Muscles Flashcards
What coordinates muscular movement
The CNS receives sensory information and decides what kind of response is needed. If it is movement the CNS send signals along neurones to tell skeletal muscles to contract
What is skeletal muscle composed of
Large bundles of cells called muscle fibres
What is the cell membrane of a muscle fibre
Sarcolemma
What are the infolds of the sarcolemma of a muscle fibre
Transverse or T tubules
What do T tubules do
Help to spread electrical impulses throughout the sarcoplasm so they reach all parts of the muscle fibre
What is the network of internal membranes in the sarcoplasm
Sarcoplasmic reticulum
What does the sarcoplasmic reticulum do
Stores and releases calcium ions that are needed for muscle contraction
Why do muscle fibres have lots of mitochondria
To provide ATP for muscle contraction
What are myofibrils
Long cylindrical organelles made up of proteins specialised for contraction. Several hundred to thousands of myofibrils are in muscle fibres
What do myofibrils contain
Thick myofilaments - myosin
Thin myofilaments - actin
What do dark bands contain and what are they called
Thick myosin filaments called the A-bands
What do light bands contain and what are they called
Thin actin filaments called the I-bands
What is a myofibril made up of
Short units called sarcomeres
What is the Z-line
The ends of sarcomeres
What is the M-line
The middle of each sarcomere and myosin filament
What is the H-zone
Section of the sarcomere that only contains myosin filaments
How do sarcomeres contract
Myosin and actin slide over one another (the myofilaments don’t contract)
What does the simultaneous contraction of lots of sarcomeres result in
The myofibrils and muscle fibres contract.
When do sarcomeres return to their original length
When the muscle relaxes
During contraction, what happens to the A-band
Stays the same length
During contraction, what happens to the I-band
Gets shorter
During contraction, what happens to the H-zone
Gets shorter
During contraction, what happens to the sarcomere length
Gets shorter
What do myosin filaments have
- Have globular heads that are hinged so can move back
- Each myosin head has a binding site for actin and a binding site for ATP