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ANAT 025 Lecture Notes - Lecture 5: Sliding Filament Theory, Sarcomere, Neuromuscular Junction

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School
Pasadena City College
Department
Anatomy
Course
ANAT 025
Professor
Borman

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Document Summary

Whole muscle (surrounded by epimysium) fascicle (surrounded by perimysium) muscle. Fiber (surrounded by endomysium) myofibrils sarcomeres myofilaments (actin & myosin) sliding filament model of contraction. Contraction: the activation of cross bridges to generate force. In the relaxed state, thin and thick filaments overlap only slightly at ends of a band. Sliding filament model of contraction states that during contraction, thin filaments slide past thick filaments, causing actin and myosin to overlap more. Neither thick nor thin filaments change length, just overlap more. When nervous system stimulates muscle fiber, myosin heads are allowed to bind to actin, forming cross bridges, which cause sliding (contraction) process to begin. Cross bridge attachments form and break several times, each time pulling thin filaments a little closer toward the center of the sarcomere in a ratcheting action: causes shortening of muscle fiber. Z discs are pulled toward m line. A bands move closer to each other.

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Related Questions

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