Muscular System Anatomy: Muscle Types, Actions, Origins & Insertions

What are the three types of muscle?

Skeletal, cardiac, and smooth.

What are the features of skeletal muscle?

Striated, voluntary, and multinucleate.

What are the features of cardiac muscle?

Striated, involuntary, and mononucleate.

What are the features of smooth muscle?

Non-striated, involuntary, and uninucleate.

What is a muscle cell?

A muscle fiber

What are myofilaments?

Actin and myosin protein chains that generate contractile forces.

What are myofibrils?

Bundles of myofilaments made of repeating sarcomeres.

What is a sarcomere?

The basic contractile unit of muscle, from Z disc to Z disc.

What is the A band?

The dark band; its length does not change during contraction.

What is the H zone?

The region containing thick myosin filaments only.

What is the I band?

The region containing thin actin filaments only.

What is the M line?

The center line of a sarcomere.

What is the origin of a muscle?

The relatively stationary attachment.

What is the insertion of a muscle?

The attachment that moves during contraction.

What is muscle contraction?

The movement produced when the muscle contracts.

What is an agonist muscle?

The muscle responsible for producing a movement.

What is an antagonist muscle?

A muscle that opposes a movement.

What do intercalated discs do?

Connect cells and coordinate contraction.

Where is smooth muscle found?

In walls of hollow organs, such as the bladder, uterus, and GI tract.

Name a function of skeletal muscle.

Voluntary movement, posture, or heat generation.

What muscle raises the eyebrows and tenses the scalp?

Occipitofrontalis

What muscle closes the eyelids?

Orbicularis oculi

What muscle closes the mouth and puckers the lips?

Orbicularis oris

What muscle draws the corners of the mouth superiorly?

Zygomaticus major

What muscle draws the upper lip superolaterally?

Zygomaticus minor

What muscle draws the lower lip inferiorly?

Depressor labii inferioris

What muscle draws the angle of the mouth superiorly?

Levator anguli oris

What muscle draws the angle of the mouth inferiorly?

Depressor anguli oris

What muscle elevates and retracts the mandible?

Temporalis

What muscle compresses the cheeks against the teeth?

Buccinator

What muscle flexes the neck and rotates the head toward the opposite side?

Sternocleidomastoid

What muscle stabilizes the scapula?

Pectoralis minor

What muscle elevates the ribs to increase thoracic volume?

External intercostals

What muscle depresses the ribs to decrease thoracic volume?

Internal intercostals

What muscle flexes the abdomen bilaterally?

External obliques

What muscle compresses the abdomen?

Transversus abdominis

What muscle rotates the scapula?

Rhomboid major & minor

What muscle abducts the humerus?

Supraspinatus

What muscle laterally rotates the humerus?

Infraspinatus

What muscle medially rotates the humerus?

Subscapularis

What muscle flexes the elbow?

Brachialis

What muscle extends the elbow?

Triceps brachii

What muscle flexes the hip?

Iliacus

What muscle adducts the hip?

Adductor longus

What muscle laterally rotates the hip?

Gluteus maximus

What muscle abducts the hip?

Gluteus medius

What muscle tenses the skin of the neck?

Platysma

What muscle protracts and stabilizes the scapula?

Serratus anterior

What muscle elevates the scapula?

Levator scapulae

What muscle retracts the scapula?

Rhomboid major and minor

What muscle is responsible for shoulder abduction?

Deltoid

What muscle is responsible for lateral rotation of the humerus?

Infraspinatus

What muscle is responsible for medial rotation of the humerus?

Subscapularis

What muscle abducts the thumb?

Abductor pollicis longus

What muscle flexes the thumb?

Flexor pollicis longus

What muscle adducts the thigh?

Adductor longus

What muscle extends the hip?

Gluteus maximus

What is a function of skeletal muscle?

Voluntary movement, posture, or heat generation.

What muscle raises eyebrows and tenses scalp?

Occipitofrontalis

What muscle draws corners of the mouth superiorly?

Zygomaticus major

What muscle draws upper lip superolaterally?

Zygomaticus minor

What muscle draws lower lip inferiorly?

Depressor labii inferioris

What muscle elevates the hyoid and depresses the mandible?

Digastric

What muscle elevates ribs to increase thoracic volume?

External intercostals

What muscle extends the shoulder and elbow?

Triceps brachii

What muscle performs abduction of the humerus?

Supraspinatus

What muscle performs medial rotation of the humerus?

Subscapularis

What muscle performs lateral rotation of the humerus?

Infraspinatus

What muscle extends the knee?

Quadriceps

What muscle flexes the knee?

Biceps femoris

What muscle plantarflexes the foot?

Gastrocnemius

What muscle dorsiflexes the foot?

Tibialis anterior

What muscle performs inversion of the foot?

Tibialis posterior

What muscle flexes digits 2-5 at PIPs?

Flexor digitorum superficialis

What muscle extends digits 2-5?

Extensor digitorum longus

What muscle performs lateral rotation of the hip?

Piriformis

What muscle performs flexion of the elbow?

Biceps brachii

What muscle performs extension of the hip?

Gluteus maximus

What muscle performs adduction of the hip?

Gracilis

What muscle performs flexion of the digits?

Flexor digitorum longus

What muscle extends the big toe?

Extensor hallucis longus