Exam 1 Histology

Question 1

Collagen Fibers

Answer 1

High tensile strength

Question 2

Elastic Fibers

Answer 2

Allows tissues/organs to stretch & return to size
Elastin fibers incorporate bundles of microfibrils that act as a scaffold during development and consist of the Glycoprotein Fibrillin.
Elastin, an amorphous component, is added later and forms the major part of the fiber.

Question 3

Reticular Fibers

Answer 3

Provides delicate framework of support

Question 4

A bands

Answer 4

(Anisotrophic) are dark bands (myosin, overlaps actin)

Question 5

I bands

Answer 5

(Isotrophic) are light bands (actin, tropomyosin, troponins)

Question 6

H band

Answer 6

the center of the A band (myosin with no overlap of actin; slightly lighter portion of middle of A band)

Question 7

Sarcomere

Answer 7

is the basic contractile unit of striated muscle.

Sarcomere repeats are represented by myofibrils.

Question 8

desmin

Answer 8

Myofibrils are held in place with each another by desmin, which is an intermediate filament proteins.
These proteins hold adjacent Z-lines (disks) together

Question 9

Titin

Answer 9

bound to the Z disk and acts like a spring to limit amount of contraction and prevent myosin form reaching Z disk

Question 10

Nebulin

Answer 10

extends form Z disk and acts as guide for actin direction and length

Question 11

Troponin

Answer 11

• consists of T, C, and I subunits
  
  • T binds to tropomyosin
  • C binds to calcium
  • I inhibits actin-myosin interaction
    When the C unit of troponin binds to calcium, it triggers a shape change moving tropomyosin away from the binding site for actin-myosin interaction

Question 12

Tropomyosin

Answer 12

found in shallow grooves of double stranded actin; runs along actin and blocks the actin-myosin interaction sites

Question 13

Cardiac Muscle

Answer 13

• Differences from skeletal muscle
  
  • mononucleated
  • Central nuclei
  • Diad vs triad of the sarcoplasm and the T tubule
  • Have intercalated disks that have gap junctions between adjoining cells that allow transmission of action potentials between cells
• Also have bifurcation’s between the cells due to the branching patterns of the tissue
• Also can have lipofuscin granules due to incomplete lysosomal degradation of the dye
• Incapable of regeneration after tissue death*

Question 14

Smooth muscle

Answer 14

• Single, elongated, oval central nucleus with torpedo/submarine shape
• Capable of division
• Z disks are not in register, so do not form striations; gives smooth appearance
• In cross section, there are not nuclei in every cell*
• Contraction is regulated by calmodulin
  
  • Calcium bods to calmodulin when activates myosin light chain kinase (MLCK)
  • MLCK phosphorylates light chains in myosin and increases myosin ATPase activity; myosin slides along actin filaments and creates muscle tension