Chapter 6 (Locomotion) Flashcards
Describe nematode locomotion.
- movement achieved by redistribution of bodily fluid
- muscle fibers contract on one side of the body and relax on the other side; body bends
Describe earthworm locomotion.
- circular muscle contracts to push coelomic fluid forward
- longitudinal muscle contracts to pull posterior body segments forward
Describe squid locomotion.
- jet propulsion forces water from body cavity through siphon
Differences between white, red and pink muscles in fish
- white muscles: glycolytic, high intensity activity
- red muscle: oxidative, most active during steady state movement
- pink muscle: separates white and red muscles; function is in between the two
myotome
- repeating units that make up fish white muscle
striated vs. smooth skeletal muscle
- striated: actin and myosin arranged in parallel (sarcomeres); skeletal and cardiac muscle
- smooth: actin and myosin not arranged in parallel (no sarcomeres)
A skeletal muscle cell is called a ___, which is composed of many ___.
myofiber; sarcomeres
thick filament vs thin filament
- thick filament: polymers of myosin
- thin filament: composed of actin
Z disk
- protein plate at the ends of each sarcomere
- point of attachment for thin filament (+ end) (anchored by CapZ)
titin
- holds thick filament in position
- anchors thick filament to the Z disk
nebulin
- parallels thin filaments
- establishes appropriate length of each thin filament
A-band (anisotropic band)
dark region of sarcomere where thick filaments occur
I-band (isotropic band)
- narrow region spanning Z disk
- the part of thin filaments that don’t overlap thick filaments (only overlaps titin)
M-line
gap between thin filaments
sarcomeres arranged in parallel vs. arranged in series
- parallel: shorten only a small amount but generate a lot of force
- series: generate less force but shorten more and shorten faster
troponin and tropomyosin
- troponin binds to every 7th actin filament
- tropomyosin spans 7 actin filaments (between troponin)
- forms complex with tropomyosin to block myosin binding site on actin during low Ca2+ levels (will roll out of the way during high Ca2+)
Describe the sliding filament model.
- myosin heads detach due to ATP binding
- ATP hydrolyzed into ADP and Pi (remain bound by myosin)
- this hydrolysis causes myosin to re-attach to actin further down
- Pi released, promoting power stroke that moves actin
- ADP released from myosin, ATP binding site on myosin free again
unitary displacement
distance that myosin steps after each cross bridge cycle (about 36 nm)
neurogenic muscles
muscles that receive signals from a motor neuron
nicotinic receptors are involved with which neurotransmitter
acetylcholine
What part of the muscle stores and releases Ca2+ during excitation-contraction coupling?
sarcoplasmic reticulum
role of Ca2+ in muscle contraction
- binds to troponin complex, causing it to unblock myosin binding site on actin
- allows myosin cross-bridges to bind to actin filaments
What triggers the release of intracellular Ca2+ in a muscle cell?
- action potentials conducted deep into the muscle fiber
- depolarization induced Ca2+ release or Ca2+ induced Ca2+ release
difference between depolarization induced Ca2+ release and Ca2+ induced Ca2+ release
- depolarization induced Ca2+ release: RyR opening triggered by changes in DHPR structure upon depolarization of plasma membrane
- Ca2+ induced Ca2+ release: RyR opening triggered by elevated cytoplasmic Ca2+ levels cause by depolarization that opens DHPR
motor pool
the collection of motor neurons that innervate a muscle
asynchronous muscle vs synchronous muscle
- asynchronous muscle contracts more than once for every one nerve signal/action potential
- synchronous muscle contracts only once for every AP
