HAN 200 - Muscles

Functions of Muscles

• Movement

• Stability

• Control of Body Openings

• Heat Production

• Hormone Secretion

• Glycemic Control

Agonist/Prime Mover

Muscle that produces most of the force of the movement (brachialis flexes elbow)

Synergist

muscle that aids the prime mover (bicep brachii assists brachialis)

Antagonist

muscle that opposes the prime mover (triceps brachii extends elbow)

Fixator

muscle that prevents a bone from moving (rhomboid muscles fix scapula when biceps contracts)

Muscles on the anterior side produces…

flexion

Muscles on the posterior side produces…

extension

Muscles on the lateral side produces…

abduction

Muscles on the medial side produces…

adduction

Fusiform muscles (definition + example)

thick in the middle, fascicles converging on each tapered end; biceps

Parallel muscles (definition + example)

uniform width, parallel fascicles; sartorius

Triangular (convergent) muscles (definition + example)

broad on one end, converging fascicles on the other end; pectoralis major

Pennate muscles

feather-shaped; the fascicle attaches obliquely on a central tendon that runs the full length of the muscle

Unipennate (definition + example)

facicles approach tendon from one side; extensor digitorum longus

Bipennate (definition + example)

fascicles approach tendon from both sides; rectus femoris

Multipennate (definition + example)

bunches of feathers converge to single point; deltoid

Circular muscles (sphincters) (definition + example)

fascicles form rings around body openings and passages; obicularis oris, orbularis oculi

Lever, Fulcrum, Effort, Load Definitions

• Lever = bone

• Fulcrum = joint

• Effort = muscle contraction

• Load = weight

First-class lever (LFE)

Fulcrum is between load and effort; neck extension (neck extenstion: fulcrum = joint b/w skull + first vertebra, load = weight of head, effort = back neck muscles)

Second-class lever (ELF)

Load is b/w effort + fulcrum; standing on tiptoes (fulcrum = ball of foot, load = body weight, effort = calf muscles)

Third-class lever (LEF)

Effort is b/w load + fulcrum; bicep curl (fulcrum = elbow, load = weight in hand, effort = bicep muscle)

Muscles for facial expression

• Zygomaticus (smile)

• Obicular Oculi (closes eyelid)

• Orbiculr Oris (puckers lips)

• Platysma (pulls down corners of mouth)

Muscles for chewing

• Temporalis

• Masseter

• Pterygoids

• Buccinator

Muscles of tongue movement

• Genioglossus

• Hyoglossus

• Stylogossus

Muscles of head movement

• Sternocleidomastoid or SCM (major head flexor, lateral head mvmt)

• Scalene (lateral head mvmt)

• Splenius capitis + cervicis portion (head extension, rotation, lateral bending)

• Semispinalis capitis (synergist of SCM)

Muscles of Neck + Vertebral Column

Erector spinae group (lateral to medial → Iliocostalis, Longissimus, Spinalis)

Muscles of the Thorax

• External intercostals: elevate ribs for inspiration

• Internal intercostals: help for expiration

• Diaphragm: divides thoracic + abdmonial cavity, important for inspiration

Muscles of Abdominal Wall

• External obliques (most superficial)

• Rectus abdominis (six-pack)

• Internal obliques

• Transversus abdominis (deepest)

Muscles of Pelvic Floor

• Levator ani

• Coccygeus

• Urogential diaphragm (most anterior)

  • has an external urethral sphincter (voluntary control of urination)

Superficial Muscles of Thorax

• Pectoralis minor (protraction/moving forward & downward rotation of scapula)

• Serratus anterior (saw tooth; protraction of scapula)

• Subclavius (stabilizes pectoral girdle)