Muscles And Movement Flashcards
How do skeletal muscles attach to bones?
By tendons
How are bones held together?
Ligaments
What is an extensor?
A muscle that straightens a joint when it contracts
Muscles that work together are called?
Antagonist pairs
What is skeletal muscle made up of?
Long muscle fibers
Describe the structure of muscle fibers
Long cells
Cell membrane is called the sarcolemma
Bits of sarcolemma fold inwards across the muscle fibre and stick into the sarcoplasm
These folds are called transverse (T) tubules and they help to spread electrical impulses throughout the sarcoplasm so they reach all parts of the muscle fibre
A network of internal membranes called the sarcoplasmic reticulum runs through the sarcoplasm
The sarcoplasmic reticulum stores and releases Ca2+ ions that are needed for muscle contraction
Muscle fibres contain lots of mitochondria to provide ATP for muscle contraction
Multinucleate (contain many nuclei)
Muscle fibres made up of long, cylindrical organelles called myofibrils which are made from proteins
What do myofibrils contain?
Thick Myosin filaments
Thin Actin filaments
What are thick myofilaments made up of?
Myosin (a protein)
What are thin myofilaments made up of?
Actin (a protein)
What would you see if you looked at a myofibril under an electron microscope?
A pattern of alternating dark and light bands
What do A-bands contain?
Thick myosin filaments and some overlapping thin Actin filaments
What do I-bands contain?
Thin Actin filaments only
What are the short units in a myofibril called?
Sarcomeres
What does a Z-line indicate?
The end of each sarcomere
What line is shown in the middle of each sarcomere and the middle of the Myosin filaments?
M-line
What does the H-zone contain?
Myosin filaments only
Explain the sliding filament theory
- Myosin and actin filaments side over one another to make the sarcomeres contract
- The simultaneous contraction of lots of sarcomeres means the myofibrils and muscle fibres contract
- Sarcomeres return to their original length as the muscle relaxes
Describe how myofilaments, muscle fibres, myofibrils and muscles are related to each other
- muscles are made up of bundles of muscle fibres
- muscle fibres contain long organelles called myofibrils
- myofibrils contain bundles of myofilaments
Describe the structure of Myosin filaments
- globular heads that are hinged to allow movement back and forth
- each head has a binding site for actin and a binding site for ATP
Describe the structure of actin filaments
- contain binding sites for myosin heads called actin-myosin binding sites
- tropomyosin and troponin are found between actin filaments
- these proteins are attached to each other and help myofilaments move past each other
Explain the role of tropomyosin in a resting muscle
- blocks the actin-myosin binding site
- this means myofilaments can’t slide past each other because the Myosin heads can’t bind to the actin-myosin binding site on the actin filaments
What triggers a muscle contraction?
An action potential
What are the two different muscle fibres present in skeletal muscles?
- Slow twitch
- Fast twitch
Properties of slow twitch muscle fibres
- Contract slowly
- Used for posture
- Good for endurance activities
- Can work for a long time without getting tired
- Energy’s released slowly through aerobic respiration. This means there is lots of mitochondria and blood vessels to supply the muscles with oxygen
- Reddish in colour as they are rich in myoglobin, a red-coloured protein
Properties of fast twitch muscle fibres
- contract very quickly
- used for fast movement
- good for short bursts of speed and power
- tire very quickly
- energy’s released quickly through anaerobic respiration using glycogen. There are few mitochondria or blood vessels
- whitish in colour because of lack of myoglobin
- this means they can’t store much oxygen
