Topic 7: Muscles and joints Flashcards
Describe the structure and function of smooth muscle
- non striated
- spindle shaped
- uninuclear fibres
- involuntary
- in walls of internal organs
Describe the structure and function of cardiac muscle
- striated
- branched
- uninuclear fibres
- involuntary
- walls of the heart
Describe the structure and function of skeletal muscle
- striated
- tubular
- multinuclear fibres (cells)
- voluntary
- attached to skeleton
What is a tendon?
joins muscles to bones
- white fibrous tissue
- bundles of collagen fibres
- inelastic
What is a ligament?
elastic tissue that holds bones to bones
What is cartilage?
tissue at the ends of bones, made of chondrocytes and collagen, to prevent bone erosion
- elastic
- shock absorber
How do muscles allow movement?
antagonist pairs which work in opposite directions:
- flexor (reduces angle)
- extensor (straightening)
What is a synovial joint?
bones separated by synovial fluid, allowing free movement
Describe the structure of a section of skeletal muscle
bundles of muscle fibres with myocytes (single muscle cells)
Describe the structure of a myocyte
- multi-nucleate
- made up of contractile myofibrils
- sarcolemma, sarcoplasm, sarcoplasmic reticulum
- sarcosomes (mitochondria) for ATP
What are myofibrils?
bundles of myofilaments, which are repeated chains of sarcomeres
What is the thick filament in myofibrils?
myosin
What is the thin filament in myofibrils?
actin
What are A bands?
dark bands contain thick myosin and overlapping thin actin
What are I bands?
light bands containing only thin actin filaments
What is the Z line?
sarcomeres are joined here
What is the M line?
middle of the myosin filaments
What does the H zone contain?
only thick myosin filaments
What is the sliding filament theory?
myosin and acting slide over each other, shortening the length of the sarcomere
What happens to the I band in contraction?
gets shorter
What happens to the A band in muscle contraction?
stays the same
What happens to the H zone in contraction?
gets shorter
What happens when muscles are relaxed?
- no Ca2+ so tropomyosin blocks the myosin binding site on actin
- myofilaments can’t slide past each other as heads can’t bind
How is muscle contraction triggered?
- nerve impulse reaches axon terminals at neuromuscular junction
- depolarises sarcolemma and spreads to sarcoplasm
- neurotransmitter released and binds to receptors on muscle cells
- Ca2+ released from sarcoplasmic reticulum
