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PY3002 Integrative Physiology The Scientific Method in Physiology

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To know how to find sources of information and how to use them. ... Uneven distribution - if you design experiment badly, you can skew your data. ... – PowerPoint PPT presentation

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Title: PY3002 Integrative Physiology The Scientific Method in Physiology


1
PY3002 Integrative PhysiologyThe Scientific
Method in Physiology
  • Dr Derek Scott

2
Lecture Objectives
  • To know how to apply the scientific method in
    order to define and test physiological problems.
  • To know how to find sources of information and
    how to use them.
  • To know how to present and communicate
    information.

3
Hypothesis-driven research
4
The Hypothetico-deductive Approach to Research
Note A hypothesis must be testable. It is often
easier to refute rather than substantiate a
hypothesis.
Test
5
Methods of Scientific Investigation
Transmit any new findings to others
6
Where do I find out about my topic of interest?
7
Types and Uses of Scientific Literature
  • Primary sources - These report original work -
    articles in peer review journals, thesis,
    published abstracts and posters.
  • Secondary sources - Reviews, monographs.
  • Tertiary sources - Textbooks.
  • Quaternary sources - Manual and computerised
    listings.

8
Using the Literature
  • Define your specific problem or area of interest,
    identify keywords, authors etc.
  • Survey the literature using quaternary sources
    (often search engines on the Web e.g.
    Entrez-PubMed, Web of Knowledge/Science).
  • Reviews are a good starting place if you are
    unsure of a topic as someone assesses the most
    important bits of data for you and tries to make
    it easily digestible.
  • Identify articles of interest and further judge
    suitability from abstracts.
  • Look up specific articles and read them
    methodically take note of those likely to be of
    use to you.

9
Examining an Article
  • TITLE - Is it general, specific or simply an
    assertion?
  • SUMMARY/ABSTRACT - Is it still of interest?
  • INTRODUCTION - Does this explain the background
    to the hypothesis and how it is to be tested?
  • METHODS - What has been measured and by what
    means?
  • RESULTS - Are they interpretable?
  • DISCUSSION - How do the results shape up to the
    objectives laid out in the introduction?
    Scientists can be mistaken or liars as well!
  • CONCLUSIONS - Do you agree with them?
  • RECORD the reference and write notes.

10
DESIGNING EXPERIMENTS
  • The need to control variables - In vivo or In
    vitro methods, use of model, the experimental
    environment.
  • Choice of appropriate controls - weight matched,
    age matched etc.
  • Statistical design - selection of subjects
    (randomisation etc), numbers of replicates needed
    to get statistical significance, systematic and
    personal error. Data distribution.
  • Logistical problems. How long will it take? Can
    you get subjects? Do you have the
    facilities/resources?
  • Can usually avoid most problems by using a bit of
    common sense!

11
Choosing subjects for a study on effects of
smoking on respiratory function
Non-smokers
Smokers
(Images taken from www.bbc.co.uk/thesmoking room
and are property of the BBC)
Are these subjects well-matched? E.g.
Age/sex/weight/lifestyle etc.
12
How do I analyse my data?
13
The Normal/Gaussian/Biological Distribution
S Standard Deviation
Frequency Coefficient
Percentages of observations falling within ranges
of Standard Deviations Indicated
14
How many subjects and how often do I measure?
  • Remember, the more subjects (n) you measure, the
    more accurate your average is likely to be, but
    it is often not feasible to repeat an experiment
    more than a few times.
  • Try and make each measurement more than once on
    each subject/cell/preparation because organisms
    are dynamic, and readings may change e.g. blood
    pressure.
  • Different types of study require different n
    numbers e.g. it may be enough to do an experiment
    4-5 times on isolated cells if the results are
    very similar, but drug/exercise trials may
    require 10s-100s of volunteers to obtain
    accurate, reproducible data.

15
Mean
Mean
Wide Distribution
Narrow Distribution
16
Mean 1
Mean 2
The null hypothesis basis of T test (normal
distributions) i.e. you assume with your
statistical test that there is no difference
between your two means, and you try to disprove
this.
17
Skewed Distribution
Uneven distribution - if you design experiment
badly, you can skew your data.
18
What is the scatter of data?(aka how wrong can
my average value be?)
  • Standard deviation or Standard error of the mean
  • s.e.m. is smaller so is often used by scientists
    to make their error bars look smaller!
  • Data distribution
  • Normal or skewed?
  • Selection of appropriate statistical tests

19
What type of experiments should I do?
20
In vivo methods
  • Human Studies
  • In general, non-invasive
  • Problems about prior history
  • Animal Studies
  • Can overcome problems listed above for humans
  • May not be good models for humans owing to
    interspecies variations
  • Remember that if you choose to use either of
    these types of studies, then there are ethical
    and welfare issues that must be considered.

21
in vivo methods continued
  • Chronic Studies
  • Use of indwelling catheters, transducers etc
  • Robustness of the animal
  • Acute Studies
  • Effects of anaesthesia
  • Perturbations from normal physiology

22
In vitro methods
  • Whole organ perfusion
  • Superfusion of tissue slices
  • Primary cell culture
  • Culture of immortalised cell lines
  • Studies on subcellular lines
  • Molecular studies on gene and protein expression
  • Remember that whilst these experiments provide
    valuable data, they may not accurately reflect
    the integrative nature of the human body in vivo.

23
Recording Results
  • Use of bound laboratory or literature record book
    - dated and numbered pages, institutional
    requirements. Recording of standard protocols.
  • Preservation of chart records and other
    recordings. Units and scales should be noted on
    all material produced.
  • Need to write summaries at regular intervals.
  • Really is important as you can go back after a
    busy couple of days, and have forgotten what you
    did when, or where you found a certain piece of
    information.

24
Reporting Results
  • Title - Authorship - Key Words
  • Summary or Abstract
  • Introduction
  • Methods
  • Results - Figures and legends, Tables
  • Discussion
  • Acknowledgements
  • References or Bibliography

25
Citing sources of evidence
  • Body of text - either place author and date i.e.
    (Smith, 2001) into text or insert number as
    superscript
  • In reference section of paper list either in
    alphabetical order of first authors name ie Smith
    A.B. (2001) The Physiology of Rhubarb Leaves.
    J.Plant Physiology.12.26-34.
  • or in numerical order of appearance in main text
    showing the number first i.e. 1 Smith A.B.
    (2001) The Physiology of Rhubarb Leaves. J.Plant
    Physiology.12.26-34.

26
  • Journal Format Author/s - Year - Title of
    Article - Name of Journal - Volume Number - Page
    Numbers.
  • For Books Author/s - Year - Title - Edition -
    Publisher - City and Country of Publication.
  • Note two authors in text quote both if using date
    ordering ie Smith Jones (2002) and if more than
    two then Smith et al (2002)

27
Finally.
  • If you are unsure, then ask! (especially true
    during your Honours project next year)
  • You can avoid many problems during a literature
    or laboratory research project by using a bit of
    common sense.
  • Preparation and planning is everything it can
    save you banging your head against the wall in
    frustration or rushing at the end of a project to
    get it finished.
  • Do the research and know your stuff find an
    angle that gets you excited (cheesy I know, but
    it does help!)
  • Have a look at examples of Honours projects on
    the School of Medical Sciences website (look in
    Undergraduate teaching, then Honours) to see what
    kind of things people study and how they describe
    their projects.
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