Cardiovascular physiology : questions for self assessment with illustrated answers

273 Pages·2010·4.03 MB·English

by  Levick

Cardiovascular
Physiology
Questions for Self Assessment
With Illustrated Answers
J Rodney Levick
DSc DPhil MA MRCP BM BCh (Oxon)
Professor of Physiology
St George’s Hospital Medical School
University of London, UK
First published in Great Britain in 2010 by
Hodder Arnold, an imprint of Hodder Education, an Hachette UK company,
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© 2010 J Rodney Levick
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Contents
Introduction v
1 Overview of the cardiovascular system 1
2 The cardiac cycle 6
3 Cardiac myocyte excitation and contraction 13
4 Initiation and nervous control of heart beat 19
5 Electrocardiography and arrhythmias 26
6 Control of stroke volume and cardiac output 30
7 Assessment of cardiac output and peripheral pulse 38
8 Haemodynamics:flow,pressure and resistance 42
9 The endothelial cell 54
10 The microcirculation and solute exchange 59
11 Circulation of fluid between plasma,interstitium and lymph 65
12 Vascular smooth muscle:excitation,contraction and relaxation 75
13 Control of blood vessels:I.Intrinsic control 82
14 Control of blood vessels:II.Extrinsic control by nerves and hormones 89
15 Specialization in individual circulations 96
16 Cardiovascular receptors,reflexes and central control 108
17 Co-ordinated cardiovascular responses 115
18 Cardiovascular responses in pathological situations 123
Figures and Tables 133
Figures 135
Figure acknowledgements 244
Tables 252
Index 258
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Introduction
Thequestionsinthislittlebookareintendedprimarilyasanaccompanimenttothefiftheditionofthe
textbook,An Introduction to Cardiovascular Physiology (JR Levick,HodderArnold,2010) – though the
explanationsandthenumerousdiagramsshouldhelpmakethisauseful‘stand-alone’volumeifdesired.
The companion volume has a small,‘taster’selection of the questions on its website.The aim of this
collection of over 230 questions is to offer students an element of self-assessment,as they progress
through the companion book or revise for examinations.Lecturers may find some of the questions
useful as a template when setting questions of their own,but should note that the questions are
primarily educational in intent; their discriminatory power has not been tested.The questions
are grouped under the same headings as the chapters of the companion textbook,so they become
progressively more advanced (see Contents).Occasional statements call for information from later
chapters.Medically relevant questions are introduced wherever they are appropriate.I have set at least
onequestiononeachlearningobjectivegivenatthestartofthechapterinthecompanionvolume,to
help you assess your achievement of the learning objectives.Some questions require you to integrate
information from other chapters too.The questions aim to test basic understanding,fundamental
principles and medical relevance.Hopefully they avoid excessive detail – always the examiner’s easy
option!
The questions. Most of the questions are multiple choice questions (MCQs),generally with five
true/false statements,but occasionally more or less than five.Although some‘educationalists’now
demand single correct answer questions (SAQs,one correct answer out of four or five options),these
test less knowledge,so the MCQ style has been retained here.To add variety,there is a sprinkling of
otherstylesofquestion,suchas‘extendedmatchingquestions’(i.e.choosethebestanswerfromalist),
data interpretation problems,and little numerical problems that test reasoning power and ability to do
simple calculations.
The answers. Each answer is accompanied by a brief explanation,and very often an illustrative
figure,whichshouldhelpifyougottheanswerwrong.Mostofthefiguresarefromtheaccompanying
textbook,buttherearealsonew,explanatorydiagramsaftersomequestions.Itissometimesdifficultto
avoidambiguityinMCQquestions;souseyourcommonsense–choosetheanswerthatwillberight
most of the time,rather than a remote,rare possibility.Nevertheless,if you disagree with the‘official’
answer,do let me know.
vi Introduction
Your score. What score represents a good performance?There are roughly equal numbers of
T and F answers.Therefore,if(cid:2)1 is allotted for each correct answer and none subtracted for a wrong
answer,a score of 50% could be achieved simply by respondingTrue (or False) to every question.
Around65%(two-thirds)correctanswerswouldprobablybea‘pass’underthismarkingscheme.Many
universities use a negative marking scheme,namely (cid:3)1 for an incorrect answer,0 for no answer
and(cid:2)1 for a correct answer.On this scheme,guessingTrue (or False) for every answer would score
roughlyzero,andthepassmarkisthereforeusuallysetatalittlebelow50%.Over60%wouldbegood,
and over 70% excellent.Good luck!
Rodney Levick
Physiology
St George’s Hospital Medical School,
University of London,UK
CHAPTER 1
Overview of the cardiovascular
system
T F
1.1 Concerning transport by the cardiovascular system,
(cid:2) (cid:2)
a. the transport of glucose by the circulation is convective rather than diffusive.
(cid:2) (cid:2)
b.diffusion depends on transport up a concentration gradient.
c. the time taken for O to diffuse a certain distance is directly proportional
2 (cid:2) (cid:2)
to the distance.
(cid:2) (cid:2)
d.O is carried from capillary blood to the tissue cells mainly by fluid filtration.
2
e.if coronary perfusion were halted,O would take about 15 hours to diffuse
2 (cid:2) (cid:2)
from the cavity of the left ventricle to the subepicardial muscle fibres.
1.2 Regarding the distribution of cardiac output (CO) to the tissues of a resting
human,
a. about 20% goes to skeletal muscle,which accounts for (cid:2)20% of resting
(cid:2) (cid:2)
O consumption.
2
b.about 20% goes to the kidneys,which account for (cid:2)6% of resting
(cid:2) (cid:2)
O consumption.
2
c. about 10% goes to the myocardium,which accounts for (cid:2)10% of resting
(cid:2) (cid:2)
O consumption.
2
d.the proportion of the CO going to a given organ is regulated mainly by the
(cid:2) (cid:2)
conduit arteries feeding the organ.
(cid:2) (cid:2)
e.about 50% goes to the lungs,due to their low vascular resistance.
1.3 Regarding the flow of blood,
a. flow is proportional to the pressure difference between the inlet and outlet
(cid:2) (cid:2)
of the blood vessel.
(cid:2) (cid:2)
b.Darcy’s law states that flow equals pressure times resistance.
c. the flow per unit pressure drop along a vessel is called the hydraulic
(cid:2) (cid:2)
conductance of the vessel.
(cid:2) (cid:2)
d.the units for hydraulic resistance are mmHg per unit flow or equivalent.
e.the flow resistance of the pulmonary circulation is about two-thirds that
(cid:2) (cid:2)
of the systemic circulation.
1.4 As blood flows around the systemic circulation,
a. its mean pressure falls markedly from the aorta to small,named arteries,
(cid:2) (cid:2)
such as the radial artery.
(cid:2) (cid:2)
b.the systolic pressure is higher in the brachial artery than the aorta.
(cid:2) (cid:2)
c. the biggest fall in pressure occurs in the resistance arteries.
(cid:2) (cid:2)
d.the greatest net,cross-sectional vascular area is encountered in the capillaries.
(cid:2) (cid:2)
e.its velocity decreases in microvessels,yet the total flow does not.
(cid:2) (cid:2)
f. its pressure falls to (cid:2)30mmHg in the antecubital vein at heart level.
2 Cardiovascular physiology Questions
T F
1.5 The conclusion that terminal arteries and arterioles offer more resistance to
blood flow than other vessels stems from the observation that
(cid:2) (cid:2)
a. they have the thickest walls,relative to lumen width.
(cid:2) (cid:2)
b.they have a rich sympathetic vasomotor innervation.
(cid:2) (cid:2)
c. they have the smallest internal radius of all blood vessels.
(cid:2) (cid:2)
d.they have the biggest pressure drop across them.
(cid:2) (cid:2)
e.they are less numerous than venules.
1.6 Blood vessels classified as
(cid:2) (cid:2)
a. elastic vessels expand to receive the stroke volume of the heart.
(cid:2) (cid:2)
b.conduit vessels conduct venous blood back to the heart.
(cid:2) (cid:2)
c. resistance vessels can actively regulate the blood flow through a tissue.
(cid:2) (cid:2)
d.exchange vessels include some venules as well as capillaries.
(cid:2) (cid:2)
e.capacitance vessels have the capacity to alter blood pressure directly.
1.7 The wall of a blood vessel
(cid:2) (cid:2)
a. is lined internally by cells that secretes anti-thrombotic agents.
(cid:2) (cid:2)
b.is divided into two layers (tunica) by a sheet of elastin.
(cid:2) (cid:2)
c. always contains tension-resisting collagen.
(cid:2) (cid:2)
d.has a higher proportion of elastin in the aorta than in distal arteries.
(cid:2) (cid:2)
e.always contains contractile smooth muscle,except in capillaries.
(cid:2) (cid:2)
f. has the lowest proportion of smooth muscle in the arterioles.
(cid:2) (cid:2)
g.rarely contains efferent nerve fibres.
1.8 Theproximalaortagivesoffarteriestothebrain;theabdominalaortagives
offarteriestotheintestine;andthedistalaortagivesoffarteriestotheleg;
buttheliverissuppliedchieflybyvenousbloodfromtheintestine.Therefore,
(cid:2) (cid:2)
a. the blood supply to the brain and intestine are in parallel.
(cid:2) (cid:2)
b.the blood supply to the intestine and leg are in series.
c. the pressure of arterial blood supplying the leg is substantially lower than
(cid:2) (cid:2)
that supplying the brain.
(cid:2) (cid:2)
d.the blood supply to the liver is in series with the intestinal supply.
(cid:2) (cid:2)
e.the blood supply to the liver is an example of a portal circulation.
1.9 Roles of different classes of systemic blood vessel
(Here is a different style of question,the extended matching question (EMQ).If you succeeded
with questions 1–8,you will find this one easy.)
Regarding the various systemic blood vessels,enter the code from the list below to answer
questions (i) to (vii).A code can be used more than once,or not at all.
a. proximal aorta
b.conduit arteries
c. arterioles
d.capillaries
e.venules
f. peripheral veins
g.central vein
(cid:2)
(i)This vessel has the largest radius.
(ii)If all the vessels in parallel are added together,this class of vessel has the
(cid:2)
greatest net cross-sectional area.
Overview of the cardiovascular system Questions 3
(cid:2)
(iii)This vessel has the slowest velocity of blood flow.
(cid:2)
(iv)This vessel has the highest velocity of blood flow.
(cid:2)
(v)This category of vessel has the greatest pressure drop across it.
(vi)Thesethreetypes of vessel together contain around two-thirds of the
(cid:2)
circulating blood volume.
(cid:2)
(vii)This vessel actively regulates the blood flow through a tissue.