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I. Animal Size/Shape and the EnvironmentII. Four tissue categoriesIV. Feedback Control and temperature regulationV. Metabolic Rate and Energy Use
VII. Summary
Lecture 12 Outline (Ch. 40)
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2What things to animals do to maintain homeostasis?
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Overview: Diverse Forms, Common Challenges
• Anatomy: study of biological form of an organism
• Physiology: study of biological functions of an organism
• Communication and integration
• Support and movement
• Regulation and maintenance
• Defense• Reproduction and
development
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Cells must continually be bathed in aqueous medium to exchange gasses, nutrients, wastes – all by
diffusion which is only effective over short distances.
A. How long does it take a small molecule to travel 1 um?
B. How long to travel 1 mm?
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0.5 cmNutrients
Digestivesystem
Lining of small intestine
MouthFood
External environment
Animalbody
CO2 O2
Circulatorysystem
Heart
Respiratorysystem
Cells
Interstitialfluid
Excretorysystem
Anus
Unabsorbedmatter (feces)
Metabolic waste products(nitrogenous waste)
Kidney tubules
10 µm
50 µ
m
Lung tissue
• More complex organisms have highly folded internal surfacesOverview: Diverse Forms, Common Challenges
Cells bathed in interstitial fluid
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How does the surface area to volume ratio change as a cell increases in size? (let’s say
cells are roughly spherical)
diameter: SA cell: Volume cell:d = 1 µmd = 10 µmd = 100 µm
SA = 4r2 V = 4/3r3
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Exchange
0.15 mm
(a) Single cell
1.5 mm
(b) Two layers of cells
Exchange
Exchange
Mouth
Gastrovascularcavity
Rate of exchange related to SAAmount of exchange related to V
Overview: Diverse Forms, Common Challenges
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• Tissues are classified into four main categories:
Tissue Structure and Function
Humans: 210 different cell types – can you name them?! ;)
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Epithelial Tissue
Cuboidalepithelium
Simplecolumnarepithelium
Pseudostratifiedciliatedcolumnarepithelium
Stratifiedsquamousepithelium
Simplesquamousepithelium
Note differences in cell shape and type of layering
Tissue Structure and Function
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Apical surface
Basal surfaceBasal lamina
40 µm
Tissue Structure and Function
Epithelial cells are attached to a basal lamina at their base.
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Connective Tissue
Connective tissue binds / supports other tissues• sparsely packed cells scattered
in extracellular matrix• matrix - fibers in a liquid,
jellylike, or solid foundation
There are six main types of connective tissue.
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Connective Tissue
Collagenous fiberLooseconnectivetissue
Elastic fiber120
µm
Cartilage
Chondrocytes
100
µm
Chondroitinsulfate
Adiposetissue
Fat droplets
150
µm
White blood cells
55 µ
m
Plasma Red bloodcells
Blood
Nuclei
Fibrousconnectivetissue
30 µ
m
Osteon
Bone
Central canal
700
µmTissue Structure and Function
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Muscle Tissue• Muscle tissue: long cells (muscle fibers) that contract in
response to nerve signals
Skeletal muscle - striated, voluntary movementSmooth muscle – not striated, involuntary body activitiesCardiac muscle – striated, contraction of the heart
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Muscle Tissue
50 µmSkeletalmuscle
Multiplenuclei
Muscle fiber
Sarcomere
100 µm
Smoothmuscle
Cardiac muscle
Nucleus
Musclefibers
25 µm
Nucleus Intercalateddisk
Tissue Structure and Function
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Glial cells
Nervous Tissue
15 µm
DendritesCell body
Axon
Neuron
Axons
Blood vessel
40 µm
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Tissue Structure and Function
• Nervous tissue senses stimuli, transmits signals Nervous tissue contains:
Neurons transmit nerve
impulsesGlial cells nourish, insulate,
and replenish neurons
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Self-Check
Tissue Category Tissues/Cells Included; Functions
Epithelial
Connective
Muscle
Nervous
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Response:Heater turnedoff
Stimulus:Control center(thermostat)reads too hot
Roomtemperaturedecreases
Setpoint:20ºC
Roomtemperature
increases
Stimulus:Control center(thermostat)
reads too cold
Response:Heater turnedon
Feedback control loops maintain the internal environment in many animals
Examples of negative and positive feedback?
Which maintains homeostasis?
• Animals manage their internal environment by regulating or conforming to the external environment
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• regulator: uses internal mechanisms to maintain during external change.• Ex: River otter
• conformer: allows internal variables to change with environment.• Ex: Largemouth bass
Temperature Regulation
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• Five general adaptations help animals thermoregulate:
– Insulation– Circulatory adaptations– Cooling by evaporative
heat loss– Behavioral responses– Adjusting metabolic heat
production
Balancing Heat Loss and Gain
Dragonfly “obelisk” posture
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Temperature Regulation
• Thermoregulation: process by which animals maintain an internal temperature
(a) A walrus, an endotherm
(b) A lizard, an ectotherm
• Endothermic animals generate heat by metabolism (birds and mammals)
• Ectothermic animals gain heat from external sources (invertebrates, fishes, amphibians, and non-avian reptiles)
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We’ve discussed several mechanisms related to homeostasis and in particular temperature
regulation.
Are all endotherms regulators? Are all ectotherms conformers?
Can you think of any examples that do not follow this trend?
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• Metabolic rate is the amount of energy an animal uses in a unit of time
Energy Use
Measured by amount of oxygen consumed or carbon dioxide produced
• Basal metabolic rate (BMR) is the metabolic rate of an endotherm at rest at a “comfortable” temperature
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Shrew
Harvest mouseMouse
Ground squirrelRat
Cat Dog
SheepHuman
Horse
Elephant
Body mass (kg) (log scale)
BM
R (L
O2/h
r) (l
og s
cale
)
(a) Relationship of BMR to body size
10–3 10–210–2
10–1
10–1
1
1
10 102 103
10
102
103
Energy Use
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10310210110–110–210–30
1
2
3
4
5
6
7
8
Body mass (kg) (log scale)
(b) Relationship of BMR per kilogram of body mass to body size
BM
R (L
O2/
hr) (
per k
g)Shrew
Harvest mouse
MouseRat
Ground squirrelCat
Sheep
DogHuman
HorseElephant
Energy Use
Human average daily metabolic rate is only 1.5X BMR!
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Which animal would have the highest BMR per unit body weight?
1. human2. dog3. mouse4. whale5. turtle
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Energy Budgeting
• Hibernation is long-term torpor that is an adaptation to winter cold and food scarcity
• Torpor = physiological state with low activity and metabolism decreased – allows animals to save energy while avoiding difficult and dangerous conditions
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In discussing homeostasis, regulation, and hibernation, consider the following:
Why would an animal use hibernation? What might be gained by this behavior?
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Additional metabolism that would benecessary to stay active in winterActual
metabolism
Arousals
Bodytemperature
Outsidetemperature Burrow
temperature
Met
abol
ic ra
te(k
cal p
er d
ay)
Tem
pera
ture
(°C
)
June August October December February April–15
–10–5
05
15
10
25
20
3530
0
100
200
Energy Use