PSIO 201 Practical 3

3 defining characteristics of skeletal muscle tissue

1. Cylindrical-shaped muscle fibers

2. 3-5 nuclei per muscle fiber

3. Striations due to organization of actin(thin) and myosin(thick) filaments

Z disc

Forms the boundary of each sarcomere

Connects and stabilizes thin filaments

I band

Contains only actin(thin filaments)

H zone

Contains only myosin(thick filaments)

A band

Spans the entire length of thick filaments, including the zone of overlap

Zone of overlap

Region where thick and thin filaments overlap to produce contraction

M line

Central structure that helps stabilize the thick filaments

Thin filaments are composed of

Actin, troponin, and tropomyosin

Thick filaments are composed of

Myosin

Origin

Fixed/less moveable attachment (proximal attachment point of muscle)

Insertion

More moveable attachment, moves toward the origin during contraction (distal attachment point)

Agonist

Prime mover: primary muscle that carries out a muscle action

Synergist

Muscle that assists the agonist

Antagonist

Muscle that performs the opposite action of the agonist

Opposes the initial muscle action

Fixator

Muscle that stabilizes the joint so the agonist can function efficiently

Synergist and Antagonist Principles

A muscle cannot be it's own antagonist!

Ex: posterior deltoid fibers can't be an antagonist to the anterior deltoid fibers

Rhomboid major

adducts/retracts, elevates and inferiorly rotates the scapula

Rhomboid minor

Adducts/retracts, elevates, and inferiorly rotates the scapula

Trapezius

Superior, middle, and inferior fibers

Superior trapezius fibers

Elevate the scapula and clavicle, extend the head, superiorly rotate the scapula

Middle trapezius fibers

Adduct/retract the scapula

Inferior Trapezius Fibers

Depress the scapula

Levator scapulae

Elevates and inferiorly rotates the scapula

Pectoralis Minor

Depresses, abducts/protracts, and inferiorly rotates the scapula

Serratus anterior

Abducts/protracts and superiorly rotates the scapula

Pectoralis Major

Flexes, adducts, and medially rotates the arm

Deltoid

Anterior, middle, and posterior fibers

Anterior deltoid fibers

Flex and medially rotate the arm

Middle deltoid fibers

Abduct the arm

Posterior deltoid fibers

Extend and laterally rotate the arm

Supraspinatus

Abducts the arm

Infraspinatus

Adducts and laterally rotates the arm

Teres major

Extends, adducts, and medially rotates the arm

Teres minor

Extends and laterally rotates the arm

Subscapularis

Medially rotates the arm

Rotator cuff muscles

SITS

Supraspinatus

Infraspinatus

Teres minor

Subscapularis

They stabilize the head of the humerus against the glenoid cavity of the scapula

Rotator cuff tear

Injury to one or more of the muscles/tendons from overuse in sports or heavy lifting

Which muscle is most commonly affected in a rotator cuff tear?

Supraspinatus due to impingement under the acromion of the scapula

Symptoms of a rotator cuff tear

Shoulder pain, weakness, and difficulty with mobility(abduction and external rotation of the arm)

Treatment for a rotator cuff tear

Ice, NSAIDs, physical therapy, surgery for severe cases

Latissimus Dorsi

Adducts, extends, and medially rotates the arm

Biceps brachii

Flexes and supinates the forearm, flexes the arm

Brachialis

Flexes the forearm

Triceps Brachii

Extends the forearm and extends the arm

Pronator Teres

Pronates and flexes the forearm

Brachioradialis

Pronates and flexes the forearm

Flexor Carpi Ulnaris

Flexes and adducts the hand

Flexor carpi radialis

Flexes and abducts the hand

Flexor digitorum superficialis

Flexes digits II-V of the hand

Flexor digitorum profundus

Flexes digits II-V of the hand

Palmaris longus

Flexes the hand

Extensor pollicis brevis

Extends the pollex(thumb)

Abductor pollicis longus

Extends and abducts the pollex

Extensor carpi radialis longus

Extends and abducts hand

Extensor carpi radialis brevis

Extends and abducts the hand

Extensor carpi ulnaris

Extends and adducts the hand

Extensor digitorum

Extends digits II-V of the hand

Extensor digiti minimi

Extends digit V

Frontalis

Elevates the eyebrows and draws the scalp anteriorly

Occipitalis

Draws the scalp posteriorly

Orbicularis oculi

Closing the eyes, blinking, and squinting

Orbicularis oris

Enables puckering and closing of the lips

Zygomaticus minor

Elevating the upper lip during smiling

Zygomaticus major

Raising the lateral corners of your mouth upward

Platysma

Helps in tensing the skin of the neck, lowering the jaw, and depressing the lower lip

Temporalis

Aids in elevating and retracting the mandible for chewing and closing the jaw

Masseter

Responsible for elevating, protracting, and retracting the mandible during chewing

Sternocleidomastoid

Helps in rotating (1 side contracts, laterally rotating to the opposite side) and flexing the head (both contract)

External oblique

Assist in trunk rotation and lateral flexion

Compress the abdomen

Rectus abdominis

Responsible for flexing the vertebral column and compressing the abdomen

Internal oblique

Rotate and flex the torso

Compress the abdomen

Transverse abdominis

Compresses the abdomen

Name the abdominal muscles from deep to superficial

Transverse abdominis

Internal oblique

Rectus abdominis

External oblique

Remember the acronym TIRE

Erector spinae

3 main muscle groups:

Iliocostalis, longissimus, and spinalis

If one side of the erector spinae contract...

Result is lateral flexion and rotation of the vertebral column

If both sides of the erector spinae contract...

Result is extension of the vertebral column

Name the erector spinae muscles from lateral to medial

Iliocostalis group, Longissimus group, Spinalis group

Diaphragm

Contracts downward during inspiration

Is active during quiet(at-rest) inspiration and labored inspiration

What does the diaphragm do during expiration?

Relaxes and moves superiorly, pushing air out of the thoracic cavity

External intercostals

Elevate the ribs during inspiration

Contract during quiet(at-rest) inspiration and labored inspiration

What do the external intercostals do during expiration?

Relax

Internal intercostals

Involved in labored expiration

They depress the ribs by pulling them downward

Flexion

Decreasing the angle between 2 bones

Extension

Increasing the angle between 2 bones

Lateral flexion

Trunk of body moves in a frontal plane laterally away from the body

Hyperextension

Joint is extended beyond it's normal range (past 180 degrees)

Abduction

Lateral movement of a body part away from the body midline

Adduction

Medial movement of a body part towards the midline

Lateral rotation

External rotation of the front of the femur or humerus away from the body's midline

Medial rotation

Internal rotation moving the front of the femur or humerus toward the midline

Supination

Forearm rotates laterally so that the palm faces anteriorly or superiorly

Pronation

Medial rotation of the forearm so the palm is directed posteriorly or inferiorly

Depression

Inferior movement of a body part

Elevation

Superior movement of a body part

Dorsiflexion

Movement at the ankle joint where the top of the foot moves toward the leg

Plantar flexion

Occurs when the foot points downward, away form the leg

Eversion

Sole of the foot faces laterally

Inversion

Sole of the foot turns medially

Protraction

Forward movement of a body part form its anatomical position

Retraction

Posterior movement of a body part, returning it to the anatomical position