Skeletal Muscle 1 (Part 2) Flashcards
What are the T-Tubule
Lateral line or “tubes” connected tot he sarcolemma
What do the T-Tubules do?
conduct action potential into fiber interior
When one t-tubule meets two lateral sac, it forms what?
Triads
T or F: Location doe not variy by species
False. At z lines of mammals and h zones of amphibians
What is the sarcoplasmic reticulum?
A membranous network of tubes and compartments surrounding the myofibrils.
What is the function of the sarcoplasmic reticulum
The function is to store & release Ca2+
What pumps aid in Ca2 trafficking?
Ryanadine recpetors and SERCA pumps
Each myofibril contains filamentous contractile proteins arranged into ____
Sarcomeres
The myofibrils contain ____
costameric proteins e.g., dystrophin
What is the cytosol?
Cytosol is the watery medium that fills each fiber and sets internal environment. (temperature, pH and ionic strength)
What does the cytosol contain?
Dissolved proteins known as metabolites (like ATP, ADP, Pi etc)
What does the cytosol do?
Permits communication
▪ between compartments
▪ between proteins
T or F: mitochondrial volume varies
True: Varies with
▪ Fiber type (slow > fast)
▪ with training (endurance > sedentary or strength)
▪ more mitochondrial volume = more endurance
What are the fraction of the mitochondria?
▪ subsarcolemma
▪ myofibrillar
What is the sarcomere?
The basic structural and contractile unit of the myofibril; The ‘bricks’ or ‘flesh part’
The sarcomere formed by ____
❑ 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
Length of a sarcomere
1.6-3.6 microns
What are the myofilaments?
❑ contractile machinery
▪ thick filaments = myosin (mostly)
▪ thin filaments = actin + regulatory proteins
What do myofilimants do?
❑ site of considerable ATPase activity
▪ where most ATP is used
What is Troponin C?
❑ binds Ca2+; is a Ca2+ “sensor”
▪ low Ca2+ occupancy turns thin filament off
▪ high Ca2+ occupancy turns thin filament on
What is tropomyosin?
❑ 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
What does Trponin I and Troponin T do?
❑ links Ca2+ binding to TnC to Tm movement
▪ different isoforms of TnI and TNT
❑ contribute to muscle fiber type differences
▪ fast vs slow
_____ is a muscle disease due to ___ in Trponin I and Troponin T
familial cardiac hypertrophy; mutations
tropomyosin ____ and ____ on thin filament surface to either allow or disallow myosin head binding to actin
Rocks and rolls
force generation by sarcomere is ___ _____ based but ___ _____ regulated.
thick filament; thin filament
Stearic Blocking model is
The “gate keeper” for cross bridge formation
Sliding filament theory
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
