Starling’s Law

A

Energy of contraction of cardiac muscle is relative to the muscle fibre length at rest.

Greater stretch of ventricle in diastole( blood entering), then greater energy of contraction and greater stroke volume achieved in systole.

52
Q

Central venous Pressure

A

mmHg end diastole pressure or filling pressure

53
Q

Molecular Basis SL- Unstretched Fibre

A

Overlapping actin/myosin, Mechanical inference, Less Cross-bridge formation available for contraction

54
Q

Molecular Basis SL- Stretched Fibre

A

Less Overlapping actin/myosin, less mechanical inference - potential for more cross-bridge formation, increased sensitivity to Ca2+ ions

55
Q

Effects of Starling’s Law

A

Balances outputs of the right ventricle and left ventricle!!!
Fall in cardiac output during a drop in blood volume or vasodilation( e.g. haemorrhage, sepsis)
Restores cardiac output in response to intravenous fluid transfusions.
Responsible for fall in cardiac output during orthostasis (standing for a long time) leading to postural hypotension & dizziness as blood pools in legs.
Contributes to increased stroke volume & cardiac output during upright exercise.

56
Q

Afterload (explained)

A

Afterload opposes the contraction that ejects blood from the heart and is determined by wall stress directed through the heart wall. Stress through the wall of the heart prevents muscle contraction.

57
Q

Laplace’s Law

A

Describes parameters that determine afterload. Wall tension (T), pressure (P) and radius (r) in a chamber
T∝Pr

58
Q

Wall stress equation linked to LL

A

S (Wall stress)= T (wall tension)/ w (wall thickness)

S= Pr/ 2w

59
Q

How do you increase afterload?

A

Increasing pressure and radius

60
Q

How do you decrease afterload?

A

Increasing wall thickness

61
Q

Why does radius affect wall stress/afterload?

A 
Small ventricle radius
•Greater wall curvature
•More wall stress directed towards centre of chamber
•Less afterload
•Better ejection
Larger ventricle radius
•Less wall curvature
•More wall stress directed through heart wall
•More afterload
•Less ejection
Huge theoretical radius
•Negligible wall curvature
•Virtually all stress directed through wall
62
Q

Importance of LL

A

Opposes Starlings Law at rest, Facilitates ejection during contraction, Contributes to a failing heart at rest and during contraction

Physiology Year 1 (5 decks)

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