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Human Physiology > Cardiovascular system > Flashcards

Cardiovascular system Flashcards

1
Q

3 principle components of CVS

A

heart
blood
blood vessels

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2
Q

what other systems impact the function of the CVS

A

endocrine
nervous
kidneys

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3
Q

2 loops of CVS

A

systemic
pulmonary

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4
Q

systemic loop

A

blood from heart to body to heart
blood leaves left ventricle via aorta which branches to form systemic arteries that branch to form the microcirculation (arterioles, capillaries, venules)
venules form veins which form into 2 large vessels: inferior vena cava and superior vena cava

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5
Q

inferior vena cava

A

collects blood from below heart

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6
Q

superior vena cava

A

collects blood from above heart

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7
Q

pulmonary system/loop

A

carries oxygen-poor blood to the lungs and back to the heart
blood leaves ventricle via pulmonary trunk which divides into pulmonary arteries
at the lungs there are arterioles, capillaries, venules, veins and blood returns to the left atrium via 4 pulmonary veins

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8
Q

2 categories of arteries

A

muscular
conduit/elastic

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9
Q

how is pressure in blood vessels measured

A

mm of mercury (Hg)

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10
Q

flow

A

volume moved, mm/min

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11
Q

resistance

A

how difficult it is for blood to flow between 2 points at any given pressure difference

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12
Q

3 factors affecting resistance

A

blood viscosity (volume, number of erythrocytes)
total blood vessel length
blood vessel diameter (relaxed vessels decrease resistance, vasoconstricted vessels increase resistance)

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13
Q

vein vs artery

A

few layers of smooth muscle and connective tissue, few elastic layers, wider lumen

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14
Q

arteriole vs vein vs capillary

A

lumen endothelium smooth muscle cells
endothelium connective tissue
endothelial cells

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15
Q

elastic arteries

A

closer to heart
eg aorta
Large lumen vessels (low resistance) that contain more elastin
than the muscular arteries
pressure reservoirs
expand and contract (recoil) as blood is ejected by the
heart. This allows blood flow to be continuous.

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16
Q

muscular arteries

A

deliver blood to specific organs (mesenteric artery, renal artery etc.).
They have proportionally the most smooth muscle and are very active in vasoconstriction.
These arteries can play a large role in the regulation of blood pressure.

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17
Q

factors effecting pressure

A

volume
compliance (degree of stretch)

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18
Q

volume effecting pressure

A

Only about 1/3 of stroke volume
leaves arteries during systole
Rest of stroke volume remains in the arteries during systole, distending them, and raising the arterial pressure
After ventricular contraction, artery recoils passively, and blood
continues to be driven into arteriole

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19
Q

systolic blood pressure

A

Maximal arterial pressure reached during peak ventricular ejection

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20
Q

diastolic blood pressure

A

Minimal arterial pressure reached just before ventricular ejection

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21
Q

pulse pressure

A

difference between systolic and diastolic blood pressure

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22
Q

what are arterioles controlled by

A

neural, hormonal and local chemicals

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23
Q

arteriole function

A

control minute-to-minute blood flow in capillary beds
contraction diverts blood flow away from the tissues
dilation increases blood flow to the tissues
impact blood pressure

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24
Q

intrinsic tone

A

basal level of contraction of arterioles

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25
Q

how is smooth muscle in arterioles regulated

A

autonomically by local or extrinsic control

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26
Q

how to decrease flow to tissues

A

increase resistance by vasoconstriction
keep pressure constant

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27
Q

how to increase flow to tissues

A

increase pressure
or vasodilate to reduce pressure

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28
Q

local control of arteriolar resistance

A

metabolism increases: oxygen dec, carbon dioxide, potassium ions, nitric oxide, hydrogen ions, adenosin increase
causes vasodilation, reduces resistance, increases blood flow

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29
Q

extrinsic control of resistance

A

hormones
sympathetic nerves

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30
Q

examples of hormones controlling resistance of arterioles

A

Epinephrine – vasodilates or constricts
depending on the tissue
Angiotensin II – constricts most arterioles
Vasopressin – constricts most arterioles

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31
Q

3 types of capillary

A

continuous
fenestrated
sinusoidal

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32
Q

continuous capillary

A

found in skin, muscle, most
common kind, have tight junctions.

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33
Q

fenestrated capillary

A

more permeable —
intestines, hormone-producing tissues, kidneys

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34
Q

sinusoidal capillary

A

only one with an incomplete
basement membrane; these are found in the liver,
bone marrow and lymphoid tissues

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35
Q

how do capillaries grow and develop

A

angiogenesis

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36
Q

VEGF

A

angiogenic factor released by vascular endothelial cells

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37
Q

what does blood flow through the capillaries depend on

A

other vessels in the microcirculation
eg, vasodilation of arterioles causes increased capillary flow

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38
Q

metarteriole

A

supplies some capillaries
can be damaged by high blood pressure

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39
Q

precapillary sphincter

A

site at which a capillary exits from a metarteriole
surrounded by a ring of smooth muscle that relaxes and contracts in responses to local stimuli

40
Q

why is blood flow through capillaries slow

A

to maximise time for substance exchange across capillary wall

41
Q

what is blood velocity dependent on

A

cross-sectional area of the blood vessel type
smaller diameter reduces speed

42
Q

pressure difference between veins and right atrium

A

veins (10-15 mmHG) and the right atrium (0 mmHG)

43
Q

major functions of veins

A

act as low pressure conduits returning blood to heart
maintain peripheral venous pressure

44
Q

factors determining venous pressure

A

volume of blood in veins
compliance of walls- their walls are very thin and compliant (low pressure)

45
Q

how is unidirectional flow maintained in veins

A

valves

46
Q

factors that can increase venous pressure

A

increase activity of sympathetic nerves to veins
increase blood volume
increase inspiration movements
increase skeletal muscle pump

47
Q

effect of increase in venous pressure

A

increase in venous return
atrial pressure increases
end-diastolic ventricular volume increases
stroke volume increases

48
Q

cardiac output

A

amount of blood pumped out of each ventricle in one minute.
It is the product of heart rate (HR) and stroke volume (SV)

49
Q

stroke volume

A

difference between end diastolic volume and the end systolic volume
Volume of blood pumped from the left ventricle per beat.
SV = EDV − ESV

50
Q

myocardium

A

muscular wall of
the heart formed from cardiac
muscle cells

51
Q

epicardium

A

fixes inner layer of
pericardium to heart

52
Q

pericardium

A

muscular sack enclosing heart

53
Q

atrioventricular septum

A

muscular wall separating the ventricles

54
Q

pulmonary semi lunar valve

A

blood from right ventricle to pulmonary trunk

55
Q

aortic semi lunar valve

A

blood from left ventricle into aorta

56
Q

Chordae tendinae

A

fasten AV valves to the papillary muscles

57
Q

papillary muscles

A

limit movement to prevent backward flow of blood

58
Q

bicuspid valve

A

2 fibrous cusps at left AV valve

59
Q

tricuspid valve

A

right Av valve
3 fibrous cusps

60
Q

how is permeability of capillaries determined

A

water filled intracellular clefts

61
Q

cardiac muscle cells

A

1-2 centrally located nuclei
striated
adjacent cells connected by intercalated disks
gap junctions essential for electrical stimulation
large mitochondria
node cells-automaticity
desmosomes

62
Q

conducting system of the heart

A

cells with specialised features for heart excitation
in electrical contact with cardiac muscle cells via gap junctions
initiates the heartbeat and helps spread the impulse rapidly throughout the
heart

63
Q

control of increase in heart rate

A

sympathetic nervous system-innervates entire heart muscle and node cells
releases norepinephrine which binds to beta-adrenergic receptors on cardiac muscle cells

64
Q

control of decrease in heart rate

A

parasympathetic nervous system
innervates node cells
release acetylcholine which binds to muscarinic receptors

65
Q

epinephrine

A

hormone released from adrenal medulla
binds to same receptors as norepinephrine with same effects

66
Q

how are action potentials transmitted through heart

A

gap junctions between myocardial cells

67
Q

transmission/path of depolarisation

A

sinoatrial node
atrial muscle cells
through internodal pathway via gap junctions to
AV node
bundle of His
left and right bundle branches
left and right perkinje fibres
ventricular muscle cells

68
Q

signal delay at AV node

A

allows atria to contract and completely fill the ventricles before they contract

69
Q

purkinje fibres and papillary muscles

A

purkinje fibres supply papillary muscles, signalling them to contract before the rest of the atria to help prevent backflow through valves

70
Q

P wave on ECG

A

depolarisation wave from the SA node to the AV node. Atria contract
0.1 second after P wave starts

71
Q

QRS complex on ECG

A

ventricular depolarisation and precedes ventricular contraction

72
Q

T wave

A

ventricular repolarisation

73
Q

effect of atrial fibrillation on ECG

A

electrical impulses in atria fire chaotically

74
Q

what is stroke volume influenced by

A

volume of blood in ventricles, sympathetic nervous system, pressure heart is pumping against

75
Q

effect of decreased heart rate on SV and CO

A

SV decreases
CO maintained by increasing HR again

76
Q

positive chronotropic factors

A

increase HR

77
Q

negative chronotropic factors

A

decrease HR

78
Q

frank starling mechanism

A

The ventricle contracts forcefully more
during systole when it has been filled to a greater degree during diastole (more venous return)
length-tension relationship. The greater the end diastolic volume, the more the muscles are stretched, and thus the greater the contraction

79
Q

contractility

A

The strength of a contraction at any given end-diastolic volume
Norepinephrine acts on beta-adrenergic receptors to increase ventricular contractility
Plasma epinephrine also increases contractility

80
Q

effect of increased contractility

A

increased stroke volume due to a more complete ejection of the end-diastolic volume

81
Q

mean arterial pressure calculation
(in terms of pressure)

A

Diastolic pressure + 1/3 (Systolic pressure − diastolic pressure)

82
Q

mean arterial pressure calculation
(in terms of CO)

A

Cardiac Output × Total Peripheral Resistance

TPR is dependent on vasculature

83
Q

mean cardiac output equation

A

stroke volume x heart rate
where heart rate dependent on +/- chronotropic factors and sympathetic or parasympathetic activity

84
Q

mean stroke volume equation

A

end diastolic volume - end systolic volume which are dependent on frank starling mechanism and contractility

85
Q

arterial baroreceptors

A

respond to short term changes in arterial pressure; nerve endings are highly sensitive to stretch or distortion (degree of stretching is directly proportional to blood pressure)

can adapt to long term changes

86
Q

response of baroreceptors to increase in mean arterial pressure

A

increase frequency of action potentials

87
Q

response of baroreceptors to decrease in mean arterial pressure

A

decrease frequency of action potentials

88
Q

what receives impulses from baroreceptors

A

medullary cardiovascular centre in medulla oblongata
input from baroreceptors determines frequency of action potentials from the CV centre

89
Q

events after baroreceptors increase frequency of action potentials

A

decrease sympathetic outflow to heart, arterioles and veins and increase parasympathetic outflow to heart

90
Q

decrease in arterial pressure-hormonal response

A

increase concentrations of angiotensin II and vasopressin which causes arterioles to constrict and increase arterial pressure again

91
Q

renin-angiotensin system

A

intra-renal baroreceptors detect changes in stretching with lower blood volume–>increase production of renin

92
Q

what happens within hours of blood loss

A

Compensatory movement of
interstitial fluid into the capillaries
to increase plasma volume (redistribution of fluid)
also: increase in thirst, decrease in salt and water excretion

93
Q

what happens within days of blood loss

A

Replacement of cells:
erythropoiesis
haematopoiesis

94
Q

key concept of diuretics

A

increase excretion of sodium and
water, decreasing cardiac output with no
change in peripheral resistance

95
Q
A

Human Physiology (11 decks)

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