APK 2105C Lecture Notes - Lecture 40: Endoplasmic Reticulum, Skeletal Muscle, Myocyte
16 Jun 2018
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Chapter 12, Lecture 1
Muscle Physiology
• Skeletal muscle structure
o CT covering the outside of the
muscle = epimysium
o Fascicles = bunches within the
muscle
▪ Paramysium =
surrounds the fascicles
and fills in gaps
between fascicle
o Myocyte = individual skeletal
muscle cell
▪ Extremely long—span
the length of the muscle
▪ Need multiple nuclei
▪ Endomysium =
surrounds the individual
myocyte
▪ Contains normal organelles and myofibrils—contractile organelle
• Myofibrils push other organelles to the edges of the cell
o Nuclei are on the outside of the cell
• Myofibrils are composed of protein filaments
o Actin
o Myosin
o Have dark and light stripes—causes striated appearance
o Blood vessels and nerves throughout each layer of cells
o Sarc = flesh
o Sarcolemma = plasma membrane of skeletal muscle cell
o Sarcoplasm = cytoplasm inside a skeletal muscle cell
• Myofibrils = contractile organelle that runs the length
of the myocyte
o Overlapping arrangement of myosin and actin
▪ Thick filament = myosin
▪ Thin filament = actin
• Actin fills up most of the
structure
o Lots of mitochondria in myocyte
o T (transverse) tubule
▪ Around and between the myofibrils
▪ Invaginations of the sarcolemma into
the cell’s interior
o Sarcoplasmic reticulum (SR) = type of ER in
skeletal muscles
▪ Surrounds each myofibril and comes
in contact with T tubule
▪ Membranous organelle that surrounds
the myofibrils
▪ Terminal cisternae = enlarged regions
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