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