Ultra-Structure of Skeletal Muscle Flashcards
Muscles can pull but cannot push. As a result of this limitation muscles generally operate in pairs.
Describe Antagonistic muscle action.
A muscle pulls in one direction at a joint and the other muscle pulls in the opposite direction
Muscles can pull but cannot push. What connects muscle to bones ?
Tendons
Give an example of Antagonistic muscle action
To raise the lower arm
The bicep contracts and the tricep relaxes
What are the specialised cells in skeletal muscle called ?
Muscle fibres
What organelle do muscle fibres have a lot of ?
Nuclei
What is the membrane surrounding each fibre called ?
Sarcolemma
What is the cytoplasm of muscle fibre called ?
Sarcoplasm
The sarcolemma has many deep tube-like projections that fold in from its outer surface:
What is the name of these projections and what do they run close to ?
T-tubules
These run close to the SR
What are the myofibrils made up of ?
Myofilaments
What does the sarcoplasm contain ?
Mitochondria
Myofibrils
What is each unit of a myofibril called ?
A sarcomere
Why is it an advantage that muscle fibres contain lots of mitochondria
The mitochondria carry out aerobic respiration to generate the ATP required for muscle contraction
What are the two different types of protein filaments that Myofibrils contain ?
Actin Filaments (thin)
Myosin Filaments (thick)
What is the A band composed of ? HINT : A band is made up of DARK BANDS
Thick myosin filaments and actin filaments
What is the I Band composed of ? HINT: I band is light
Thin actin filaments
What is the Z line and where is it found ?
Attachment site for actin
The centre of the I band
The distance from one z line to another z line is known as what ?
a sarcomere
What is the M line and where is it found ?
attachment site for myosin
found in the centre of the A band.
Where it the H zone found ?
the centre of the A band
Describe the Ultrastructure of Skeletal muscle
Muscle fibres are made up of numerous parallel myofibrils
These are subdivided into myofilaments
The myofilaments are made up of actin (thin filaments) and myosin (thick filaments)
Describe what a tendon is and its function
Lengths of connective tissue
That join skeletal muscle to bone
Describe what happens to the length of the i bands and the length of the A bands during muscle contraction.
The A band would stay the same size / will not change
Because it is the region containing both myosin and actin filaments and the filaments themselves do not change length during contraction
AND
The I band would decrease / become smaller
Because it is the region containing only actin filaments between which myosin filaments slide
