11.2 Skeletal Muscle Part 2 Flashcards
What is the I band?
portion of the sarcomere that is solely composed of thin filament
What is the A band?
full length of thick filaments
What is the H zone?
thick filament only region of the sarcomere
Where are contractions generated in muscle cells?
overlapping region of thick and thin filaments
What powers filament sliding?
ATP hydrolysis
What is the function of the myosin head?
attaches to a specific site on an actin molecule called the myosin binding site
What is a cross bridge?
when actin and myosin are attached
What are the four steps of filament sliding?
- binding of myosin head to actin
- power stroke
- binding of a new ATP molecule releasing actin from myosin head
- ATP hydrolysis causes myosin head to cock
In the myofiber when does contraction occur?
when calcium concentration in cytoplasm increases
What is the function of the troponin-tropomyosin complex?
prevents contraction when calcium is not present
What is troponin?
globular protein bound to tropomyosin that can bind calcium
What is tropomyosin?
long fibrous protein that winds around actin polymer blocking all myosin binding sites
What occurs when troponin binds calcium?
troponin undergoes a conformational change moving tropomyosin out of the way so myosin head can attach to actin
What is the neuromuscular junction?
synapse between an axon terminus and a myofiber
What is the motor end plate?
postsynaptic membrane (myofiber cell membrane)
What is the neurotransmitter found at the neuromuscular junction?
acetylcholine
What is the end plate potential?
depolarization of postsynaptic membrane caused by an influx of sodium
What is a miniature end plate potential?
smallest measurable EPP caused by exocytosis of a single ACh vesicle
What is acetylcholinesterase and what is its function?
enzyme that destroys ACh by hydrolyzing it into a choline and acetyl unit
What are transverse tubules?
deep invaginations in myofiber allowing action potentials to travel through the thick cell
