Transcript 40Animal Structure - Mid

Chap 40
Animal Structure and Function
• Epithelia are classified by the number of cell
layers and the shape of the cells on the free
surface.
• A simple epithelium has
a single layer of cells, and
a stratified epithelium
has multiple tiers of cells.
• The shapes of cells may
be cuboidal (like dice),
columnar (like bricks on
end), or squamous (flat
like floor tiles).
Fig. 40.1
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•
There are three kinds of connective tissue
fibers, which are all proteins: collagenous
fibers, elastic fibers, and reticular fibers.
1. Collagenous fibers are made of collagen.
–
Collagenous fibers are nonelastic and do not tear
easily when pulled lengthwise.
2. Elastic fibers are long threads of elastin.
–
Elastin fiber provide a rubbery quality.
3. Reticular fibers are very thin and branched.
–
Composed of collagen and continuous with
collagenous fibers, they form a tightly woven fabric
that joins connective tissue to adjacent tissues.
CoREl
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Six major types of connective tissues in
vertebrates are:
1. loose connective tissue,
2. adipose tissue,
3. fibrous connective tissue,
4. cartilage,
5. bone, and
6. blood.
–
Each has a
structure
correlated
with its
specialized Laura finds computers at Best Buy.
function.
Fig. 40.2
Pads, insulates,
stores fuel
2
4
6
5
1
Binds epithelia to
underlying tisssue
3
Tendons and
ligaments
Loose connective tissue binds
epithelia to underlying tissues and
functions as packing materials, holding
organs in place.
– Loose connective tissue has all three fiber
types.
Two cell types predominated in the
fibrous mesh of loose connective
tissue.
– Fibroblasts secrete the protein
ingredients of the extracellular fibers.
– Macrophages are amoeboid cells that
roam the maze of fibers, engulfing
bacteria and the debris of dead cells by
phagocytosis.
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• Blood functions differently from other
connective tissues, but it does have an extensive
extracellular matrix.
– The matrix is a liquid called plasma, consisting of
water, salts, and a variety of dissolved proteins.
– Suspended in the plasma are erythrocytes (red blood
cells), leukocytes (white blood cells) and cell
fragments called platelets.
• Red cells carry oxygen.
• White cells function in defense against viruses, bacteria,
and other invaders.
• Platelets aid in blood clotting.
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Cartilage has an abundance of collagenous fibers
embedded in a rubbery matrix made of a substance
called chondroitin sulfate, a protein-carbohydrate
complex.
– Chondrocytes secrete collagen and chondroitin sulfate.
– The composite of collagenous fibers and chondroitin sulfate
makes cartilage a strong yet somewhat flexible support
material.
– The skeleton of a shark is made of cartilage and the embryonic
skeletons of many vertebrates are cartilaginous.
– We retain cartilage as flexible supports in certain locations,
such as the nose, ears, and vertebral disks.
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• The skeleton supporting most vertebrates is made of
bone, a mineralized connective tissue.
– Osteoblasts deposit a matrix of collagen.
– Then, calcium, magnesium, and phosphate ions combine and
harden within the matrix into the mineral hydroxyapatite.
– The osteoblast becomes an osteocyte in the Lacuna.
– The combination of hard mineral and flexible collagen
makes bone harder than cartilage without being brittle.
– The microscopic structure of hard mammalian bones
consists of repeating units called osteons (or Haversian
systems)..
osteon
• Each osteon has concentric layers of
mineralized matrix deposited around a
central canal containing blood vessels
and nerves that service the bone.
–The osteoblast becomes an osteocyte in the Lacuna.
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• Nervous tissue senses stimuli and transmits
signals from one part of the animal to another.
– The functional unit of nervous tissue is the neuron,
or nerve cell.
– It consists of a cell body and two or more
extensions, called dendrites and axons.
– Dendrites transmit nerve impulses from their tips
toward the rest of the neuron.
– Axons transmit impulses toward
another neuron or toward an
effector, such as a muscle cell.
Fig. 40.3
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• There are three types of muscle tissue in the vertebrate
body: skeletal muscle, cardiac muscle, and smooth
muscle.
One cell
Fig. 40.4
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• Attached to bones by tendons, skeletal muscle
is responsible for voluntary movements.
– Skeletal muscle is also called striated muscle
because the overlapping filaments give the cells a
striped (striated) appearance under the microscope.
• Cardiac muscle forms the contractile wall of
the heart.
– It is striated like cardiac muscle, but cardiac cells
are branched.
– The ends of the cells are joined by intercalated
disks, which relay signals from cell to cell during a
heartbeat.
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Animals w/o a circulatory system must keep a large SA/Volume ratio
Multi-celled Animals are two layered thick so each cell is in contact with
the environment.
• Organisms with more complex body plans
– Have highly folded internal surfaces specialized for
exchanging materials
External environment
Mouth
Food
CO2
O2
Respiratory
system
0.5 cm
Cells
Heart
Nutrients
Circulatory
system
A microscopic view of the lung reveals
that it is much more spongelike than
balloonlike. This construction provides
an expansive wet surface for gas
exchange with the environment (SEM).
10 µm
Interstitial
fluid
Digestive
system
Excretory
system
The lining of the small intestine, a digestive organ, is elaborated with fingerlike
projections that expand the surface area
for nutrient absorption (cross-section, SEM).
Anus
Unabsorbed
matter (feces)
Figure 40.4
50 µm
Animal
body
Metabolic waste
products (urine)
Inside a kidney is a mass of microscopic
tubules that exhange chemicals with
blood flowing through a web of tiny
vessels called capillaries (SEM).
Metabolic rate provides clues to an
animal’s bioenergetic “strategy”
• The amount of energy an animal uses in a unit
of time is called its metabolic rate - the sum of
all the energy-requiring biochemical reactions
occurring over a given time interval.
– Energy is measured in calories (cal) or kilocalories
(kcal).
• A kilocalorie is 1,000 calories.
• The term Calorie, with a capital C, as used by many
nutritionists, is actually a kilocalorie.
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• There are two basic bioenergetic “strategies”
used by animals.
– Birds and mammals are mainly endothermic,
maintaining their body temperature at a certain level
with heat generated by metabolism.
• Endothermy is a high-energy strategy that permits
intense, long-duration activity of a wide range of
environmental temperatures.
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– Most fishes, amphibians, reptiles, and invertebrates
are ectothermic, meaning they do not produce
enough metabolic heat to have much effect on body
temperature.
• The ectothermic strategy requires much less energy than
is needed by endotherms, because of the energy cost of
heating (or cooling) an endothermic body.
• However, ectotherms are generally incapable of intense
activity over long periods.
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3. Metabolic rate per gram is
inversely related to body size
among similar animals
• One of animal biology’s most intriguing, but
largely unanswered questions has to do with the
relationship between body size and metabolic
rate.
– Physiologists have shown that the amount of energy it
takes to maintain each gram of body weight is
inversely related to body size.
– For example, each gram of a mouse consumes about
20 times more calories than a gram of an elephant.
• One hypothesis for the inverse relationship
between metabolic rate and size is that the
smaller the size of an endotherm, the greater the
energy cost of maintaining a stable body
temperature.
– The smaller the animal, the greater its surface to
volume ratio, and thus the greater loss of heat to (or
gain from) the surroundings.
• However, this hypothesis fails to explain the
inverse relationship between metabolism and size
in ectotherms.
• Nor is it supported by experimental tests.
• Researchers continue to search for causes
underlying this inverse relationship.
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Activity and Metabolic Rate
• The basal metabolic rate (BMR)
– Is the metabolic rate of an endotherm at rest
• The standard metabolic rate (SMR)
– Is the metabolic rate of an ectotherm at rest
• For both endotherms and ectotherms
– Activity has a large effect on metabolic rate
Size and Metabolic Rate
• Metabolic rate per gram
– Is inversely related to body size among similar
animals
– Is inversely related
to the duration of
the activity
A = 60-kg alligator
A H
100
A
Maximum metabolic rate
(kcal/min; log scale)
• In general, an
animal’s maximum
possible metabolic
rate
500
H
H = 60-kg human
50
H
10
H
H
5
A
1
A
A
0.5
0.1
1
second
1
minute
1
hour
Time interval
Key
Existing intracellular ATP
ATP from glycolysis
Figure 40.9
ATP from aerobic respiration
1
day
1
week
• The BMR of a human is much higher than the
SMR of an alligator.
• Both can reach high
levels of maximum
potential metabolic
rates for short
periods, but metabolic
rate drops as the
duration of the activity
increases and the
source of energy shifts
toward aerobic
respiration.
Fig. 40.12
• Sustained activity depends on the aerobic
process of cellular respiration for ATP supply.
– An endotherm’s respiration rate is about 10 times
greater than an ectotherm’s.
– Only endotherms are capable of long-duration
activities such as distance running.
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• An animal’s use of energy
– Is partitioned to BMR (or SMR), activity,
homeostasis, growth, and reproduction
Annual energy expenditure (kcal/yr)
800,000
Reproduction
Basal
metabolic
rate
Ectotherm
Temperature
regulation costs
Growth
Activity
costs
340,000
8,000
4,000
60-kg female human
from temperate climate
4-kg male Adélie penguin
from Antarctica (brooding)
(a) Total annual energy expenditures
0.025-kg female deer mouse
from temperate
North America
4-kg female python
from Australia
438
Energy expenditure per unit mass
(kcal/kg•day)
igure 40.10a, b
Endotherms
(b)
Human
233
Python
Deer mouse
Adélie penguin
36.5
5.5
Energy expenditures per unit mass (kcal/kg•day)
• Concept 40.4: Animals regulate their internal
environment within relatively narrow limits
• The internal environment of vertebrates
– Is called the interstitial fluid, and is very different
from the external environment
• Homeostasis is a balance between external
changes
– And the animal’s internal control mechanisms that
oppose the changes
Regulating and Conforming
• Regulating and conforming
– Are two extremes in how animals cope with
environmental fluctuations
• An animal is said to be a regulator
– If it uses internal control mechanisms to moderate
internal change in the face of external, environmental
fluctuation
• An animal is said to be a conformer
– If it allows its internal condition to vary with certain
external changes
Mechanisms of Homeostasis
• Mechanisms of homeostasis
– Moderate changes in the internal environment
• A homeostatic control system has three
functional components
– A receptor, a control center, and an effector
Response
No heat
produced
Heater
turned
off
Room
temperature
decreases
Too
hot
Set
point
Too
cold
Set
point
Set point
Control center:
thermostat
Room
temperature
increases
Heater
turned
on
Response
Figure 40.11
Heat
produced
• Most homeostatic control systems function
by negative feedback
– Where buildup of the end product of the
system shuts the system off
• A second type of homeostatic control
system is positive feedback
– Which involves a change in some variable that
triggers mechanisms that amplify the change
• Concept 40.5: Thermoregulation contributes to
homeostasis and involves anatomy, physiology,
and behavior
• Thermoregulation
– Is the process by which animals maintain an
internal temperature within a tolerable range
Ectotherms and Endotherms
• Ectotherms
– Include most invertebrates, fishes, amphibians, and
non-bird reptiles
• Endotherms
– Include birds and mammals
• In general,
ectotherms
40
– Tolerate greater
variation in internal
temperature than
endotherms
Body temperature (°C)
River otter (endotherm)
30
20
Largemouth bass (ectotherm)
10
0
Figure 40.12
10
20
30
40
Ambient (environmental) temperature (°C)
• Endothermy is more energetically
expensive than ectothermy
– But buffers animals’ internal temperatures
against external fluctuations
– And enables the animals to maintain a high
level of aerobic metabolism
Modes of Heat Exchange
• Organisms exchange heat by four physical
processes
Radiation is the emission of electromagnetic
waves by all objects warmer than absolute
zero. Radiation can transfer heat between
objects that are not in direct contact, as when
a lizard absorbs heat radiating from the sun.
Figure 40.13
Convection is the transfer of heat by the
movement of air or liquid past a surface,
as when a breeze contributes to heat loss
from a lizard’s dry skin, or blood moves
heat from the body core to the extremities.
Evaporation is the removal of heat from the surface of a
liquid that is losing some of its molecules as gas.
Evaporation of water from a lizard’s moist surfaces that
are exposed to the environment has a strong cooling effect.
Conduction is the direct transfer of thermal motion (heat)
between molecules of objects in direct contact with each
other, as when a lizard sits on a hot rock.
Balancing Heat Loss and Gain
• Thermoregulation involves physiological
and behavioral adjustments
– That balance heat gain and loss
Insulation
• Insulation, which is a major
thermoregulatory adaptation in mammals
and birds
– Reduces the flow of heat between an animal
and its environment
– May include feathers, fur, or blubber
• In mammals, the integumentary system
– Acts as insulating material
Hair
Epidermis
Sweat
pore
Muscle
Dermis
Nerve
Sweat
gland
Hypodermis
Adipose tissue
Figure 40.14
Blood vessels
Oil gland
Hair follicle
Circulatory Adaptations
• Many endotherms and some ectotherms
– Can alter the amount of blood flowing between
the body core and the skin
• In vasodilation
– Blood flow in the skin increases, facilitating heat loss
• In vasoconstriction
– Blood flow in the skin decreases, lowering heat loss
• Many marine
mammals and
birds
– Have
arrangements
of blood
vessels called
countercurrent
heat exchangers
that are
important for
reducing heat
loss
1 Arteries carrying warm blood down the
legs of a goose or the flippers of a dolphin
are in close contact with veins conveying
cool blood in the opposite direction, back
toward the trunk of the body. This
arrangement facilitates heat transfer
from arteries to veins (black
arrows) along the entire length
of the blood vessels.
Canada
goose
Artery
1
3
35°C
30º
2 Near the end of the leg or flipper, where
arterial blood has been cooled to far below
Vein
the animal’s core temperature, the artery
can still transfer heat to the even colder
blood of an adjacent vein. The venous blood
33°
continues to absorb heat as it passes warmer
and warmer arterial blood traveling in the
opposite direction.
27º
20º
18º
10º
9º
2
Pacific
bottlenose
dolphin
1
3
Blood flow
3
Vein
Artery
2
3 As the venous blood approaches the
center of the body, it is almost as warm
as the body core, minimizing the heat lost
as a result of supplying blood to body parts
immersed in cold water.
Figure 40.15
In the flippers of a dolphin, each artery is
surrounded by several veins in a
countercurrent arrangement, allowing
efficient heat exchange between arterial
and venous blood.
• Some specialized bony fishes and sharks
– Also possess countercurrent heat exchangers
21º
25º 23º
27º
(a) Bluefin tuna. Unlike most fishes, the bluefin tuna maintains
temperatures in its main swimming muscles that are much higher
than the surrounding water (colors indicate swimming muscles cut
in transverse section). These temperatures were recorded for a tuna
in 19°C water.
(b) Great white shark. Like the bluefin tuna, the great white shark
has a countercurrent heat exchanger in its swimming muscles that
reduces the loss of metabolic heat. All bony fishes and sharks lose
heat to the surrounding water when their blood passes through the
gills. However, endothermic sharks have a small dorsal aorta,
and as a result, relatively little cold blood from the gills goes directly
to the core of the body. Instead, most of the blood leaving the gills
is conveyed via large arteries just under the skin, keeping cool blood
away from the body core. As shown in the enlargement, small
arteries carrying cool blood inward from the large arteries under the
skin are paralleled by small veins carrying warm blood outward from
the inner body. This countercurrent flow retains heat in the muscles.
Figure 40.16a, b
29º
31º
Body cavity
Skin
Artery
Vein
Blood
vessels
in gills
Heart
Capillary
network within
muscle
Artery and
vein under Dorsal aorta
the skin
• Many endothermic
insects
– Have countercurrent
heat exchangers that
help maintain a high
temperature in the
thorax
Figure 40.17
Cooling by Evaporative Heat
Loss
• Many types of animals
– Lose heat through the evaporation of water in
sweat
– Use panting to cool their bodies
• Bathing moistens the skin
– Which helps to cool an animal down
Figure 40.18
Behavioral Responses
• Both endotherms and ectotherms
– Use a variety of behavioral responses to control
body temperature
Some terrestrial
invertebrates
– Have certain
postures that enable
them to minimize or
maximize their
absorption of heat
from the sun
Figure 40.19
Adjusting Metabolic Heat
Production
• Some animals can regulate body
temperature
– By adjusting their rate of metabolic heat
production
• Many species
of flying
insects
PREFLIGHT
40
Temperature (°C)
– Use shivering
to warm up
before taking
flight
PREFLIGHT
WARMUP
FLIGHT
Thorax
35
30
Abdomen
25
Figure 40.20
0
2
Time from onset of warmup (min)
4
Feedback Mechanisms in
Thermoregulation
• Mammals regulate their body temperature
– By a complex negative feedback system that
involves several organ systems
Sweat glands secrete
sweat that evaporates,
cooling the body.
Thermostat in
hypothalamus
activates cooling
mechanisms.
• In humans, a specific
part of the brain, the
hypothalamus
– Contains a group of
nerve
cells that function as
a thermostat
Blood vessels
in skin dilate:
capillaries fill
with warm blood;
heat radiates from
skin surface.
Increased body
temperature (such
as when exercising
or in hot
surroundings)
HOT
Body temperature
decreases;
thermostat
shuts off cooling
mechanisms.
Homeostasis:
Internal body temperature
of approximately 36–38C
Body temperature
increases;
thermostat
shuts off warming
mechanisms.
COLD
Decreased body
temperature
(such as when
in cold
surroundings)
Blood vessels in skin
constrict, diverting blood
from skin to deeper tissues
and reducing heat loss
from skin surface.
Figure 40.21
Skeletal muscles rapidly
contract, causing shivering,
which generates heat.
Thermostat in
hypothalamus
activates
warming
mechanisms.
Adjustment to Changing
Temperatures
• In a process known as acclimatization
– Many animals can adjust to a new range of
environmental temperatures over a period of
days or weeks
• Acclimatization may involve cellular
adjustments
– Or in the case of birds and mammals,
adjustments of insulation and metabolic heat
production
Torpor and Energy Conservation
• Torpor
– Is an adaptation that enables animals to save
energy while avoiding difficult and dangerous
conditions
– Is a physiological state in which activity is low
and metabolism decreases
• Hibernation is long-term torpor
– That is an adaptation to winter cold and food scarcity
during which the animal’s body temperature declines
Additional metabolism that would be
necessary to stay active in winter
Actual
metabolism
100
0
35
30
Temperature (°C)
Figure 40.22
Metabolic rate
(kcal per day)
200
Arousals
Body
temperature
25
20
15
10
5
0
-5
Outside
temperature
Burrow
temperature
-10
-15
June
August
October
December
February
April
• Estivation, or summer torpor
– Enables animals to survive long periods of high
temperatures and scarce water supplies
• Daily torpor
– Is exhibited by many small mammals and birds and
seems to be adapted to their feeding patterns