Kin 216 chapters 11 $ 12

Patterns of fascicle arrangement

• circular

• parallel

• convergent

• pennate

Circular arrangement

Fascicles arranged concentrically around an opening

• Ex: orbicularis oculi,

Parallel arrangement

Fascicles are parallel to the long axis of the muscle

• Ex: biceps brachii

Convergent arrangement

Fascicles are widespread (triangular muscles) which converge at a common attachment site

• Considered “versatile”

  • Change movement/directions based on stimulated muscle fibers

  • Ex. pectoralis major muscle of the chest

Pennate (“feather”) arrangement

Fascicles are arranged at an oblique angle to the tendon

Unipennate

same side of tendon

• extensor digitorum

Bipennate

both sides of tendon

• rectus femoris

Multipennate

tendon branches within muscle

• deltoid

Levers

Elongated, rigid bar (bone) that rotates around a fixed point, which is called a fulcrum (joint)

Forces

Two opposing forces where movement occurs when the effort applied to one point of the lever exceeds the resistance at another point

Effort force

(applied force); force to move resistance (load)

Resistance (load)

object being moved

Effort Arm

portion of the level from the fulcrum to effort

Resistance Arm

portion of the lever from the fulcrum to resistance

Mechanical Advantage 

Effort arm (distance from fulcrum to effort) is greater than the resistance arm (distance from fulcrum to resistance)

First-class lever

• Effort: End of lever

• Fulcrum: Middle (between effort & resistance)

• Resistance: End of lever

• Example:

  • Atlanto-occipital joint

Second-class lever

• Effort: End of lever

• Fulcrum: End of lever

• Resistance: Middle (between effort and fulcrum)

  • Uncommon in the human body

• Example:

  • Wheelbarrow; standing on toes

Third-class lever

• Effort: Middle (between fulcrum & resistance)

• Fulcrum: End of lever

• Resistance: End of lever

  • Most common in body

• Example:

  • Elbow flexion (biceps brachii)

Agonist

Muscle contracting produces the movement

• Ex: Triceps brachii (elbow extension)

Antagonist

Muscle whose action opposes the agonist

• Ex: Biceps brachii is the antagonist to the triceps brachii for elbow extension

Synergist

Muscle that assists the agonist in performing the action

• Includes stabilizer muscles

Skeletal Muscle includes

Origin:

• Attaches to bone at a relatively fixed point (the origin).

• Example: The biceps brachii originates at the scapula.

Insertion:

• Attaches to bone that moves when the muscle contracts.

• Example: The biceps brachii inserts on the radius.

Action:

• Voluntary contraction moves the skeleton (e.g., flexion, extension, abduction).

• Controlled by the somatic nervous system.

Smooth Muscle includes

Origin / Insertion:

• Not attached to bones — found in walls of hollow organs (e.g., intestines, blood vessels, bladder).

• Fibers are arranged in layers rather than having defined origin and insertion points.

Action:

• Involuntary contractions move materials through organs (peristalsis, vasoconstriction, etc.).

• Controlled by the autonomic nervous system.Cardiac

Cardiac Muscle includes

Origin / Insertion:

• Found only in the heart — cells interconnect at intercalated discs.

• No distinct origin/insertion points like skeletal muscle.

Action:

• Involuntary rhythmic contractions pump blood throughout the body.

• Generates its own electrical impulses (autorhythmic).

Unilateral

one muscle (left or right) contracts

Bilateral

both muscles (right and left) contract

Sternocleidomastoid

• Origin: Manubrium and sternal end of clavicle

• Insertion: Mastoid process of temporal bone

• Action(s):

  • Unilateral: Lateral flexion of neck; rotation of head

  • Bilateral: Neck flexion

Erector spinae

• Muscles that maintain posture

• Actions:

  • Unilateral: Flexion of vertebral column (towards contracting side)

  • Bilateral: Extension of vertebral column

Iliocostalis (erector spinae)

most lateral group

• Origin(s): Iliac crest, sacrum, lumbar vertebrae (spinous process)

• Insertion(s): ribs, cervical vertebrae

Longissiumus (erector spinae)

intermediate group

• Origin(s): Iliac crest, sacrum, lumbar vertebrae (spinous process)

• Insertion(s): mastoid process (temporal bone), cervical and thoracic vertebrae

Spinalis (erector spinae)

most medial group

• Origin(s): Spinous processes of lumbar vertebrae & C7

• Insertion(s): Spinous process of axis (C2) and thoracic vertebrae

Diaphragm

• Origin(s): xiphoid process (sternum), ribs 5-10, lumbar vertebrae

• Insertion(s): central tendon of diaphragm

• Action: contraction via flattening of muscle; expansion of thoracic cavity

Internal/External Intercostals

• Origin(s): inferior border of superior rib

• Insertion(s): superior border of inferior rib

• Actions:

  • External: elevates ribs during inhalation

  • Internal: depress ribs during forced exhalation

Abdomen (sheets of muscle)

Action(s):

• Unilateral: laterally flexes vertebral column

• Bilateral: flexes and stabilizes vertebral column

Abdominal Muscles 

• Rectus abdominis

• External oblique

• Internal oblique

• Transverse abdominis

Rectus Abdominis

• Origin: xiphoid process (sternum), ribs 5-7

• Insertion: superior surface of pubis near pubis symphysis

• Action: flexes vertebral column (trunk flexion)

Pectoral Girdle

Muscles that stabilize or move the scapula

• Major muscle(s):

  • Trapezius (posterior)

Trapezius

• Origin: occipital bone, C7-T12

• Insertion: clavicle, acromion process (scapula) & spine (scapula)

• Actions:

  • Elevation, retraction, depression of scapula

Glenohumeral Joint

• Muscles that move the arm at the glenohumeral joint can have two separate proximal attachment locations (origins):

• 1) Located on axial skeleton (2)

• 2) Located on the scapula (7)

Latissimus dorsi

• Origin(s): thoracic vertebrae, ribs, iliac crest

• Insertion: Intertubercular sulcus (humerus)

• Action(s): Agonist of arm extension; adducts arm; medially rotates arm

Pectoralis Major

• Origin(s): clavicle, costal cartilage (ribs 2-6), body of sternum

• Insertion: lateral part of intertubercular sulcus (humerus)

• Action(s): Agonist of arm flexion; adducts arm; medially rotates arm

Deltoid

Multi-pennate muscle

• Action(s):

  • Anterior – Shoulder flexion

  • Middle – Shoulder abduction

  • Posterior – Shoulder extension

Supraspinatus

shoulder abduction

Infraspinatus

lateral rotation (shoulder)

Subscapularis

medial rotation (shoulder)

Teres minor

lateral rotation teres (shoulder)

Arm

• Anterior compartment (flexors)

• Posterior compartment (extensors)

• Anterior compartment

  • Biceps brachii

• Posterior compartment

  • Triceps brachii

Biceps Brachii

• Origin(s):

• Short head: coracoid process (scapula)

• Long head: supraglenoid tubercle (scapula)

• Insertion: radial tuberosity

• Action(s): elbow flexion and supination

Tricpes Brachii

• Origin(s):

• Long head: infraglenoid tubercle (scapula)

• Medial head: lower half of humerus (posterior)

• Lateral head: upper half of humerus (posterior)

• Insertion: olecranon process of ulna

• Action(s): elbow extension

Hip Joint actions

• rectus femoris - hip flexion

• glutes

• hamstrings - hip extension

Gluteus maximus

hip/thigh extension; laterally rotates thigh

Gluteus medius

hip/thigh abduction; medially rotates thigh

Gluteus minimus

hip/thigh abduction; medially rotates thigh

Knee Joint actions

• quadriceps femoris - knee extension

• hamstrings - knee flexion

Leg Muscles

• tibialis anterior

• gastrocnemius

• soleus

Tibialis Anterior

• Origin(s): lateral/proximal shaft of tibia, interosseous membrane

• Insertion: medial cuneiform, 1^st metatarsal

• Action(s): Agonist for dorsiflexion (foot)

Gastrocnemius (calf)

• Origin(s):

• Lateral head: lateral condyle of femur

• Medial head: medial condyle of femur

• Insertion: calcaneus

• Action(s): Agonist for plantarflexion (foot)

Soleus

• Origin(s): proximal shaft of fibula; medial border of tibia

• Insertion: calcaneus

• Action(s): plantarflexion (foot)