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9        

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