MUSCULAR SYSTEM

Skeletal muscles

• Organs of the muscular system

• Most of them are attached to bone

FUNCTIONS OF THE MUSCULAR SYSTEM

• Locomotion

• Posture 

• Respiration

• Communication

• Constriction 

• Heartbeat

• Body heat regulation

NERVOUS SYSTEM

• Primary coordinating and controlling system of the body

• Divided into:

  • Central nervous system

  • Peripheral nervous system

PROPERTIES OF MUSCLE

• Extensibility

• Elasticity 

• Contractility 

MUSCLE INTERACTION

• Insertion: movable attachment of a muscle

• Origin: immovable attachment

• When a muscle contracts, the insertion is pulled toward the origin

• Agonists: group of muscles producing an action

• Antagonists: opposing  group of muscles

NAMING SKELETAL MUSCLES

• Action: some muscle names include references to their actions in the body

• Attachment: the points of origin and insertion of some muscles

• Location: certain muscles have a reference to location in their names

• Shape: name of certain muscles include references to their shape

• Size relationship: sometimes a muscle names describe a muscle’s size in relation to others

Mobility

• Muscles allow you to move

• When they contract, they allow you to move

• Gross/large movement: walking, running, swimming

• Fine/small movement: writing, using phone, talking

Anterior view = front

Posterior view = back

MAJOR SKELETAL MUSCLES: FACE

• Buccinator: compresses cheeks inward

• Epicranius

• Frontal belly: elevates eyebrows and wrinkles forehead

• Occipital belly: pulls scalp posteriorly

• Orbicularis oculi: closes eye

• Orbicularis oris: closes eye

• Orbicularis oris: closes and puckers lips; shapes lips during speech

• Platysma: draws angle of mouth inferiorly

• Zygomaticus: elevates corners of mouth (smiling)

• Masseter: elevates mandible

• Temporalis: elevates mandible

MUSCLES THAT MOVE THE PECTORAL GIRDLE

• Trapezius: elevates clavicle; abducts and elevates scapula; extends head

• Rhomboid major and minor: adducts and elevates scapula

• Levator scapulae: elevates scapula

• Serratus anterior: depresses, protracts, and rotates scapula

• Pectoralis minor: depresses and protracts scapula

ACTIONS OF THE SCAPULAR MUSCLES

• Scapular muscles perform two functions:

  • Stabilizing scapula when the shoulder complex is loaded

  • Moving and positioning the scapula to facilitate movement 

MUSCLES THAT MOVE THE ARM

• Pectoralis major: abducts, flexes, and medially rotates arm

• Deltoid: abducts, flexes, and extends arm

• Latissimus dorsi: adducts, extends, and medially rotates arm

• Teres major: same as latissimus dorsi

ROTATOR CUFF MUSCLES

• Supraspinatus: abducts arm

• Infraspinatus: laterally rotates arm

• Teres minor: laterally rotates arm

• Subscapularis: medially rotates arm

MUSCLES THAT MOVE THE FOREARM

• Biceps brachii: flexes forearm and supination, also flexes arm

• Brachialis: flexes forearm

• Brachioradialis: flexes forearm

• Triceps brachii: extends forearm, also extends arm

MUSCLES THAT MOVE THE WRIST AND FINGERS

• Flexor carpi radialis: flexes and abducts wrist

• Flexor carpi ulnaris: flexes and adducts wrist

• Palmaris longus: flexes wrist

• Extensor carpi radialis longus: extends and abducts wrist

• Extensor carpi ulnaris: extends and adducts wrist

• Extensor digitorum: extends fingers

MUSCLES IN THE ABDOMINAL WALL (FOR BREATHING)

• Rectus adonis: tightens abdominal wall; flexes the vertebral column

• External oblique: tightens abdominal wall; rotation and lateral flexion of the vertebral column

• Internal oblique: same as above

• Transversus abdominis: tightens abdominal wall

• Diaphragm: forms floor of thoracic cavity; depresses during contraction, causing inspiration

• External intercostals: elevates and protracts ribs during inspiration

• Internal intercostals: depresses and retracts ribs during expiration

MUSCLES THAT MOVE THE THIGH

• Illiacus: flexes thigh

• Psoas major: flexes thigh

• Gluteus maximus: extends and laterally rotates thigh

• Gluteus medius: abducts and medially rotates thigh

• Tensor fasciae latae: flexes and abducts thigh

• Adductor longus: adducts, flexes, and laterally rotates thigh

• Adductor magnus: same as above

MUSCLES THAT MOVE THE LEGS

• Extends leg and flexes thigh

  • Quadriceps femoris

  • Rectus femoris

• Extends leg

  • Vastus lateralis

  • Vastus medialis

  • Vastus intermedius

HAMSTRINGS

• Biceps femoris: flexes and laterally rotates leg; extends thigh

• Flexes and medially rotates thigh

  • Semitendinosus

  • Semimembranosus

• Gracilis: adducts thigh; flexes leg and locks knee

• Sartorius: flexes thigh and leg; abducts and laterally rotates thigh

MUSCLES THAT MOVE THE FOOT AND TOES

• Gastrocnemius: plantar flexes foot and flexes leg

• Solenus: plantar flexes foot

• Fibularis longus: plantar flexes and everts foot; supports arch

• Tibialis anterior: dorsiflexes and inverts foot

• Extensor digitorum longus: dorsiflexes and everts foot; extends toes

3 MAIN TYPES OF MUSCLE CONTRACTION

1. Isotonic and concentric

   • Muscle shortens

   • Generate force by changing the length of the muscle

   • Concentric 

   • Eccentric 

2. Isotonic and eccentric

3. Isometric 

Concentric contraction: muscle shortens; produces tension while shortening to overcome external resistance

Eccentric contraction: muscle lengthens; produces tension while lengthening; bringing weight down

Isometric: muscles stay the same length as they contract; ends of the muscles stay the same distance apart; stabilizing muscles hold parts of the body steady

HOW DO MUSCLES WORK TOGETHER

• If one muscle contracts to bring two bones together, another muscle is needed to contract the bones apart again

• Muscles always work in pairs

• Human needs large numbers of pairs of muscles to work together in diff ways for even simple body movements

• Muscles are usually attached to 2 or more diff bones

Tendon: muscles fiber end in this strong white flexible cord

Periostium: at the bone where the fibers of the tendon are embedded