mechanical components of muscle fiber/ action potentials Flashcards
two mechanical components
myofibrils and myofilaments
myofibrils
protein filaments long thread like structure that extend entire end of muscle fiber
made up of sacromeres put together
sacromeres
functional and structural unit of muscle cell
smallest part that can contract
made of myofilaments
z disks
filamentous network protein that serves as attachment site for actin (thin) filament in sarcomere
region of sacromere (I band)
lighter stained
cotains z disk and extends to ends of mysoin filament
region of sacromere ( A bands)
dark stained
overlaping myosin and actin (except at center)
region of sacromere (h zone)
area in a band where myosin and actin do not overlap
M line
region of sacromere
mdille of h zone—delicate fliaments holding myosin in place
Actin Filament
thin filament
attach at either end of sacromere
two strands of fibrous actin to form double helix
three parts of actin filament
G-actin
Troponin
Tropomyosin
G actin
(actin flimanet)
has active site for myosin head bonding during muscle contraction
Tropomyosin
(of actin)
protein that lies in grove of fibrous actin strand
when relaxed cover G actin binding sites
cannot contract until uncovers site
Troponin
(of actin)
consists of 3 subunits
1. anchors troponin to actin
2. prevents tropomyosin from uncovering G site
3. Binds to calcium
Tropomyosin/Troponin complex regulates interaction between G site and myosin T/F
True
Myosin filament
thick filament
composed of myosin heavy chains to form rod and two myosin heads
look like golf club
Myosin head functions (3)
- can bind to active sites on G actin of Actin
- attach to rod portion by hinge that can bend during contraction
- are ATPase enzymes and actively breakdown ATP and release energy–part used to bend during contraction
when muscle contracts- what happens to the length of mysoin and actin filaments
stays the same
when muscle contracts what happens to the a zone
stays the same
when muscle contracts what happens to the H zone
disappears
resting membrane potential
charge of membrane at rest
inside of cell more negative at rest and outside more positive
ensured by NaK pump
inside of cell more negative because
cumulation of large negative protein molecules
more K on inside than on outside
outside of cell more postive bc
more Na on outside of cell than on inside
NaK pump
for every three Na pumped out 2 K are pumped in
depolarization
inside of plasma membrane becomes more positive (less negative) if change reaches THRESHOLD action potential triggered