11.2.muscles and movement. state the roles of bones, ligaments, muscles, tendons and nerves in human...
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• State the roles of bones, ligaments, muscles, tendons and nerves in human movement.
• Label a diagram of the human elbow joint, including cartilage, synovial fluid, joint capsule, named bones and antagonistic muscles (biceps and triceps).
• Outline the functions of the structures in the human elbow joint named above.
• Compare the movements of the hip joint and the knee joint.
• Describe the structure of striated muscle fibres, including the myofibrils with light and dark bands, mitochondria, the sarcoplasmic reticulum, nuclei and the sarcolemma
• Draw and label a diagram to show the structure of a sarcomere, including Z lines, actin filaments, myosin filaments with heads, and the resultant light and dark bands.
• Explain how skeletal muscle contracts, including the release of calcium ions from the sarcoplasmic reticulum, the formation of cross-bridges, the sliding of actin and myosin filaments, and the use of ATP to break cross-bridges and re-set myosin heads.
• Analyse electron micrographs to find the state of contraction of muscle fibres.
Components of our locomotory system
Bones: support and partially protect the body parts.Ligaments: hold bones together and form protective capsules around the moveable joints. They are made of strong lightly elastic tissue.Muscles: cause movements by contraction.
a. skeletalb. smoothc. cardiac
Tendons: attach muscles to bones at their points of anchorage. They are made of dense connective tissue.Nerves: connect central nervous system to other parts of the body. They are bundles of many nerve fibers. They stimulate muscles for movement.
The components of human elbow jointHumerus, radius, ulna:Biceps muscle:Triceps muscles:Ligaments:Capsule:Synovial membrane:Synovial fluid:Cartilage:
Types of joints:
• Movable joints: provide controlled movement also known as synovial joints.
a. Ball and socket joints: are found in hip joints that permit movements in all three planes (circular movement: circumduction)
b. Hinge joint: restricts the movement to one plane (flexion and extension. Example: Knee joint
• Muscles and bones interact to produce movement.
• Muscles– are connected to bones by tendons and– can only contract, requiring an antagonistic
muscle to• reverse the action and• relengthen muscles.
The skeleton and muscles interact in movement
© 2012 Parson Education, Inc.
Figure 30.7A
Biceps contracted,triceps relaxed(extended)
Biceps
Triceps
TendonsTriceps
Biceps
Tricepscontracted,bicepsrelaxed
• Muscle fibers are cells that consist of bundles of myofibrils. Skeletal muscle cells– are cylindrical,– have many nuclei, and– are oriented parallel to each other.
• Myofibrils contain overlapping– thick filaments composed primarily of the
protein myosin and– thin filaments composed primarily of the
protein actin.
Each muscle cell has its own contractile apparatus
© 2012 Parson Education, Inc.
• Sarcomeres are– repeating groups of overlapping thick and thin
filaments and– the contractile unit—the fundamental unit of
muscle action.
Each muscle cell has its own contractile apparatus
© 2012 Parson Education, Inc.
Figure 30.8Muscle
Several muscle fibers
Single muscle fiber(cell)
Plasma membrane
Nuclei
Myofibril
Lightband
Darkband
Lightband
Z line
Sarcomere
SarcomereZ lineZ line
Thickfilaments(myosin)
Thinfilaments(actin)U
ltra
stru
ctur
e of
mus
cle
fiber
Figure 30.8_2
Plasma membrane
Nuclei
Myofibril
Lightband
Darkband
Lightband
Z line
Sarcomere
Single muscle fiber(cell)
Figure 30.8_3
SarcomereZ lineZ line
Thickfilaments(myosin)
Thinfilaments(actin)
Lightband
Darkband
Lightband
Z line
Sarcomere
• According to the sliding-filament model of muscle contraction, a sarcomere contracts (shortens) when its thin filaments slide across its thick filaments.– Contraction shortens the sarcomere without
changing the lengths of the thick and thin filaments.
– When the muscle is fully contracted, the thin filaments overlap in the middle of the sarcomere.
A muscle contracts when thin filaments slide along thick filaments
© 2012 Parson Education, Inc.
Figure 30.9A
Relaxed muscle
Contractingmuscle
Fully contractedmuscle
Dark band
Sarcomere
Contracted sarcomere
Z Z
• Myosin heads of the thick filaments– bind ATP and– extend to high-energy states.
• Myosin heads then – attach to binding sites on the actin molecules
and– pull the thin filaments toward the center of the
sarcomere.
A muscle contracts when thin filaments slide along thick filaments
© 2012 Parson Education, Inc.
Figure 30.9BThinfilaments
Thinfilament
Thickfilament
Thick filament
Z lineActin
Myosin head (low-energy configuration)
Myosin head (high-energy configuration)
Cross-bridge
Newpositionof Z lineThin filament moves
toward center of sarcomere.
1
2
3
ATP
ADPP
ADPP
4
ADP P
5
Myosin head (pivoting tolow-energy configuration)
ATP Myosin head (low-energy configuration)
Figure 30.9B_s2
Thinfilaments
Thick filament
Z line
Myosin head (low-energy configuration)
Actin
Thinfilament
Thickfilament
1
ATP
Figure 30.9B_s3
Thinfilaments
Thick filament
Z line
Myosin head (low-energy configuration)
Myosin head (high-energy configuration)
Actin
Thinfilament
Thickfilament
1
2
ATP
ADPP
Figure 30.9B_s5
Myosin head(pivoting)
4
Newpositionof Z lineThin filament
moves toward center.
ADP P
Cross-bridge
3
ADPP
Figure 30.9B_s6
Myosin head(low-energy)
Myosin head(pivoting)
ATP
5
4
Newpositionof Z lineThin filament
moves toward center.
ADP P
Cross-bridge
3
ADPP
• A motor neuron– carries an action potential to a muscle cell,– releases the neurotransmitter acetylcholine
from its synaptic terminal, and– initiates a muscle contraction.
Motor neurons stimulate muscle contraction
© 2012 Parson Education, Inc.
Figure 30.10A
Motor neuronaxon
Synapticterminal
T tubule
Action potentialMitochondrion
Endoplasmicreticulum (ER)
Myofibril
Plasma membraneSarcomere
Ca2
releasedfrom ER
• An action potential in a muscle cell– passes along T tubules and– into the center of the muscle fiber.
• Calcium ions– are released from the endoplasmic reticulum
and– initiate muscle contraction by moving the
regulatory protein tropomyosin away from the myosin-binding sites on actin.
Motor neurons stimulate muscle contraction
© 2012 Parson Education, Inc.
Figure 30.10B
Myosin-binding sites blocked
Myosin-binding sites exposed
Myosin-binding site
Ca2 floods thecytoplasmicfluid
ActinTropomyosin Ca2-binding sites
Troponin complex
• A motor unit consists of– a neuron and– the set of muscle fibers it controls.
• More forceful muscle contractions result when additional motor units are activated.
Motor neurons stimulate muscle contraction
© 2012 Parson Education, Inc.
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