Muscles

Muscles

MusclesThere are over 660 skeletal muscles in the body.Used to create all voluntary movement.Contract and relax

There are three types of muscle tissue:SkeletalCardiacSmooth

Skeletal MusclesAttached to bones and/or skinAlso known as striated musclesResponsible for movement and postureAny other functions?

Anterior and posterior view of superficial muscles

Anterior and posterior view of major muscles of the arms, torso & legs

How muscles work

A muscles origin occurs where it is attached to a stable bone.A muscles insertion occurs where it attached to a bone that it pulls on and moves.

Muscles work in pairs or groups. The muscle that creates the movement is known as the agonist whilst the opposite muscle is known as the antagonist.

Reciprocal inhibition occurs when one muscle contracts and its opposite relaxes to allow movements to occur.

Smooth MuscleSmooth muscle is found in the walls of hollow visceral (internal) organs such as the stomach, bladder and respiratory passages. Smooth muscle acts to propel substances along a pathway. Involuntary

Cardiac MuscleCardiac muscle is found only in the heart. When these muscles contract the internal chambers of the heart become smaller, forcing blood into the large arteries that leave the heart.Involuntary

Connective TissueCartilage:Slightly elastic tissue that is found on the ends of bones in synovial joints, in between vertebrae, joining the ribs to the sternum, in the pubic arch and in the ears and nose.Ligaments Cross over joints, joining bone to bone and providing stability at the joints.Slightly elastic TendonsAttach muscle to bones and allows the muscles to move the bones.Inelastic

CartilageHyaline cartilageEnd of bones (in joints), nose, ribs, trachea, larynxEmbryonic skeletonElastic cartilageEarsEpiglottisFibrocartilageIntervertebral discs & pubic archWhere tendons and ligaments join to bone

*The next image shows surgery on an Achilles tendon. It contains blood etc.

Nervous control of muscle contractionsNerves deliver messages to the muscles to tell them to contract.

Muscle fibresFusiformFibres run in the same direction as the tendon.Low force but large movement. Quick contractions and high power.Long muscle fibres.

PenniformFibres run at angles to the tendon.75% of all skeletal muscle.Great force/strength but slower contractions than fusiform.Short muscle fibres.Muscle fibre arrangement

The microscopic structure of musclesp 16 18*

Each muscle belly consists of thousands of fibres.Each fibre is surrounded by endomysium.Bundles of fibres are called fascicles.Fascicles are surrounded by perimysium.Bundles of fascicles are held together by epimysium (outside of the muscle).

The microscopic structure of muscles

Muscle fibres are made up of myofibrils.Myofibrils consist of sarcomeres, which are arranged end to end for the entire length of the fibre, and are separated by dark lines called Z-lines.Myofibrils are further divided into myofilaments.Myofilamentsa think filament (myosin)a thin filament (actin)

The microscopic structure of muscles

Nervous control of muscular contractions

Motor neurons convey nerve impulses from the brain to muscles

A motor neuron and the fibres it controls/stimulates are known as the motor unit

Sensory neurons convey nerve impulses from muscles, organs and cells to the brain

The all or nothing principles states:

It is not until an electrical threshold is surpassed that all of the fibres linked to a motor unit will fire together and maximally.

Gross movements requiring major muscle involvement require more motor units than precise/ fine movements

Fibres will be recruited according to the activity demand and this is known as preferential recruitment

How muscles contract (p. 21)

Insert 1.23

Types of ContractionsThere are three types of muscular contraction:IsotonicIsometricIsokineticIsotonicThese contractions change the length of the muscle while creating the force. There are two types of isotonic contractions:ConcentricShortening the muscleEccentricLengthening the muscle

IsometricThese contractions create a force, but do not change the length of the muscle. For example:Pushing against an opponentHolding a netballThese types of contractions create more force than any other type of contraction, and cause the muscle to tire quickly.

IsokineticTension developed is maximal throughout the entire range of motion and is common on hydraulic fitness equipment. The amount of force applied by the machine always equals the amount of force applied by the muscle.This can only be done with isokinetic equipment.

Muscle FibresSlow twitchType I fibresSuited to endurance athletesIncreased capacity to use oxygenContract slowly with less forceCapacity to contract for long period of timeDont fatigue easily

Muscle Fibres contFast twitchType II fibresType A partially aerobicType B purely aerobicSuited to speed and strengthContract rapidly with greater forceCapacity to contract for short periods of timeFatigue easily

% of fast-twitch muscle fibres found in various athletes

Characteristics of muscle fibresTable 1.4, page 25.

Factors affecting muscle strengthFibre arrangementPennate Vs FusiformMuscle fibre recruitmentMore motor units recruited = more strengthMuscle fibre typeFast twitch are stronger than slow twitchSpeed of contractionAs the speed of contraction increases, strength decreases.Gender differencesSame cross-sectional area = same strengthAge differencesMuscles are strongest between 20-30.ActivityChoose three actions/physical activities:Name the major muscles being used.Name the type of contraction being demonstrated.Name the muscle fibre needed to best perform this action, and explain why.