6. Consensus model to explain extension and withdrawal
of pseudopodia and ameboid crawling:
1. hyaline cap appears
7. Consensus model to explain extension and withdrawal
of pseudopodia and ameboid crawling:
2. endoplasm flows toward hyaline cap
8. Consensus model to explain extension and withdrawal
of pseudopodia and ameboid crawling:
3. actin subunits attach to regulatory proteins
9. Consensus model to explain extension and withdrawal
of pseudopodia and ameboid crawling:
4. endoplasm fountains out to the periphery
10. Consensus model to explain extension and withdrawal
of pseudopodia and ameboid crawling:
5. actin subunits released and polymerized
11. Consensus model to explain extension and withdrawal
of pseudopodia and ameboid crawling:
6. microfilaments cross-linked
12. Consensus model to explain extension and withdrawal
of pseudopodia and ameboid crawling:
7. Ca2+ activate actin-severing protein
13. Consensus model to explain extension and withdrawal
of pseudopodia and ameboid crawling:
8. myosin associate with and pull on microfilaments
14. Ciliary and Flagellar Movement
Cilia
–
minute, hairlike, motile processes
–
occur in large numbers
–
ciliate protistans
–
found in all major groups of animals
–
move organisms through aquatic environment
–
propel fluids and materials across surfaces
15.
16. Ciliary and Flagellar Movement
Flagella
–
whiplike
–
present singly or in small numbers
–
occur in unicellular eukaryotes
–
animal spermatozoa
–
sponges
17. • both cilia and flagella have the same ultrastructure
– a core of microtubules sheathed by the plasma
membrane
18. • both cilia and flagella have the same ultrastructure
– “9 + 2” pattern
– flexible “wheels” of proteins connect outer doublets to
each other and to the core
19. • both cilia and flagella have the same ultrastructure
– outer doublets are
connected by
motor proteins
– anchored in the
cell by a basal
body
20. •
The bending of cilia and flagella is driven by the
arms of a motor protein, dynein.
21. •
Addition to dynein of a phosphate group from
ATP and its removal causes conformation changes
in the protein.
•
Dynein arms alternately grab, move, and release
the outer microtubules.
22. •
Protein cross-links limit sliding and the force
is expressed as bending.
23. •
A flagellum has an undulatory movement
–
force is generated parallel to the flagellum’s axis
24. •
Cilia move more like oars with alternating
power and recovery strokes
–
generate force perpendicular to the cilia’s axis
25. Invertebrate Muscle
Bivalve molluscan muscles
– 2 kinds of fibers:
• fast muscle fibers = striated, can contract rapidly
• smooth muscle = capable of slow, long-lasting
contractions
26.
27. Invertebrate Muscle
Insect flight muscles (fibrillar muscle)
– wings of small flies operate at 1000 beats/sec
– limited extensibility; shorten only slightly
32. Sliding Filament Model
• Actin filaments at both ends of sarcomere
– one end of each filament attached to a Z-plate at one end
of the sarcomere
– other end suspended in sarcoplasm
33. Sliding Filament Model
• Myosin filaments suspended in between Z-plates
– myosin filaments contain cross-bridges which pull the actin filaments
inward
– causes Z-plates to move toward each other
– shortens sarcomere
– sarcomeres stacked together in series and cause myofiber to shorten
34. Sliding Filament Model
• Working muscles require ATP
– myosin breaks down ATP
– sustained exercise
• requires cellular respiration
• regenerates ATP
35. 35
Muscle Innervation
•
Neuromuscular junction
–
the synaptic contact between a nerve fiber and a
muscle fiber
–
nerve impulses bring about the release of a
neurotransmitter that crosses the synaptic cleft
–
signals the muscle fiber to contract
36.
37.
38.
39.
40.
41. Human Muscular System
•
Skeletal muscles
–
attached to the skeleton by cable-like fibrous
connective tissue called tendons
–
arranged in antagonistic pairs
• can only contract, cannot push
• when one muscle contracts, it stretches its
antagonistic partner
•
a muscle at “rest” exhibits tone (minimal
contraction)
•
a muscle in tetany is at maximum sustained
contraction
44. Muscle Performance
– slow oxidative fibers (red muscles)
• for slow, sustained contractions without
fatigue
• contain extensive blood supply
• high density of mitochondria
• abundant stored myoglobin
• important in maintaining posture in terrestrial
vertebrates
45. Muscle Performance
fast fibers
1. fast glycolytic fiber (white muscles)
• lacks efficient blood supply
• pale in color
• function anaerobically
• fatigue rapidly
2. fast oxidative fiber
• extensive blood supply
• high density of mitochondria and myoglobin
• function aerobically
• for rapid, sustained activities
46. Energy for Contraction
– ATP, immediate source of energy
– glucose broken down during aerobic metabolism
– glycogen stores can supply glucose
– muscles have creatine phosphate, an energy
reserve
– slow and fast oxidative fibers rely heavily on
glucose and oxygen
– fast glycolytic fibers rely on anaerobic glycolysis
– muscles incur oxygen debt during anaerobic
glycolysis
