BIOL 2021 Chapter Notes - Chapter 16.5: Neuromuscular Junction, T-Tubule, Sarcomere

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11 Feb 2018

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Sarcomere Structure

- Sarcomere: one contractile unit inside a myofibril

o Made up of thin actin filaments (light bands) and thick myosin

filaments (dark band)

o Actin’s plus ends are attached to Z discs at each end of the

sarcomere

o The M line (midline) is where myosin molecules are

linked together

o Contraction is the sliding of myosin against actin

o Nothing shortens except the entire sarcomere itself

(actin and myosin stay the same length)

o Don’t need to know accessory proteins

- Neuromuscular junction: nerve cell

contacts the muscle cell

o An action potential causes a

synapse, which causes another

action potential in the muscle cell

- Sarcoplasmic reticulum: (sarco =

muscle) the ER in muscle cells that is

responsible for storing calcium

- T tubules are extensions of the PM

(continuous with PM)

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