Contractile Fibre / structures of Sarcomeres Flashcards
What is the Basic Functional units of a Myofibril?
The filaments inside a Myofibril do not extend the entire length of the Muscle fibre.
They are arranged in sections called Sarcomeres.
What does a Sarcomeres consist of?
The Sarcomeres are organized into Bands & Zones:
A Band, Zone of overlap, I Band, H Zone & M line.
What is a Z disc?
This is a Narrow plate shaped region of dense protein material called Z Discs.
They separate one sarcomere from the next.
What is the zone of overlap within a Sarcomeres?
This is the part of the “A band” where the Thick and Thin filaments lay side by side.
What is the I Band portion of a Sarcomere?
This is a Lighter, less dense area that contains the rest of the Thin filaments but no Thick filaments.
A Z disc passes through the centre of each I Band.
What creates the “Striations” Within the Myofibril?
The alternating Dark A bands & light I Bands create striations that can be seen in Myofibrils.
What are the 2 main types of Filaments within a Myofibrils?
Thick and Thin Filaments.
What is an H Zone?
This is at the centre of each Sarcomere containing only thick Filaments.
What is an M Line?
This is a layer of supporting proteins that hold the Thick filaments together at the H zone.
What are the 2 Contractile fibres of a Myofibril?
The 2 contractile proteins in a muscle are:
Myosin & Actin.
What is Myosin?
Myosin is the main component of thick filaments and functions as a motor protein.
What is Actin?
This is a Contractile protein and is the main component of the Thin filament.
Each Actin molecule has a myosin binding site for the Myosin head to bind during muscle contraction.
What do Motor proteins do in muscle fibres?
They Pull various cellular structures to achieve movement by converting chemical energy into mechanical energy.
What are the contractile proteins of the Muscle Fibre?
Actin & Myosin
What is a Fascicle?
These are bundles of muscle fibres wrapped in Perimysium.
What is a Myofibril?
This is Threadlike contractile elements within Sarcoplasm of muscle fibre that extend the entire length of the fibre and is composed of Filaments.
What is a Myofilament?
This is a set of contractile proteins within myofibrils and they have thick and thin filaments composed of Myosin and Actin.
Sliding of Thin filaments past Thick filaments creates Shortening of the muscle.
What are Thin Filaments composed of?
Actin, Tropomyosin and Troponin.
What are Tropomyosin and Troponin?
These are regulatory proteins that help turn on and off muscle contraction.
What is Tropomyosin?
When skeletal muscle fibres are relaxed it covers myosin binding sites on actin, and preventing myosin from binding to actin.
What is Troponin?
When calcium ions bind to Troponin it changes shape and moves tropomyosin away from myosin binding sites on actin.
Muscle contraction subsequently begins as myosin binds to actin.
