L.+Muscle+Physiology

 **We want to pump you UP!**
 * MUSCLE PHYSIOLOGY **

 Muscles? Arnold, Are you there? Ew…Not my thing! How many muscles do you think each human body has? Well, not every human is the same but, about 656 to 850 depending on the professional you ask. That is a LOT! Muscles are the meat and potatoes of our body that allows us to move, helps us make heat for our body and helps protect our organs too.

*Attached to bones by tendons and are striated *Composed of separate cells, also called fibers that are attached in parallel to the tendons *Endomysium covers individual muscle fibers *Perimysium covers bundles of fibers called fascicles *Epimysium covers the entire muscle *Requires neural stimulation to contract by external stimulation by somatic motor nerves and then it can product an action potential *During //in vitro// muscles can experience twitch, summation, and tetanus *The strength of a muscle contraction is dependent on its resting length
 * I. Skeletal Muscle **



*Is striated and contain sarcomeres, which are the structural subunit of a myofibril in a striated muscle *Short and branched cells *Stimilations by neurons is not required because action potential in the heart originates in myocardial cells *Action potentials can cross from one myocardial cell to another *Gap junctions, or electrical synapses join together adjacent myocardial cells that is tubular in shape
 * II. Cardiac (Heart) Muscle **

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*Considered a “single-unit” *Characteristics of thin and thick filaments NOT organized into sarcomeres *Thin filaments stretch from the plasma membrane and from dense bodies in the cytoplasms *Depolarization are conducted and graded from one smooth muscle cell to the next one *In order to produce contractions, phosphorlyation of the myosin head is required to be able to bind to the actin *//Synapses en passant// are created when autonomic neurons have varicosities that release neurotransmitters all along their length of contact with the smooth muscle cells
 * III. Smooth Muscle **

**APPLICATION:** A familiar hormone we have read about all semester long, epinephrine is an example of a drug used in hospitals and emergency situations that helps contraction by stretching the heart chambers. As an aspiring pharmacist and working at the Mayo hospital as a technician, we constantly see cardiac drugs being used. It is vital to have an understanding of what our muscles do and how they contract and what kind of drugs can affect our muscles. Another good example is Flexeril, or the generic name is Cyclobenzaprine. It is a skeletal muscle relaxer that is used for rest, during physical therapy and other measures to relieve pain and discomfort caused by strains, sprains and other muscle injuries. I am very familiar with this particular drug because my Father uses this drug regularly due to muscle pain that he has continued to have since a farming accident. He says it is very helpful for him.

THE SLIDING FILAMENT THEORY When our muscle contracts it decreases in length because the individual fibers actually shorten. The myofibrils shorten because the fibers shorten. It is like a domino effect taking place in the body. Next, you will see the shortening in the Z disc to Z disc distance. The filaments SLIDE, which explains why we call this the sliding filament theory and the Z lines are brought together and the sacromeres actually get shorter. The sliding is induced by the power strokes from the cross bridges of myosin. Troponin is attached to the tropomyosin. These are important proteins. It pulls the actin (thin) filaments over the myosin (thick) filaments. There are myosin heads allow the attaching of the cross bridges but, ATP must split before they can attach. This includes then Pi and ADP. The Ca2+ is actively transported into the sarcoplasmic reticulumn and when our muscle is at rest the sarcoplasm is very low and cross bridges are prevented from attaching to actin. Once our action potential stops, the Ca2+ release channels into the sarcoplasmic reticulmn that close. Once the removal of Ca2+ tales place from troponin, the muscle relaxes. ATP is the fuel to build cross bridges for muscle contractions and calcium and ATP together regulate the process of relaxation and contraction.
 * ESSENTIAL QUESTIONS **

 http://arnold-schwarzenegger-bodybuilding.net/wp-content/uploads/2009/10/arnold-schwarzenegger-roids2.jpg  http://prescriptionskeywest.com/flexeril.php <span style="color: #a91e1e; font-family: Georgia,serif; font-size: 150%;"> http://www.youtube.com/watch?v=tCLJlvhyUrY&feature=related <span style="color: #a91e1e; font-family: Georgia,serif; font-size: 150%;"> http://wikis.lib.ncsu.edu/images/b/ba/Skeletalmuscle1.jpg
 * <span style="color: #a91e1e; font-family: Georgia,serif; font-size: 150%;">Sources: **