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21 Cards in this Set
- Front
- Back
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Physiology
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Mechanisms by which organisms function – how the body works
- integrated approach |
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Integrated Function
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Integrated perspective on function using physiochemical properties to functionally link molecules, cells, tissues, systems and organisms
Relationship of structure to function at multiple levels |
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Physiological Environment
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Mechanisms by which organisms interact with their environments
Exchange and transport of vital substances |
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Why do some organisms need organ systems?
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Size
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Are large complex organisms better or more capable in any way?
What is the value of large complex organ systems? |
Bacteria are among most successful organisms on earth
Bacteria are successful without complex organ systems |
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The importance of organ systems: Bacteria
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Bacteria are among most successful organisms on earth, and they complete this without a complex organ system.
Humans exchange the same things with their environment as bacteria do, but require a much more complicated system to get it done. |
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What must all organisms accomplish to survive?
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Exchange
Transport |
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Exchange and transfer are limited by?
Why did large organ systems evolve? |
Size!
Exchange: limited by surface to volume ratio Transport: limited by distance Large organ systems have evolved because of constraints not benefits. |
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Solutions to surface to volume ratio constraints?
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Increase surface area
-Folds (increases surface area) -2D Size Increase Decrease volume -become hollow |
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Distance constrains transport because...
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Diffusion-
Requires no energy Requires favorable concentration gradient Works over microscopic distances only Active Transport- Requires energy Works against concentration gradient Works over microscopic distances only |
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Distance constrains transport – solutions? Bulk Transport Systems!
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-Use large muscular pumps to force mass quantities of substances through pipes
-Requires energy Main Principle: Able to manipulate concentration gradients to allow individual cells to use diffusion and save energy |
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Summary: Why do large, complex organisms have organ systems?
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-ecause of their size, large organisms have difficulty exchanging and transporting vital substances
-Large, complex organ systems have evolved in large organisms to overcome the problems created by their size |
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What is homoeostasis?
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Relatively stable condition of extracellular fluid that results from regulatory system actions
Two important components: -Relative stability or constancy -Active regulation |
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How constant is the internal environment? Golden-mantled Ground Squirrel Body Temperature Example
But is it homeostasis? |
) Challenge the animal
2) See if it works to restore homeostasis Example: Challenge: drop temperature in burrow of hibernating ground squirrel Two Possible Results: Squirrel body temperature drops = no active regulation, the squirrel has abandoned homeostasis Squirrel shivers to maintain body temperature of 10 C = squirrel is actively regulating |
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Traditional View of Homeostasis:
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Organisms work tirelessly to maintain all parameters of their internal state within narrowly defined limits and use active regulation to buffer all environmental challenges
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Reality of Homeostasis:
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Homeostasis is at best imperfect
applies to only some parameters Many parameters vary widely Imperfect |
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Alternatives to Homeostasis?
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Organism’s First Choice:
Tolerance or Conforming: Coping with environmental challenge by tolerating as much internal change as possible and conforming to the environment Organism’s Second Choice: Active Regulation (homeostasis): Once tolerance limits are exceeded, expend energy as a last resort to keep parameter in tolerable range |
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Set point and error signal
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Set point is where the internal body temperature should be ideally, the error signal is the difference between the set point and what the body homeostatically adjusts to during active regulation
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Negative Feedback
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Body compensates for a disturbance in a way that reduces the disturbance (thermostat)
Most common regulatory response in the body Examples: body temperature, osmolality, blood calcium, etc., etc., etc. |
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Positive Feedback
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Body reacts to a disturbance in such a way that increases the disturbance
Rare since it results in a variable that spirals out of control and must be terminated by some dramatic event Examples: birth, vomiting, ovulation, recruitment of leucocytes to wound |
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Feed Forward
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Body anticipates future disturbance and prepares in a way that reduces disturbance when it occurs
Examples: premigratory fattening in birds, circadian rhythms, American eating habits |
