Monday, February 4, 2008

Muscle System

Last week we learned about muscle. Muscle is broken down into three different categories
Smooth Muscle- Involuntary, Non-striated Muscle found in the digestive tract
Skeletal Muscle- Voluntary, Striated Muscle usually attatched to skeleton used to create movement
Cardiac Muscle- Involuntary, Striated auto-rhythmic, found in the heart

There are also three types of joints:
Ball and Socket Joints- Allow for 360 degree rotation example of this is the shoulder joint
Hinge joint- Allows for forward and backward motion such as that in your knee
Pivot Joint- allows for twisting motion such as that in your wrist or ankle

Muscles do work by contracting. When you flex your muscle the muscle shortens and thus enlargen in width. Skeletal muscles come in antagonist pairs flexor v. extensor: when flexing the bicep the bicep is contracting becoming the flexor and the tricep is stretched becoming the extensor. Tendons connect bone to muscle where ligaments connect bone to bone. Sarcomere is the unit responsible for muscle contraction, made up of thin and thick filaments Actin and Myosin. These interact at cross bridges between myosin heads and actin which are responsible for the shortening in muscles. The cleaving of atp to adp allows for myosin heads to bind to the actin filament. The shortening of the sarcomere allows for the contraction of the muscle when the (Z lines) move closer together.

The "Ratchet" System is due to the bonding of myosin with actin, then the sliding of thin and thick filaments past each other, then myosin head releases and binds to the active site on actin, and the muscle is unable to relax until Ca+2 is repumped into the sarcomeric reticulum. When all of this occurs the ratchet of the muscle occurs and muscles contract. For this to occur ATP is needed and greatly appreciated.

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