Overview of muscle contraction Flashcards
What is a muscle fibre ?
Large, single, elongated, multinuclear cell
What does each fibre contain?
About 1,000 myofibrils, each consisting of thick and thin filaments and surrounded by sarcoplasmic reticulum
What is a sarcomere ?
Muscle cells contain numerous myofibrils, consisting of interlocking thick and thin filaments arranged into repeating units
What are the thick and thin filaments are made of ?
Different proteins and form a striated pattern when viewed under the microscope
What are filaments anchored by ?
Titin to the Z-disk
What are t-tubules ?
Invaginations off the plasma membrane
What is the sarcoplasmic reticulum (SR) ?
The specialised muscle ER
What is an A band ?
Stretches the length of the thick filament
What is an I band ?
Contains only thin filaments
What is the Z disk ?
Attachment site for thin filaments
What is the M line ?
Bisects the A band
During contraction there is a decrease in sarcomere length by ?
Reduction of the I band, with no change in the width of the A band
Thick and thin filaments slide along one another but do not change in?
Length
The thick filaments consist of?
Myosin molecules
Thin filaments consist of?
Actin, with tropomyosin, and the troponin complex
The troponin complex is involved in ?
The regulation of muscle contraction
What are the two heavy chains that myosin has ?
The carboxyl termini forming an extended coiled coil (tail) and the amino termini having globular domains (heads) with ATPase activity.
What is F-actin composed of?
G-actin monomers that polymerize two by two, giving the appearance of two filaments spiraling about one another in a right-handed fashion
Each actin monomer in the thin filament binds to ?
One myosin head group
Availability of myosin-binding sites on actin is regulated by? and avoids ?
Troponin and tropomyosin.
- avoids continuous muscle contraction
Troponin Complex:
Troponin I = ?
Troponin C = ?
Troponin T = ?
Troponin I = inhibitory subunit
Troponin C = calcium binding subunit
Troponin T = tropomyosin binding subunit
Nerve impulse triggers release of Ca2+ causing ?
Conformational changes to tropomyosin-troponin complex, exposing myosin-binding sites
Skeletal muscle contraction is regulated by ?
A Ca2+-dependent thin filament-based regulatory mechanism
Sarcomere Ca2+ concentration is regulated by?
Release and uptake into the sarcoplasmic reticulum (SR)
ATP binding causes?
Release of myosin from thin filament
Hydrolysis of ATP rotates myosin into ?
“Cocked” state
What is a power stroke caused by ?
Release of phosphate
