Transcript chapter 1

Chapter One
**Keep up with the readings***
 Introduction to Physiology (pgs 7 – 14)
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Homeostasis
 Seven themes in physiology
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Why learn physiology.
How to think like a physiologist.
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Levels of Organization
Figure 1-1: Levels of organization and the related fields of study
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Integration of body function
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How do we understand what is going on?
Use flow charts
 Use maps
 Recognize repeating patterns & themes.
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Figure 1-3: Maps for physiology
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Some Ideas
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2.
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6.
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Homeostasis and control systems
Structure/function relationships
Communication
Substances move across membranes
Need energy
Mass balance
Mass flow
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Homeostasis
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The body as a whole copes with a variable
external environment.
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Only a small minority of cells are in direct
contact with the external environment.
Most cells are surrounded by extracellular fluid.
These cells are not very tolerant of changes
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Physiological Systems
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Cell
Intracellular fluid
Extracellular fluid
Organism
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Protective cells
Exchange cells
External environment
Figure 1-4: The internal and external environments
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Homeostasis
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Body’s ability to maintain the composition
of the extracellular fluid.
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A number of mechanisms have evolved to
maintain the composition of the
extracellular fluid with within a narrow
range of values.
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Homeostasis
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The body is able to maintain the
composition of the extracellular fluid
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Some key functions are regulated.
Glucose levels
 Blood pressure.
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Control Systems
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E.g. a car needs gas. You watch the gas
gauge, you fill up with gas. You are the
integrator. The gas gauge is the sensor.
Tissues (effectors) are controlled by
integrating centers.
 E.g. Muscles are effectors, the nervous
system is an integrator, eyes are sensors.
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2. Structure /function relations
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Structure influences function
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E.g. muscle filaments contraction
Molecular interactions
 Molecules form bonds
 E.g. enzymes bind components to speed up a
reaction. E.g. carbonic anhydrase.
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2. Structure /function relations
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Mechanical properties
Cells (and extracellular parts)
 Tissues
 Organs
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E.g. –contraction, compliance, elasticity,
changes during the life cycle too
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2. Structure /function relations
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Compartments
At many levels, subcellular, cellular, organs,
body linings,
 e.g. digestive system
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• Lumen, lining, muscle, different function in
different parts
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3. Communication
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Information is spread quickly and
accurately
E.g. thirsty, not hot
 Response is to drink, not run.
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E.g. you need to run, heart rate increases
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3. Communication
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Signaling molecules
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Nervous system, blood vessels
Cells respond e.g. receptor proteins, signal
transduction molecules to communicate
within a cell.
 E.g. hormone (estrogen) binds to a receptor
 response
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4. Substances move across the
cell membrane
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Gases, water, glucose, ions etc.
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The cell membrane regulates the
movement of some molecules.
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Some Ideas
1.
2.
3.
4.
5.
6.
7.
Homeostasis and control systems
Structure/function relationships
Communication
Substances move across membranes
Need energy
Mass balance
Mass flow
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5. Biological energy
Need energy for life
 E.g. gas for car, money for society.
 Biological energy is stored in chemical
bonds.
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6. Mass Balance
Must put energy in, to get energy out.
 Any gain must be off-set by an equal loss
for the amount of a substance in the body
to remain constant.
 The body is always switched on, there is
always something going on.
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7. Mass Flow
Things go on at a specific rate.
 E.g. water flows through a sprinkler a
specific rate to water the lawn.
 E.g. rate for blood flow through the
circulatory system is regulated.
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The Science of Physiology
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Scientific Inquiry
Curiosity
 Observation
 Experiments
 Theories
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The Science of Physiology
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The Investigator
Observes a phenomenon (event)
 Uses background knowledge
 Proposes an idea (hypothesis)
 Designs an experiment to test the hypothesis
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The Science of Physiology
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E.g. background, Olfactory sensory
neurons contact both the environment
and the brain. Could these cells have
specific defenses against toxins?
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Hypothesis: The olfactory sensory
neurons are able to detoxify compounds.
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The Science of Physiology
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Experiments
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Change the part of the experiment that the
investigator is testing (independant variable)
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Eg. Expose the animal to different levels of
copper. The copper is the independent
variable.
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The Science of Physiology
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Dependent variable. What you measure
in the experiment.
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E.g. measure the activity of a detoxifying
enzyme in the olfactory sensory neurons
during copper exposures.
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The Science of Physiology
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Control: everything but the treatment
(independent variable)
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E.g. Measure the activity of detoxifying
enzymes in olfactory sensory neurons
following no copper treatment.
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The Science of Physiology
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Collect the data, replicate
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E.g. Make quite a few measurements of
detoxyfiying enzyme activity with several
different concentrations of copper.
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The Science of Physiology
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After many expeirments, using different
techniques, the hypothesis becomes a scientific
theory.
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E.g. Use several different techniques
(biochemistry, histochemistry,
immunohistochemistry, molecular biology) to
show that olfactory sensory neurons detoxify
toxins.
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The Science of Physiology
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The material in this course is based on
theoretical models from many
experiments and theories. As new
analyses are made, the material will
change. Physiology is an experimental
science.
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The Science of Physiology
Experimental models for human
physiology
 Non human organisms, from insects,
squids, mice, rats etc.
 Pharmaceutical industry must have
human trials
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Human Experiments
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For disease treatment
Variability
 Ethical considerations
 Psychological variation
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Human Experiments
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Variability
Vs. inbred animal stocks
 For humans, averaged values used
 --> cross-over study, a person is his/her own
control (before treatment, after treatment),
one group takes a placebo.
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Human Experiments
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Psychological factors
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May show improvement even with placebo
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Nocebo - if people are warned of side effects,
subjects will report side-effects, compared to
subjects who have not been warned of side
effects.
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Human Experiments
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Control for the placebo effect
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Blind study - subject does not know if they
are receiving a placebo or a treatment, but
the researcher knows.
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Double blind study - neither the subject or the
researcher know who is treated or who is
given the placebo. A third person tracks the
data.
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Human Experiments
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Double blind cross over study.
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The control group (placebo) becomes the
experimental group half-way through the
study.
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Human Experiments: ethical
considerations
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If a treatment is so good, is it ethical to
withdraw treatment from the untreated
group?
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If a treatment is less effective than a
conventional treatment, is it ethical to
continue the test? Important to constantly
monitor subjects.
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Human Experiments: ethical
considerations
Often, clinical data are ambiguous.
 E.g HRT
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+ lower colon cancer
 + lower bone fractures
 - increase cardiovascular disease
 - increase breast cancer
 --> HRT withdrawn.
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Clinical Trials
Look for the duration of a trial
 Look for the sample size in a study
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Often studies do not agree, because of
sample size or experimental design
 Can use statistical methods to compare
similar studies.
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Supplements to human trials
Animal models
 Cultured cells
 Computer modeling
 Molecular biology
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Many ideas in the physiology
text are theories backed up by
experimental evidence.
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