Principles of Science for Nurses

269 Pages·2002·2.367 MB·English

by  Joyce James, Colin Baker, Helen Swain(auth.)

Principles of Science for Nurses
PRINCIPLES OF SCIENCE FOR NURSES
Joyce James, Colin Baker & Helen Swain
Blackwell
Science
© 2002 by Blackwell Science Ltd, First published 2002 by Blackwell Science Ltd
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CONTENTS
Preface viii Bonding in water 19
Water as a solvent 21
Concentrations 25
Introduction ix
Diffusion and osmosis 27
Tonicity of cells 30
Homeostasis ix
Filtration 32
Measurement and units x
Electrolyte balance 32
Summary xvii
Water in the body 33
Review questions xvii
Water balance 35
Water regulation 37
Chapter One – Atoms 1 Dialysis 38
Summary 39
Learning objectives 1 Review questions 39
Introduction 1 Further reading 39
Matter 1
Atoms 3
Chapter Three – Acids and bases 40
Elements 4
Atomic number and mass number 6
Learning objectives 40
Isotopes 6
Introduction 40
Relative atomic mass 6
Acids 40
Electron arrangement 7
Bases 41
Compounds 8
Neutralisation 42
Chemical equations 8
Salts 42
Chemical bonding 10
Strong and weak acids and bases 43
The mole 15
The pH scale 45
Relative formula mass 17
pH of body fluids 47
Summary 17
Chemical buffers 48
Review questions 17
Respiratory regulation of pH 50
Further reading 18
Renal regulation of pH 52
When the balancing act no longer works 53
Chapter Two – Water and Compensation – systems working
electrolyte balance 19 together 56
Summary 56
Learning objectives 19 Review questions 57
Introduction 19 Further reading 57
vi Contents
Chapter Four – Biomolecules 58 Microorganisms 109
Microorganism structure 109
Learning objectives 58 Growth 112
Introduction 58 Laboratory techniques 114
Organic chemistry 58 Infection 115
Carbohydrates 59 Prevention of infection 117
Lipids 63 Drug-resistant bacteria 120
Proteins 66 Summary 123
Nucleic acids 70 Review questions 123
Digestion and absorption of Further reading 123
biomolecules 72
Summary 75
Chapter Eight – Immunology 124
Review questions 75
Further reading 76
Learning objectives 124
Introduction 124
Chapter Five – Cells 77 The immune system 124
Innate and adaptive immunity 125
Learning objectives 77 Immune system structure 127
Introduction 77 Defective immune responses 131
Two cell types 77 Applications of the immune system 132
Viruses and prions 78 Summary 136
Cell structure 79 Review questions 136
Human cell organelles 82 Further reading 136
Growth of cells and cell division 88
Summary 91
Chapter Nine – Fluids – liquids
Review questions 91
and gases 137
Further reading 91
Learning objectives 137
Chapter Six – Genetics 92 Introduction 137
Pressure 137
Learning objectives 92 Atmospheric pressure 137
Introduction 92 Liquids 139
Genes 92 Blood – pressure, resistance and flow 140
Gene inheritance patterns 95 Gases 146
Genetic disorders 97 Summary 155
Characteristics of single-gene disorders 99 Review questions 156
Genetic techniques 104 Further reading 156
Summary 108
Review questions 108
Chapter Ten – Nutrition and
Further reading 108
metabolism 157
Chapter Seven – Microorganisms 109 Learning objectives 157
Introduction 157
Learning objectives 109 Definition of energy 157
Introduction 109 Nutrition 159
Contents vii
Adenosine triphosphate – ATP 163 Review questions 201
Metabolism 164 Further reading 201
Metabolic pathways 165
Basal metabolic rate (BMR) 173
Chapter Thirteen – Forces and
Summary 175
mechanics 202
Review questions 175
Further reading 176
Learning objectives 202
Introduction 202
Chapter Eleven – Electromagnetic Getting things moving – Newton’s
radiation 177 laws of motion 202
The force of gravity 204
Learning objectives 177 Friction 206
Introduction 177 Levers 208
What is electromagnetic radiation? 177 Pulleys 210
The sun and electromagnetic radiation 178 Forces, levers and moving and
Non-ionising radiation 180 handling issues 210
Radioisotopes 180 Summary 212
Monitoring exposure and reducing Review questions 212
dosage 183 Further reading 212
Clinical uses of radioisotopes 183
Non-invasive imaging techniques 185 Chapter Fourteen – Electricity 213
Summary 189
Review questions 189 Learning objectives 213
Further reading 190 Introduction 213
Electricity 213
Electricity and the body 217
Chapter Twelve – Temperature
Medical applications of electricity 223
and heat 191
Summary 226
Review questions 226
Learning objectives 191
Further reading 227
Introduction 191
Heat and temperature 191
Latent heat 194 Periodic table of the elements 228
Transmission of heat 195
Temperature homeostasis – heat Glossary 229
balance in the body 197
Control of abnormal body temperatures Answers 236
– hypothermia and hyperthermia 199
Summary 200 Index 245
PREFACE
The nursing profession has steadily developed • Why is the bottle placed above the patient’s
from an untrained workforce to one that pro- head?
vides the highly skilled and educated nurses • What is normal saline?
required in today’s health service. Ever since • Why is it important to keep the lines sterile?
Florence Nightingale started the first nursing
We hope to stimulate this spirit of enquiry in
school at St Thomas’s Hospital the need for
you.
educated nurses has been recognised. The con-
There are a number of ways in which you
tinued development of nursing education has
may wish to use this book but as we recognise
seen nurses change from dependent to inde-
that you are not likely to study more than one
pendent decision makers, a need which has
chapter at a time, each chapter is designed to
become more important as specialist fields of
‘stand alone’ as far as is possible. As you work
expertise have evolved. A basic understanding
through a chapter, activities and exercises are
of science and technology is vital to working
provided to encourage enquiry and test your
effectively in this environment.
understanding as you go. Simple and clear
This book explains basic scientific concepts
diagrams are provided where appropriate to
that are related to nursing practice. This will
support the explanations in the text. At the end
encourage and enable you to apply these
of the chapter there are further questions to try,
concepts to your everyday working experience.
with answers provided.
Both the simplest and the most advanced
There are several other important features. A
practices and procedures have a fundamental
glossary is provided which may be helpful for
underlying scientific principle. The ability to
quick reference if there are terms in the text
recognise this will provide a greater under-
that you are uncertain about. At the start of this
standing of why things are done the way they
book important aspects of expressing measure-
are and should give you more confidence in
ments and the use of units have been sum-
contributing to the total care of your patients as
marised. These are essential for accurate
well as enhancing your personal satisfaction and
reporting of the readings you have to record
achievement.
each day on the ward. Lastly, there are sug-
A simple activity like giving a saline drip to
gestions for further reading and some internet
restore fluid balance for example, could trigger
sites you can visit.
a series of questions:
We wish you good luck with your studies!
• Why does the fluid balance need restoring?
Acknowledgements
Thank you to Lynn Jarvis for doing the graphics and to Deanne Cox our nurse advisor for all her
help throughout the book.
INTRODUCTION
Homeostasis back mechanism has three parts: a set point, a
sensory receptor and an effector.
The set point is used as a reference to
Human beings are made up of millions of cells
compare the fluid passing through it to the
which are organised into tissues, organs and
‘norm’ for that fluid. Many set points are found
systems. The conditions inside the body are
in the hypothalamus which controls the release
constantly changing as we break down food and
of hormones from the pituitary gland. The
synthesise molecules in response to particular
hypothalamus is connected to the pituitary
situations. However, for each cell to function
gland and is located in the forebrain beneath
properly the fluid that surrounds the cell (extra-
the cerebral cortex. Sometimes the set point is
cellular fluid) and the fluid inside the cell (intra-
referred to as an integrator because it receives
cellular fluid) have to stay roughly the same. All
information and selects different information,
the parts of the body work together to keep the
for the effectors, to bring about change
extracellular and intracellular fluids as close
(Fig. 0.1). One example is the control of body
as possible to the best or optimum conditions
temperature; sensory receptors in the skin will
for the cell. The preservation of this internal
respond to the environmental temperature and
environment of the body is called homeostasis.
send a signal to the set point (integrator) in the
There are only about 15 litres (L) of extra-
brain The integrator responds by sending out
cellular fluid (including blood) in the body, which
signals to the muscles and glands which cause
has to cope with eliminating waste products and
the correct response to maintain homeostasis.
transporting nutrients to all of the cells within
This type of control is called negative feed-
the body. Moreover, the concentrations of ions
back and is used by the body in hundreds of
such as potassium and hydrogen within a cell
situations. Its effect is to cancel out the change
have also to be maintained by transport into
(either less or more of a component) so that the
and out of the same fluids. An enormous task!
levels are returned to the normal range.
It is easy to understand that the levels of all
The same kind of system is used to control
these factors will be constantly changing but
the temperature of central heating, ovens and
must be quickly corrected to keep the extracel-
irons, when one part doesn’t work the whole
lular fluid at an optimum for cell function. An
system is affected. Generally the speed at which
uncorrected effect in an individual cell can
homeostatic negative feedback occurs is not
quickly affect surrounding cells and ultimately
very fast, for example changes in blood glucose
loss of whole organ function and death.
levels rely on the circulation of the blood to
register that the glucose levels are not normal.
They are also not corrected very accurately and
Feedback mechanisms
overshooting the mark is common, which will
Homeostasis can be thought of as a constantly have to be corrected again by the effectors.
self-adjusting or dynamic system which keeps These reactions are automatic and self-
the extracellular fluid within a fairly narrow adjusting: we cannot control them voluntarily.
range of parameters. This is made possible by Nurses need to realise that ‘normal’ levels
a number of feedback mechanisms. Each feed- will be within an acceptable range and should
x Principles of Science for Nurses
STIMULUS
RECEPTOR EFFECTOR
INTEGRATOR/
set point
RESPONSE Fig. 0.1 Negative feedback
mechanism.
be able to judge when changes occur. Taking it becomes irreversible and death results
the temperature of the patient is just one activ- (Fig. 0.2).
ity, which can indicate a homeostatic mecha-
nism which is in or out of control.
Negative feedback control is used to control Unstable homeostatic states
many different body functions which include
When homeostatic mechanisms can no longer
respiration, breathing, and body temperature,
function, an unstable state or a stressed state
but it is not the only type of control system,
predominates. Stress can be temporary (acute),
there are a few positive mechanisms as well.
e.g. injury or shock, or continual (chronic) as in
Positive feedback increases an activity for a
long term disease. As we get older we become
limited time to bring about a desired effect. A
increasingly unable to respond to stress because
good example is the series of uterine contrac-
our homeostatic mechanisms do not seem to
tions which expel the baby from the uterus in
function as well.
childbirth. This can be thought of as an unsta-
Many of the activities of a nurse are about
ble homeostatic state that lasts for a relatively
restoring a homeostatic state to the patient who
short time. The fetus (stimulus) presses on the
has become ill because they can no longer
walls of the uterus and causes the pituitary gland
control their internal environment. Helping the
to stimulate the production and secretion of
patient to restore normal body temperature,
oxytocin, which makes the muscles in the uterus
fluid volume, chemical composition and elec-
wall contract, increasing the pressure on the
trolyte concentration, nutrients or the correct
fetus until it is expelled.
pH is a vital role for the nurse. Techniques and
Many positive feedback mechanisms are
practices are constantly changing to accommo-
harmful, e.g. cardiogenic shock (reduced blood
date new knowledge and better patient care but
flow to organs due to heart attack). During a
all have the same objective – to achieve the set
heart attack less blood is circulated to the
point for the patient.
tissues, which become starved of oxygen. The
tissues respond by changing their metabolism
so that less oxygen is required. This leads to an
Measurement and units
increase in the volume of fluid bathing the cells
(interstitial fluid) and a decrease in the volume
of circulating blood. The positive feedback loop Blood pressure, pulse, temperature, height
continues and makes the condition worse until and weight are a few of the measurements
Introduction xi
DEATH
HEART ATTACK
HYPOXIA ANAEROBIC
(decrease of oxygen in tissue) METABOLISM
Decrease in circulating Increase in volume of
Fig. 0.2 Positive feedback – blood volume interstitial fluid
cardiogenic shock.
and recordings done by a nurse every day. measured. This will normally require the use
There is always a need for accurate mea- of an instrument to make the measurement.
surement and accurate recording. Records need Examples are the measurement of height,
to be interpreted by other staff so what is weight, temperature and blood pressure.
recorded must be clear and unambiguous. Con- Most measurements of this type also require
tinuous monitoring of a patient enables a good a unit to define the measurement. For
patient history to be built up and allows any example, it is not adequate to express body
changes in patient condition to be picked up weight as 65 – do we mean pounds or kilo-
early. It is equally important to understand grams? If it is kilograms then we must
measurements correctly in providing doses of express the body weight as 65kg to avoid
medication. any ambiguity! This type of measurement
can be considered to be objective as it is
based on a universally accepted scale.
Qualitative and quantitative
An example of qualitative signs being con-
measurement
verted to relative numerical values is the Apgar
score used to indicate the condition of a new
There are three different types of measurement:
infant (Table 0.1).
• Qualitative measurements are based on A score is given for each of the five signs
visual signs or the absence of signs but do 1 and 5 minutes after the birth. A score
not involve numbers. They rely on the of seven or above is considered satisfactory.
observer’s judgement so they are subjective. Scores lower than seven indicate that some
• Semi-qualitative measurements record resuscitation may be required. In such cases,
information on a relative scale. They are scores at subsequent 5-minute intervals would
numerical estimates of an observation, for indicate the extent of recovery. In practice, the
example a score of 5.3 in competitive ice- midwife will probably simply estimate the
skating. score without going through the whole pro-
• Quantitative measurement – numbers are cess. Experience allows this to be done with
used to state the quantity which has been accuracy.