Muscles of the Body with pictures

Sternocleidomastoid*

Action: together they flex the neck; alone they rotate the head

Platysma

Action: tense skin of neck; depress mandible

Pectorals Major*

Action: flexion, adduction, and medial rotation of shoulder

Pectoralis Minor

Action: depress and protract shoulder, rotate glenoid cavity inferiorly or elevate ribs(scapula fixed)

Rectus Abdominus*

Action: flex spinal column

Diaphragm

Action: expand thorax, compress abdomen(respiration)

External Oblique

Action: compress abdomen, depress ribs, flex or rotate spine

Internal Oblique

Action: compress abdomen, depress ribs, flex or rotate spine

Transversus Abdominus

Action: compress abdomen

Trapezius*

Action: extend neck; elevate, retract, depress, or rotate scapula upward; elevate clavicle

Teres Major

Action: extension, medial rotation, adduction of shoulder

Teres Minor

Action: lateral rotation of shoulder

Latissimus Dorsi*

*Action: extension, medial rotation, adduction of shoulder

Erector Spinae Group*

Action: extend spine, flex spine, extend neck

Serratus Anterior

Action: protract shoulder, rotate glenoid cav superiorly or elevate ribs (scap fixed)

Subscapularis

Action: medial rotation of shoulder

Infraspinatus

Action: lateral rotation of shoulder

Supraspinatus

Action: abduction of shoulder

Rhomboid Major

Action: adduct scapula, downward rotation of scapula

Rhomboid Minor

Action: adduct scapula, downward rotation of scapula

Occipitofrontalis (epicranius)

Action: raise eyebrows, wrinkle forehead

Orbicularis Oris

Action: compress lips, pucker lips(kissing muscle)

Orbicularis Oculi

Action: close eyelids(blink)

Zygomaticus Major

Action: retract and elevate corner of mouth

Zygomaticus Minor

Action: retract and elevate upper teeth

Masseter*

Action: elevate mandible

Buccinator

Action: pull back corners of lips

Temporalis*

Action: elevate mandible

Sternohyoid

Action: depress hyoid bone and larynx

Deltoid*

Action: together:abduction of shoulder; anterior part: flexion and medial rotation of shoulder; posterior part: extension and lateral rotation of shoulder

Biceps Brachii

Action: flexion of elbow, flexion of shoulder, assist supination

Triceps Brachii

Action: extension of elbow(long head also contributes to extension and adduction of shoulder)

Brachialis

Action: flexion of elbow

Brachioradialis

Action: flexion of elbow

Pronator Teres

Action: pronation of forearm

Extensor Digitorum

Action: extension of fingers and wrist

Palmaris Longus

Origin: medial epicondyle of humerus

Insertion: palmar aponeurosis and flexor retinaculum

Action: flexion of wrist

Flexor Carpi Radialis

Action: flexion and abduction of wrist

Flexor Carpi Ulnaris

Action: flexion and adduction of wrist

Extensor Carpi Ulnaris

Action: extension and adduction of wrist

Extensor Carpi Radialis Longus

l

Action: extension and abduction of wrist

Abductor Pollicis Longus

Action:abduction of thumb and wrist

Rectus Femoris*

Action: extension of knee, flexion of hip

Vastus Lateralis

Action: extension of knee

Vastus Medialis

Action: extension of knee

Vastus Intermedius

Action:extension of knee

Sartorius*

Action: flexion of knee, flexion and lateral rotation of hip

Biceps Femoris

Action: flexion of knee, extension and lateral rotation of hip

Semitendinosus

Action: flexion of knee, extension and medial rotation of hip

Semimembranosus

Action: flexion of knee, extension and medial rotation of hip

Adductor Magnus

Action: adduction and medial rotation of hip

Adductor Longus

Action: adduction, flexion, and medial rotation of hip

Gluteus Maximus*

Action: extension and lateral rotation of hip

Gluteus Medius

Action: abduction and medial rotation of hip

Gluteus Minimus

Action: abduction and medial rotation of hip

Tensor Fasciae Latae

Action: flexion and medial rotation of hip, support and knee joint

Iliopsoas

Action: flexion of hip

Iliotibial Tract

Band of longitudinal fibers on lateral side of fascia lata, connects distally to the lateral condyle of tibia

Gracilis

Action: flexion of knee, adduction and medial rotation of hip

Gastrocnemius*

Action: ankle extension, foot inversion, and knee flexion

Soleus*

Action: ankle extension

Tibialis Anterior

Action: ankle flexion, inversion of foot

Pectineus

Action: flexion, medial rotation and adduction of hip

Plantaris

Action: ankle extension, knee flexion

Piriformis

Action: abduction of hip

Extensor Digitorum Longus

Action: extension of toes 2-5

Fibularis (peroneus) Longus*

Action: foot eversion, ankle extension

Fibularis (peroneus) Brevis*

Action:foot eversion, ankle extension

Flexor Hallucis Longus*

Action: flexion of great toe

skeletal muscle

A muscle that is attached to the bones of the skeleton and provides the force that moves the bones.

cardiac muscle

Involuntary muscle tissue found only in the heart.

smooth muscle

Involuntary muscle found inside many internal organs of the body

function of muscle tissue

-movement

–maintain posture

–stabilize joints

–generate heat

–regulate flow of materials through hollow organs

Properties of muscle tissue

excitability, contractility, extensibility, elasticity, conductivity

structure of muscle fiber

each fiber cell is packed with myofibrils which is packed with myofilaments.

myocyte/muscle fiber

individual muscle cell inside fascicle

Sarcoplasm

cytoplasm of a muscle cell

Sarcolemma

plasma membrane of a muscle fiber

sarcoplasmic reticulum

Organelle of the muscle fiber that stores calcium.

Myofibrils

Microscopic protein filaments that make up muscle cells.

Endomysium

Connective tissue surrounding a muscle fiber

transverse tubules

System of tubules that provides channels for ion flow throughout the muscle fibers to facilitate the propagation of an action potential.

Myofilaments

filaments of myofibrils, constructed from proteins, principally myosin or actin

thick filaments

composed of myosin

thin filaments

composed of actin

Sarcomere

Contractile unit of muscle

I bands (light)

-Composed of thin actin filaments

-attach to Z disks or Z lines (A Z line is the point at which the actin filaments from adjacent sarcomeres interweave to create lines.)

Z disc

coin-shaped sheet of proteins that anchors the thin filaments and connects myofibrils to one another

Fascicle

bundle of muscle fibers

Perimysium

Connective tissue surrounding a fascicle

Epimysium

surrounds entire muscle

fascia

a band or sheet of fibrous connective tissue that covers, supports, and separates muscle

sliding filament mechanism

The explanation of how thick and thin filaments slide relative to one another during striated muscle contraction to decrease sarcomere length

membrane potential

The voltage across a cell's plasma membrane.

neuromuscular junction

point of contact between a motor neuron and a skeletal muscle cell

muscle contraction steps

1) Motor neuron releases acetylcholine into the neuromuscular junction and causes the depolarization of the sarcolemma.

2) Depolarization spreads down the sarcolemma to the T-tubules, triggering the release of Ca2+ ions.

3) Ca2+ binds to troponin, causing a shift in tropomyosin and exposure of the myosin-binding site on the actin filament.

4) Shortening of the sarcomere occurs as the myosin head binds to the exposed sites of actin, forming a cross-bridge and pulling the actin filament along the thick filament, resulting in contraction.

5) Muscle relaxes when acetylcholine is degraded by acetylcholine esterase and the allowing Ca2+ is brought back into the SR. ATP binds to myosin head, allowing it to relax from actin.

How does muscle contraction occur?

The cross bridges 'grab hold' of the actin filaments and pull them in order to cause contraction - ATP supplies energy for this

Troponin

regulatory protein that binds to actin, tropomyosin, and calcium

Tropomyosin

covers myosin binding sites on the actin molecules

Actin

A globular protein that links into chains, two of which twist helically about each other, forming microfilaments in muscle and other contractile elements in cells.