UNIT 4 part 5: THE MUSCLES!

MAJOR SKELETAL MUSCLES *The names of muscles often describe them…a name may indicate a muscle’s relative size, shape, location, action, number of origins, location of attachments, or the direction of its fibers.*

MAJOR SKELETAL MUSCLES Examples: Triceps brachii: having 3 heads (triceps) or points of origin and located in the brachium (arm). Pectoralis minor: of small size (minor) located in the pectoral region (chest). Zygomaticus: located over the zygomatic bone in the face. Internal (abdominal) obliques: Located near the inside with fibers that run obliquely (in a slanting direction).

 Muscles of Facial Expression: ● Lie beneath the skin of the face and scalp and are used to communicate emotion through facial expression

 Muscles of Facial Expression: What do these do? Orbicularis oculi Orbicularis oris Zygomaticus Platysma Buccinator Risorius

 Muscles of Mastication: ● These muscles attach to the mandible and are used in chewing Masseter Temporalis

 Muscles that move the head: ● Muscles in the neck and upper back used to move the head: Sternocleidomastoid

 Muscles of the Neck, Shoulder, & Torso: Deltoid- abduction of arm Pectoralis major- arm to chest flexion Latissimus dorsi- arm away from chest extension Trapezius- stabilizes, raises, retracts & rotates scapula Latissimus dorsii

 Muscles of the Neck, Shoulder, & Torso: External abdominal oblique- when pair contracts together, aids rectus abdominus; if just one  trunk rotation Rectus abdominus- stabilize pelvis during walking (flexes vert. column) Serratus anterior- pushing/punching “boxer’s muscle”

 Muscles of the Neck, Shoulder, & Torso: External intercostals- open up rib cage (increase volume) Internal intercostals- contracts rib cage (decrease volume) Breathing!

 Muscles of the Arm: Biceps brachii (flex) Triceps brachii (extend)

Flexors of arm/hand Extensors of arm/hand

 Muscles of the Hip & Leg: Gluteus maximus- major thigh/leg extensor; complex & powerful! Gluteus medius- steadies pelvis; important in walking, etc.; abducts & rotates thigh medially

 Muscles of the Hip & Leg: Sartorius- flexes & laterally rotates thigh/leg Gracilis- adducts thigh/leg

 Muscles of the Hip & Leg: QUADRICEP MUSCLES Vastus lateralis- extends knee; leg flexion Rectus femoris- extends knee; leg flexion Vastus medialis- extends knee; leg flexion (vastus intermedius underneath; don’t need to know)

 Muscles of the Hip & Leg: Gastrocnemius- one of two major muscles of calf (plantar flexion); Soleus- calf muscle underneath gastrocnemius (plantar flexion) Tibialis anterior- dorsiflexion of foot

 Muscles of the Hip & Leg: HAMSTRING MUSCLES Biceps femoris- extends leg back & flexes knee Semitendonosus- extends leg back & flexes knee Semimembranosus- extends leg back & flexes knee

*Calcaneal tendon (Achilles) Rectus femoris- patellar tendon *Patellar tendon (tendon); extends from rectus femoris to tibial tuberosity (Osgood-Schlatter) *Calcaneal tendon (Achilles)

 Miscellaneous: Retinaculum- strong ligaments that secure a group of tendons in place

Diseases/Conditions that Affect the Muscular System: Lou Gehrig’s (ALS): motor neurons break down so the impulse can’t travel to muscles Botulism: toxin produced by a particular strain of bacteria; interferes with the release of acetylcholine  die of respiratory failure

Muscle atrophy: degeneration & loss of muscle mass Myasthenia gravis: body’s immune system produces antibodies that block muscle receptors for acetylcholine released from nerve at neuromuscular junction Muscle atrophy: degeneration & loss of muscle mass From bed-rest or loss of neural stimulation

Muscular Dystrophy: group of diseases that cause progressive weakness and loss of muscle mass. abnormal genes (mutations) interfere with the production of proteins needed to form & maintain healthy muscle

Spasm: muscle cramp often due to overuse, dehydration, electrolyte abnormalities, or poor circulation Treatment: drink water/Gatorade; stop & gently stretch muscle; ice/heat muscle