6.3 lecture - muscle EMs, cytoskeleton, & embryology

Question 1

in smooth muscle, calcium is

Answer 1

start

Question 2

the sarcoplasmic reticulum ends in tubular structures called

Answer 2

terminal cisternae

Question 3

VGCa++ channels in t-tubules

Answer 3

DHP dihydropyridine receptors

Question 4

T/F in all types of muscle, calcium is shuttled into the cell via caveolae and sequestered in the SR until an electrical signal is received

Answer 4

true

Question 5

in addation to actin, dense bodies bind to intermediate filaments, which are typically __ in visceral muscle and __ in vascular muscle

Answer 5

desmin in visceral smooth muscle

vimentin in vascular smooth muscle

Question 6

what are the intermediate filaments in:

• visceral smooth muscle
• vascular smooth muscle

Answer 6

• desmin

- vimentin

Question 7

this intermediate filament connects Z-lines of myofibrils with each other

Answer 7

desmin

Question 8

muscular dystrophy is due to a problem with this protein

Answer 8

dystrophin

part of costamere complex that anchors Z lines to sarcolemma

Question 9

muscular dystrophy is due to a lack of this protein

Answer 9

dystrophin

part of costamere complex that anchors Z lines to sarcolemma

Question 10

myotube

Answer 10

early formation with central nuclei and a few peripheral myofibers that will eventually grow into myofibers of adult skeletal muscle

Question 11

T/F adult myofibers can increase in number

Answer 11

false

can only change in size by addition or subtraction of myofibrils

Question 12

how are muscle external membrane, nerve external membrane, and basement membrane functionally similar?

Answer 12

serves as scaffolding for tissue repair

-disruption makes regeneration response more difficult

Question 13

T/F intermediate filaments seem to have little importance in skeletal muscle

Answer 13

true

Question 14

T/F cardiac and skeletal muscle contain intermediate filaments

Answer 14

true

connecting Z-lines and anchoring z-lines to costameres

Question 15

why is the occasional cardiac myocyte binucleated?

Answer 15

failure of division

not a combination to form a functional syncytium as with skeletal muscle

Question 16

T/F cardiac cells can have multiple nuclei within sarcolemma

Answer 16

true

occasionally a failure of division results in binucleated cardiac myocytes

Question 17

what 3 junctions does an intercalated disk consist of?

Answer 17

fascia adherens (actin + catenin)
desmosomes (intermediate filament + catenin)
gap junctions

Question 18

other than myocytes, other specialized cardiac cells include

Answer 18

cardiac endocrine cell (mostly atrial)

cardiac conducting cell (in myocardial layer)

Question 19

which layer of heart wall has major blood vessels?

Answer 19

epicardium

Question 20

how would a type I red muscle fiber compare to a type IIb white muscle fiber on H&E?

Answer 20

*not going to be able to tell the difference, need PAS stain
BUT if really pressed to try:
white probably larger
red probably more darkly eosinophilic (more mitochondria)

Question 21

how would a type I red muscle fiber compare to a type IIb white muscle fiber on H&E?

Answer 21

white probably larger

red probably more darkly eosinophilic (more mitochondria)

Question 22

chief materials of:
lamina lucida
lamina densa
lamina retucularis

Answer 22

lucida - glycoproteins (laminin, fibronectin)
densa - type IV collagen
reticularis - type IV collagen; type VII collagen

Question 23

chief materials of:
lamina lucida
lamina densa
lamina retucularis

Answer 23

lucida - glycoproteins (laminin, fibronectin)
densa - type IV collagen
reticularis - type IV collagen; type VII collagen

Question 24

T/F satellite cells are within external membrane of muscle fiber but outside sarcolemma

Answer 24

true

but will never be able to make this out on LM

Question 25

quiescent precursors that become activated to divide and differentiate in response to the needs of muscle growth and damage

Answer 25

``` satellite cells (quiescent but actively monitoring and moving along surface) ```

Question 26

T/F external membrane is a barrier to neurotransmitter and therefore does not exist in neuromuscular junciton

Answer 26

false not a barrier to NT exists in NMJ same as everywhere else

Question 27

T/F external membrane is a barrier to neurotransmitter and therefore does not exist in neuromuscular junciton

Answer 27

false not a barrier to NT exists in NMJ same as everywhere else

Question 28

T/F adipocytes have an external membrane

Answer 28

true muscle cells nervous cells adipocytes

Question 29

T/F smooth muscle motor end plates have junctional folds

Answer 29

false | at least not as significantly as skeletal muscle

Question 30

T/F smooth muscle motor end plates have junctional folds

Answer 30

false | at least not as significantly as skeletal muscle

Question 31

why do muscle spindle and golgi tendon organ include small muscle fibers in addition to nerves?

Answer 31

muscle fiber contracts and stretches proportionally to the other fibers so that nerves can sense length in the case of the muscle spindle and force exerted in the case of the golgi tendon organ

Question 32

why do muscle spindle and golgi tendon organ include small muscle fibers in addition to nerves?

Answer 32

muscle fiber contracts and stretches proportionally to the other fibers so that nerves can sense length in the case of the muscle spindle and force exerted in the case of the golgi tendon organ

Question 33

muscle spindle is encapsulated by ...

Answer 33

perimysium (kind of a perineurium too)

Question 34

musculotendinous junction

Answer 34

actin filaments directly anchored to cell membrane in structure similar to fascia adherens

Question 35

musculotendinous junction

Answer 35

actin filaments directly anchored to cell membrane in structure similar to fascia adherens

Question 36

what does an muscle external membrane directly surround?

Answer 36

plasmalemma bound units, including: -skeletal muscle fibers -cardiac myocytes -smooth muscle cells NOT skeletal muscle fascicles (not directly) NOT smooth muscle bundles (not directly) NOT skeletal muscle fibrils (not directly)

Question 37

what does an muscle external membrane directly surround?

Answer 37

plasmalemma bound units, including: -skeletal muscle fibers -cardiac myocytes -smooth muscle cells NOT skeletal muscle fascicles (not directly) NOT smooth muscle bundles (not directly) NOT skeletal muscle fibrils (not directly)

Question 38

what will break first, plasmalemma or external membrane?

Answer 38

plasmalemma (external membrane is very tough) -can have broken plasma membrane but intact external membrane