B6.036 Prework 2: NMJ

Question 1

M line

Answer 1

alignment of lateral assembled tails of myosin

Question 2

myosin headgroup structure

Answer 2

actin binding and ATPase domains

ATP drives movement of myosin heads along actin filaments

Question 3

isozymes of myosin heavy chains

Answer 3

slow type 1
fast type 2
others: super fast, slow tonic, fetal, cardiac

Question 4

MW of myosin light chains

Answer 4

20,000

Question 5

myosin light chain types in skeletal muscle

Answer 5

slow, fast, fetal

Question 6

properties of myosin light chains

Answer 6

bind Ca2+ w high affinity
phosphorylated by myosin light chain kinase (MLCK)
-changes conformation of heads
-increased population placed close to thin filaments
-potentiated actin-myosin interaction at low Ca2+ levels
regulation of myosins ATPase activity
regulate myosin assembly into thick filaments

Question 7

motor unit

Answer 7

number of muscle fibers innervated by a single motor neuron

Question 8

normal muscle fiber distribution

Answer 8

random pattern of interspersed dark (fast) fibers and light (slow) fibers

Question 9

what are muscle spindles

Answer 9

found throughout muscle
force and velocity of muscle movement are translated by spindle to inform CNS of force and velocity produced
stretch of spindle deforms the afferent sensory endings

Question 10

sensory endings

Answer 10

mechanical deformation of sensory endings leads to generation of action potential
goes from muscle to CNS via intramuscular nerves

Question 11

monosynaptic stretch reflex

Answer 11

tap patellar tendon to stretch quad muscles
stretch generates an AP at sensory endings at muscle spindle
AP travels to spinal cord and synapses to produce and AP in the alpha motor neuron
this AP contracts the muscles of the quads, moving the leg forward