MSK 11 - Muscles-I

Question 1

What do the terms “sarcoplasm” and “sarcolema” refer to?

Answer 1

The cytoplasm and plasma membrane of a myocyte, respectively.

Question 2

What is a syncytium?

Answer 2

A single cell or cytoplasmic mass containing several nuclei, formed by fusion of cells or by division of nuclei. Skeletal muscle fibers are a syncytium.

Question 3

How many myocytes make up a single muscle fiber? How is the muscle fiber formed?

Answer 3

A muscle fiber consists of just one myocyte that is a syncytium of numerous myoblasts.

Question 4

What is the length of a muscle fiber?

Answer 4

Varies from milimeters to almost a meter

Question 5

How do muscle fiber repair, heal, and renew?

Answer 5

Question 6

How do myocytes appear on a light micrograph?

Answer 6

Question 7

Answer 7

Question 8

What is an endomysium? Discuss its composition and function.

Answer 8

Question 9

What is a perimysium? Discuss composition and function.

Answer 9

A layer of connective tissue that surrounds each muscle fascicle and contains blood vessels and nerves that are larger than those found in endomysium

Question 10

What is an epimysium? Discuss composition and function

Answer 10

Question 11

What are the four ways skeletal muscle is classified?

Answer 11

Question 12

Facts to know about Type 1 Skeletal Muscle

Answer 12

Question 13

Facts to know about Type IIa skeletal muscle

Answer 13

Question 14

Facts to know about Type IIb skeletal muscle

Answer 14

Question 15

What is a myofibril? Discuss composition and function

Answer 15

Question 16

Answer 16

Question 17

On a light micrograph of skeletal muscle tissue there will be striations and dark and light bands present. What are these?

Answer 17

Striations are caused by the regular arrangement of the myofilaments and the fact that one of the filaments is thick (myosin-II, dark band) and the other is thin (actin, light band)

The light band is the I band and the dark band is the A band.

Question 18

Answer 18

Question 19

Discuss the polarity of the thin filament in a sarcomere.

Answer 19

Question 20

What is the tromponin complex made up of? What do each of these components do?

Answer 20

Question 21

What is the thick filament composed of and how are these components arranged?

Answer 21

Question 22

Answer 22

Question 23

Answer 23

Question 24

Answer 24

Question 25

What is titin and what does it do in skeletal muscle?

Answer 25

Titin is an accessory muscle protein that anchors the thick filament to the Z line

Question 26

What is myomesin and what does it do in skeletal muscle?

Answer 26

Myomesin is an accessory muscle protein that binds myosin and helps to align the thick filaments at the M-line

Question 27

What is alpha-actinin and what does is do in skeletal muscle?

Answer 27

Alpha-actinin is an accessory muscle protein that binds actin that helps to bundle and anchor the thin filaments at the Z-line

Question 28

What is nebulin and what does it do in skeletal muscle?

Answer 28

Nebulin is an accessory muscle protein that helps anchor thin filaments at the Z-line and regulates their length during development

Question 29

What is C-protein and what does it do in skeletal muscle?

Answer 29

C-protein is an accessory muscle protein that binds myosin and helps to align thick filaments at the M-line

Question 30

What is tropomodulin and what does it do in skeletal muscle?

Answer 30

Tropomodulin is an accessory muscle protein that maintains and regulates the length of the actin filament by acting as an actin cap

Question 31

What is desmin and what does it do in skeletal muscle?

Answer 31

Desmin is an intermediate filament that surrounds the sarcomere at Z-lines and attaches them to one another and to the plasma membrane.

Question 32

What is dystrophin and what does it do in skeletal muscle?

Answer 32

Question 33

Facts to know about Duchenne Muscular Dystrophy.

Answer 33

Question 34

What does this image depict?

Answer 34

Muscle fibers without dystrophin. A result of DMD

Question 35

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Question 36

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Question 37

Answer 37

SR - Sarcoplamic Reticulum Td - Triad Tc - Terminal cisternae M - mitochondria

Question 38

What is a motor unit? How many types of muscle fibers can be in a motor unit?

Answer 38

Question 39

What occurs if a muscle loses innervation?

Answer 39

It atrophies

Question 40

Answer 40

The bottom one is synaptic cleft

Question 41

What is Myasthenia Gravis? Discuss causes and symptoms

Answer 41