2Assessment statements State the roles of bones, ligaments, muscles, tendons and nerves in human movement.Label a diagram of the human elbow joint, including cartilage, synovial fluid, joint capsule, named bones and antagonistic muscles (biceps and triceps).Outline the functions of the structures in the human elbow joint named inCompare the movements of the hip joint and the knee joint.Describe the structure of striated muscle fibres, including the myofibrils with light and dark bands, mitochondria, the sarcoplasmic reticulum, nuclei and the sarcolemma.Draw and label a diagram to show the structure of a sarcomere, including Z lines, actin filaments, myosin filaments with heads, and the resultant light and dark bands.Explain how skeletal muscle contracts, including the release of calcium ions from the sarcoplasmic reticulum, the formation of cross-bridges, the sliding of actin and myosin filaments, and the use of ATP to break cross-bridges and re-set myosin heads.Analyse electron micrographs to find the state of contraction of muscle fibres.
3JointsArticulation or arthrosis, point where two or more bones contact one anotherArthrology is the scientific study of jointsRheumatology is the branch of medicine devoted to joint disease and conditionsKinesiology is the scientific study of the movement of the human bodyJoints provide mobility and hold the body togetherInclude: bones, ligaments, muscles, tendons, and nerves
4Bones (living organs) Provide a hard framework to support the body Allow protection of vulnerable softer tissue and organsAct as levers so that body movement can occurForms blood cells in the bone marrowAllows storage of minerals, especially calcium and phosphorus
5Muscles and tendons Muscles attached to bones by tendons Tendons are cords of dense connective tissueArrangement of the bones and the design of the joints determine the type or range of motion possible in any particular area of the bodyMuscles provide force necessary for movement by shortening the length of the fibers or cellsOccur as antagonistic pairs which allow the body part to return to its original position after movement
6Ligaments and nervesLigaments are band-like connective tissue that serves to strengthen the joint and provide stabilityHave many different types of sensory nerve endings which that help to prevent over-extension of the joint and its partsProprioceptors in ligaments and muscles allow constant monitoring of the position of the joint parts
7Elbow jointSynovial fluid is located within the synovial cavity. This cavity is located within the joint capsule. The joint capsule is composed of dense connective tissue that is continuous with the membrane of the involved bones.Joint capsuleEnds of bones lined with cartilageSynovial cavity containing synovial fluid
8Elbow parts and their functions Joint partFunctionCartilageReduces friction and absorbs compressionSynovial fluidLubricates to reduce friction and provides nutrients to the cells of the cartilageJoint capsuleSurrounds the joint, encloses the synovial cavity, and unites the connecting bonesTendonsAttach muscle to boneLigamentsConnect bone to boneBiceps muscleContracts to bring about flexion (bending) of the armTriceps muscleContracts to cause extension (straightening) of the armHumerusActs as a lever that allows anchorage of the muscles of the elbowRadiusActs as a lever for the biceps muscleUlnaActs as a lever for the triceps muscle
9Types of joints Synovial – contain synovial cavity Diarthrotic – freely movableHinge – provides an opening-and-closing type of movementBall-and-socket – permits movement in several directions
10Comparison of the hip and knee joints Hip jointKnee jointFreely movableAngular motions in many directions and rotational movementsAngular motion in one directionMotions possible are flexion, extension, abduction, circumduction, and rotationMotions possible are flexion and extensionBat-like structure fits into a cup-like depressionConvex surface fits into a concave surface
11Definitions Flexion – decrease in angle between connecting bones Extension – increase in angle between connecting bonesAbduction – movement of bone away from body midlineAdduction – movement of bone toward midlineCircumduction – distal or far end of a limb moves in a circleRotation – a bone revolves around its own longitudinal axis
12Muscle Three types: Skeletal or striated Cardiac Smooth or non-striated
13Striated muscle cellsComposed of thousands of cells, which are called muscle fibers b/c of their elongated shapeBlood vessels and nerves penetrate the muscle bodyEach muscle fiber contains multiple nuclei that lie just inside the plasma membrane, which is called the sarcolema
15Sarcolemma has multiple tunnel-like extensions that penetrate the interior of the cell called transverse or T tubulescytoplasm of muscle fibers is called the sarcoplasmSarcoplasm contains large numbers of glycosomes that store glycogenSarcoplasm also contains large amounts of myoglobin
16Sarcoplasmic reticulum is a fluid-filled system of membranous sacs surrounding the muscle myofibrils Myofibrils are rod-shaped bodies that run the length of the cell and are the contractile elements of the muscle cellMyofibrils run parallel to one another and have numerous mitochondria squeezed between them
17Myofibrils Made up of sarcomeres which allow movement Often described as banded:Z lines mark the ends of the sarcomereA bands are dark in color and extend the entire length of the myosin filaments; narrow H band occurs in the middle containing only myosin, no actin; supporting protein occurs in the middle of myosin producing M lineI bands are light in color and contain only actin, no myosin
19Two types of filaments or myofilaments that cause the banded appearance of the muscle fiber These two myofilaments are composed of two contractile proteins, actin and myosin
20ActinMyosinThin filaments (8 nm in diameter)Thick filaments (16 nm in diameter)Contains myosin-binding sitesContains myosin heads that have actin-binding sitesIndividual molecules form helical structuresIndividual molecules form a common shaft-like region with outward protruding headsIncludes two regulatory proteins, tropomyosin and troponinHeads are referred to as cross-bridges and contain ATP-binding sites and ATPase enzymes
21Muscle ContractionExplained by the sliding filament theory proposed by Hugh Huxley in 1954States that muscles contract when actin myofilaments slide over myosin myofilaments
22Sliding Filament Theory Motor neuron carries an action potential until it reaches a neuromuscular junctionNeurotransmitter called acetylcholine is released into the gap between the axon terminal and the sarcolemma of the muscle fiberAcetylcholine bines to receptors in the sarcolemmaSarcolemma ion channels open and sodium ions move through the membrane
23Muscle action potential is generated Muscle action potential moves along the membrane and through the T tubulesAcetylcholine is broken down by acetylcholinesteraseMuscle action potential moving along T tubule causes release of calcium ions from the sarcoplasmic reticulum. Calcium ions flood into the sarcoplasm
24Calcium ions bind to troponin on the actin myofilaments Calcium ions bind to troponin on the actin myofilaments. This exposes the myosin-binding sitesMyosin heads include ATPase which splits ATP and releases energyMyosin heads then bind to the myosin-binding sites on the actin with the help of the protein called tropomyosinMyosin-actin cross-bridges rotate toward the center of the sarcomere. This produces the power or working stroke.
25ATP once again binds to the myosin head resulting in the detachment of myosin from the actin If there are no further action potentials, the level of calcium ions in the sarcoplasm falls. The troponin-tropomyosin complex then moves to its original position, thus blocking the myosin-binding sites. The muscle then relaxes.
27Rigor mortisAfter death, calcium ions leak out of the sarcoplasmic reticulum and bind to troponinThis allows actin to slide, but lack of ATP production prevents myosin heads from detaching from the actinResult is rigidity for about 24 hours unter further muscle deterioration occurs
29When the muscle is maximally contracted, the H zone disappears, the Z lines move closer together, the I bands are no longer present, and the A bands appear to run the complete length of the sarcomeresCan be in various states of partial contractionThis causes a difference in the position of the sarcomere partsThe number of muscle fibers in a muscle going through contraction determines the overall strength of a muscle contraction