Chapter 1: Introduction
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Human Physiology
Bio 5
Denise Lim, Instructor
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Use Your Textbook Wisely
Some other words of advice
❚  Glossary/Index
❚  Concept Reviews (Blue Headings)
❚  "Focus On…” in Chapter 1
–  Concept Mapping
–  Graphing
❚  Concept Checks
–  (Answers in Appendix A)
❚  Running Problems (case studies)
❚  Chapter Summaries
❚  Review Questions (Answers in Appendix A)
❚  Appendix B: Physics and Math basics
❚  Manage your time well
❚  Pay attention to detail
❚  Learn to be a good communicator
❚  Be professional
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Bio5, Denise Lim
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Chapter 1: Introduction
Introduction
Chapter 1
Organization: small to big
❚  Atoms
❚  Molecules
❚  Cells
❚  Tissues
❚  Organs
❚  Organ
systems
❚  What is Physiology?
❚  The integration of function across
many levels of organization
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Why is physiology so hard to
study?
Function and Mechanism:
"Why" versus "How"
❚  Complexity
❚  "Why" = Purpose
❚  "How" = Mechanism
❚  Need to understand both purpose and
mechanistic, but focus on mechanism
– Conditions both inside and outside
the body constantly change
– Interplay between body systems
change as conditions change
❚  Variation between individuals
– Genetic predisposition, life style
❚  Safety, ethics
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Bio5, Denise Lim
– Investigative methods can be invasive
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Chapter 1: Introduction
Homeostasis is maintained
through mass balance and mass
flow
Important physiological themes
❚  Structure/Function relationships
❚  Energy
– Metabolism
❚  Communication coordinates
function
❚  Homeostasis & Regulation
– Maintaining the constancy or
stability of the internal environment
within a range of tolerance
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Flow of exchange between the
body’s external and internal
environment
❚  What goes in must go out
❚  What is lost must be replaced
Fig. 1.5, pg. 11
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Local versus
longdistance
control of
homeostasis
Fig. 1-9, pg. 14
Fig. 1.4, pg 11
Bio5, Denise Lim
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❚  Local response: intrinsic control
❚  Reflex response: extrinsic control
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Chapter 1: Introduction
Homeostasis depends on communication and feedback
Activity 1
❚  Stimulus
❚  Receptor or sensor
– Detects the stimulus
❚  Integrating center
determines setpoint
❚  Effector produces
response
Fig. 1-10, pg. 15
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Negative feedback counteracts the
stimulus, maintains conditions within
a range around a setpoint (range of tolerance)
Fig. 1-11, pg. 16
Bio5, Denise Lim
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Example: blood glucose
❚  Glucose levels
drop after
fasting: hungry
❚  Glucose rises
after a meal
❚  Insulin brings
levels back to
setpoint
❚  May overshoot
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Fig. 22-19, pg. 716
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Chapter 1: Introduction
Positive feedback amplifies
body’s response; NOT
homeostatic
Glucose Homeostasis
❚  Stimulus
–  Increased blood glucose
❚  Receptor
–  Beta cells in pancreas
❚  Afferent Pathway
❚  Inflammatory
response
❚  Childbirth
–  ATP production increases when more glucose is available
❚  Integrating Center
–  Pancreas: releases insulin when ATP in beta cells is high
❚  Efferent Pathway
–  Insulin
❚  Effector
–  Liver and muscle cells: insulin triggers glucose uptake
❚  Response
–  Decreases blood glucose
Figure 1.12 A positive feedback loop
Fig. 1-12b, pg. 16
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Baby drops
lower in uterus to
initiate labor
Cervical
stretch
causing
stimulates
Push baby
against
cervix
Oxytocin
release
Positive feedback loop
causes
Uterine
contractions
Delivery of baby
stops the cycle
Fig. 1.13, pg 17
Bio5, Denise Lim
HCl production in stomach
❚  Presence of
food in
stomach
activates
pepsin
❚  Emptying
stomach
shuts it off 20
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