Muscular System Chapter 8

The 3 Muscle Types The job of all muscles is to contract The 3 Muscle Types Are: Skeletal Muscle Cardiac Muscle Smooth Muscle

Skeletal Muscle Cigar Shaped Multinucleated Striated Voluntary Can Be Involuntary When Reflexes Are Involved Very Strong and Fast But Needs Rest Most Attached to Bone

Skeletal Muscle Cell

Cardiac Muscle

Smooth Muscle Long thin nuclei and no striations

How are Muscles Structured? Muscle Cells have a plasma membrane called a Sarcolemma. The muscle fiber is enclosed in Endomysieum. (Endo= , Mys= ) Many Muscle fibers bound together make a Fascicle. The Fascicle is wrapped in a membrane called the Perimysieum (Peri= ).

Muscle Structure Continued Many fascicles are wrapped together by an Epimysium. (Epi= ) Epimysia attach to tendons

Skeletal Muscle

Inside the Muscle Fiber

What is the major Organelle of the Muscle Cell? Myofibril(s)=Working unit of the muscle cell. Made of Subunits called sarcomeres. Give muscles the striped or striated appearance The light band = I-band The dark band = A-band Between the I-bands = Z-line Between the A-bands = H-zone Match the Terms

Mechanism of muscle contraction The above micrographs show that the sarcomere gets shorter when the muscle contracts The light (I) bands become shorter The dark bands (A) bands stay the same length

Take a long deep breath, its not that bad. And remember a bicycle cannot stand alone, because it is two tired. Now lets go on. But lets first watch this short video clip. Overview of the Job of the Bands

So how do these bands work? The myofibrils are surrounded by the sarcoplasmic reticulum, a specialized form of smooth endoplasmic reticulum that releases calcium. They are made of bands of Actin (the thin filaments) that make up the I-bands Myosin (the thick filaments) that make up the A-bands

How does ACh stimulate the muscle? ACh causes the sarcolema to release Calcium (Ca+) Ca+ binds to the actin causing it to change shape. Myosin finds actin’s new shape attractive and grabs hold.

What happens after the Myosin grabs hold? Myosin’s head snap towards the H-band of the sarcomere. ATP releases and rearranges the myosin Only some myosin heads move at one time. Description of Muscle movement

How does the muscle relax? When the action potential ends: Sarcomere absorb Ca+ ATP releases myosin heads Actin takes on its former and less attractive shape. Muscle Cells can relax Myofilament Contraction

It is important to remember the heirarchy myosin myofibrils fasicles myofilaments actin

It is important to remember the heirarchy fasicles myofibrils myofilaments actin myosin

muscle fiber myofilament myofibrils epimysium muscle sarcomere

myofilament muscle sarcomere epimysium myofibrils muscle fiber

How do muscles work together? Prime Mover: Major muscle doing the bulk of the work contracting. Synergist: Group of muscles working together to contract. Antagonist: Muscle that works against the prime mover and or synergists.

To exercise the: Quadriceps

To exercise the: Gastronemius

To exercise the: Hamstring Group Includes the bicepts femoris

Exercise the: Trapezius

Exercise for: Deltoid

Exercise For: Gluteus Maximus

Exercises for: Oblique

Exercises for: Rectus Abdominus

Exercise for: Pectoralis Major Push up: Works Pecs on The Up-Motion

Exercises for: Bicep