Module 7 HW Questions Flashcards
What skeletal muscle fiber structure contains T tubules?
sarcolemma
What skeletal muscle fiber structure stores intracellular calcium ions?
sarcoplasmic reticulum
What skeletal muscle fiber structure is segmented by sarcomeres?
myofibrils
What skeletal muscle fiber structure is the smallest contractile unit of a muscle fiber?
sarcomeres
What skeletal muscle fiber structure has both actin and myosin?
myofilaments
What skeletal muscle fiber structure is a thick myofilament with heads?
myosin
What skeletal muscle fiber structure is a thin myofilament with myosin binding sites?
actin
What skeletal muscle fiber structure attaches actin to the sarcolemma?
dystrophin
What category of muscle contraction does not change the length of the muscle?
isometric
Which type of muscle contraction causes the muscle to lengthen?
eccentric
Which category of muscle contraction causes the muscle to change length?
isotonic
What type of muscle contraction causes the muscle to shorten?
concentric
Which protein covers myosin binding site in the relaxed state of a muscle cell?
tropomyosin
Which protein hold tropomyosin in place during the resting state of a muscle cell?
troponin
How many APs does a motor neuron have to send to cause a muscle cell to contract?
1
Do all local motor endplate depolarization at a NMJ generate an AP in the muscle cell?
yes
How does the sarcolemma propagate an AP?
-opens voltage gated Na channels
-peak
-closes voltage gated Na channels and opens voltage gated K+ channels
Which ion depolarizes the motor end plate of a NMJ?
sodium
What event causes voltage gated calcium channels to open on the sarcoplasmic reticulum?
AP moving down the T tubules
What causes an increase in intracellular calcium in skeletal muscle?
opening of voltage gated calcium channels in the SR
What does calcium bind to in order to expose myosin binding sites?
troponin
What event begins the contraction of a muscle fiber?
cross bridge formation
What causes the myosin head to detach from the actin myofilament?
ATP binds to myosin
What is the role of ATP in the cross bridge formation?
energizes the myosin head
What does calcium bind to inside the SR?
calsequestrin
What specific type of receptors in the T tubules must open to release the calcium from the SR?
ryanodine
How long can a muscle cell contraction continue?
for as long as intracellular calcium ions remain high and sufficient ATP available
What must happen for a muscle cell to relax?
calcium must be pumped out of the cytoplasm and back into the SR
What is the sliding filament theory?
the action of actin and myosin sliding across each other
What structure shortens in a muscle cell contraction?
sarcomere
Which antagonistic function do curare poisions and drugs have at the NMJ?
blocks ACh receptors on the motor endplate
What antagonistic effect does botulism toxins have on a motor neuron at the NMJ?
decreases or prevents ACh release
How does hypocalcemia affect somatic motor neurons?
can spontaneously generate APs
How does hypocalcemia affect skeletal muscle?
causes fasciculations and or muscle twitches
What is a motor unit?
a motor neuron and all the muscle fibers it innervates
What is muscle cell recruitment?
more and more muscle fibers to contract to increase the strength of the whole muscle
What is summation of muscle contraction?
adding together individual twitch contractions
What is a tetanic contraction?
successive frequent contractions that causes a smooth continuous contraction
How does the body maintain muscle tone while a whole muscle is at rest?
intermittent and alternating stimulation of different motor units
How does regular stretching affect the number of sarcomeres within a muscle fiber?
increases their number
