The Muscular System

• Muscles are attached to bones by tendons which are thick cords of collagen.

• One end of a muscle will be relatively fixed and is called the Origin, eg the Pectorals attach at one end to the sternum which does not move.

• The other end attaches to a bone that moves and this connection is called the Insertion, eg the pectorals attach at one end to the humerus which is pulled towards the sternum when the pectorals contract.

The Muscular SystemAgonist (or Prime Mover) – is the muscle mainly

responsible for causing an action, eg Biceps is the main muscle causing elbow flexion.

Antagonist – is the muscle that is mainly responsible for opposing an action.

Synergists – are muscles that assist agonists in causing a movement, eg Brachioradialis helps the Biceps cause elbow flexion.

Stabilisers – are muscles that keep the body parts in the correct position (stabilised) so an action can occur, eg in a bench press stabilisers keep the arms steady and in the correct position for pushing the weight up.

The Muscular SystemReciprocal Inhibition• In each action the Agonist contracts and the Antagonist

relaxes.

• The Antagonist controls how quickly the Agonist contracts by how slowly it relaxes.

The Muscular System

Biceps Brachii

• Origin – 2 different spots on the scapula

• Insertion – Radius

• Main Action - Elbow flexion

The Muscular System

Triceps Brachii

Origin – scapula & 2 different spots on the humerus

Insertion – Ulna

Main Action – Elbow extension

Synergist Action – shoulder extension

The Muscular System

Erector Spinae

Origin – Ilium(pelvis bone) & various vertebrae

Insertion – Ribs, vertebrae and cranium

Main Action – Spine extension including neck

The Muscular System

Rhomboids

Origin – Spinous process of Cervical no. 7 & first 5 thoracic vertebrae

Insertion – medial border of scapula

Main Action – adducts scapula, slight elevation of scapula and rotation of scapula

The Muscular System

TrapeziusOrigin – base of cranium,

ligaments of neck & cervical 7 and all thoracic vertebrae

Insertion – outer third of clavicle, scapula

Main Action – adducts scapula, slight elevation of scapula and rotation of scapula

The Muscular System

Levator Scapulae

Origin – transverse process of first 4 cervical vertebrae

Insertion – upper medial

border of scapula

Main Action – elevates the scapula, rotates the scapula

The Muscular System

Latissimus Dorsi

Origin – crest of Ilium, sacrum, lumbar and lower 5 thoracic vertebrae

Insertion – humerus

Main Action – adduction of shoulder, extension of shoulder, inward rotation of shoulder

The Muscular System

Pectoralis Major

Origin – clavicle & sternum

Insertion – humerus

Main Action – adduction of shoulder, inward rotation of shoulder

The Muscular System

Deltoid

Origin – clavicle & scapula

Insertion – humerus

Main Action – abduction, flexion, extension of shoulder

The Muscular System

Rectus Abdominis

Origin – crest of Pubis

Insertion – cartilage of 5th, 6th & 7th Ribs

Main Action – flexion of spine

The Muscular System

External Oblique Abdominals

Origin – border of lower 8 ribs

Insertion – crest of Ilium & Pubis, inguinal ligament

Main Action – flexion of spine, right side twists spine left, left side twists spine right

The Muscular System

Internal Oblique Abdominals

Origin – inguinal ligament, crest of Ilium

Insertion – cartilage of 8th, 9th & 10th ribs

Main Action – flexion of spine, right side twists spine right, left side twists spine left

The Muscular System

Transverse Abdominals

Origin – inguinal ligament, crest of Ilium, lower 6 ribs

Insertion – crest of pubis

Main Action – pulls abdominal wall in

The Muscular System

Hamstrings – Biceps Femoris

Origin – Ishium, femur

Insertion – Tibia & Fibula

Main Action – hip extension, knee flexion, outward rotation of thigh

The Muscular System

Hamstrings – Semitendinosus

Origin – Ishium

Insertion – Tibia

Main Action – hip extension, knee flexion, inward rotation of thigh

The Muscular System

Hamstrings – Semimembranosus

Origin – Ishium

Insertion – Tibia

Main Action – hip extension, knee flexion, inward rotation of thigh

The Muscular System

Quadriceps – Rectus Femoris

Origin – Ilium

Insertion – Patella and patella ligament to Tibia

Main Action – hip flexion, knee extension

The Muscular System

Quadriceps – Vastus Lateralis

Origin – Femur

Insertion – Patella and patella ligament to Tibia

Main Action – knee extension

The Muscular System

Quadriceps – Vastus Medialis

Origin – Femur

Insertion – Patella and patella ligament to Tibia

Main Action – knee extension

The Muscular System

Quadriceps – Vastus Intermedius

Origin – Femur

Insertion – Patella and patella ligament to Tibia

Main Action – knee extension

The Muscular System

Iliopsoas

Origin – Inner Ilium, sacrum, last thoracic and all lumber vertebrae

Insertion – Femur

Main Action – Hip flexion, outward rotation of thigh.

The Muscular System

Adductor Longus

Origin – Pubis

Insertion – Femur

Main Action – Hip adduction

Synergist Action – flexion of hip

The Muscular System

Gluteus MaximusOrigin – crest of Ilium,

sacrumInsertion – Femur

Main Action – Hip extension, outwards rotation of thigh

Synergist Action – lower fibre assist in adduction of hip

The Muscular System

Gluteus Medius

Origin – just below crest

Ilium

Insertion – Femur

Main Action – Hip abduction, outwards rotation of thigh

The Muscular System

Gastrocnemius

Origin – bottom of femur

Insertion – Calcaneous(heel bone)

Main Action – Plantar Flexion of ankle, flexion of knee.

The Muscular System

Soleus

Origin – top two 3rds of Tibia & Fibula

Insertion – Calcaneous(heel bone), joins the tendon of the Gastrocnemius.

Main Action – Plantar Flexion of ankle

The Muscular System

Tibialis Anterior

Origin – top two 3rds of front of Tibia

Insertion – tarsal and 1st metatarsal.

Main Action – Dorsi flexion, adduction, inversion.

The Muscular System

Serratus Anterior

Origin – top 9 ribs at side of chest.

Insertion – underneath the medial border of the scapula.

Main Action – Abduction of scapula(shoulder girdle), slight rotation

Muscle typesMuscle types

• SkeletalSkeletal– Striated,– Most of the muscle

mass in the body– Voluntary

• CardiacCardiac– Striated, – Heart– Involuntary

Muscle types continuedMuscle types continued

• SmoothSmooth– Nonstriated, – viscera and all blood

vessels– Involuntary

Comparison

Skeletal MuscleSkeletal Muscle

Skeletal MuscleSkeletal Muscle

SarcomeresSarcomeres• Functional contractile unit of striated muscle• Striations

– Represent the transverse alignment of myofibrils in sarcomeres

– Made up of regular overlapping pattern• of actin (thin filaments)• myosin (thick filaments)

– Delineated by Z lines– Center line is I band– 2-3 m in length

Sliding filament mechanismSliding filament mechanism

• Sarcomeres shortened• Thin filaments(actin)

slide over thick filament(myosin)

• Requires ATP– other proteins and calcium

Motor nerve supplyMotor nerve supply• Neuromuscular Neuromuscular

junctionjunction – motor neuron

and its axonal branches sitting on the skeletal muscle fibers it innervates

• Motor end plateMotor end plate– The end plate of

the neuron

Motor nerve supplyMotor nerve supply• Motor UnitMotor Unit

– The motor neuron and the muscle fibers it innervates

– When a motor unit fires ALL the muscle fibres connected to the motor unit contract.