Lecture 9/10

Question 1

shape and characteristics of muscle cells

Answer 1

Elongated cells containing a
great number of cytoplasmic filaments

Question 2

origin of muscle cells

Answer 2

Mesodermal. Differentiation occurs mainly by a
process of cell lengthening and synthesis of myofibrillar
proteins

Question 3

different types of muscle and general differentiations.

Answer 3

1. Skeletal striated muscle presents cross striations, is voluntary and is attached by
   connective tissue to bones
2. Smooth muscle does not have cross striations and is involuntary
3. Cardiac muscle is striated and involuntary

Question 4

most abundant type of muscle

Answer 4

skeletal muscle

Question 5

how are muscle cells attached to CT?

Answer 5

attached to collagen by junctional complexes associated with infolding of the plasma membrane (sarcolemma) of the muscle fibre

Question 6

what are 3 coats of CT that organize the muscle?

classify each

Answer 6

• Epimysium is the dense connective tissue that surrounds the entire muscle.
• Perimysium is the connective tissue that surrounds each bundle of fibres or fascicles.
• Endomysium is the thin layer of connective tissue surrounding each muscle fibre

Question 7

what fibers and structures are found in the endomysium?

Answer 7

• reticular fibrils (collagen type III)
• elastic fibres
• capillaries

Question 8

how are muscle fibers made?

Answer 8

multinucleated and results from the embryonic fusion of uninucleated myoblasts

Question 9

what is the sarcolemma?

Answer 9

cell membrane, or unit membrane

Question 10

what is the sarcoplasm?

Answer 10

the cytoplasm

Question 11

where are the nuclei located in skeletal muscle?

Answer 11

peripherally, just under the sarcolemma

Question 12

what are satellite cells?

Answer 12

stem cells that sit between the
basal lamina and the sarcolemma

Question 13

what are the main organelles in muscle fibrils?

Answer 13

• myofibrils
• mitochondria
• sER

Question 14

when does hypertrophy occur in muscle?

Answer 14

in striated muscle (normal in skeletal and abnormal in cardiac)

Question 15

when does hyperplasia occur in muscle?

Answer 15

normal in smooth muscle

Question 16

role of CT in skeletal muscle?

Answer 16

mechanical tranducer to
the forces generated by the
contracting muscle cells.

Question 17

fascicle

Answer 17

bundle of muscle fibers

Question 18

what are the different lines and bands in the sarcomere?

Answer 18

• Z-line
• I-band
• A-band
• H-band
• m-line

Question 19

what is the sacromere?

Answer 19

smallest repetitive subunit of the contractile apparatus. The
sarcomere extends from Z line to Z line

Question 20

what makes up thick filaments?

Answer 20

myosin (2 heavy chains and 4 light chains)

Question 21

what is present in the M-line?

Answer 21

creatine kinase, which makes ATP from phosphocreatine

Question 22

role of satellite cells?

Answer 22

make skeletal muscle have limited regeneration since can “give” one of their nuclei to the muscle fiber

Question 23

what does chymotrypsin do?

Answer 23

cleave the myosin into light meromyosin (LMM) and heavy MM (HMM)

Question 24

what does papin do?

Answer 24

cleave the HMM into HMMS-1 and 2

Question 25

what is HMMS-1?

Answer 25

an ATPase and actin binding site

Question 26

what makes up the thin filaments?

Answer 26

actin

Question 27

what are the troponin subunits and their roles?

Answer 27

- Tnl: inhibit the actin-myosin interaction - TnC: binds Ca2+, allowing binding of myosin and therefore cause movement - TnT: anchors to tropomyosin

Question 28

where is titin found and what is its role?

Answer 28

in sarcomere, in the I-band where there isn't any thick filaments, found in between the thin filaments and provides stability by anchoring the thick filaments with the z-disc

Question 29

where is calcium ATPase and calsequestrin found?

Answer 29

in a terminal cisterna (at an A to I band junction)

Question 30

Myelinated motor nerves branch out within the ____________ where each nerve gives rise to several terminal wigs called ____________.

Answer 30

perimysium and endomysium; terminal boutons.

Question 31

what makes up the intercalated disk? | and what are the component of each seperate part?

Answer 31

- zonula adherens: α-Actinin/Vinculin/cadherens - macula adherens (desmosome): Desmocollin/Desmoglein and Desmoplakins I and II, Plakoglobin, Desmocalmin - gap junction (the lateral part): connexin 48 (predominantly)

Question 32

what fibers/filaments are present in smooth muscle and how are they organized?

Answer 32

on dense bodies, where actin filaments branch out. then, myosin filaments are scattered on the actin. reticular fibers are found outside the BM