Integrated SequencePhysics Chemistry Organic Biology

Web Resources

Kimball's Biology Pages - Activation of Skeletal Muscle

The Medical Biochemistry Page - Neuromuscular Transmission
Very interesting discussion of neuromuscular transmission which seques into the cholinergic agonists and antagonists, integrating knowledge of muscle contraction and endocrine control.

  click if a link is broken

Special points of emphasis


Biological Membranes

The Eukaryotic Cell

The Nervous System

The Musculoskeletal System

Molecules of tropomyosin situated in the grooves of the actin helix prevent myosin heads from binding actin. Also present are molecules of troponin. Binding both actin and tropomyosin, troponin may also bind calcium ions. In a normal cell, cytoplasmic calcium is kept very low by pumping the calcium into the extracellular space or into mitochondria. In skeletal-muscle cells, the sacroplasmic reticulum is present as a calcium reservoir. The sarcoplasmic reticulum is interwoven with another specialized feature, T-tubules, which conduct an action potential into and throughout the muscle cell after sufficient acetylcholine has crossed the neuromuscular junction, causing calcium release through out the cell. The calcium binds troponin which shifts tropomyosin away from the myosin binding sites on actin. When the myosin head binds to actin the interaction with actin promotes a major change in conformation (the power stroke). The power stroke is not accompanied by the hydrolysis of ATP. Hydrolysis of ATP 'cocks's the myosin head, priming it for the power stroke, before attachment to actin.

The WikiPremed MCAT Course is a free comprehensive course in the undergraduate level general sciences. Undergraduate level physics, chemistry, organic chemistry and biology are presented by this course as a unified whole within a spiraling curriculum.

Please read our policies on privacy and shipping & returns.  Contact Us.
MCAT is a registered trademark of the Association of American Medical Colleges, which does not endorse the WikiPremed Course.

Creative Commons License
The work of WikiPremed is published under a Creative Commons Attribution Share Alike 3.0 License. There are elements of work here, such as a subset of the images in the archive from WikiPedia, that originated as GNU General Public License works, so take care to follow the unique stipulations of that license in printed reproductions. You can use the resources here for commercial or non-commercial purposes, but please give attribution and a link to the production credits and edit history of the resource. For the works here which began as my individual work, please attribute "John Wetzel, an author at".