BIOL 1361 Lecture 13: Ch39 Homeostasis
21 Nov 2016
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BIOL 1361
Homeostasis: Nutrients & Thermoregulation
Chapter 39, sections 39.1, 39.3, 39.4 & 39.5
I. Bioenergetics
1. The overall flow and transformation of energy in an animal
II. Challenges and Adaptation
1. Challenges – obtain water O2, and food to survive
2. Constraints – Physical laws governing diffusion(influences the structure of
animals), heat exchange, and electrical conduction
3. Adaptations
1. Heritable characteristics that enhance survival and reproduction in the
current environment
2. Genetic change occurs in populations:
1) Natural selection increases proportion of individuals with an adaptive
trait
2) Frequency of trait changes between generations
3. Adaptations are good enough but not perfect
4. Acclimatization – change within an individual in response to short-term
environmental changes (seasonal change)
III. Surface area: Volume
1. Important in energy exchange
2. Smaller animals have more surface area per unit volume
3. Greater SA: V
1. More exchange of
1) Heat, water, solutes
2. Higher maintenance costs
IV. Homeostasis
1. Definition – maintaining a predictable internal environment (variable is
maintained between upper and lower limit)
2. Conformity vs Regulation [Fig. 32.3]
1. Conformity – Animal’s internal environment changes with the external
environment
2. Regulation – Animal’s internal environment remains stable even when
external environment fluctuates
1) Partial regulator
a. Regulates an internal variable at a specific level over a range of
external conditions, but conforms at extreme external values
b. Maintains an internal variable at a fixed amount above or below
ambient conditions
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BIOL 1361
3. Negative feedback [Fig. 32.4]
1. Mechanism for regulationg a variable at a set point
2. Factor that causes fluctuations in variable=stimulus
3. Change in variable is detected by a sensor
4. Control centerintegrator triggers a response that returns variable to set
point
V. Regulation of blood (glucose)
1. Glucose absorbed intestine into bloodstream
2. Blood glucose enters liver and muscle cells
3. In cells, glucose polymerized to glycogen
VI. Retrieval of stored glucose for use
1. Hydrolysis of glycosidic linkages between glucose monomers
2. Glucose released from liver cells into bloodstream
3. Other cells can take up to glucose from the blood to use for energy
VII. Thermoregulation
1. Source of body heat
1. Endotherm – internal metabolism (warm-blooded)
2. Ectotherm – external environment (cold-blooded)
2. Heat exchange with the environment [Fig. 32.6]
1. Conduction – Direct transfer of heat between objects in contact
2. Convection – Heat transfer by body fluid
1) EX: breeze, water flow
3. Radiation – Electromagnetic radiation coming from objects warmer than
absolute zero
1) Most animals: infared
4. Evaporation – Liquid molecules with enough kinetic energy to escape as gas
1) Departing high energy molecules remove heat
3. Regulating heat exchange
1. Behavior
1) Seeking or avoiding environmental heat
a. Basking to warm
b. Seeking shade to cool
2. Insulation
1) Feathers of hair
a. ↑ or ↓ thickness by fluffing
b. Traps warm air next to body
2) Blubber
a. Subcutaneous fat in marine mammals
3. Circulation of body fluids
a. Vasodilation
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Document Summary
Chapter 39, sections 39. 1, 39. 3, 39. 4 & 39. 5. Bioenergetics: the overall flow and transformation of energy in an animal. Surface area: volume: important in energy exchange, smaller animals have more surface area per unit volume, greater sa: v, more exchange of, heat, water, solutes, higher maintenance costs. 32. 4: mechanism for regulationg a variable at a set point, factor that causes fluctuations in variable=stimulus, change in variable is detected by a sensor, control center(cid:523)(cid:498)integrator(cid:499)(cid:524) triggers a response that returns variable to set point. Regulation of blood (glucose: glucose absorbed intestine into bloodstream, blood glucose enters liver and muscle cells, in cells, glucose polymerized to glycogen. Retrieval of stored glucose for use: hydrolysis of glycosidic linkages between glucose monomers, glucose released from liver cells into bloodstream, other cells can take up to glucose from the blood to use for energy. Thermoregulation: source of body heat, heat exchange with the environment [fig.
