EXAM 3 Flashcards
(183 cards)
skeletal muscle is responsible for _
- 400+ in body
- ~40-45% of body weight
all movement and support
skeletal muscle is mostly made up of _
- 20% protein
- 5% other: fats, CHO, high energy phosphates, urea, lactic acid, enzymes, Na+, K+, Cl-, and minerals - Ca2+, Mg, and phosphorous
water (75%)
skeletal muscle is _ in appearance
- structure is fascia and connective tissue sheaths which separate individual muscles and hold muscles in place
- under fascia: epimysium
- under epimysium: fascicles
- there are ~ 150 fibers/fasciculus
striated
connective tissue surrounding muscle
epimysium
- bundle of muscle cells (fibers) surrounded by perimysium
- each fiber in _ is surrounded by endomysium
- under endomysium is _, cell membrane
- connective tissue surrounds muscle and forms a network that extends throughout the muscle
- fasciulus
- sarcolemma
bundles of muscle fibers enclosed by perimysium
fascicles
- cytoplasm of muscle cell
- under sarcolemma
- contains contractile proteins, enzymes, fat, and glycogen particles, nuclei, and specialized cellular organelles
sarcoplasm
greatest amounts:
- myosin
- actin
- tropomyosin
- also, large amounts of myoglobin
proteins in skeletal muscle
muscles cells are: _ and _
- multi-nucleated
- striated appearance
- embedded in sarcoplasm
- network of channels and vesicles
- lies parallel to the myofibrils
- lateral end: sac-like cisternae which stores Ca2+
sarcoplasmic reticulum (SR)
- perpendicular to myofibril
- _ and two terminal cisternae are the region of the Z line
- called a triad
- two triads/sacromere
- one sacromere: Z line to Z line
- Tubules open to the outside of each muscle fiber
- functioning as a network, spreading the AP from outer to inner portions of muscle fiber
Transverse Tubules (T-Tubules)
- composed of 6 polypeptide chains
- 2 heavy
- 4 light
- one myosin filament is made up of 200 or more myosin molecules
- exactly 1.6 micrometers in length
myosin molecule
Myosin molecule:
- _ are in center
- _ coming out from center (0.2 micrometers)
- hinges at two points
- arm separates from the filament
- where the head attaches to the arm
- filament is twisted, cross-bridges are displaced from previous set by 120 degrees
- ensures that cross-bridge extend in _ from the filament
- tails
- heads
- all directions
- primary protein
- forms backbone of filament
- approx. 3,000 actin/myofibril
- Troponin and Tropomyosin
- two other proteins in filament
actin
Two shapes of actin:
- globular (G-actin)
- Fibrous (F-actin)
Type of shape of actin:
- polymerizes and unfolds
globular (G-actin)
Type of shape of actin:
- double stranded in helix, complete revolution every 70 nanometers
fibrous (F-actin)
- 13 _ molecules in each revolution of the helical strand
- Each G-actin has an _ molecule attached to it
- ADP are purported to be the active sites on the actin for _ interaction
- active sites are staggered, one site on total filament every 2.7 nanometers
- each actin is 1mm long
- G-actin
- ADP
- cross-bridge
- inserted into Z discs, other end protrudes into sacromere
- in spaces between myosin molecules
filament bases
- actin filaments extending from either side
- into neighboring sacromeres
- passes from myofibril to myofibril
- attaching the myofilaments to each other across the muscle fiber
Z line
Basic contractile unit, Z line to Z line
sacromere
- associated with the actin filament
- loosely connected to the F-actin strands
- wrap themselves spirally around the sides of the F-actin helix
- at rest, _ molecules lie on top of the actin sites, inhibiting interaction between actin and myosin
- each _ covers about 7 active sites
tropomyosin
- protein attached near one end of each tropomyosin molecule
- complex of 3 protein subunits
- _ complex may attach the tropomyosin to the actin
- each subunit plays a role in the contractile process
troponin
Troponin complex:
- strong affinity for actin
Troponin I (TnI)