muscle and movement topic 11.2. assessment statements 11.2.1 state the roles of bones, ligaments,...
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Muscle and movement
Topic 11.2
Assessment statements
11.2.1 State the roles of bones, ligaments, muscles, tendons and nerves in human movement.
11.2.2 Label a diagram of the human elbow joint, including cartilage, synovial fluid, joint capsule, named bones and antagonistic muscles (biceps and triceps).
11.2.3 Outline the functions of the structures in the human elbow joint named in 11.2.2.
11.2.4 Compare the movements of the hip joint and the knee joint.
11.2.5 Describe the structure of striated muscle fibres, including the myofibrils with light and dark bands, mitochondria, the sarcoplasmic reticulum, nuclei and the sarcolemma.
11.2.6 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.
11.2.7 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.
11.2.8 Analyse electron micrographs to find the state of contraction of muscle fibres.
Joints
Articulation or arthrosis, point where two Articulation or arthrosis, point where two or more bones contact one anotheror more bones contact one another
Arthrology is the scientific study of jointsArthrology is the scientific study of joints Rheumatology is the branch of medicine Rheumatology is the branch of medicine
devoted to joint disease and conditionsdevoted to joint disease and conditions Kinesiology is the scientific study of the Kinesiology is the scientific study of the
movement of the human bodymovement of the human body Joints provide mobility and hold the body Joints provide mobility and hold the body
togethertogether Include: bones, ligaments, muscles, Include: bones, ligaments, muscles,
tendons, and nervestendons, and nerves
Bones (living organs)
Provide a hard framework to support Provide a hard framework to support the bodythe body
Allow protection of vulnerable softer Allow protection of vulnerable softer tissue and organstissue and organs
Act as levers so that body movement Act as levers so that body movement can occurcan occur
Forms blood cells in the bone marrowForms blood cells in the bone marrow Allows storage of minerals, especially Allows storage of minerals, especially
calcium and phosphoruscalcium and phosphorus
Muscles and tendons Muscles attached to bones by tendonsMuscles attached to bones by tendons Tendons are cords of dense connective tissueTendons are cords of dense connective tissue Arrangement of the bones and the design of Arrangement of the bones and the design of
the joints determine the type or range of the joints determine the type or range of motion possible in any particular area of the motion possible in any particular area of the bodybody
Muscles provide force necessary for Muscles provide force necessary for movement by shortening the length of the movement by shortening the length of the fibers or cellsfibers or cells
Occur as antagonistic pairs which allow the Occur as antagonistic pairs which allow the body part to return to its original position body part to return to its original position after movementafter movement
Ligaments and nerves
Ligaments are band-like connective Ligaments are band-like connective tissue that serves to strengthen the tissue that serves to strengthen the joint and provide stabilityjoint and provide stability
Have many different types of sensory Have many different types of sensory nerve endings which that help to nerve endings which that help to prevent over-extension of the joint prevent over-extension of the joint and its partsand its parts
Proprioceptors in ligaments and Proprioceptors in ligaments and muscles allow constant monitoring of muscles allow constant monitoring of the position of the joint partsthe position of the joint parts
Elbow joint
Ends of bones lined with cartilage
Synovial cavity containing synovial fluid
Joint capsule
Synovial 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.
Elbow parts and their functions
Joint part Function
Cartilage Reduces friction and absorbs compression
Synovial fluid Lubricates to reduce friction and provides nutrients to the cells of the cartilage
Joint capsule Surrounds the joint, encloses the synovial cavity, and unites the connecting bones
Tendons Attach muscle to bone
Ligaments Connect bone to bone
Biceps muscle Contracts to bring about flexion (bending) of the arm
Triceps muscle Contracts to cause extension (straightening) of the arm
Humerus Acts as a lever that allows anchorage of the muscles of the elbow
Radius Acts as a lever for the biceps muscle
Ulna Acts as a lever for the triceps muscle
Types of joints
Synovial – contain synovial cavitySynovial – contain synovial cavity Diarthrotic – freely movableDiarthrotic – freely movable Hinge – provides an opening-and-Hinge – provides an opening-and-
closing type of movementclosing type of movement Ball-and-socket – permits Ball-and-socket – permits
movement in several directionsmovement in several directions
Comparison of the hip and knee joints
Hip joint Knee joint
Freely movable Freely movable
Angular motions in many directions and rotational movements
Angular motion in one direction
Motions possible are flexion, extension, abduction, circumduction, and rotation
Motions possible are flexion and extension
Bat-like structure fits into a cup-like depression
Convex surface fits into a concave surface
Definitions Flexion – decrease in angle between Flexion – decrease in angle between
connecting bonesconnecting bones Extension – increase in angle between Extension – increase in angle between
connecting bonesconnecting bones Abduction – movement of bone away from Abduction – movement of bone away from
body midlinebody midline Adduction – movement of bone toward Adduction – movement of bone toward
midlinemidline Circumduction – distal or far end of a limb Circumduction – distal or far end of a limb
moves in a circlemoves in a circle Rotation – a bone revolves around its own Rotation – a bone revolves around its own
longitudinal axislongitudinal axis
Muscle
Three types:Three types: Skeletal or striatedSkeletal or striated CardiacCardiac Smooth or non-striatedSmooth or non-striated
Striated muscle cells
Composed of thousands of cells, Composed of thousands of cells, which are called muscle fibers b/c which are called muscle fibers b/c of their elongated shapeof their elongated shape
Blood vessels and nerves Blood vessels and nerves penetrate the muscle bodypenetrate the muscle body
Each muscle fiber contains Each muscle fiber contains multiple nuclei that lie just inside multiple nuclei that lie just inside the plasma membrane, which is the plasma membrane, which is called the called the sarcolemasarcolema
Sarcolemma has multiple tunnel-like Sarcolemma has multiple tunnel-like extensions that penetrate the interior extensions that penetrate the interior of the cell called of the cell called transverse or T transverse or T tubulestubules
cytoplasm of muscle fibers is called cytoplasm of muscle fibers is called the the sarcoplasmsarcoplasm
Sarcoplasm contains large numbers of Sarcoplasm contains large numbers of glycosomes that store glycogenglycosomes that store glycogen
Sarcoplasm also contains large Sarcoplasm also contains large amounts of amounts of myoglobinmyoglobin
Sarcoplasmic reticulumSarcoplasmic reticulum is a fluid-filled is a fluid-filled system of membranous sacs system of membranous sacs surrounding the muscle myofibrilssurrounding the muscle myofibrils
MyofibrilsMyofibrils are rod-shaped bodies that are rod-shaped bodies that run the length of the cell and are the run the length of the cell and are the contractile elements of the muscle contractile elements of the muscle cellcell
Myofibrils run parallel to one another Myofibrils run parallel to one another and have numerous mitochondria and have numerous mitochondria squeezed between themsqueezed between them
Myofibrils Made up of sarcomeres which allow Made up of sarcomeres which allow
movementmovement Often described as banded:Often described as banded:
Z lines mark the ends of the sarcomereZ lines mark the ends of the sarcomere A bands are dark in color and extend the A bands are dark in color and extend the
entire length of the myosin filaments; entire length of the myosin filaments; narrow H band occurs in the middle narrow H band occurs in the middle containing only myosin, no actin; containing only myosin, no actin; supporting protein occurs in the middle of supporting protein occurs in the middle of myosin producing M linemyosin producing M line
I bands are light in color and contain only I bands are light in color and contain only actin, no myosinactin, no myosin
Two types of filaments or Two types of filaments or myofilaments that cause the myofilaments that cause the banded appearance of the muscle banded appearance of the muscle fiberfiber
These two myofilaments are These two myofilaments are composed of two contractile composed of two contractile proteins, proteins, actinactin and and myosinmyosin
Actin Myosin
Thin filaments (8 nm in diameter)
Thick filaments (16 nm in diameter)
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 with outward protruding heads
Includes two regulatory proteins, tropomyosin and troponin
Heads are referred to as cross-bridges and contain ATP-binding sites and ATPase enzymes
Muscle Contraction
Explained by the sliding filament theory proposed by Hugh Huxley in 1954
States that muscles contract when actin myofilaments slide over myosin myofilaments
Sliding Filament Theory
1.1. Motor neuron carries an action potential until Motor neuron carries an action potential until it reaches a neuromuscular junctionit reaches a neuromuscular junction
2.2. Neurotransmitter called acetylcholine is Neurotransmitter called acetylcholine is released into the gap between the axon released into the gap between the axon terminal and the sarcolemma of the muscle terminal and the sarcolemma of the muscle fiberfiber
3.3. Acetylcholine bines to receptors in the Acetylcholine bines to receptors in the sarcolemmasarcolemma
4.4. Sarcolemma ion channels open and sodium Sarcolemma ion channels open and sodium ions move through the membraneions move through the membrane
5.5. Muscle action potential is generatedMuscle action potential is generated
6.6. Muscle action potential moves along the Muscle action potential moves along the membrane and through the T tubulesmembrane and through the T tubules
7.7. Acetylcholine is broken down by Acetylcholine is broken down by acetylcholinesterase acetylcholinesterase
8.8. Muscle action potential moving along T Muscle action potential moving along T tubule causes release of calcium ions tubule causes release of calcium ions from the sarcoplasmic reticulum. from the sarcoplasmic reticulum. Calcium ions flood into the sarcoplasmCalcium ions flood into the sarcoplasm
9.9. Calcium ions bind to troponin on the actin Calcium ions bind to troponin on the actin myofilaments. This exposes the myosin-myofilaments. This exposes the myosin-binding sitesbinding sites
10.10. Myosin heads include ATPase which splits Myosin heads include ATPase which splits ATP and releases energyATP and releases energy
11.11. Myosin heads then bind to the myosin-Myosin heads then bind to the myosin-binding sites on the actin with the help of binding sites on the actin with the help of the protein called tropomyosinthe protein called tropomyosin
12.12. Myosin-actin cross-bridges rotate toward Myosin-actin cross-bridges rotate toward the center of the sarcomere. This produces the center of the sarcomere. This produces the power or working stroke.the power or working stroke.
13.13.ATP once again binds to the myosin head ATP once again binds to the myosin head resulting in the detachment of myosin resulting in the detachment of myosin from the actinfrom the actin
14.14. If there are no further action potentials, If there are no further action potentials, the level of calcium ions in the sarcoplasm the level of calcium ions in the sarcoplasm falls. The troponin-tropomyosin complex falls. The troponin-tropomyosin complex then moves to its original position, thus then moves to its original position, thus blocking the myosin-binding sites. The blocking the myosin-binding sites. The muscle then relaxes.muscle then relaxes.
Useful websites
http://3dotstudio.com/zz.htmlhttp://3dotstudio.com/zz.html http://www.blackwellpublishing.com/http://www.blackwellpublishing.com/
Matthews/myosin.htmlMatthews/myosin.html http://entochem.tamu.edu/http://entochem.tamu.edu/
musclestruccontractswf/index.htmlmusclestruccontractswf/index.html http://highered.mcgraw-hill.com/http://highered.mcgraw-hill.com/
sites/0072495855/student_view0/sites/0072495855/student_view0/chapter10/chapter10/animation__sarcomere_contraction.htanimation__sarcomere_contraction.htmlml
Rigor mortis
After death, calcium ions leak out of After death, calcium ions leak out of the sarcoplasmic reticulum and bind the sarcoplasmic reticulum and bind to troponinto troponin
This allows actin to slide, but lack of This allows actin to slide, but lack of ATP production prevents myosin ATP production prevents myosin heads from detaching from the actinheads from detaching from the actin
Result is rigidity for about 24 hours Result is rigidity for about 24 hours unter further muscle deterioration unter further muscle deterioration occursoccurs
Electron Micrograph
When the muscle is maximally contracted, the When the muscle is maximally contracted, the H zone disappears, the Z lines move closer H zone disappears, the Z lines move closer together, the I bands are no longer present, together, the I bands are no longer present, and the A bands appear to run the complete and the A bands appear to run the complete length of the sarcomereslength of the sarcomeres
Can be in various states of partial contractionCan be in various states of partial contraction This causes a difference in the position of the This causes a difference in the position of the
sarcomere partssarcomere parts The number of muscle fibers in a muscle going The number of muscle fibers in a muscle going
through contraction determines the overall through contraction determines the overall strength of a muscle contractionstrength of a muscle contraction