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Flashcards in Exam 1 Histology Deck (14):
1

Collagen Fibers

High tensile strength

2

Elastic Fibers

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.

3

Reticular Fibers

Provides delicate framework of support

4

A bands

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

5

I bands

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

6

H band

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

7

Sarcomere

is the basic contractile unit of striated muscle.

Sarcomere repeats are represented by myofibrils.

8

desmin

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

9

Titin

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

10

Nebulin

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

11

Troponin

* 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

12

Tropomyosin

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

13

Cardiac Muscle

* 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*

14

Smooth muscle

* 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