Home > Uncategorized > Introduction to Human Anatomy Lecture 81 Notes: Muscular Histology

Introduction to Human Anatomy Lecture 81 Notes: Muscular Histology


Long lecture today at 58 minutes on the skeletal muscle of the body. 



Muscle comes in several flavors: smooth, cardiac, and skeletal. 

Skeletal muscles have striations, multinucleated, many mitochondria, T tubules.

Sarcoplasmic reticulum. 

A fibril is a bundle of muscle proteins.  The dark line is the Z line.  The distance between z lines is the sacromere. 

2 proteins in a muscle cell: actin and myosin.

Actin myofilaments are thin, attached to the z line and extend towards the middle.  Myosin myofilaments are thicker. 

Dark bands indicate greater density of proteins. 

How a muscle contracts: Sliding Filament Theory of Muscle Contraction

A z line on the left, a z line on the right.  Actin and myosin.  The legs of the men are cross bridging of the myosin.  Men roped to a telephone pole.  Feet are the myosin cross bridges.  ATP makes the feet move. 

All modern medicine comes from the molecular, cellular level. 

The sarcolemma is the muscle cell membrane.  Tissue fluid fills up the transverse tubules, rich in Na+.  Sarcoplasmic reticulum have lateral sace adn are  endoplasmic reticulum of the muscle cell. 

When sodium flows into a cell, an action potential is created. 


Na + flows into the muscle cell, AP created.

AP causes the release of Ca+ from the lateral sacs.

The Ca2+ causes the myosin cross bridges to start pushing the actin myofilaments inward “contraction.” 

There are several types of muscle cells: fusiform

Jocks and wimps.  Jocks have larger muscles but not more muscle cells.  One brother is a wrestler and one is a long distance runner. 

Brief Maximal Training:


Muscle Fiber Characteristics:

large diameter muscle fibers

fast rate of contraction

high power development

Increased protein synthesis, more actin and myosin

low myoglobin

white coloration of muscle fibers

Endurance, Sustained Training

long distance running


small diameter fibers
slow rate of contraction
high endurance
high myoglobin content permits O2 storage


Electrophiles are positive, nucleophiles are negative

Activators donate electrons to the ring, deactivators take electrons from the ring

Cat hearing – 80 Hz to 80 kHz

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