Skeletal Muscle 1 (Part 2)

Question 1

What are the T-Tubule

Answer 1

Lateral line or “tubes” connected tot he sarcolemma

Question 2

What do the T-Tubules do?

Answer 2

conduct action potential into fiber interior

Question 3

When one t-tubule meets two lateral sac, it forms what?

Answer 3

Triads

Question 4

T or F: Location doe not variy by species

Answer 4

False. At z lines of mammals and h zones of amphibians

Question 5

What is the sarcoplasmic reticulum?

Answer 5

A membranous network of tubes and compartments surrounding the myofibrils.

Question 6

What is the function of the sarcoplasmic reticulum

Answer 6

The function is to store & release Ca2+

Question 7

What pumps aid in Ca2 trafficking?

Answer 7

Ryanadine recpetors and SERCA pumps

Question 8

Each myofibril contains filamentous contractile proteins arranged into ____

Answer 8

Sarcomeres

Question 9

The myofibrils contain ____

Answer 9

costameric proteins e.g., dystrophin

Question 10

What is the cytosol?

Answer 10

Cytosol is the watery medium that fills each fiber and sets internal environment. (temperature, pH and ionic strength)

Question 11

What does the cytosol contain?

Answer 11

Dissolved proteins known as metabolites (like ATP, ADP, Pi etc)

Question 12

What does the cytosol do?

Answer 12

Permits communication
▪ between compartments
▪ between proteins

Question 13

T or F: mitochondrial volume varies

Answer 13

True: Varies with
▪ Fiber type (slow > fast)
▪ with training (endurance > sedentary or strength)
▪ more mitochondrial volume = more endurance

Question 14

What are the fraction of the mitochondria?

Answer 14

▪ subsarcolemma

▪ myofibrillar

Question 15

What is the sarcomere?

Answer 15

The basic structural and contractile unit of the myofibril; The ‘bricks’ or ‘flesh part’

Question 16

The sarcomere formed by ____

Answer 16

❑ formed by parallel array of myofilaments
▪ containing myosin and actin
• contractile
▪ containing connectin (or titin)
• elastic
❑ and transverse “disc” structures
▪ Z-lines (alpha-actinin)
▪ M lines (meromyosin)
• connective

Question 17

Length of a sarcomere

Answer 17

1.6-3.6 microns

Question 18

What are the myofilaments?

Answer 18

❑ contractile machinery
▪ thick filaments = myosin (mostly)
▪ thin filaments = actin + regulatory proteins

Question 19

What do myofilimants do?

Answer 19

❑ site of considerable ATPase activity

▪ where most ATP is used

Question 20

What is Troponin C?

Answer 20

❑ binds Ca2+; is a Ca2+ “sensor”
▪ low Ca2+ occupancy turns thin filament off
▪ high Ca2+ occupancy turns thin filament on

Question 21

What is tropomyosin?

Answer 21

❑ cable like and fluid, position influenced by Ca2+
▪ low Ca2+ occupancy: blocks myosin from binding
▪ high Ca2+ occupancy: allows myosin to bind
▪ consists of 7 monomers

Question 22

What does Trponin I and Troponin T do?

Answer 22

❑ links Ca2+ binding to TnC to Tm movement
▪ different isoforms of TnI and TNT
❑ contribute to muscle fiber type differences
▪ fast vs slow

Question 23

_____ is a muscle disease due to ___ in Trponin I and Troponin T

Answer 23

familial cardiac hypertrophy; mutations

Question 24

tropomyosin ____ and ____ on thin filament surface to either allow or disallow myosin head binding to actin

Answer 24

Rocks and rolls

Question 25

force generation by sarcomere is ___ _____ based but ___ _____ regulated.

Answer 25

thick filament; thin filament

Question 26

Stearic Blocking model is

Answer 26

The “gate keeper” for cross bridge formation

Question 27

Sliding filament theory

Answer 27

During Sarcomere Shortening
o myofilaments stay same length
o change relative position by “sliding”
o the A band stays same length
o the I band changes in width