ZOO 3200 Lecture Notes - Lecture 1: Homeostasis, Teleost, Positive Feedback
2 May 2018
School
Department
Course
Professor
Definition
○
The August Krogh Principle
○
What is comparative animal physiology?
•
Homeostasis
○
Conformity vs Regulation
○
Positive vs Negative Feedback
○
Acclimation, Acclimatization, Adaptation
○
Physiological Regulation
•
Outline:
Reading: Chapter 1
The study of how animals function at all levels of organization
•
By studying how animals function in diverse environments,
comparative animal physiologists try to understand the nature of
physiological diversity
•
August Krogh (1874-1949) won the 1920 Nobel Prize in
Physiology
○
Or… there is an optimally-suited animal to study most
biological problems
!
Principle: "for a large number of problems there will be some
animal of choice, or a few of such animals, on which it can be
most conveniently studied"
○
Using squid giant axons to study the properties of action
potentials
!
Using zebrafish embryos to study the impact of global
environmental changes on the development and function
of the stress response
!
Examples:
○
The August Krogh Principle
•
What is Comparative Animal Physiology?
Physiological Regulation
The tendency for animals to maintain relative internal stability in the
face of external fluctuations
•
Homeostasis is maintained by regulatory systems
•
Homeostasis is not constancy
•
Homeostasis:
Animals have different strategies for coping with changing
environmental conditions
•
E.g. Chlorine regulation in sea urchins (osmo-conformers)
○
The tissue chlorine concentration conforms with the
concentration in water
○
Conformers:
•
E.g. Chlorine regulation in teleost fish
○
There is a zone of stability where homeostasis (of the chlorine
plasma concentration) is maintained
○
Regulators:
•
Each strategy has benefits and costs
•
Whether an animal uses one strategy or the other is parameter specific
•
Effects of changes in external temperature in lizards -
conformity
○
Effects of changes in external water chlorine concentration (in
teleost fish) -regulation
○
Examples:
•
Conformity vs. Regulation:
Negative feedback control systems regulate a variable by opposing its
deviation from a set point thereby keeping the variable within its
homeostatic range
•
Stimulates beta cells -- insulin release -- blood glucose
decreases
!
Stimulus: eating carbohydrates
○
Stimulates alpha cells -- glucagon release -- blood glucose
increases
!
Stimulus: fasting
○
Example: regulation of blood glucose
•
Negative Feedback:
Positive feedback control systems regulate non-homeostatic change
and create a rapid change away from a set point (i.e. promoting
explosive response that are unidirectional)
•
Signal from mature fetus -- uterus begins contractions -- stretch
sensors -- mothers hypothalamus -- pituitary gland -- secretion
of oxytocin -- enhanced contractions
○
Example: the regulation of birth (parturition) in mammals
•
Positive Feedback:
Ex. Shifting temperature of goldfish
○
Acclimation -process of change in response to a controlled
environmental variable in the lab
•
Summer -increases at a higher rate below 10 degrees
!
Winter -increases at a lower rate below -10 degrees
!
Ex. Red fox -as ambient temperature decreases, their resting
rate of oxygen consumption increases
○
Acclimatization -process of change in response to a natural
environmental variation
•
Acclimation vs. Acclimatization:
Adaptation -process of change through natural selection leading to an
organism whose physiology, anatomy and behaviour are matched to
the demands of its environment
•
This takes place over many generations (resulting from changes in the
DNA) and is usually irreversible
•
Ex. Adaptation of the antelope jackrabbit to living in the desert
•
Adaptation:
Central Themes in Animal Physiology
Thursday,+ September+ 7,+2017
12:57+PM
