8.7 Skeletal Muscle Action

Skeletal Muscle Actions Skeletal muscles provide a variety of body movements The movements largely depend on the origin and insertion of the muscle

Skeletal Muscle Actions The origin in the muscle attachment at the immovable end For the biceps brachii, this is two places on the scapula

Skeletal Muscle Actions The insertion is the movable end, it is pulled towards the origin The insertion on the biceps brachii is on the radius

Skeletal Muscle Actions Skeletal muscles almost always function in groups. For a body movement to occur, more than one muscle must contract.

Skeletal Muscle Actions The main muscle that is responsible for a movement is called the prime mover (agonist) Muscles that contract to assist the prime mover are called synergists

Skeletal Muscle Actions Some muscles can resist the prime mover, these are called antagonists If both a prime mover and antagonist contract, then the part they act on is rigid

Skeletal Muscle Actions For a motion to happen, the prime mover contracts and the antagonists relaxes

Muscles of Facial expression

Muscles of Facial Expression Facial muscles Enable us to communicate feelings through facial expression

Muscles of Facial Expression Epicranius Frontalis Epicranial aponeurosis Occipitalis http://antranik.org/wp-content/uploads/2011/10/muscles-of-the-head-facial-expression.jpg

Muscles of Facial Expression Epicranius Origin – occipital bone Insertion – skin and muscle around superior portion of eyes Action: raises eyebrows http://antranik.org/wp-content/uploads/2011/10/muscles-of-the-head-facial-expression.jpg

Muscles of Facial Expression Orbicularis oculi Muscle around the eye Origin: maxillary/frontal bones Insertion: skin around the eye Action: closes eye http://antranik.org/wp-content/uploads/2011/10/muscles-of-the-head-facial-expression.jpg

Muscles of Facial Expression Orbicularis oris The kissing muscle Origin: muscles near the mouth Insertion: skin of lips Action: closes and protrudes lips http://antranik.org/wp-content/uploads/2011/10/muscles-of-the-head-facial-expression.jpg

Muscles of Facial Expression Buccinator Cheek muscle Means “trumpet” Origin: outer surface of maxilla/mandible Insertion: orbicularis oris Action: compresses cheeks inward Helps you keep food between teeth http://antranik.org/wp-content/uploads/2011/10/muscles-of-the-head-facial-expression.jpg

Muscles of Facial Expression Zygomaticus “smiling” muscle Origin: zygomatic arch Insertion: orbicularis oris Action: raises corner of mouth http://antranik.org/wp-content/uploads/2011/10/muscles-of-the-head-facial-expression.jpg

Muscles of mastication (chewing)

Muscles of mastication Masseter Origin: Lower part of zygomatic arch Insertion: Lateral surface of the mandible Action: elevates mandible http://antranik.org/wp-content/uploads/2011/10/muscles-of-the-head-facial-expression.jpg

Muscles of mastication Temporalis Origin: temporal bone Insertion: Lateral surface of mandible Action: Elevates mandible http://antranik.org/wp-content/uploads/2011/10/muscles-of-the-head-facial-expression.jpg

Muscles of Mastication movements