11.2: Muscles & Movement

Which structure is responsible for passing messages directly to effector organs?

11.2.1 State the roles of ...in human movement. Bones Lever for movement Frame to support body Protect tissue/organs Form blood cells (marrow) Store minerals Ligaments Strengthen joint stabilize bone to bone connections Muscles Provide force for movemt by contracting Shortening length of cells Occur in antagonistic pairs Tendons Attach muscle to bone Nerves Sensory ends @ ligaments and muscles Help prevent over-extension @ joints Coordinate muscle contraction

11.2.2 Label a diagram of human elbow joint: cartilage, synovial fluid, joint capsule, named bones (humerus, radius, ulna), antagonistic muscles (biceps, triceps)

11.2.2 Label a diagram of human elbow joint: cartilage, synovial fluid, joint capsule, named bones (humerus, radius, ulna), antagonistic muscles (biceps, triceps) http://www.asmi.org/sportsmed/anatomy/elbow.html www.Click4biology.com

11.2.3 Outline the functions of the structures in the human elbow joint. Hinge joint Synovial fluid w/in synovial cavity, w/in joint capsule—dense connective tissue, continuous w/bone membranes www.heinemann.co.uk/hotlinks 4242P; weblink 11.1

Joint part Function Cartilage Reduces friction, absorbs compression Synovial fluid Lubricates to reduce friction; provides nutrients to cells of cartilage Joint capsule Surrounds joint; encloses syn cavity; unites connecting bones Tendons Attach muscle to bone Ligaments Connect bone to bone Biceps Contracts  flexion (bending) of arm Triceps Contracts  extension (straightening) Humerus Lever, allows anchorage of elbow muscles Radius Lever for biceps Ulna Lever for triceps

11.2.4 Compare the movements at the hip and knee joint. Hip Joint Knee Joint Freely movable Angular motions in many directions & rotational movements Angular motion in one direction Motions possible: flexion, extension, abduction, adduction, circumduction, and rotation Flexion and extension only Ball-like structure fits into a cup-like depression (ball-and-socket joint) Convex surface fits into a concave surface (hinge joint)

11.2.4 Compare the movements at the hip and knee joint.

“muscle” = 1000s of cells, nerves, vessels 11.2.5 Describe the structure of striated muscle fibers: myofibrils w/light and dark bands, mitochondria, sarcoplasmic reticulum, nuclei, sarcolemma Skeletal movement Muscle fibers = cells Multinucleate Plasma membrane = sarcolemma T tubules = “tunnels” penetrating cell’s interior Cytoplasm = sarcoplasm LOTS of stored glycogen (glycosomes) LOTS of myoglobin (protein) SR = sarcoplasmic reticulum = smooth ER Myofibrils = rod-shaped bodies, run length of cell Lots, packed parallel to each other, lots mitochondria in b/w Contractile units of the muscle cell; give it striated pattern “muscle” = 1000s of cells, nerves, vessels

Myofibrils: Sarcomere = unit of movemt Z lines @ ends 11.2.6 Draw and label a diagram to show structure of a sarcomere: z lines, actin filaments, myosin filaments with heads, and resultant light and dark bands. Myofibrils: Sarcomere = unit of movemt Z lines @ ends A bands (dArk), length of myosin filaments H band (narrow) @ middle of A band (myosin only, no actin) w/M line in middle—supporting protein for myosin filaments I bands (LIght), only actin—no myosin http://entochem.tamu.edu/musclestruccontractswf/index.html

11.2.6 Draw and label a diagram to show structure of a sarcomere: z lines, actin filaments, myosin filaments with heads, and resultant light and dark bands. Actin Myosin Thin (8nm diam) Thick (16 nm diam) Contains myosin-binding sites Contains myosin heads that have actin-binding sites Individual molecules form helical structures Individual molecules form a common shaft-like region w/outward protruding heads Includes 2 regulatory proteins (tropomyosin & troponin) Heads referred to as cross-bridges, contain ATP-binding sites and ATPase enzymes

Sliding filament theory 11.2.7 Explain how skeletal muscle contracts, including the release of calcium ions from the SR, the formation of cross-bridges, sliding action of actin and myosin filaments, and use of ATP to break cross bridges and re-set myosin heads. Sliding filament theory Actin myofilaments slide over myosin myofilaments—they don’t shorten! The sarcomere shortens when they slide over each other http://3dotstudio.com/zz.html www.thelifewire.com

Sliding Filament Theory: Motor neuron carries action potential to NMJ (neuromuscular junction) Neurotransmitter, acetylcholine, released into gap b/w axon terminal and sarcolemma of muscle fiber ACh binds to receptors on sarcolemma Sarcolemma ion channels open, Na+ move through Generates muscle action potential Moves along membrane, through T tubules ACh broken down by acetylcholinesterase to make sure one nerve action potential causes only one muscle action potential

Sliding Filament Theory: 8. Muscle action potential going through T tubules causes release of Ca ions from SR. Flood into sarcoplasm. 9. Ca ions bind to troponin on actin—exposes myosin-binding sites 10. Myosin heads include ATPase which splits ATP and releases energy

Sliding Filament Theory: 11. Myosin heads bind to myosin-binding sites on actin with help of tropomyosin (protein) 12. Myosin-actin crossbridges rotate toward center of sarcomere, producing the “power stroke” 13. ATP binds again to myosin head, resulting in detachment of myosin from actin 14. If no more action potentials, Ca ion level in sarcoplasm falls. Troponin-tropomyosin complex moves to its original position, blocking myosin binding sites...muscle relaxes.

WHOAAAA.... When you die...Ca++ leak out of SR, bind to troponin...allows actin to slide. But, no ATP produced when you’re dead, so myosin heads can’t detach from actin: RIGOR MORTIS! Lasts ~24 hrs until muscles deteriorate. Muscle filaments don’t change in length during contraction. The sarcomere shortens (Z line to Z line)...can see in electromicrographs.

11.2.8 Analyze electron micrographs to find the state of contraction of muscle fibers. Which is relaxed, which is contracted? You should also be able to label this!