.: Muscle Physiology:.


Summary:
Our bodies are made up of many systems. One of these systems is the musculare system. This system helps us eat, run, play and do many other activities. If we take a closer look into just what makes us up we'll find that there are three types of muscle that make us up. Each of the different kinds of muscle has unique and functional characteristics

Skeletal-
This type of muscle is attached to bones. It has striations that are caused by the sacromeres. This tissue makes up the biceps and other muscles that are voluntary.

Smooth-
This type of muscle is tissue is in the walls of hollow organs such as veins and intestines. It doesn't produce scaromeres but it does produce a large amount of actin and some myosin . Smooth muscle is involuntary

Cardiac-
This type of muscle makes up the heart. It is recognizable by intercalated discs each muscle cell is made up of thin and think filaments and these make up a sacromeres. Cardiac muscle is involuntary.






How does this apply to my career?

As a nurse I would have to administer muscle relaxers and other drugs that take effect on the body. Muscle physiology would be useful to understand just what those drugs are doing and will do to the patient. Also with the rise of baby boomers later in life the nursing home rate will increase. With that increase will be nurses to take care of people that have contracted muscles due to inactivity or disease. Understand how muscles contract and relax is important to help people regain their strength to live life more independently. Another reason is that knowing the recovery time and just how far muscles can go is important for the recovery of hip surgery and other surgery that cut into the muscle tissues. These are a few disease/ disorder I might encounter at work: Diseases of the muscular system

Looking inside the muscle

1. Describe the sliding filament theory of muscle contraction.
When a muscle contracts the Z- lines push the sacromere together. This makes the sacromere shorter but the actin(thin filaments) move toward the center causing the contraction of the muscle. The more contracted the muscle the more over lapping happens of the actin.
MuscleSarcomere.gif

3. Why it is called the sliding filament theory?
This is called the sliding filament theory because when the muscle contracts the filaments don't get shorter they "slide" together until they overlap themselves in full contraction. Then when relaxation happens the filaments "slide back to their normal position.

4. Describe the action of the cross bridges that cause a power stroke.

I like to think of the cross bridge causing a power stroke like a pitcher in a base ball game...

The myosin protein that forms a arm and a head has been activated by separation of ATP to ADP and Pi. After the myosin head ( the pitcher) changes (throws) Pi, it changes and bends forward. This moves the actin towards the middle of the sacromer. This is called a power stroke.













4. What is the role of calcium and ATP in muscle contraction and relaxation?

Contraction Phase

  1. Resting state
  2. Motor nerve action potential arrives at motor end plate
  3. Acetylcholine released, sarcolemma and membranes depolarized (Na+ flux into fiber)
  4. Action potential transmitted via T-tubules to SR
  5. Ca+ released from SR terminal into sarcoplasm
  6. Ca+ bound by troponin
  7. Myosin ATPase activated and ATP hydrolyzed
  8. Tropomyosin shift from actin binding site
  9. Actin-myosin cross bridge formation
  10. Repeated formation & breaking of crossbridges resulting in sliding of filaments and sarcomere shortening

Relaxation Phase

  1. Cholinesterase released and acetylcholine breakdown
  2. Sarcolemma & T-tubules repolarized
  3. SR Ca+ pump activated & Ca++ returned to SR terminal cisternae
  4. Actin-myosin crossbridge formation terminated
  5. Return of tropomyosin to actin binding site
  6. Mg+ complex formed with ATP
  7. Passive sliding of filaments
  8. Sarcomeres return to resting state

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Fun Fact: Muscle account for approximately 40% of your body weight.


Thanks to:http://meat.tamu.edu/muscontract.html
http://library.thinkquest.org/5777/mus3.htm
youtube.com
http://www.blackwellpublishing.com/matthews/myosin.html
http://tanyastroh.wordpress.com/2009/05/18/10-fun-facts-about-your-muscles/
http://www.buzzle.com/articles/disorders-of-the-muscular-system.html
Human physiology 11th edition -McGraw-Hill
Anatomy and Physiology 4th edition-Mcgraw-Hill