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X Physiology 1A > Cardiovascular System > Flashcards

Cardiovascular System Flashcards

1
Q

What is the essential role of the cardiovascular system?

A

meeting the metabolic demands of almost every cell, tissue and organ in the body

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2
Q

What happens to speed of diffusion rates over long distances?

A

become very slow

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3
Q

Can diffusion meet physiological demands over large distances?

A

no

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4
Q

What sort of transport system is the cardio vascular system?

A

bulk/convective transport system

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5
Q

What does the cardiovascular system transport?

A

respiratory gasses, nutrients, hormonal signals

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6
Q

What organs does the pulmonary circulation provide?

A

lungs

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7
Q

What processes are supported by systemic circulation?

A

metabolic

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8
Q

in what part of the cardiovascular system does diffusion occur?

A

capillaries in tissues and the lungs

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9
Q

Describe the flow of blood through the heart.

A

deoxygenated blood from the body flows into the right atrium from the vena cava and into the right ventricle, out of the pulmonary artery and to the lungs for exchange of O2 and CO2. From the lungs blood flows through the pulmonary vein into the left atrium and then left ventricle. Blood flows out of the left ventricle into the aorta.

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10
Q

Name the 5 primary functions of the cardiovascular systems.

A 
respiratory gas exchange
nutrient supply/waste removal
hormonal signalling
fluid maintenance
body temperature regulation
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11
Q

How does the cardiovascular system regulate body temperature?

A

brings blood from deep tissues and organs to the skin so heat can be lost during vasodilation. Vasoconstriction reduces blood flow to peripheries so it isn’t lost in this way

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12
Q

What can be done to a sample of blood in a tube to separate it’s contents?

A

centrifugation

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13
Q

What are the components of blood?

A

Plasma, white blood cells, red blood cells

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14
Q

How will a sample of centrifuged blood look?

A

plasma on the top with a buffy coat in the middle of white blood cells. Red blood cells form the bottom layer

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15
Q

What colour is plasma?

A

straw coloured

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16
Q

what does plasma consist of?

A

mainly water but, also contains electrolytes, glucose plasma proteins and other organic molecules

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17
Q

What is the total blood volume in an average human?

A

5l

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18
Q

What is the average plasma volume of a human?

A

3l

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19
Q

where are most plasma proteins produced?

A

the liver

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20
Q

what are immunoglobulins produced by?

A

mature B lymphocytes

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21
Q

what is serum?

A

plasma with clotting agents removed

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22
Q

What the 3 major fluid compartments of the body?

A

intracellular, interstitial and vascular

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23
Q

what proportion of body water is intracellular?

A

2/3

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24
Q

What gradient moves blood around the body?

A

pressure gradient generated by pump action of heart

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25
Q

what is the resting blood pressure in the left ventricle?

A

120 mmHg

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26
Q

What structure in the aorta prevents backflow during diastole?

A

aortic valve

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27
Q

What is the average systolic blood pressure in main arteries?

A

120 mmHg

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28
Q

What is the average diastolic blood pressure in the main arteries?

A

80 mmHg

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29
Q

What are the function of the atria?

A

receives blood from veins

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30
Q

what are the function of the ventricles?

A

pump blood into arteries

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31
Q

How does the length of the relaxation phase in the heart compare to the length of the contraction phase?

A

usually twice as long

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32
Q

What is systole?

A

contraction of the heart

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33
Q

Is blood pressure in veins lower or higher than that in the arteries?

A

lower - approx 10 mmHg

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34
Q

What are the major types of blood vessel?

A

arteries (arterioles)
veins
capillaries

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35
Q

What do arterioles control?

A

entry of blood into capillaries

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36
Q

How do veins compare to arteries?

A

more elastic and thinner walled

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37
Q

How thick are capillary walls?

A

single celled

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38
Q

What is the distribution of blood volume in a resting human?

A 
systemic veins and venules: 60-70%
pulmonary circulation: 10-12%
heart: 8-11%
systemic arteries: 10-12%
systemic capillaries: 4-5%
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39
Q

how is percentage of blood volume in systemic veins and venules affected by exercize?

A

much reduced

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40
Q

What does autonomic regulation of the cardiovascular system ensure for the body?

A

metabolic demands of body are met despite changes in activity

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41
Q

What afferent feedback is given from the cardiovascular system?

A

blood pressure, O2 level, pH level

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42
Q

Why is bulk transport necessary?

A

diffusion is too slow to meet the metabolic demands of the body

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43
Q

What part of the nervous system is the cardiovascular system under the control of?

A

autonomic

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44
Q

where does electrical activity in the heart arise from?

A

sino-atrial node

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45
Q

What sort of cell are all cells in the heart?

A

muscle cells

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46
Q

In normal hearts how many routes are there for action potential to travel to the ventricles?

A

one

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47
Q

Is the fibrous septum conductive or non-conductive?

A

non-conductive

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48
Q

what is the name of the fibres that supply electrical signal to the ventricles down the septum?

A

purkinje fibres

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49
Q

How long is the duration of a cardiac action potential?

A

long (300-350 ms)

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50
Q

How does the length of action potential compare between atria and ventricles?

A

atrial AP is much shorter

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51
Q

How many phases are there of the ventricular action potential?

A

5 (0-4)

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52
Q

What happens during phase 0 of the ventricular action potential?

A

due to activation of voltage gated Na+ channels there is an inward current of Na+ (movement towards Na+ equilibrium potential) and a rapid upstroke of action potential

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53
Q

How does the membrane potential change during phase 0 of ventricular action potential?

A

membrane becomes + (depolarizes) as permeability to sodium increases

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54
Q

What happens during phase 1 of the ventricular action potential?

A

early repolarisation of the membrane due to inactivation of sodium channels

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55
Q

How does the membrane potential change during phase 1 of ventricular action potential?

A

starts to become more negative

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56
Q

What is phase 2 of the ventricular action potential known as?

A

plateau phase

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57
Q

What happens during phase 2 of the ventricular action potential?

A

plateau phase due to inward current through voltage gated calcium channels.

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58
Q

How quick are calcium channels to activate and inactivate?

A

slow

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59
Q

What happens during phase 3 of the ventricular action potential?

A

repolarization brought about by inactivation of calcium channels and increase in membrane permeability to potassium

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60
Q

What happens during phase 4 of the ventricular action potential?

A

corresponds to the resting membrane potential and is largely determined by permeability to K+

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61
Q

What action triggers Ca2+ release from the sarcoplasmic reticulum?

A

Ca influx through open gated Ca channels

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62
Q

What process initiates cardiac muscle contraction?

A

Ca influx through open gated Ca channels triggers Ca2+ release from the sarcoplasmic reticulum

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63
Q

What does the inward current of Ca delay?

A

repolarization

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64
Q

What does delayed repolarization of cardiac myocytes maintain?

A

plateau phase of ventricular contraction cycle

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65
Q

What is the second part of the plateau phase?

A

the refractory period

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66
Q

How excitable is the cell while it is depolarized?

A

it is electrically in excitable

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67
Q

Why is it important that the cell is in-excitable while depolarized?

A

each action potential only generates a single twitch as tetany would be fatal

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68
Q

What state are sodium channels in during the absolute refractory period?

A

sodium channels are inactivated

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69
Q

When do sodium channels begin to recover from inactivation ?

A

as the membrane potential repolarizes from -50mV

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70
Q

What is the process of sodium channels recovering from inactivation called?

A

relative refractory period

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71
Q

Why do sinoatrial nodes show an unstable resting membrane potential?

A

combination of slow inward sodium and calcium currents

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72
Q

Which branches of the autonomic nervous system innervate sino-atrial and conduction fibres?

A

both sympathetic and parasympathetic neurons

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73
Q

How does sympathetic fibre activity accelerate the heart?

A

noradrenaline binds to beta1-adrenoreceptors resulting in an increased slope of the pacemaker potential

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74
Q

What is the acceleration of heart rate called?

A

positive chronotropism

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75
Q

How does parasympathetic fibre activity slow the heart?

A

acetylcholine binds to muscarinic receptors causing a decrease in the slope of the pacemaker potential and also slight hyperpolarisation

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76
Q

What is deceleration of the heart called?

A

negative chronotropism

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77
Q

What is found within intercalated disks which aid the transfer of electrical signal between myocytes?

A

gap junctions

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78
Q

Why is the conduction velocity of the AV node relatively slow?

A

ensures atrial filling of the ventricles is complete before the ventricles contract

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79
Q

What does the electrocardiogram detect?

A

electrical field around the heart set up by the conduction of action potential throughout the heart

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80
Q

what does the P wave on a ECG show?

A

atrial depolarisation

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81
Q

What does the QRS complex on a ECG show?

A

ventricular depolarization

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82
Q

What does the T wave on an ECG show?

A

ventricular repolarisation

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83
Q

during which of the waves of a ECG does atrial repolarisation occur?

A

QRS

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84
Q

What occurs during the R wave?

A

depolarization spreads downwards and outwards from the ventricular septum

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85
Q

What happens in the heart and on the ECG during the ST segment?

A

ventricles are depolarized and ECG returns to isoelectric line

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86
Q

What happens in the heart during the T wave?

A

repolarization spreading inwards towards the ventricular septum

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87
Q

Where do action-potentials arrive?

A

specialised cardiac myocytes in the sinoatrial nodes

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88
Q

What is heart rate controlled by?

A

changing the rate of diastolic depolarization of pacemaker cells in the sinoatrial node

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89
Q

What is the action potential conducted around the heart by?

A

conduction system of specialised cardiac myocytes

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90
Q

What phase is the plateau phase?

A

2

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91
Q

What does Ca influx during phase 2 trigger?

A

Ca release and cardiac muscle contraction

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92
Q

what does the plateau phase establish?

A

a relatively long refractory period that prevents sustained contraction and re-entrant arrhythmias

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93
Q

What substances does the ideal gas law apply to?

A

fluid and gas

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94
Q

what key substance in the body can the ideal gas law be applied to?

A

blood

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95
Q

What does the ideal gas law state?

A

as pressure increases volume will reduce

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96
Q

What is the name of the right atrial valve?

A

tricuspid valve

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97
Q

What is the name of the right aortic valve?

A

pulmonary artery valve

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98
Q

what is the name of the left atrial valve?

A

mitral valve

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99
Q

what is the name of the left aortic valve?

A

aortic valve

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100
Q

How many pumps are contained within the heart?

A

2

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101
Q

What part of the ECG shows the onset of atrial depolarisation and systole?

A

P wave

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102
Q

what part of the ECG shows depolarization of ventricles?

A

QRS complex

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103
Q

When does passive ventricle filling occur?

A

diastole

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104
Q

What part of the ECG shows pressure decrease in LV and aortic valve closing?

A

T

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105
Q

Why is it important that the aortic and pulmonary valves close once the pressure in the ventricles decreases?

A

prevents back flow

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106
Q

What happens to ventricular volume during ventricular filling?

A

passive filling of ventricles so volume increases

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107
Q

What does ventricular filling end with?

A

atrial systole

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108
Q

What is isovolumetric contraction?

A

Ventricle is contracting but the aortic valve remains closed. Pressure is high enough to close mitral valve but not to open aortic valve

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109
Q

What happens during the ejection phase?

A

aortic valve opens and blood is expelled, volume of ventricles decreases rapidly

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110
Q

What happens during isovolumetric relaxation in the left ventricle?

A

aortic valve closes, mitral valve remains closed

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111
Q

What is end diastolic volume (EDV)?

A

volume of ventricles before atrial systole (maximum volume)

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112
Q

Does EDV or ESV describe the maximum ventricular volume?

A

EDV

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113
Q

Does EDV or ESV describe the minimum ventricular volume?

A

ESV

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114
Q

What is end systolic volume (ESV)?

A

volume of ventricles after ventricular systole and before mitral/tricuspid valves reopen

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115
Q

What is the difference between end diastolic volume and end systolic volume known as?

A

stroke volume

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116
Q

Define stroke volume

A

volume of blood ejected from each ventricle on each beat

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117
Q

when does the aortic valve open in the left ventricle?

A

when ventricular pressure is greater than aortic pressure

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118
Q

what phase of ventricular volume changes is started by the opening of the aortic valve?

A

ejection phase

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119
Q

What pressure changes must take place in the left ventricle before the aortic valve closes?

A

when ventricular pressure is less than aortic pressure

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120
Q

what pressure changes must take place in the left ventricle before the mitral valve opens?

A

ventricular pressure is greater than atrial pressure

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121
Q

what is the dicrotic notch?

A

slight rise in aortic blood pressure after the aortic valve closes

122
Q

define cardiac output (CO)

A

volume of blood in litres pumped by the heart per unit time

123
Q

what is stroke volume measured in?

A

litres per beat

124
Q

what is the equation for cardiac output?

A

CO = stroke volume(litres per beat) X HR (bpm)

125
Q

what is average cardiac output?

A

4-7 litres per minute

126
Q

what is pre-load?

A

degree of stretch on resting muscle prior to contraction

127
Q

what is after load?

A

tension against which the muscle must contract

128
Q

How does cardiac muscle behave in high inotropic state?

A

has higher elasticity so the stretch in muscle prior to contraction will produce greater tension

129
Q

what effect does increase in preload have on cardiac muscle?

A

stretches the sarcomeres

130
Q

What do starling curves show the relationship between?

A

pre-load and amount of blood ejected

131
Q

what does a starling curve show the volume ejected from heart at each beat depends on?

A

filling pressure of the ventricles

132
Q

What does stretch during preload do to the force of contraction?

A

increases it

133
Q

How does a fuller ventricle affect stroke volume?

A

greater stroke volume

134
Q

What is Starlings Law of the Heart?

A

the energy of contraction of a cardiac muscle fibre is proportional to the initial fibre length at rest

135
Q

What are the heart inlet valves?

A

tricuspid and mitral (left)

136
Q

what are the heart outlet valves?

A

pulmonary and aortic (left)

137
Q

When does atrial contraction become significant in filling the ventricles?

A

where HR is elevated above rest

138
Q

In a normal heart how much of stroke volume is ejected at each beat?

A

~60%

139
Q

What do stroke volume and cardiac output depend on?

A

filling of the ventricle during diastole

140
Q

What process determines preload?

A

filling of the ventricle during diastole

141
Q

What does a greater preload lead to?

A

greater energy of subsequent contraction

142
Q

What are the 3 physiological consequences of Starlings law?

A

Output of right and left ventricles is matched
pooling of blood in veins assists with increasing preload and therefore stroke volume during the onset of exercise
heart is sensitive to changes in posture as preload reduces for a short period when moving from lying to standing

143
Q

What are the 3 basic layers of muscular blood vessels?

A

intima
media
adventitia

144
Q

what is contained within the intima layer of muscular blood vessels?

A

specialised endothelial cells, basal lamina, intimal connective tissue

145
Q

what is contained within the media layer of muscular blood vessels?

A

elastin and smooth muscle

146
Q

what is contained within the adventitia layer of muscular blood vessels?

A

connective tissue, vasoconstrictor fibres (sympathetic nerve fibres)

147
Q

what does connective tissue in the adventitia layer provide?

A

support for the blood vessels

148
Q

name the 6 vessel types

A 
large elastic artery
muscular arteries
arterioles
capillaries
venules 
veins
149
Q

give 3 examples of large elastic arteries

A

aorta
pulmonary arteries
carotid arteries

150
Q

what is the wall thickness of the large elastic artery?

A

2mm

151
Q

what is the lumen diameter of large elastic arteries?

A

25mm

152
Q

describe the histology of large elastic arteries

A

thick tunica media with lots of elastin

153
Q

give 3 examples of muscular arteries

A

radial, femoral, coronary

154
Q

what is the wall thickness of the muscular arteries?

A

1mm

155
Q

what is the lumen diameter of the muscular arteries?

A

4.5mm

156
Q

describe the histology of muscular arteries

A

media mainly composed of smooth muscle. well defined elastic laminae

157
Q

what is the function of large elastic arteries?

A

windkessel stretch to accommodate blood in systole

158
Q

what is the Windkessel stretch?

A

energy from systole is stored in the elastic walls and used during diastole

159
Q

what is the function of muscular arteries?

A

distributing vessels

160
Q

what is the wall thickness of arterioles?

A

20 micro metres

161
Q

what is the lumen diameter of arterioles?

A

30 micro metres

162
Q

describe the histology of arterioles

A

contain one to several layers of smooth muscle

163
Q

what is the function of arterioles?

A

resistance vessels and act as a gateway to the micro circulation. Dampen oscillations in flow and pressure

164
Q

what is the wall thickness of capillaries?

A

1 micro metre

165
Q

what is the lumen diameter of capillaries?

A

6 micro metres

166
Q

describe the histology of capillaries

A

endothelial cell layer resting on the basement membrane. No smooth muscle

167
Q

describe the function of capillaries

A

blood travels slowly through these exchange vessels allowing time for diffusion

168
Q

what is the wall thickness of venules?

A

2 micro metres

169
Q

what is the lumen diameter in venules?

A

20 micro metres

170
Q

describe the histology of venules

A

some smooth muscle

171
Q

what is the function of venules?

A

collecting vessels as blood leaves the capillaries

172
Q

give 2 examples of veins

A

vena cava, jugular

173
Q

what is the wall thickness of veins?

A

1.5mm

174
Q

what is the lumen diameter of veins?

A

30mm

175
Q

describe the histology of veins

A

thinner walls than arteries, less elastic tissue. Easily distended. Valves present in veins of limbs

176
Q

what is the function of veins?

A

capacitance vessels act as a reservoir of blood before it returns to the heart

177
Q

what will doubling the radius of the vessel do to the flow?

A

increase the flow by 16 times (r to the power 4)

178
Q

what is an increase in lumen radius called?

A

vasodilation

179
Q

what is a decrease in lumen radius called?

A

vasoconstriction

180
Q

what is vascular tone?

A

the degree of vasoconstriction/vasodilation of a vessel

181
Q

what does Darcy’s law predict?

A

flow through a tube of fixed radius will increase in proportion to a rise in pressure

182
Q

why may there be a disproportionate increase in flow for a given pressure in blood vessels?

A

blood vessels are not rigid tubes. They have elastic tissues in their walls which allows them to be stretched .

183
Q

which is the compliance of blood vessels?

A

the degree to which blood vessels can be stretched due to their elastic walls

184
Q

why are veins described as capacitance vessels?

A

due to their ability to markedly increase volume at low pressures

185
Q

what does the capacitance of veins depend on?

A

tone of the smooth muscle within the venous walls

186
Q

what is the tone of smooth venous muscle controlled by?

A

sympathetic nervous system

187
Q

what is total peripheral resistance (TPR)?

A

resistance to flow across systemic circulation

188
Q

does pulmonary circulation operate at a lower or higher pressure than the systemic circulation?

A

lower

189
Q

where does most resistance to flow occur in the CVS?

A

arterioles

190
Q

what is the total resistance of a system the sum of?

A

the resistors in the series

191
Q

how can pulse pressure be calculated?

A

PP= systolic blood pressure - diastolic blood pressure

192
Q

how can mean arterial blood pressure be calculated?

A

MABP = diastolic blood pressure + one third of pulse pressure

193
Q

how can cardiac output be calculated?

A

Mean arterial blood pressure divided by total peripheral resistance

194
Q

what is CVP?

A

blood pressure in the right atrium (usually around 0 mmHg)

195
Q

what is the primary function of pulmonary circulation?

A

to perfuse the alveoli of the lung for respiratory gas exchange

196
Q

What does all the volume of the right ventricle pass through?

A

the alveoli

197
Q

Why is there high capillary density in alveoli?

A

to optimise gas exchange

198
Q

why does the pulmonary circulation operate at much lower pressure than in the systemic circulation?

A

because the resistance to flow is very low

199
Q

what are the systolic and diastolic blood pressures in human pulmonary circulation?

A

systolic: 20-25 mmHg
distolic: 8-12 mmHg

200
Q

what is flow through blood vessels driven by?

A

pressure gradient

201
Q

what does the circular smooth muscle of the medial layer of arteries and veins control?

A

flow through the arteries and compliance of veins

202
Q

what does contraction of vascular smooth muscle produce?

A

vasoconstriction

203
Q

what does relaxation of vascular smooth muscle produce?

A

vasodilation

204
Q

what represents the balance between constriction and dilation?

A

vascular tone

205
Q

what gradient does pumping by the heart maintain?

A

arterial pressure gradient

206
Q

what part of the nervous system is involved in short term regulation of blood pressure?

A

sympathetic

207
Q

what is the increase in blood flow through exersizing tissues known as?

A

active or metabolic hyperaemia

208
Q

what causes vasodilation in the arterioles supplying the exercizing tissues?

A

release of metabolites from the active tissue

209
Q

what are examples of vasodilatory metabolites?

A

K+, ATP and adenosine

210
Q

what effect can hypoxia (reduced o2 levels) have?

A

vasodilation

211
Q

why is there hyperaemia after exercise?

A

remains until all metabolites are cleared

212
Q

what does hypoxia in pulmonary blood vessels produce?

A

vasoconstriction of blood vessels

213
Q

why is ventilation perfusion matching so important?

A

matching alveolar perfusion with alveolar ventilation to optimise local Va/Q

214
Q

what happens in pulmonary circulation at high altitude?

A

partial pressure of oxygen in air is low so there is generalised pulmonary vasoconstriction producing pulmonary hypertension

215
Q

what is pulmonary hypertension?

A

elevated pulmonary artery pressure

216
Q

what is total peripheral resistance determined by?

A

arteriolar tone

217
Q

what is arteriolar tone controlled by?

A

metabolites and local hormones

218
Q

what effect does the parasymapthetic nervous system have on heart rate?

A

reduces it

219
Q

what do baroreceptors monitor?

A

pressure

220
Q

what effect do changes in pressure have on baroreceptors?

A

stretch/relaxation of vessel walls, information is sent to the medulla

221
Q

via what nerves is information sent to the medulla from baroreceptors?

A

vagal and glosso-pharyngeal nerves

222
Q

what is a dynamic response in baroreceptors?

A

frequency of AP is higher as pressure changes

223
Q

what does reduction in pressure produce in the carotid sinus wall?

A

relaxation which results in a decrease in firing of the afferent fibre

224
Q

what is the set point of a reflex?

A

the pressure that the reflex strives to maintain

225
Q

how can set point be altered?

A

by interaction with central neurons (as occurs in exercise

226
Q

how does the kidney regulate blood pressure?

A

by removal of fluid (plasma) in the urine

227
Q

describe the feedback loop in kidney interaction with blood pressure

A 
increased arterial pressure
increased renal output of sodium and water
reduced ECF volume
reduced plasma (blood) volume
reduced central venous pressure
reduced cardiac output
228
Q

in systemic circulation what does metabolic activity cause?

A

vasodilation of the arterioles supplying that tissue through action of metabolites and low oxygen

229
Q

in pulmonary circulation what does low oxygen cause?

A

vasoconstriction which is important to ventilation-perfusion matching

230
Q

where do baroreceptors relay information about arterial pressure to in the brain?

A

nucleus tractus solitarius of the brainstem

231
Q

what governs the short term regulation of blood pressure?

A

baroreceptor reflex

232
Q

what governs the long term regulation of blood pressure?

A

kidney control of fluid and electrolyte balance

233
Q

what effect does the high density, thin walled nature of capillaries have?

A

reduced diffusion distance

234
Q

what is the name of the cell layer within capillaries?

A

endothelial cells

235
Q

what type of solutes cross the capillary walls easily?

A

lipophillic

236
Q

how thick is the capillary cell wall?

A

one cell

237
Q

what molcules need to pass through gaps in the capillary wall?

A

lipophobic

238
Q

what are the 3 types of capillary?

A

continuous
fenestrated
discontinuous

239
Q

describe the structure of a continuous capillary

A

continuous endothelial cell layer around lumen

240
Q

describe the structure of a fenestrated capillary

A

in between endothelial cells there are gaps in the capillary cell wall to allow transfer of higher weight molecules

241
Q

describe the structure of a discontinuous capillary

A

large gaps in cell endothelium which allow cells to be passed though the capillary wall

242
Q

give an example of where continuous capillaries can be found

A

heart and lungs

243
Q

give an example of where fenestrated capillaries can be found

A

kidney and small intestine (sites of significant water transfer)

244
Q

give an example of where discontinuous capillaries can be found

A

liver and spleen

245
Q

how does metabolite and gas exchange occur across the capillary wall?

A

diffusion

246
Q

what happens to the concentration of metabolite in the capillary as blood travels down it?

A

falls with exponential relation

247
Q

what is capillary wall less permeable to?

A

plasma proteins

248
Q

how do plasma proteins enter interstitium through the capillary wall?

A

slowly and with great difficulty

249
Q

why do plasma proteins exert osmotic pressure across capillary walls?

A

capillary wall is less permeable to them and so they cross slowly and with difficulty

250
Q

what is the osmotic pressure exerted by plasma proteins known as?

A

colloid osmotic pressure (COP)

251
Q

what are the principal plasma proteins?

A

ablumin and gamma globulins

252
Q

what is the colloid osmotic pressure of plasma?

A

21-29 mmHg

253
Q

what is the starling principle?

A

the balance between forces causing movement of water into and out from the capillary lumen

254
Q

what are starling forces?

A

forces that tend to cause bulk movement of water across the capillary wall

255
Q

what is the reflection coefficient?

A

how leaky the capillary wall is

256
Q

what would a reflection coefficient of 1 mean?

A

capillary is not at all permeable to plasma proteins

257
Q

what would a reflection coefficient of 0 mean?

A

capillary is very leaky to plasma proteins

258
Q

where does net filtration occur within the capillaries?

A

arteriolar end

259
Q

where does net absorption occur within the capillaries?

A

at the venous end

260
Q

what is oedema?

A

excess tissue fluid and leads to a water-logged interstitium

261
Q

what can oedema effect?

A

metabolite and gas exchange

262
Q

when does oedema arise?

A

when fluid production by capillaries is greater than the fluid removal by lymphatics

263
Q

what is elephantitis?

A

a condition caused by a parasitic nematode worm that blocks the lymphatic drainage to the leg

264
Q

what can local oedema be caused by?

A

venous/lymphatic obstruction and increased capillary permeability due to injury

265
Q

what can generalised oedema be caused by?

A

heart failure

hypo-proteinaemia (a fall in colloid osmotic pressure)

266
Q

how are respiratory gasses and metabolites transfurred across the capillary wall?

A

diffusion

267
Q

what is ultrafiltration?

A

the process by which water is transferred across the capillary wall

268
Q

what does ultrafiltration depend on?

A

balance of hydrostatic and oncotic pressures and the reflection coefficient of the capillary wall

269
Q

what is excess fluid production across the capillary walls drained by?

A

the lymphatic system

270
Q

how does oedema limit the effectiveness of respiratory gas and metabolite exchange?

A

by increasing diffusion distances

271
Q

how is venous blood distributed while you’re lying down (supine)?

A

evenly distributed throughout the body

272
Q

how is venous blood distributed when you move from lying down (supine) to standing?

A

pools in the legs under the influence of gravity

273
Q

what is reduced as an individual moves from supine to standing position?

A

central venous pressure is reduced

mean arterial blood pressure

274
Q

what is transient hypotension?

A

temporary reduction in blood pressure due to pooling of blood in the legs after standing

275
Q

what does transient hypotension trigger?

A

the baroreceptor reflex

276
Q

what does the baroreceptor detection of transient hypotension trigger?

A

increased sympathetic output from the medulla
increase in heart rate and total peripheral resistance
mean arterial blood pressure recovers

277
Q

in what areas does blood flow increase in response to leg exercise?

A

leg muscle - build up of metabolites
heart
skin - heat loss
lungs - reflects the increase in cardiac output

278
Q

what is the Fick Principle?

A

rate of O2 consumption must be matched by rate of O2 uptake

279
Q

what is metabolic hyperaemia?

A

increased blood flow during exercise

280
Q

what causes metabolic hyperaemia?

A

build up of metabolites causes vasodilation, in arterioles supplying exercising muscles, and local increase in blood flow

281
Q

what information relating to the cardiovascular system do chemoreceptors feed to the brainstem?

A

circulating O2 and CO2 and blood pH

282
Q

during exercise, what branch of the nervous system does feedback from baroreceptors and chemoreceptors influence?

A

sympathetic branch of ANS

283
Q

what is the set point of a reflex?

A

the pressure which the reflex tries to maintain

284
Q

how can the set point of a reflex be altered?

A

central nervous system can alter the set point in response to exercise

285
Q

what are the cardiovascular responses to exercise?

A 
metabolic vasodilation
coronary vasodilation
pulmonary blood flow increase
stroke volume increase
splanchnic/renal vasoconstriction
skin blood flow
286
Q

what does coronary vasodilation cause?

A

increased blood flow to the heart

287
Q

why does stroke volume increase plateau?

A

increased heart rate means that filling time is shortened which means that preload is reduced and volume expelled is smaller

288
Q

why can diastolic blood pressure fall during exercise?

A

depends on the total peripheral resistance

289
Q

why may total peripheral resistance fall?

A

vasodilation of exercising muscles and blood vessels at the skin to remove heat

290
Q

what is dynamic exercise?

A

alternating contraction and relaxation of exercising muscles

291
Q

what are the effects of dynamic exercise on the cardiovascular system?

A

systolic BP increases as a result of increased cardiac output
diastolic BP may decrease owing to a fall in TPR
vasodilation to aid heat loss

292
Q

what is static exercise?

A

sustained contraction of exercising muscles

293
Q

what are the effects of static exercise on the cardiovascular system?

A

both systolic and diastolic BP increase
compression of muscle impairs blood flow
muscle metaboloreceptors mediate a peripheral vasoconstriction

294
Q

what is the central command hypothesis?

A

anticipation of exercise leads to heart rate and breathing increase

295
Q

what does the cerebral cortex influence?

A

autonomic and respiratory neurones of the brainstem

296
Q

Is the central command effect seen when there is partial neuromuscular blockade?

A

yes

297
Q

where is acral skin found?

A

fingers, toes, palms and the sole of the foot

298
Q

what are arteriovenous anastomosis?

A

allow bypass of the capillary bed and come closer to the skin

299
Q

what effect does dilation of arteriovenous anastomosis have?

A

increases skin blood flow to increase heat loss

300
Q

why does arterial blood pressure vary around the day?

A

in response to changing activity and circadian rhythms in the regulation of blood pressure

301
Q

why do responses to static exercise differ to responses to dynamic exercise?

A

differences in effects on total peripheral resistance

X Physiology 1A (9 decks)

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