Lecture 12 Outline (Ch. 40)
I.
Animal Size/Shape and the Environment
II.
Four tissue categories
IV. Feedback Control and temperature regulation
V.
Metabolic Rate and Energy Use
VII. Summary
What things to animals do to maintain homeostasis?
2
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
3
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?
Overview: Diverse Forms, Common Challenges
• More complex organisms have highly folded internal surfaces
Animal
body
Respiratory
system
0.5 cm
50 µm
Cells bathed in
interstitial fluid
External environment
CO2
Food
O2
Mouth
Lung tissue
Nutrients
Heart
Cells
Circulatory
system
10 µm
Interstitial
fluid
Digestive
system
Excretory
system
Lining of small intestine
Kidney tubules
Anus
Unabsorbed
matter (feces)
Metabolic waste products
(nitrogenous waste)
5
How does the surface area to volume ratio
change as a cell increases in size? (let’s say
cells are roughly spherical)
SA = r2
diameter:
d = 1 µm
d = 10 µm
d = 100 µm
V=
SA cell:
r3
Volume cell:
Overview: Diverse Forms, Common Challenges
Rate of exchange related to SA
Amount of exchange related to V
Mouth
Gastrovascular
cavity
Exchange
Exchange
Exchange
0.15 mm
1.5 mm
(a) Single cell
(b) Two layers of cells
7
Tissue Structure and Function
• Tissues are classified into four main categories:
Humans: 210 different cell types – can you name them?! ;)
8
Tissue Structure and Function
Epithelial Tissue
Cuboidal
epithelium
Simple
columnar
epithelium
Pseudostratified
ciliated
columnar
epithelium
Stratified
squamous
epithelium
Simple
squamous
epithelium
Note differences in cell shape and type of layering
9
Tissue Structure and Function
Apical surface
Basal surface
Basal lamina
40 µm
Epithelial cells are attached to a basal lamina at their base.
10
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.
11
Tissue Structure and Function
Connective Tissue
Loose
connective
tissue
Chondrocytes
Cartilage
Elastic fiber
Chondroitin
sulfate
Nuclei
Fat droplets
Adipose
tissue
Osteon
150 µm
Fibrous
connective
tissue
30 µm
100 µm
120 µm
Collagenous fiber
White blood cells
Blood
55 µm
700 µm
Bone
Central canal
Plasma
Red blood 12
cells
Muscle Tissue
• Muscle tissue: long cells (muscle fibers) that contract in
response to nerve signals
Skeletal muscle striated, voluntary
movement
Smooth muscle –
not striated,
involuntary body
activities
Cardiac muscle –
striated, contraction of
the heart
13
Tissue Structure and Function
Muscle Tissue
Multiple
nuclei
Muscle fiber
Sarcomere
Skeletal
muscle
Nucleus
100 µm
Intercalated
disk
50 µm
Cardiac muscle
Nucleus
Smooth
muscle
Muscle
fibers
25 µm
14
Tissue Structure and Function
Nervous Tissue
• Nervous tissue senses stimuli, transmits signals
Nervous tissue contains:
Dendrites
Neurons
transmit nerve
impulses
Glial cells
nourish, insulate,
and replenish
neurons
40 µm
Cell body
Glial cells
Axon
Neuron
Axons
Blood vessel
15 µm
15
Self-Check
Tissue Category
Tissues/Cells Included; Functions
Epithelial
Connective
Muscle
Nervous
16
Feedback control loops maintain the internal environment in
many animals
Examples of negative
and positive feedback?
Which
maintains
homeostasis?
Response:
Heater
turned
off
Room
temperature
decreases
• Animals manage their
internal environment
Room
by regulating or
temperature
increases
conforming to the
external environment
Stimulus:
Control center
(thermostat)
reads too hot
Set
point:
20ºC
Stimulus:
Control center
(thermostat)
reads too cold
Response:
Heater
turned
on
17
Temperature Regulation
• regulator: uses internal
mechanisms to maintain
during external change.
• Ex: River otter
• conformer: allows internal
variables to change with
environment.
• Ex: Largemouth bass
18
Balancing Heat Loss and Gain
• Five general adaptations
help animals thermoregulate:
– Insulation
– Circulatory adaptations
– Cooling by evaporative
heat loss
– Behavioral responses
– Adjusting metabolic heat
production
Dragonfly “obelisk” posture
19
Temperature Regulation
• Thermoregulation: process by
which animals maintain an
internal temperature
• Endothermic animals
generate heat by
metabolism (birds and
mammals)
• Ectothermic animals gain
heat from external sources
(invertebrates, fishes,
amphibians, and nonavian reptiles)
(a) A walrus, an endotherm
(b) A lizard, an ectotherm
20
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?
Energy Use
• Metabolic rate is the amount of energy an animal uses in a unit
of time
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
22
Energy Use
103
BMR (L O2/hr) (log scale)
Elephant
Horse
102
Human
Sheep
10
Cat
Dog
1
10–1
Rat
Ground squirrel
Shrew
Mouse
Harvest mouse
10–2
10–3
10–2
102
1
10–1
10
Body mass (kg) (log scale)
(a) Relationship of BMR to body size
103
23
Energy Use
8
Shrew
BMR (L O2/hr) (per kg)
7
Human average daily metabolic
rate is only 1.5X BMR!
6
5
4
Harvest mouse
3
Mouse
2
Rat
1
Ground squirrel
0
10–3
10–2
Sheep
Human Elephant
Cat
Dog
Horse
1
10
102
10–1
Body mass (kg) (log scale)
103
(b) Relationship of BMR per kilogram of body mass to body size
24
Which animal would have the
highest BMR per unit body weight?
1.
2.
3.
4.
5.
human
dog
mouse
whale
turtle
Energy Budgeting
• Torpor =
physiological
state with low
activity and
metabolism
decreased –
allows animals
to save energy
while avoiding
difficult and
dangerous
conditions
• Hibernation is long-term torpor that is an adaptation to
winter cold and food scarcity
26
In discussing homeostasis, regulation, and
hibernation, consider the following:
Why would an animal use hibernation?
What might be gained by this behavior?
Metabolic rate
(kcal per day)
Energy Use
200
Actual
metabolism
100
0
35
30
Temperature (°C)
Additional metabolism that would be
necessary to stay active in winter
Arousals
Body
temperature
25
20
15
10
5
0
–5
Outside
temperature
Burrow
temperature
–10
–15
June
August
October
December
February
April
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