lecture 10 Flashcards
Skeletal muscle
How do you tell the difference in the appearance of the 3 muscle types
Smooth looks pancaked and is the most unorganised, Skeletal is striated and organised, cardiac is striated and unorganised
Describe the layout of a muscle group starting from the smallest unit and how are they contained
Myofibrils(made of thin and thick filaments), many of these make up a singular massive muscle cell known as a fibre that are visible with the naked eye. Fibres bundle up to make fascicles which form together to make a muscle.
the fascicles and fibres are held contained by connective tissue to allow for smooth frictionless movement
How are myofibrils made and how are they nucleated
They’re multinucleated and made up of many fused myoblasts that differentiated to become muscle cells
Define a sarcomere and the main units of them
The individual contractile repeating units of skeletal muscle.
The main section from left to right and then down are the: Z line, A band, I band(surrounding Z line) -down: H band(surrounding m line) and M line(very middle)
What type of filaments does the I band and Z line centre around
Theyre around the actin filaments/thin filaments
What type of filaments does the A band, H band and M line centre around
The myosin filaments/ thick filaments
What are the lines/bands of focus
M line and Z line
What is the ratio of Actin filaments to myosin filaments
2:1
Describe the actin portion of the thin filaments
Making up 20-25% of the total muscle protein, there are 2 types the globular singular ones which are of focus and the fibrous linear strands
Describe the Tropomyosin portion of the Thin filaments
Making up 5-6% of the total muscle protein, it’s a thread like protein that covers the binding sites on the globular actin
Describe the troponin portion of the thin filaments
Making up 5-6% of the total muscle protein, there are 3 different globular proteins for one complex. TnC, which is a binding site for Ca2+, when this is activated it causes TnT, which is bound to tropomyosin, to activate and pull the tropomyosin off of the binding sites. The final unit is TnI which binds to actin
Describe the thick filament portion of a sarcomere
Made up of myosin and contributing to 50-55% of total muscle protein. A myosin molecule is shaped as two bulbous heads made up with regulatory and alkali light chains of the surface, these heads are called cross bridges. The rest of the molecule is made up of heavy chains and the heads have tails that are intertwined along with a hinge region that allow for the flexion needed for cross bridge cycling
Describe the alkali portion of the light chains of myosin
Its a type of light chain thats essential with the proper name of MyLC1. It’s necessary for promoting movement
Describe the regulatory light chains portion of myosin
MyLC2 have a regulatory function for the myosin
What are the remaining less important parts of the contractile proteins
Alpha-actinin, makes up the Z line and provides binding sites for most cytoskeletal proteins
Titin- A very large protein that has the structural role of connecting the myosin filaments to the Z-line. Makes up the core of thick filaments which recoil post stretch
Nebulin- makes up ~3% of the total muscle protein and has the role of the structural protein of the fine filament of actin and is likely a determinant of the length of the total thin filament
Describe the region of t tubules
called the triad, the transverse tubule goes through the muscle fibre as an extension of the sarcolemma. inbetween 2 terminal cisternae of the sarcoplasmic reticulum.
