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BIOL 2410 Lecture Notes - Lecture 26: Upper Motor Neuron, Neuromuscular Junction, Calcium Atpase

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School
University of Manitoba
Department
Biological Sciences
Course
BIOL 2410
Professor
Diana Mlinar

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Document Summary

To bind to actin it must bind to the myosin binding sites present on actin. When calcium is present and troponin moves tropomyosin away from myosin binding sites on actin, myosin heads attach and pull on the thin laments in a power stroke event. This shortens the muscle bre (and this the entire whole muscle shortens) The myosin atpase hydrolyzes a molecule of atp forming adp and pi. This energizes the myosin head so that it is prepared for the power stroke/contraction. Adp and pi remain attached to the energized myosin head. Once the myosin head completes the contraction event (powerstroke), adp and pi are removed from the myosin head and replaces with a fresh molecule of atp. This is needed to detach the myosin head from the myosin binding site -> relaxes the muscle and restores the resting state.

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Related Questions

Put the events of a single cross-bridge cycle in the properorder. Start with Calcium is released from the sarcoplasmicreticulum.

a) myosin binds to actin

b) ATP binds to myosin, cross-bridge disconnect

c) ATP splits into ADP and Pi

d) Myosin head re-energized, repositions into high energystate

e) Calcium resequestered into sarcoplasmic reticulum

f) Cross-bridge power stroke

g) Calcium binds to troponin , and actin binding sites areexposed

Describe the process of skeletal muscle contraction by assembling the following 10 events in the proper order. Your answer must be written in complete sentences- do not just list the letters or the events- write it out. Begin your description with an action potential traveling down a motor neuron and end with the muscle in it's relaxed state.

A) T and T system undergoes a conformational change, exposing the myosin binding sites on actin

B) myosin heads/cross bridges bind to actin and flex, shortening the sacromere

C) the motor neuron triggers an action potential at the neuromuscular junction

D) calcium ions bind to the T and T system

E) actin filaments are pulled toward the center of the sacromere, shortening the muscle fiber

F) muscle fiber is stimulated at the neuromuscular junction

G) myosin head/cross-bridges bind to actin

H) APs travel down the T-tubules to the sarcoplasmic reticulum

I) in response to an AP, calcium ions are released into the cytosol/space around the myofibrils

J) calcium ions actively transported into the sarcoplasmic reticulum

K) myosin head continues to attach, flex, release, extend, and reattach as long as calcium ions are present