Chedy - theme 11 Flashcards
What’s the difference between red and white meat?
Red has more blood. **more on this later i think
Types of muscle tissue (vertebrates):
Skeletal, cardiac, smooth.
Which types of muscle are striated? voluntary?
Striated: skeletal, cardiac
Voluntary: skeletal
Levels of organization in skeletal muscle:
Myofibers, fascicles, muscles. Also, tendons.
Myofibers:
Long, cylindrical, multinucleated cells. This means they can develop more mitochondria!
Sarcomere:
Basic unit of myofiber contraction. Fibers slide over each other.
Tendons:
Connective tissue that links skeletal muscle to bones
Fascicles:
Bundles of myofibers bound together
Muscles: (organizational)
Groupings of fascicles
Myofilaments of myofibrils:
Thick filament - lots of myosin (motor protein), ATPase in A band
Thin filament - helix of two chains of actin
Thick and thin filaments interdigitate
Actin:
Cytoskeletal protein that form polymers with troponin and tropomyosin
Cross-bridges between myofilaments:
Projections of myosin from thick filament interacts with thin filament actin to generate force for contraction.
Accessory proteins for contraction:
Titin, troponin, tropomyosin
Titin:
Structural elastic proteins that align myosin and actin. Maintain the thick filament at the sarcomere - responsible for passive elasticity.
Troponin and tropomyosin:
Associate with thin filament myosin. Regulate contraction by controlling cross bridges.
In the absence of Ca2+, tropomyosin covers myosin binding sites.
In the presence of Ca2+, troponin binds Ca2+ and pushes tropomyosin off of the myosin binding site so contraction can begin.
Calcium in muscle contraction:
Ca is the intracellular signal for contraction. Stored in the ER of cells.
String? Spring?
Muscle contraction is fibres SLIDING ACROSS each other, not condensing. NOT spring.
Signals for muscle contraction:
Somatic NS motor neurons generate APs and release ACh. ACh is bound by nicotinic receptors in muscle cell membranes, which releases Ca2+ from the sarcoplasmic reticulum.
Crossbridge structure:
Long tail and two heads. The tail lies along the thick filament axis and the heads form the crossbridges. Each head binds actin and ATP.
The two roles of ATP:
Binding ATP to myosin weakens myosin-actin bond (but ATP is not hydrolyzed yet). Following dissociation, ATP is hydrolyzed, energizing myosin.
The process of muscle contraction:
When it is hydrolyzed, the ADP, phosphate, and energy are stored in the myosin head. When myosin binds to actin, it releases the ADP and phosphate, causing the head to pull the thin filament over the thick filament.
Muscle relaxation:
ATP initiates cross-bridge cycling.
*** WHAT DOES THIS MEAN
Ca2+ is taken up by the sarcoplasmic reticulum, making Ca2+ run away from troponin. Tropomyosin blocks myosin-binding sites again.
Myosin ATPase:
Different muscle fibres have different forms of myosin that can hydrolyze ATP at different rates. Slow fibres go slow; fast fibres go fast. Maximal force is the same - only speed varies.
Three kinds of muscle fibres:
Slow oxidative, fast oxidative, fast glycolitic.