Muscle Contraction Flashcards
What are myofibrils?
The millions of tiny muscle fibres that make up individual muscles.
On their own they have almost no force but are powerful collectively
How are muscle cells different?
The separate cells become fused together into muscle fibres
They share nuclei and a cytoplasm called a sarcoplasm
What organelles are found in large concentrations in the sarcoplasm?
Mitochondria and endoplasmic reticulum
What is actin?
A protein filament
Thinner and consists of two strands twisted around each other
What is myosin?
A protein filament
Thicker and consists of two long rod shaped fibres
Bulbous heads that project to the side
I - bands (isotropic)
LIght bands
Because the filaments don’t overlap
A - bands (anisotropic)
DArk bands
Because the filaments do overlap
Z - line
The line at the centre of the I-bands
H - zone
The lighter area at the centre each A-band
What is a sarcomere?
The distance between adjacent Z-lines
What happens when a muscle contracts?
The sarcomeres shorten I-band becomes narrower Z-lines mover closer H-zone becomes narrower A-bands remain the same length
