9a-1 student slides · 2019. 11. 4. · 11/30/15 1 9...
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Muscles and Muscle Tissue: Part A-‐1
Three Types of Muscle Tissue
1. ______________ muscle Assue: – ABached to bones and skin – Striated – Voluntary (i.e., conscious control) – Powerful – Primary topic of this chapter
Three Types of Muscle Tissue
2. ________________ muscle Assue: – Only in the heart – Striated – Involuntary – More details in Chapter 18 (*The Cardiovascular
System)
Three Types of Muscle Tissue
3. _______________ muscle Assue: – In the walls of hollow organs, e.g., stomach,
urinary bladder, and airways – Not striated – Involuntary – More details later in this chapter
Table 9.3
Special CharacterisAcs of Muscle Tissue
• ________________ (responsiveness or irritability): ability to receive and respond to sAmuli
• ________________: ability to shorten when sAmulated
• ________________: ability to be stretched • ________________: ability to recoil to resAng length
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Muscle FuncAons
1. ________________ of bones or fluids (e.g., blood)
2. Maintaining ________________ and body posiAon
3. Stabilizing ________________ 4. ________________ generaAon (especially
skeletal muscle)
Skeletal Muscle
• Each ________________ is served by one artery, one nerve, and one or more veins
Skeletal Muscle • ConnecAve Assue sheaths of skeletal muscle:
– ________________: dense regular connecAve Assue surrounding enAre muscle
– ________________: fibrous connecAve Assue surrounding fascicles (groups of muscle fibers)
– ________________: fine areolar connecAve Assue surrounding each muscle fiber
Figure 9.1
Bone
Perimysium
Endomysium (between individual muscle fibers)
Muscle fiber
Fascicle (wrapped by perimysium)
Epimysium
Tendon
Epimysium
Muscle fiber in middle of a fascicle
Blood vessel
Perimysium Endomysium
Fascicle (a)
(b)
Skeletal Muscle: ABachments
• Muscles aBach: – ________________—epimysium of muscle is fused to the periosteum of bone or perichondrium of carAlage
– ________________—connecAve Assue wrappings extend beyond the muscle as a ropelike tendon or sheetlike aponeurosis
Table 9.1
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Microscopic Anatomy of a Skeletal Muscle Fiber
• ________________ cell 10 to 100 µm in diameter, up to 30 cm long
• MulAple peripheral ________________ • Many ________________ • Glycosomes for glycogen storage, myoglobin for O2 storage
• Also contain myofibrils, sarcoplasmic reAculum, and T tubules
Myofibrils
• ________________ packed, rodlike elements • ~80% of cell ________________ • Exhibit striaAons: perfectly aligned repeaAng series of dark ___ bands and light ___ bands
Nucleus Light I band Dark A band
Sarcolemma
Mitochondrion
(b) Diagram of part of a muscle fiber showing the myofibrils. One myofibril is extended afrom the cut end of the fiber.
Myofibril
Sarcomere
• Smallest ________________ unit (funcAonal unit) of a muscle fiber
• The region of a myofibril between two successive ________________
• Composed of thick and thin myofilaments made of ________________ proteins
Features of a Sarcomere
• ____________________: run the enAre length of an A band
• ____________________: run the length of the I band and partway into the A band
• ________________: coin-‐shaped sheet of proteins that anchors the thin filaments and connects myofibrils to one another
• ________________: lighter midregion where filaments do not overlap
• ________________: line of protein myomesin that holds adjacent thick filaments together
Figure 9.2c, d
I band I band A band Sarcomere
H zone Thin (actin) filament
Thick (myosin) filament
Z disc Z disc
M line
(c) Small part of one myofibril enlarged to show the myofilaments responsible for the banding pattern. Each sarcomere extends from one Z disc to the next.
Z disc Z disc M line Sarcomere
Thin (actin) filament
Thick (myosin) filament
Elastic (titin) filaments
(d) Enlargement of one sarcomere (sectioned lengthwise). Notice the myosin heads on the thick filaments.
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Ultrastructure of Thick Filament
• Composed of the protein ________________ – Myosin ______________ contain:
• 2 interwoven, heavy polypepAde chains – Myosin ______________ contain:
• 2 smaller, light polypepAde chains that act as cross bridges during contracAon
• Binding sites for acAn of thin filaments • Binding sites for ATP • ATPase enzymes
Ultrastructure of Thin Filament
• Twisted double strand of fibrous protein F ________________
• F acAn consists of G (globular) acAn subunits • G acAn bears acAve sites for myosin head aBachment during ________________
• Tropomyosin and troponin: regulatory proteins bound to ______________
Figure 9.3
Flexible hinge region
Tail
Tropomyosin Troponin Actin Myosin head
ATP- binding site
Heads Active sites for myosin attachment
Actin subunits
Actin-binding sites
Thick filament Each thick filament consists of many myosin molecules whose heads protrude at opposite ends of the filament.
Thin filament A thin filament consists of two strands of actin subunits twisted into a helix plus two types of regulatory proteins (troponin and tropomyosin).
Thin filament Thick filament
In the center of the sarcomere, the thick filaments lack myosin heads. Myosin heads are present only in areas of myosin-actin overlap.
Longitudinal section of filaments within one sarcomere of a myofibril
Portion of a thick filament Portion of a thin filament
Myosin molecule Actin subunits
Sarcoplasmic ReAculum (SR)
• Network of smooth ________________ ________________surrounding each myofibril
• Pairs of terminal cisternae form perpendicular cross channels
• FuncAons in the regulaAon of intracellular ___________ levels
T Tubules
• ConAnuous with the ________________ • Penetrate the cell’s interior at each A band–I band juncAon
• Associate with the paired terminal cisternae to form triads that encircle each ________________
Figure 9.5
Myofibril
Myofibrils
Triad:
Tubules of the SR
Sarcolemma
Sarcolemma
Mitochondria
I band I band A band H zone Z disc Z disc
Part of a skeletal muscle fiber (cell)
• T tubule • Terminal
cisternae of the SR (2)
M line
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Triad RelaAonships
• T tubules conduct ________________ deep into muscle fiber
• Integral proteins protrude into the ________________ space from T tubule and SR cisternae membranes
• T tubule proteins: voltage ________________ • SR foot proteins: gated channels that regulate ____________ release from the SR cisternae