2/7/2011
40 Physiology, Homeostasis,
and Temperature Regulation
KEY CONCEPTS
1. Four Tissue Types in Animals
2. Energy & Metabolism
3. Why/how do Animals Regulate Internal Environment?
HOMEOSTASIS
4. How does temperature affect animals & how do they
regulate their body temperature?
Animal Form & Function
• Anatomy –
• Physiology –
• STRUCTURE LINKED TO FUNCTION
Structure and function
2x
• Key theme: structure is linked to function
• Ex. Compare appendages of vertebrates:
elephant ears
rabbit ears
whale and dolphin flukes/dorsal fin
X=1
2x
x
x
2x
x
Surface area = 6x2
Volume = x3
Surface area = 6(2x)2 = 24x2
Volume = (2x)3 = 8x2
Ratio of SA to V:
6:1
3:1
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Four types of tissue:
• Epithelial
• Connective
• Muscle
• Nervous
Tissues Form Organs
Organs: consist of multiple tissues
Organ system: group of organs that
function together
Energy Sources & Allocation
ORGAN: STOMACH
Stomach wall arranged in layers:
• Epithelial tissue (lines inner surface)
• Connective tissue (support)
• Muscle (Smooth) tissue (stomach contraction)
• Nervous tissue (controls movement &
influences secretions)
Animals harvest chemical energy from food
Energy-containing molecules from food used
to make ATP (Adenosine Triphosphate;
powers cellular work)
ORGAN SYSTEM: DIGESTIVE SYSTEM
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Metabolic rate
• Metabolic rate -
Quantifying Energy Use
• Direct calorimetry
• Calorie (cal) –
• Indirect calorimetry
Metabolic Rates
METABOLIC RATE INCREASES WITH BODY MASS
Basal Metabolic Rate (BMR): Endotherm
What does this mean?
Standard Metabolic Rate (SMR): Ectotherm
Fasted, Resting, No Growth, No Reproduction
Slope of curve = 0.75: Slope < 1, so as body
size increases energy required per g decreases
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Why does mass specific
metabolic rate decrease with
larger body size?
Animals regulate their
internal environment
1.Single-celled & simple multicellular (i.e.
sponge) organisms:
Short Answer – Don’t know!!!
Long answer –several hypotheses:
Animals regulate their
internal environment
Homeostasis
2. Multicellular organisms:
Homeostasis
• Conformers –
• Regulators –
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What kind of variables are
regulated?
For Humans:
How is homeostasis controlled?
Homeostatic control mechanism
Receptor –
Control center –
Effector –
Regulation Controlled by
Nervous & Endocrine Systems
Information required:
• Set point:
• Feedback information:
• Error signal:
How is homeostasis controlled?
Negative feedback:
Positive feedback:
Feedforward information:
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Homeostasis
*Homeostasis does NOT mean that
physiological variables do not change
Temperature affects physiological processes
(rate increases w/ increasing temperature)
Q10
- Homeostasis is EXPENSIVE!
Regulating Body Remperature:
Model for homeostasis
Energy Budget
(for temperature regulators)
Endotherms
Ectotherms
Poikilotherm
Homeotherm
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Heat Production
Heat Loss
Heat Loss
Metabolism
Convection
Radiation
Non-shivering thermogenesis
Evaporation
Shivering thermogenesis
Tiki
Conduction
Thermoregulatory Strategies
Strategies for Staying Warm and Cool
Circulatory Adaptations
Counter Current Heat Exchangers (CCHE)–
Scholander and Schevill, 1955
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Circulatory Adaptations
Thermal Windows
Torpor vs. Hibernation
Behavior
Behavior: Can increase or decrease heat loss
Body temperature regulation reliant on feedback
Hypothalamus: “thermostat”
Negative Feedback Mechanism
Set Point can Change
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