muscle general structure Flashcards
What is skeletal muscle made of? (2)
Large bundles of long cells;
Muscle fibres
What are muscle fibres made of? (1)
Bundles of myofibrils
What are myofibrils made of? (3)
Made of bundles of myofilaments;
Actin (thin);
Myosin (thick)
What is the sarcolemma? (1)
Cell membrane of muscle fibre cells
What is the sarcoplasm? (1)
The cytoplasm of a muscle cell
What is the function of the sarcoplasmic reticulum in muscle fibres? (2)
Runs through the sarcoplasm;
Stores/releases calcium ions for muscle contraction
What are T-tubules, and what do they do? (3)
Folds of the sarcolemma that stick into the sarcoplasm;
They help to spread electrical impulses through the sarcoplasm;
So they reach all parts of the muscle fibre
Why do muscle fibres have many mitochondria? (1)
To provide ATP for muscle contraction
What does it mean for muscle fibres to be multinucleate?
Contain multiple nuclei
What are myofibrils, and what do they contain? (3)
Myofibrils are long, cylindrical organelles in muscle fibres;
They contain bundles of thick and thin myofilaments;
Thick myofilaments are made of myosin
What are thin myofilaments made of? (1)
Actin
What are A bands in myofibrils? (2)
A bands are dark bands;
That contain thick myosin filaments and some overlapping thin actin filaments
What are I bands in myofibrils? (1)
Light bands that contain only thin actin filaments
What are sarcomeres, and how are they structured? (2)
Sarcomeres are the functional units of myofibrils;
The ends of each sarcomere are marked by Z-lines
What is the M-line in a sarcomere? (2)
The M-line is the line in the middle of the sarcomere;
In the middle of the myosin filaments
What is the H-zone in a sarcomere? (2)
Surrounds the M-line;
Contains only myosin filaments
How do the lengths of the different bands in a myofibril change during muscle contraction? (4)
A bands = Stay the same length;
I bands = Get shorter;
H zones = Get shorter;
Z lines = Move closer together
