Transcript Muscles move skeletal parts by contracting

CHAPTER 49
SENSORY AND MOTOR SYSTEMS
Section F1: Movement And Locomotion
1. Locomotion requires energy to overcome friction and gravity
2. Skeletons support and protect the animal body and are essential to
movement
3. Physical support on land depends on adaptations of body proportions
and posture
4. Muscles move skeletal parts by contracting
5. Interactions between myosin and actin generate force during muscle
contractions
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Locomotion is active movement from one place to another.
Locomotion requires energy to overcome friction and gravity
• A comparison of the energy costs of various modes of
locomotion.
Fig. 49.25
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• Swimming.
– Since water is buoyant gravity is less of a
problem when swimming than for other modes of
locomotion.
• However, since water is dense, friction is more
of a problem.
– Fast swimmers have fusiform bodies.
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• For locomotion on land powerful muscles and
skeletal support are more important than a
streamlined shape.
– When hopping the tendons in kangaroos legs store and
release energy like a spring that is compressed and
released – the tail helps in the maintenance of balance.
– When walking having one foot on the ground helps in the
maintenance of balance.
– When running momentum helps in the maintenance of
balance.
– Crawling requires a considerable expenditure of energy
to overcome friction – but maintaining balance is not a
problem.
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• Gravity poses a major problem when flying.
– The key to flight is the aerodynamic structure of wings.
Fig. 34.26
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• Cellular and Skeletal Underpinning of Locomotion.
– On a cellular level all movement is based on contraction.
• Either the contraction of microtubules or the
contraction of microfilaments.
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Figure 49.x3 Swimming
Figure 49.x4 Locomotion on land
Figure 49.29 Posture helps support large land vertebrates, such as bears, deer,
moose, and cheetahs
Figure 49.x5 Flying
Skeletons support and protect the animal
body and are essential to movement
• Hydrostatic skeleton: consists of fluid held under
pressure in a closed body compartment.
– Form and movement is controlled by changing the shape
of this compartment.
– The hydrostatic skeleton of earthworms allow them to
move by peristalsis.
– Advantageous in aquatic environments and can support
crawling and burrowing.
– Do not allow for running or walking.
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Figure 49.27 Peristaltic locomotion in an earthworm
Many groups of invertebrates use hydrostatic skeleton
to provide the rigid structure upon which muscles can act.
However the same in in many other some parts of a body
May rely on containing fluid in a structure to maintain the
form or shape, e.g. trunk of elephant where fluid in tissues
provide rigidity, tongue of animals, penis is mammals, and etc.
Exoskeletons: hard encasements deposited
on the surface of an animal
Mollusks are enclosed in a
calcareous exoskeleton.
The jointed exoskeleton of
arthropods is composed of a
cuticle.
Regions of the cuticle can vary in
hardness and degree of flexibility.
About 30 – 50% of the cuticle
consists of chitin.
Muscles are attached to the interior
surface of the cuticle.
This type of exoskeleton must be
molted to allow for growth.
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Examples of other arthropods with exoskeletons
http://stammhirn.biologie.uni-ulm.de/w4fly/aktuell0208_en.html
http://hannover.park.org/Canada/Museum/insects/evolution/muscles.html
Four anatomical features characterize the
phylum Chordata
• Although chordates vary widely in appearance, all share the
presence of four anatomical structures at some point in their
lifetime.
– These chordate
characteristics are
a notochord; a dorsal,
hollow nerve cord;
pharyngeal slits;
and a muscular,
Fig. 34.2
postanal tail.
The notochord is the basic skeletal element in the early
Chordate groups that are ancestral to all vertebrates
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(a)
(b)
Fig. 34.4
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Vertebrates either developed a cartilaginous skeleton (e.g
sharks) or a boney skeleton (all other vertebrates) based on the
underlying chordate plan outlined above. The skeletal elements
are the support structures upon which the muscles act.
Figure 25.0
Fossil of a fish:
perch
Body/Caudal Fin Propulsion
The following diagramm depicts the specific swimming modes identified
within BCF propulsion, based on the (extended) classification scheme
proposed originally by Breder in1926.
BCF propulsion modes, based on Lindsey (1978).
http://www.ece.eps.hw.ac.uk/Research/oceans/projects/flaps/bcfmodes.htm
Skeletal elements are modified to take on new support functions to assist in
development of new functions and expand the diversity of the group.
Figure 34.10 Hypothesis for the evolution of vertebrate jaws
Figure 34.12a Ray-finned fishes
(class Actinopterygii): yellow perch
Figure 34.13
Physical support on land depends on
adaptations of body proportions and
posture
• In the support of body
weight posture is
more important than
body proportions.
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Limb bone modifications that
are adaptations for certain
forms of movement
Convergent evolution of
structures for gliding
Figure 34.27x
Archaeopteryx,
a fossil in the ancestoral
linkage of birds and reptiles
Figure 34.25
Form fits function: the avian wind and feather
in modern bird. The feathers forming a flight
surface and hollow bones reduce the weight
Figure 34.30 Evolution of the mammalian jaw and ear bones
Fig. 49.17
Fig. 49.28
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Muscles move skeletal parts by
contracting
• Muscles come in antagonistic pairs.
Fig. 49.30
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Interactions between myosin and actin
generate force during muscle contractions
• The sliding-filament model of muscle contraction.
Energy
Need
supplied
by ATP
Actin
Myosin
Fig. 49.33
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• Structure and Function of
Vertebrate Skeletal Muscle.
– The sarcomere is the
functional unit of muscle
contraction.
– Thin filaments consist of
two strands of actin and one
tropomyosin coiled about
each other.
– Thick filaments consist of
myosin molecules.
– When a contraction occurs
the sarcomere shortens, m
line disappears and I band
shortens.
Fig. 49.31
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Follow the action potential.
When an action potential meets the muscle cell’s sarcoplasmic
reticulum (SR) stored Ca2+ is released.
Calcium ions and regulatory proteins control muscle contraction
Fig. 49.35
Diverse body movements require variation
in muscle activity
• An individual muscle cell either contracts completely or not
all.
• Individual muscles, composed of many individual muscle
fibers (cells), can contract to varying degrees.
– One way variation is
accomplished by varying
the frequency of action
potentials reach the
muscle from a single
motor neuron.
Fig. 49.37
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– Graded
muscle
contraction
can also be
controlled by
regulating the
number of
motor units
involved in
the
contraction.
Fig. 49.38
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– Recruitment of motor neurons increases the number of
muscle cells involved in a contraction.
– Some muscles, such as those involved in posture, are
always at least partially contracted.
• Fatigue is avoided by rotating among motor units.
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– Cardiac muscle: similar to skeletal muscle
• Cardiac muscle: similar to skeletal muscle
– Smooth muscle: lacks the striations seen in both
skeletal and cardiac muscle.
• Contracts with less tension, but over a greater range of
lengths, than skeletal muscle.
• Slow contractions, with more control over contraction
strength than with skeletal muscle.
• Found lining the walls of hollow organs.
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