Histology - Muscle

Question 1

Intermediate filaments of muscle

Answer 1

Desmin replaces keratin in muscle cells

Question 2

Satellite cells

Answer 2

Undifferentiated myoblasts - able to regenerate muscle tissue by “satellite cell hyperplasia)

Question 3

Transcription factor only active in satellite cells

Answer 3

PAX 7

Question 4

Myocyte

Answer 4

Cardiac muscle cell

Question 5

Epimysium

Answer 5

Dense irregular CT - surrounds entire muscle

Question 6

Perimysium

Answer 6

Derived from epimysium (less dense CT) surrounds fascicle

Question 7

Endomysiu

Answer 7

• loose CT (reticular fibers) and basal lámina surround each muscle fiber (cell)

Question 8

Duchenne muscular dystrophy

Answer 8

Mutation in dystrophin (links actin in sarcomere to the plasma membrane of striated cells

Question 9

(-) end of actin

Answer 9

Tropomodulin - prevents depolymerization

Question 10

(+) of actin

Answer 10

Bound to z-line by alpha-actinin (prevents polymerization)

Question 11

Thick filaments

Answer 11

Myosin II

Question 12

Thin filaments

Answer 12

F actin - tropomysoin + troponin

Tropomyosjn regulates binding of actin and myosin

Question 13

Proprioception

Cellular mechanism

Answer 13

Muscle spindles and golgi tendon organs allow for this

Spindle - monitor strain/stretch
Golgi (in tendon) - monitor intensity of muscle contraction

Both can inhibit contraction if limits exceeded

Question 14

Muscle spindles

Answer 14

Intrafusal fibers -

Question 15

Myocytes vs. skeletal muscle

Answer 15

T-tubules are 3x diameter compared to skeletal muscle with dyads near the z-line

Secrete ANP - excrete NaCl

And BNP - longer lasting compared to ANP but 10x less concentrated

Question 16

Myocytes vs. skeletal muscle

Answer 16

T-tubules are 3x diameter compared to skeletal muscle with dyads near the z-line

Secrete ANP - excrete NaCl

And BNP - longer lasting compared to ANP but 10x less concentrated

Question 17

Plasma serum levels of BNP >400 pg/mL

Answer 17

Indicative of heart failure

Question 18

What holds myocytes together at intercalated disk?

Answer 18

The fascia adherents

Question 19

What holds myocytes together at intercalated disk?

Answer 19

The fascia adherents

Question 20

Prevents myocytes from pulling apart during contraction

Answer 20

Desmosomes - at transverse and lateral regions

Question 21

Modified z-line in myocyte

Answer 21

Intercalated disk

Question 22

ID tissue in blue box

Answer 22

Skeletal muscle

Nuclei are predominantly located at the periphery of the cells (whereas nuclei would be centralized in cardiac muscle). Furthermore, the superior tissue is tendon.

Skeletal muscle cells are also larger in diameter than cardiac myocytes (smooth muscle cdells are the smallest in diameter)

Question 23

Pax-7 is a transcription factor known to play a role in the regulation of satellite cells in mammals. Pax-7 knockout mice might be expected to have deficits in regeneration of which tissue under experimental conditions of induced injury?

Answer 23

Skeletal muscle

Question 24

An injury that results in death of skeletal muscle cells can heal because skeletal muscle contains a population of stem cells known as:

Answer 24

Satellite cells

Question 25

Duchenne muscular dystrophy is an X-linked recessive disease caused by a mutation in the gene that codes for dystrophin. The disease gets progressively worse; it results in damage to mature muscles and is often fatal. What is the normal function of dystrophin in healthy muscle?

Answer 25

Helps to link actin to membrane proteins of the sarcolemma

Question 26

ID

Answer 26

Skeletal muscle

Question 27

ID

Answer 27

Cardiac muscle

Question 27

Answer 27

Lipofuscin - a byproduct of the breakdown and absorption of damaged blood cells “the pigment of aging”

Question 28

Muscle growth in weight lifting

Answer 28

Muscle fibers do not divide, but undergo hypertropy (increasing the myofilaments)

When muscles are injured satellite cells divide to form myotubes - then myotubes fuse to become mature muscle cells

Question 29

Answer 29

Motor end-plates (darker stain)