Muscular System Muscles

Review Define the following words: Inferior Superior Proximal Distal Deep Superficial Medial Lateral

Golden Rule of Skeletal Muscle Activity With few exception, all muscles cross at least one joint Typically, the bulk of muscles lies proximal to the joint crossed All muscles have at least two attachments to muscle: the origin and the insertion Muscles can only pull, they can never push During contraction, the muscle insertion moves towards the origin

Insertion: attachment to the moveable bone Origin: the part of the muscle that is attached to the immovable or less moveable bone Insertion: attachment to the moveable bone The insertion point will always move toward the origin when muscles contract Many muscles have interchangeable origins and insertions

Body Movements They come in mostly opposite pairs Be ready to move with me!

Body movements Flexion: decreases the angle of the joint Extension: increases the angle of the two bones or parts of the body

Body movements Rotation: movement of the bone around its longitudinal axis Prime example: shaking your head “no”

Body movements Abduction: moving the limb away from the midline Think about the word: if someone abducts you, they are taking you away from home Adduction: movement of a limb towards the body midline

Body movements Circumduction: a combo of flexion, extension, abduction, and adduction The whole limb outlines a cone

Body movements Dorsiflexion or plantar flexion: up and down movements of the foot Lifting the foot towards your shin = dorsiflexion Pointing your toe = plantar flexion

Body movements Inversion: turning the sole of your foot medially Eversion: turning the sole of your foot laterally

Body movements Supination: palm faces anteriorly Like you are holding a cup of soup Pronation: palm faces posteriorly Like you are dribbling a ball like a “pro” W/NBA player

Body movements Opposition: thumb touches the tips of your other fingers Remember: the opposable thumb is one of the things that separates us from monkeys

Muscles to know We will focus on agonist pairs This means that they oppose each other Ie one will flex and the other will extend Let’s start from the head down!

Head/neck-Anterior Sternocleidomastoid Flex your neck when both sides contract Rotate your neck when one side contracts

Head/neck-posterior Trapezius Extend the head Adduct the shoulders Work to have your shoulder blades touch

Chest/shoulder Pectoralis major Adducts and flexes the arm

Chest/shoulder Deltoid Arm abduction

Trunk-anterior Rectus abdominis Flex the vertebral column

Trunk-posterior Erector spinae Back extensors Very deep to the spine

Upper limb-anterior Biceps brachii Flexion of the forearm

Upper limb-posterior Triceps brachii Extension of the forearm

hips Gluteus maximus Hip extensor

Thigh-anterior Quadriceps group Rectus femoris Vastus medialis Vastus intermedius Vastus lateralis Flex the hips Extend knee

Thigh-posterior Hamstrings Biceps femoris Semimembranosus Semitendinosus Flex the knee

Leg-anterior Tibialis anterior Dorsiflex and invert the foot

Leg-posterior Gastrocnemius and soleus Plantar flexion