Structure & Function 1

Mr. WhedonWed 7:25

By: Marc Magliaro Deisy Maguirre

Shquanda Meylor

The SarcomereA sarcomere is the basic unit of a Muscle 's cross-striated myofibril.Myofibrils are thread like structure Which consist of two types of protein filaments. Myosin which is a thick filament and Actin which is a thin filament.

Sarcomere

The striations form a repeating pattern of units called Sarcomeres along each muscle fiber. Muscle fibers in a way themselves are basically collections of sarcomeres.

Myofibrils may be thought of as sacromeres joined end to end.

Myofibrils There are two types of Myofibrils One type is actin which is a thin filament

and the other is myosin which is composed of a thick filament.

The origination ofthese filaments produce striation characteristics ofskeletal musclefiber.

The Striation Pattern

There are 2 main parts of the striation pattern

• The two parts are called I bands and A Bands.

• The I bands are composed of the Thin filaments (actin) and the A bands are composed of Thick (myosin) and Thin (actin) filaments.

I band (Thin Filaments) These Actin filaments ( thin) are held

by direct attachments to structures called the Z Line. ( Z Band) The Z line is in the center of the I band.

A Band

The A Band consist of thick myosin filament

overlapping with thin actin filaments.The A band also consist of a region where only thick filaments exist. This regions is called the H-Zone

M- Line The A band includes a thickening

which is know as the M- Line, which consist of proteins that help hold the thick filaments place.

H- Zone The H- Zone consist of only thick

filaments and is also located in the A band.

The H zone may change depending on the degree of filament overlap.

Z – Line A singel sarcomere extends from one

Z line to the other Z line.

Myosin: H Zone

Actin: I band Actin and Myosin: A Band

Sacomere Endline: Z line which is located in the I Band

Sacomere Midline: M line which is located in the H Zone.

Myofilments Thick Filaments are composed many

molecules of myosin. Each myosin molecules consist of two twisted protein strands called cross-bridges.

Myofilments Thin filaments consist of double

strands of actin twisted. Thin Filaments also consist of two typs of protein troponin and tropomyosin.