Topic 7 Flashcards
(113 cards)
What attaches skeletal muscle to bones?
Tendons
What attaches bones to other bones?
Ligaments
What is an antagonistic pair?
Muscles that work together to move a bone
How does an arm bend?
Biceps contracts, triceps relax.
This pulls the bone so arm flexes (bends)
What is a flexor?
A muscle that bends a joint when contracts
How does an arm straighten?
Triceps contract, biceps relax.
This pulls the bone so arm extends (straightens)
What is an extensor?
A muscle that straightens a joint when contracts
What is skeletal muscle made up of?
Large bundles of long cells called muscle fibres
What is the cell membrane of muscle fibre cells called?
Sarcolemma
What are Transverse (T) tubules?
Parts of the Sarcolemma fold inwards across muscle fibre and stick into the sarcoplasm.
They help spread electrical impulses throughout the sarcoplasm so they reach all parts of the muscle fibre.
What is the sarcoplasmic reticulum?
A network of internal membranes that runs through the sarcoplasm.
It stores and releases calcium ions for muscle contraction.
What does multinucleate mean?
Contains many nuclei
What are myofibrils?
Long, cylindrical organelles.
Made up of proteins and are highly specialised for contraction.
What do myofibrils contain?
Thick myosin filaments and thin actin filaments
What are sarcomeres?
Short units in a myofibril
What is an A-band?
Dark bands that show up on an electron microscope as a result of the thick myosin filaments and some overlapping the thin actin filaments
What is an I-band?
Light bands that show up on an electron microscope as a result of the thin actin filaments
What is a Z-band?
The ends of each sarcomere are marked with Z-lines
What is the M-line?
The middle of each sarcomere, in the middle of the myosin filaments
What is the H-zone?
Around the M-line, contains only myosin filaments
How does a muscle contract?
Myosin and actin filaments slide over each other to make sarcomeres contract.
Myofilaments themselves don’t contract .
Myosin and actin molecules stay the same length.
Simultaneous contraction of lots of sarcomeres means myofibrils and muscle fibres contract.
Describe myosin filaments.
- Globular heads that are hinged so can move back and forth
- Each head has a binding site for actin and a binding site for ATP
Describe actin filaments.
- Binding sites for myosin heads called actin-myosin binding sites.
- Two other proteins called tropomyosin and troponin are found between filaments.
- These proteins are attached to each other and they help myofilaments move past each other
Describe the binding sites on myofilaments in a resting muscle.
- Actin-myosin binding site is blocked by tropomyosin, which is held in place by troponin
- Myofilaments can’t slide past each other because myosin heads can’t bind