7.Muscle histology

Question 1

classify muscle tissue

Answer 1

1. striated
   
   1. cardiac
   2. skeletal
2. smooth

Question 2

define the terms

1. myofiber.aka.aka
2. sarcolemma
3. sarcoplasm
4. sarcoplasmic reticulum
5. sarkos

Answer 2

1. myofiber.muscle fiber. myocyte
   
   1. a single mature muscle cell
2. sarcolemma
   
   1. muscle cell membrane
3. sarcoplasm
   
   1. cytoplasm of the muscle cell
4. sarcoplasmic reticulum
   
   1. sER
5. sarkos
   
   1. flesh

Question 3

draw and generalize the muscle organization.

what do blood vessels traverse?

Answer 3

1. muscle cell form long multinucleated syncytium(a single cell or cytoplasmic mass containing several nuclei, formed by fusion of cells or by division of nuclei.) grouped in bundles surrounded by sheaths. blood vessels use these sheaths.
   
   1. epimysium
   2. perimysium
   3. endomysium

Question 4

describe and define the muscle fiber organization in skeletal muscle

Answer 4

with in sarcoplasm, myofibrils run parallel

1. myofibrils
   
   1. surrounded by repeating units of mitochondria
   2. structures
      
      1. sarcomere-functional contracting subunit
         
         1. 1/2 I band + 1 complete A band +1/2 I band
         2. seperated by the Z-disc
         3. ~2.5micrometers long, in resting muscle
      2. dark bands
         
         1. A bands-anisotropic
            
            1. bisected by H band
               
               1. H band
                  
                  1. creatine kinase = main enzyme, catalyzes formation of ATP from creatine phosphate and ADP
                  2. bisected by Mline
                     
                     1. Mline
                        
                        1. ​center point for the mysosin head attachment
      3. light bands
         
         1. I bands isotropic
         2. light b/c of [actin]

Question 5

discuss structure and function of the triad

Answer 5

triad

1. sturcture
   
   1. 1=T tubules
      
      1. invaginations of cell membrane penetrate deeply into the sarcoplasm near the A and I band boundaries of the sarcomere
   2. 2=Terminal sisternae
      
      1. the end of the sarcoplasmic reticulum that articulates with the t tubule
2. function
   
   1. allows depolarization of sarcolemma in at t tubule
   2. this depolarization lead to the release of Ca++ from the SR in to the cytoplasm

Question 6

components of thick and thin filaments. do the ychange size?

Answer 6

1. thick
   
   1. Myosin 2
      
      1. 500 kDa
      2. 2 heavy chains and 2 light chains
         
         1. heavy
            
            1. globular head tha has 2 specific sites
               
               1. ATP
               2. Actin
2. thin
   
   1. actin
      
      1. contains a binding site for myosin
      2. thin filaments have 2 tightly regulatory proteins
         
         1. tropomyosin
         2. toponin

these do not change size, but slide over eachother.

Question 7

in the mechanism of muscle contraction, discuss in three steps. what does and does not change size, with respect to the sarcomere regions.

Answer 7

during muscle contraction the muscle hortens about 1/3 of its original length

1. thick and thin filaments DO NOT change size
2. does not change size
   
   1. A band
3. does minmize in size
   
   1. I band
   2. H band
   3. Z-lines get closer

force of contraction is generated by the process that moves one type of filament past the adjacent filament of the other type.

Question 8

describe the neuromuscular junction. Draw and diagram the important componenets of the junction

Answer 8

neuromuscular junctinon=motor end plate

1. axon branches to muscle cell surface to generate neuromuscular junction
2. branches
   
   1. form synaptic buttons
      
      1. covered in Schwann cells
      2. buttons lie over the motor end region, separated from the sarcolemma by the synaptic clefts
      3. two types of synaptic clefts
         
         1. primary synaptic cleft
            
            1. neronal side where ACh is released
         2. junctional folds (secondary synaptic cleft)
            
            1. crest of junctional folds contains the ACh receptors
            2. ​ basal lamina is where the AChesterase is released.
            3. at the base, is where the voltage-gated Na+ channels are located
               4.

Question 9

what is the action, presentatio and treatment of Myasthenia gravis

Answer 9

Extra ocular muscles of the eye are commonly affected first

increase the amount of ACh that stimulate the receptors

Question 10

How do you notice the contraction of your muscles. Describe the structure, organiazation and function of the structures.

Answer 10

neuromuscular spindles

1. skeletal muscle and myotendinous junction contain sensory receptors acting as proprioceptors
2. struture
   
   1. tendonextension contains the golgi tendon organ, while the extrafusal muscle fibers surround capsule( continuous with the tendon) that contains intrafusal fibers of a muscle spindle.
3. contents-muscle portions
   
   1. musle spindles
      
      1. found among the muscle fascicles
      2. encapsulated by perimysium
      3. each has intrafusal fibers
         
         1. ​layer of flattened cells, containing interstitial fluid and a few thin muscle fibers
         2. several sensory nerve axons penetrate each muscle spindle and wrap around individual intrafusal fibers
      4. function
         
         1. changes in length of extrafusal muscle fibers is detct4d by muscle spindles and sensory nerve relay this information to spinal cord.
   2. Glogi tendon organ
      
      1. small encapsulated structures tat enclose the sensory axos penetrating the collagen bundles at the muscle-tendon joint
      2. function
         
         1. tendon organ detects
            
            1. changes in tension within tendons produced by muscle contraction
            2. Act to inhibit motor activity if tension becomes too excesive

Question 11

Categorize skeletal muscle fibers give definition of categorical arrangment, types, purpose, contents and appearance

Answer 11

1. their maximal rate of contraction
   
   1. fast
   2. slow
2. their major ATP synthesis pathway
   
   1. oxidateive phosphorylation
   2. glycolysis

different types of muscles fibers

1. slow oxidative muscle fibers
   
   1. adapted for slow contractions over long periods of time w/o fatigue
   2. have many mitochondria
   3. rich capillary network
   4. high in myoglobin
      
      1. generating a dark/red fiberous appearance
   5. example
      
      1. deep back muscles
2. fast glycolytic fibers
   
   1. ​ specialized for contraction that are
      
      1. rapid
      2. short term
   2. ATP
      
      1. anaerobic metabolism of stored glucose from stored glycogen.
   3. content
      
      1. few mitchondria
      2. few capillaries
   4. appearance
      
      1. white and fatigue rapidly
3. fast oxidative -glycolytic
   
   1. have physiological and histological features between oxidative slow and fast glycolytic

Question 12

diagram concept map of skeletal muscles

Answer 12

Question 13

after a deep cut to the hand, I recovered after several weeks. What repaired my muscles?

Answer 13

repair and regeneration

1. satellite cells
   
   1. location
      
      1. just underneathe the sarcolemma
   2. considerable significance in muscle
      
      1. maintenance
      2. repair
      3. regeneration
   3. dormancy
      
      1. are mitotically quiescent in adults, but can resume self-renewal and proliferation in response to stress or trauma.
         
         1. the idea behind muscle injuries and degenerative disease like muscular dystrophies