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HOM: cardiovascular physiology > Lecture 1: overview > Flashcards

Lecture 1: overview Flashcards

1
Q

What Einstein’s equation showing the reletionship between diffusion time and distance?

A

t α x2

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2
Q

What is the average distance of a neuromusclular gap?

How long does it take for diffusion to occur across this?

A

0.1µm

5x10-6 s

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3
Q

What is the average distance of a diffusion across a capillary wall?

how long does this take?

A

1µm

5x10-4 s

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4
Q

What is the average diffusion distance from a cell to a capillary?

How long does this take?

A

10µm

0.05s

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5
Q

What is the distance across the ventricle wall?

How long would it take for blood to diffuse across this distance?

A

1cm

15.5 hours

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6
Q

Why is pressure in the lungs low?

A

More time for diffusion since blood travels at a lowe velocity

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7
Q

What is William Harvey known for?

A

First person to describe the properties of blood being pumped around the body by the heart

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8
Q

How much blood is pumped by the human heart over the average lifetime?

A

200,000,000 litres

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9
Q

What is the ‘skeleton’ of the heart made from?

What does this form?

A

Collagen

Junction between atria and ventricles

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10
Q

Where are the cardiac valves held?

A

The annulus fibrosus

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11
Q

What is the epicardium?

A

A serous membrane that forms the innermost layer of the pericardium, attached to the muscles of the wall of the heart.

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12
Q

What is the myocardium?

A

The muscular tissue of the heart (middle layer)

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13
Q

What is the endocardium?

A

The thin, smooth membrane which lines the inside of the chambers of the heart and forms the surface of the valves

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14
Q

What are the 3 layers of all blood vessels, except capillaries?

A

Tunica intima

Tunica media

Tunica adventitia

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15
Q

What is the tunica intima?

A

The single layer of endothelial cells and the supporting internal elastic lamina lining the inside of vessels

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16
Q

What is the tunica media composed of?

A

A dense population of smooth muscle cells organised concentrically with bands or fibres of elastic tissue

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17
Q

What is the tunica adventitia composed of?

A

A collagenous extracellular martix containing fibroblasts, blood vessels and nerves

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18
Q

What is the function of the tunica adventitia?

A

Adds rigidity anf form to the blood vessel

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19
Q

Which layer of blood vessels varies most?

Why is this?

A

Tunica media

Allows large elastic arteries to stretch and recoil during systole and diastole to smooth pressure surges

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20
Q

Nearly all cells in the body are within what distance of a capillary?

A

10µm

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21
Q

Does most resistance come from arteries or veins?

A

Arteries

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22
Q

Why do veins offer low resistance?

A

Large cross-sectional area

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23
Q

How do veins prevent backflow of blood?

A

Pocket valves

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24
Q

What proportion of blood in the system is stored in the veins at any given time?

A

2/3

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25
Q

How do large vessels receive their blood supply?

A

Via the vasa vasorum

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26
Q

How are valves useful in venepuncture?

A

Adding pressure to valves makes veins more superficial

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27
Q

Where are nociceptive fibres located within blood vessels?

A

Tunica adventitia

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28
Q

Does fetal haemoglobin have a higher or lower affinity for oxygen than maternal haemoglobin?

A

Higher

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29
Q

What does P50 represent in terms of oxygen saturation?

Is this value higher in fetus or mother?

A

The partial pressure of oxygen at which 50% of the haemoglobin is saturated

Mother

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30
Q

What are the axis of the oxygen dissociation curve?

What shape does it form?

A

X: Partial pressure of oxygen

Y: Oxygen saturation of haemoglobin

Sigmoidal

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31
Q

What is preferential streaming in the fetus important?

A

Ensures adequate supply of oxygenated blood to tissues most at risk of hypoxic damage e.g. the brain

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32
Q

What are the fetal shunts?

A

Ductus venosus

Ductus arteriosus

Foramen ovale

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33
Q

Where does the ductus venosus shunt blood to?

A

Placenta to right atrium of fetal heart, bypassing most of the fetal liver circulation

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34
Q

Where does the ductus arteriosus shunt blood?

A

Pulmonary artery to descending aorta

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35
Q

Where does the foramen ovale shunt blood?

A

Right atrium to left atrium

36
Q

How much blood enters the ventricles when the atria are relaxed?

A

80%

37
Q

What is the atrial kick/boost?

A

increased flow into the ventricles via atrial contraction during increased exercise

38
Q

Does all blood travel forwards during atrial contraction?

Why is this?

A

No

A small amount of blood is forced backwards into the venae cavae because there are no one-way valves to prevent backflow

Backflow is reduced by narrowing of veins during contraction

39
Q

What causes the pulse seen in the jugular vein?

When is this pulse most visible?

A

Backwards movement of blood from right atrium to venae cavae during atrial contraction

When person is lying horizontally with head and chest elevated at 30º

40
Q

What is indicated by a jugular pulse located higher on the neck when sitting upright?

A

High right atrial pressure

41
Q

What is meant by isovolumetric contraction?

A

Ventricular contraction without any change in ventricular volume (AV and SL valves closed)

42
Q

Why do large elastic arteries become distended during ventricuar ejection?

A

Ventricular blood enters the aorta faster than it can leave

43
Q

What is the reason for the dicrotic notch?

A

Small amount of backflow as ventricular pressure falls below arterial pressure, causing closure of SL valves

44
Q

What proportion of blood flow out of the ventricle is due to contraction?

What causes the movement of the remaining blood?

A

2/3

Kinetic energy

45
Q

What is the term for listenning to heart sounds?

A

Auscultation

46
Q

What is the first heart sound (lub) associated with?

A

Closure of AV valves

47
Q

What is the second heart sound (dub) associated with?

A

Closure of SL valves

48
Q

What is an electromyogram?

A

2 electrodes placed about 2cm apart across a muscle e.g.biceps so that a burst of electrical activity can be recorded when the muscle is contracted

49
Q

What is an electroencephalogram (EEG)?

A

Electrodes placed on skull potentials to record neuronal activity

50
Q

What is an electroretinogram?

A

Electrodes placed on the eye to record electrical activity from light flashes

51
Q

What is an electrocardiogram (ECG)?

A

A process whereby small potenials (approx. 1mv)are recorded between different locations on the skin that reflect the underlying activity of the heart

52
Q

Who discovered the ECG and when?

A

William Einthoven and Augustus Waller

53
Q

What does the P wave on an ECG correspond to?

A

Atrial depolarisation

54
Q

What does the QRS complex on an ECG correspond to?

A

ventricular depolarisation

55
Q

What does the T wave on an ECG correspond to?

A

Ventricular repolarisation

56
Q

Why is atrial repolarisation not represented on an ECG trace?

A

Masked by QRS complex

57
Q

How can heart rate be measured from an ECG?

A
58
Q

How may a long QT interval in an ECG (long Q-T syndrome) be caused?

A
  1. Inherited channelopathies in which mutations occur in myocardial Na+ and K+ channels
  2. Side effects from seldane (non-sedating antihisthamine) which binds to K+ repolarisation channels
59
Q

What does the width of the pressure volume loop represent?

A
60
Q

What does the area within the pressure-volume loop represent?

A

Ventricular stroke work

61
Q

What is aortic stenosis?

A

Impairment of left ventricular emptying because of high outflow resistance caused by a reduction in the valve orifice area when it opens

62
Q

What are the effects of aortic stenosis?

A
  • Increased pressure in ventricle
  • Increased cardiac afterload
  • Decreased stroke volume
  • Increased end systolic volume
  • Increased cardiac muscle mass
  • Increased risk of heart failure
63
Q

What is the contractility of the heart dependent on?

A

Degree of stetch of the myocytes

64
Q

What is the end diastolic volume (EDV)?

A

Amount of blood left at the end of cardiac filling

65
Q

What is the end systolic volume (ESV)?

A

Amount of blood left in the heart at the end of ventricuar ejection

66
Q

What is afterload equivalent to?

A

Peripheral resistance

67
Q

What happens to cardiac output when afterload and heart rate are maintained at a constant level and pre-load is increased?

What else is affected as a result of this?

A

Cardiac output increases

  • Left ventricular and aortic pressures increase
  • Increased EDV
68
Q

What does Starling’s law state?

A

The energy of contraction is a function of the length of the muscle fibre

69
Q

Why is the cardiac response to increased afterload described as bi-phasic?

A

Initial decrease in CO (1-2 beats)

Followed by increased/recovery of CO

70
Q

What happens to CO when afterload is increased

A

Initial decrease in CO

heart is pumping against increased resistance so less emptying of ventricles and increased ESV lead to decreased stroke volume and subsequent decrease in CO

Then CO increases

Afterload increases EDV which increases stretch and therefore increases CO (Starling)

71
Q

What is the Anrep effect?

A

An autoregulation method in which myocardial contractility increases with afterload

72
Q

According to the Anrep effect, how does sustained myocardial contracility increase CO?

A
  • Activates tension dependent Na+/K+ exhangers bringing Na+ into the sarcolemma
  • Reduces Na+ gradient so sodium-calcium exhanger (NCX) stops working effectively
  • Ca2+ accumulates inside sarcolemma, taken up by SERCA pumps
  • CICR from SR by action potential
  • Increased force of contraction = increased SV = Increased CO to maintain perfusion
73
Q

How is the heart innervated?

What does this control?

A

Parasympathetic and sympathetic branches of the autonomic nervous system

Rate and force of contraction

74
Q

Where do the nerves supplying the heart originate?

A

Cardio-vascular centre of the medulla oblongata

75
Q

What are the sympathetic nerves supplying the heart?

A

Cardiac accelerator nerves

76
Q

Where do sympathetic nerves supplying the heart travel?

A

Cardiovascular centres in medulla oblongata

↓

Thorocic region of spinal cord

↓

SA node, AV node and most portions of the myocardium

77
Q

What is released by sympathetic cardiac nerves?

Where does this bind?

A

Noradrenaline

β1 receptors on cardiac muscle fibres

78
Q

What is the physiological effect of increased sympathetic innervation of the heart?

A

At SA node frequency of contaction increased (positive chronotropic effect)

At contractile fibres in the ventricle, contraction increased (positive inotropic effect)

79
Q

Which nerves control parasympathetic innervation of the heart?

A

Vagus nerves

80
Q

What neurotransmitter is released by the vagus nerves?

A

Acetylcholine

81
Q

Where does acetylcholine act in the heart?

A

Muscarinic receptors at the AV and SA nodes and at the atrial myocardium

82
Q

What is the physiological effect of increased parasympathetic innervation of the heart?

A

Decreased heart rate (negative chronotropic effect)

Little effect on contractility of the ventricles

83
Q

How does adrenaline effect heart rate?

A

Acts on β1 receptors to increase frequency an force of contraction

84
Q

What is the chronotropic effect?

A

Change in heart rate

85
Q

What is the inotropic effect?

A

Force of contraction

86
Q

What is the initial membrane potential of the SA node?

A

-60mV

87
Q

What is the threshold value of nodal cells?

A

-40mV

HOM: cardiovascular physiology (7 decks)

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