Polvie lec #16 Flashcards
What does myosin type 2 have roles in?
Has roles in muscle contraction, splitting cells during cell division, and cell migration/motility
What is the S1 fragment in myosin type 2?
Is where all the machinery required for motor activity is contained in a single head and neck
How do myosin type 2 tails allow the protein to form filaments?
The tails of the myosin type 2 filament point towards the center and the heads point towards the outside a bundle of myosin type two bundle to form filaments
What are the characteristics of a myosin filament?
They are bipolar and thick
What are skeletal muscles attached to?
bones
What are muscle fibers?
are cells in skeletal muscles and are composed of hundreds of myofibrils
What are myofibriles?
in skeletal muscle cells, are composed of action and myosin and composed of sacromeres
What are sarcomeres?
Are contracting units that make up the myofibrils- are made of both a thick filament(s)(myosin) and thin filaments (actin)
What characteristic banding is in sacromeres? Why?
There are I bands- which are lightly stained and contain only thin filaments
There are A bands- which have both thin and thick filaments overlapping and includes H one
There are H zones- which includes only hick filaments
There’s the Z line- which is ends of thin filament (and contain proteins important for sarcomere structure and stability)
There’s the M line- which is dark staining as is middle of H zone, has anchoring proteins
What bands in sarcomeres contract when muscles contract? Which one’s dont?
The I bands and the H zone, the A bands don’t
How do we know how sarcomeres move? How do they move?
know how they move through seeing what zones contract, know that actin filaments are pulled towards M line.
They move by myosin two heads binding to six actin filaments and the myosin moving drags the actin.
What is the process of myosin moving and dragging actin with it?
- ATP binds to the myosin head and myosin leaves actin, the atp gets gydrolyzed and myosin binds to ATP again, the P in the ADP+P remaning leaves and that triggers a confirmational chnage which results in a power stroke moving actin to center of sarcomere, ADP gets released
What is a neuromuscular junction?
is the point of contact between motor neurons and muscle fibers
How does excitation-contraction coupling work (ie how does the motor neuron signal cause the muscle to move?)
the tranverse tubules allow action potential to get into the muscle cell, the sarcoplasmic reticulum (special smooth ER in muscle cells), then relases CA 2+ into the cytoplasm this then binds to the troponin in the thin filaments which moves tropomyosin and then allows the myosin heads to bind to atp and allow the power cycle to occur.
What happens when there is now Ca2+ cause there’s np action potential delivered to the sarcoplasmic reticulum?
troponin will continue to place tropomysoin on myosins binding head causing it to not move.
